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rev.7.4 _20 pwm control, pwm/pfm switching control step-down switching regulator controllers s-8520/8521 series seiko instruments inc. 1 the s-8520/8521 series consists of cmos step-down switching regulator-controllers with pwm control (s-8520 series) and pwm/pfm switching control (s-8521 series). these devices contain a reference voltage source, oscillation circuit, error amplifier, and other components. the s-8520 series provides low-ripple power, high- efficiency, and excellent transi ent characteristics thanks to a pwm control circuit capable of varying the duty ratio linearly from 0 % up to 100 %. the series also contains an error amplifier circuit as well as a soft-start circuit that prevents overshoot at startup. the s-8521 series works with either pwm control or pfm control, and can switch from one to the other. it normally operates using pwm control with a duty ratio of 25 % to 100 %, but under a light load, it automatically switches to pfm control with a duty ratio of 25 %. this series ensures high efficiency over a wide range of conditions, from standby mode to operation of peripheral equipment. with the addition of an external pch power mos fet or pnp transistor, a coil, c apacitors, and a diode connected externally, these ics can f unction as step-down switching regulators. they serve as ideal power supply units for portable devices when coupled with the sot-23-5 small package, providing such out standing features as low current consumption. since this series can accommodate an input voltage of up to 16 v, it is also ideal when operating via an ac adapter. features ? low current consumption during operation: 60 a max. (a, b types) 21 a max. (c, d types) 100 a max. (e, f types) during shutdown: 0.5 a max. ? input voltage: 2.5 v to 16 v (b, d, f types) 2.5 v to 10 v (a, c, e types) ? output voltage: selectable betw een 1.5 v and 6.0 v in 0.1 v step ? duty ratio: 0 % to 100 % pwm control (s-8520 series) 25 % to 100 % pwm/pfm switching control (s-8521 series) ? the only peripheral components that can be used wi th this ic are a pch power mos fet or pnp transistor, a coil, a diode, and capacit ors (if a pnp transistor is used, a base resistance and a capacitor will also be required). ? oscillation frequency: 180 khz typ. (a, b types) 60 khz typ. (c, d types) 300 khz typ. (e, f types) ? soft-start function: 8 ms. typ. (a, b types) 12 ms. typ. (c, d types) 4.5 ms. typ. (e, f types) ? with a shutdown function ? with a built-in overload protection circuit overload detection time: 4 ms. typ. (a type) 14 ms. typ. (c type) 2.6 ms. typ. (e type)
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 2 seiko instruments inc. applications ? on-board power supplies of battery devices for portable telephones, electronic notebooks, pdas. ? power supplies for audio equipment, including portable cd players and headphone stereo equipment. ? fixed voltage power supply for cameras, video equipment and communications equipment. ? power supplies for microcomputers. ? conversion from four nih or nicd cells or two lithium-ion cells to 3.3 v/3 v. ? conversion of ac adapter input to 5 v/3 v. package package name drawing code package tape reel sot-23-5 mp005-a mp005-a mp005-a
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 3 block diagrams 1. s-8520 series vout vss l sd c out ? + vin t r ext v in c in + pwm control circuit + reference voltage source with soft-start oscillation circuit off / on off / on v remark all the diodes in the figure are parasitic diodes. figure 1 2. s-8521 series vout vss l sd c out ? + vin t r ext v in c in + pwm/pfm switching control circuit + reference voltage source with soft-start oscillation circuit off / on off / on v remark all the diodes in the figure are parasitic diodes. figure 2
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 4 seiko instruments inc. product name structure 1. product name s-852 x x xx mc - xxx - t2 ic direction in tape specifications * 1 product code *2 package code mc: sot-23-5 output voltage 15 to 60 (ex. when the output voltage is 1.5 v, it is expressed as 15.) product type a: oscillation frequency of 180 khz, with overload protection circuit. b: oscillation frequency of 180 khz, without overload protection circuit. c: oscillation frequency of 60 khz, with overload protection circuit. d: oscillation frequency of 60 khz, without overload protection circuit. e: oscillation frequency of 300 khz, with overload protection circuit. f: oscillation frequency of 300 khz, without overload protection circuit. control system 0: pwm control 1: pwm/pfm switching control *1. refer to the taping specific ations at the end of this book. *2. refer to the table 1 and table 2 in the ? 2. product name list ?. 2. product name list 2-1. s-8520 series table 1 (1/2) series output voltage [v] s-8520axxmc series s-8520bxxmc series s-8520cxxmc series 1.8 ? s-8520b18mc-ard-t2 ? 2.1 s-8520a21mc-avg-t2 ? ? 2.4 ? s-8520b24mc-arj-t2 ? 2.5 s-8520a25mc-avk-t2 s-8520b25mc- ark-t2 s-8520c25mc-brk-t2 2.6 s-8520a26mc-avl-t2 ? ? 2.7 s-8520a27mc-avm-t2 s-8520b27m c-arm-t2 s-8520c27mc-brm-t2 2.8 s-8520a28mc-avn-t2 s-8520b28mc-arn-t2 s-8520c28mc-brn-t2 2.9 s-8520a29mc-avo-t2 s-8520b29m c-aro-t2 s-8520c29mc-bro-t2 3.0 s-8520a30mc-avp-t2 s-8520b30mc- arp-t2 s-8520c30mc-brp-t2 3.1 s-8520a31mc-avq-t2 s-8520b31m c-arq-t2 s-8520c31mc-brq-t2 3.2 s-8520a32mc-avr-t2 s-8520b32mc-arr-t2 s-8520c32mc-brr-t2 3.3 s-8520a33mc-avs-t2 s-8520b33mc- ars-t2 s-8520c33mc-brs-t2 3.4 s-8520a34mc-avt-t2 s-8520b34m c-art-t2 s-8520c34mc-brt-t2 3.5 s-8520a35mc-avu-t2 s-8520b35mc-aru-t2 s-8520c35mc-bru-t2 3.6 s-8520a36mc-avv-t2 s-8520b36mc- arv-t2 s-8520c36mc-brv-t2 4.3 ? s-8520b43mc-asc-t2 ? 5.0 s-8520a50mc-awj-t2 s-8520a50m c-asj-t2 s-8520c50mc-bsj-t2 5.3 ? s-8520b53mc-asm-t2 ?
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 5 table 1 (2/2) series output voltage [v] s-8520dxxmc series s-8520exxmc series s-8520fxxmc series 1.5 ? s-8520e15mc-bja-t2 s-8520f15mc-bna-t2 1.6 ? s-8520e16mc-bjb-t2 s-8520f16mc-bnb-t2 1.7 ? s-8520e17mc-bjc-t2 s-8520f17mc-bnc-t2 1.8 ? s-8520e18mc-bjd-t2 s-8520f18mc-bnd-t2 1.9 ? s-8520e19mc-bje-t2 s-8520f19mc-bne-t2 2.0 ? s-8520e20mc-bjf-t2 s-8520f20mc-bnf-t2 2.1 ? s-8520e21mc-bjg-t2 s-8520f21mc-bng-t2 2.2 ? s-8520e22mc-bjh-t2 s-8520f22mc-bnh-t2 2.3 ? s-8520e23mc-bji-t2 s-8520f23mc-bni-t2 2.4 ? s-8520e24mc-bjj-t2 s-8520f24mc-bnj-t2 2.5 s-8520d25mc-bvk-t2 s-8520e25mc- bjk-t2 s-8520f25mc-bnk-t2 2.6 ? s-8520e26mc-bjl-t2 s-8520f26mc-bnl-t2 2.7 ? s-8520e27mc-bjm-t2 s-8520f27mc-bnm-t2 2.8 ? s-8520e28mc-bjn-t2 s-8520f28mc-bnn-t2 2.9 ? s-8520e29mc-bjo-t2 s-8520f29mc-bno-t2 3.0 ? s-8520e30mc-bjp-t2 s-8520f30mc-bnp-t2 3.1 ? s-8520e31mc-bjq-t2 s-8520f31mc-bnq-t2 3.2 ? s-8520e32mc-bjr-t2 s-8520f32mc-bnr-t2 3.3 ? s-8520e33mc-bjs-t2 s-8520f33mc-bns-t2 3.4 ? s-8520e34mc-bjt-t2 s-8520f34mc-bnt-t2 3.5 ? s-8520e35mc-bju-t2 s-8520f35mc-bnu-t2 3.6 ? s-8520e36mc-bjv-t2 s-8520f36mc-bnv-t2 3.7 ? s-8520e37mc-bjw-t2 s-8520f37mc-bnw-t2 3.8 ? s-8520e38mc-bjx-t2 s-8520f38mc-bnx-t2 3.9 ? s-8520e39mc-bjy-t2 s-8520f39mc-bny-t2 4.0 ? s-8520e40mc-bjz-t2 s-8520f40mc-bnz-t2 4.1 ? s-8520e41mc-bka-t2 s-8520f41mc-boa-t2 4.2 ? s-8520e42mc-bkb-t2 s-8520f42mc-bob-t2 4.3 ? s-8520e43mc-bkc-t2 s-8520f43mc-boc-t2 4.4 ? s-8520e44mc-bkd-t2 s-8520f44mc-bod-t2 4.5 ? s-8520e45mc-bke-t2 s-8520f45mc-boe-t2 4.6 ? s-8520e46mc-bkf-t2 s-8520f46mc-bof-t2 4.7 ? s-8520e47mc-bkg-t2 s-8520f47mc-bog-t2 4.8 ? s-8520e48mc-bkh-t2 s-8520f48mc-boh-t2 4.9 ? s-8520e49mc-bki-t2 s-8520f49mc-boi-t2 5.0 s-8520d50mc-bwj-t2 s- 8520e50mc-bkj-t2 s-8520f50mc-boj-t2 5.1 ? s-8520e51mc-bkk-t2 s-8520f51mc-bok-t2 5.2 ? s-8520e52mc-bkl-t2 s-8520f52mc-bol-t2 5.3 ? s-8520e53mc-bkm-t2 s-8520f53mc-bom-t2 5.4 ? s-8520e54mc-bkn-t2 s-8520f54mc-bon-t2 5.5 ? s-8520e55mc-bko-t2 s-8520f55mc-boo-t2 5.6 ? s-8520e56mc-bkp-t2 s-8520f56mc-bop-t2 5.7 ? s-8520e57mc-bkq-t2 s-8520f57mc-boq-t2 5.8 ? s-8520e58mc-bkr-t2 s-8520f58mc-bor-t2 5.9 ? s-8520e59mc-bks-t2 s-8520f59mc-bos-t2 6.0 ? s-8520e60mc-bkt-t2 s-8520f60mc-bot-t2 remark please contact the sii marketing department fo r the availability of product samples other than those specified above.
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 6 seiko instruments inc. 2-2. s-8521 series table 2 (1/2) series output voltage [v ] s-8521axxmc series s-8521bxxmc series s-8521cxxmc series 1.5 ? s-8521b15mc-ata-t2 ? 1.6 ? ? s-8521c16mc-btb-t2 1.8 ? s-8521b18mc-atd-t2 ? 1.9 ? s-8521b19mc-ate-t2 ? 2.0 ? s-8521b20mc-atf-t2 ? 2.1 ? s-8521b21mc-atg-t2 ? 2.3 ? s-8521b23mc-ati-t2 ? 2.5 s-8521a25mc-axk-t2 s-8521b25mc- atk-t2 s-8521c25mc-btk-t2 2.6 ? s-8521b26mc-atl-t2 ? 2.7 s-8521a27mc-axm-t2 s-8521b27mc-atm-t2 s-8521c27mc-btm-t2 2.8 s-8521a28mc-axn-t2 s-8521b28mc-atn-t2 s-8521c28mc-btn-t2 2.9 s-8521a29mc-axo-t2 s-8521b29mc-ato-t2 s-8521c29mc-bto-t2 3.0 s-8521a30mc-axp-t2 s-8521b30mc- atp-t2 s-8521c30mc-btp-t2 3.1 s-8521a31mc-axq-t2 s-8521b31mc-atq-t2 s-8521c31mc-btq-t2 3.2 s-8521a32mc-axr-t2 s-8521b32mc-atr-t2 s-8521c32mc-btr-t2 3.3 s-8521a33mc-axs-t2 s-8521b33mc- ats-t2 s-8521c33mc-bts-t2 3.4 s-8521a34mc-axt-t2 s-8521b34mc-att-t2 s-8521c34mc-btt-t2 3.5 s-8521a35mc-axu-t2 s-8521b35mc-atu-t2 s-8521c35mc-btu-t2 3.6 s-8521a36mc-axv-t2 s-8521b36mc- atv-t2 s-8521c36mc-btv-t2 4.4 ? s-8521b44mc-aud-t2 ? 5.0 s-8521a50mc-ayj-t2 s-8521b50m c-auj-t2 s-8521c50mc-buj-t2
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 7 table 2 (2/2) series output voltage [v] s-8521dxxmc series s-8521exxmc series s-8521fxxmc series 1.5 ? s-8521e15mc-bla-t2 s-8521f15mc-bpa-t2 1.6 s-8521d16mc-bxb-t2 s-8521e16m c-blb-t2 s-8521f16mc-bpb-t2 1.7 ? s-8521e17mc-blc-t2 s-8521f17mc-bpc-t2 1.8 ? s-8521e18mc-bld-t2 s-8521f18mc-bpd-t2 1.9 ? s-8521e19mc-ble-t2 s-8521f19mc-bpe-t2 2.0 s-8521d20mc-bxf-t2 s-8521e20mc-blf-t2 s-8521f20mc-bpf-t2 2.1 ? s-8521e21mc-blg-t2 s-8521f21mc-bpg-t2 2.2 ? s-8521e22mc-blh-t2 s-8521f22mc-bph-t2 2.3 ? s-8521e23mc-bli-t2 s-8521f23mc-bpi-t2 2.4 ? s-8521e24mc-blj-t2 s-8521f24mc-bpj-t2 2.5 s-8521d25mc-bxk-t2 s-8521e25m c-blk-t2 s-8521f25mc-bpk-t2 2.6 s-8521d27mc-bxm-t2 s- 8521e26mc-bll-t2 s-8521f26mc-bpl-t2 2.7 ? s-8521e27mc-blm-t2 s-8521f27mc-bpm-t2 2.8 s-8521d28mc-bxn-t2 s-8521e28mc-bln-t2 s-8521f28mc-bpn-t2 2.9 s-8521d29mc-bxo-t2 s- 8521e29mc-blo-t2 s-8521f29mc-bpo-t2 3.0 s-8521d30mc-bxp-t2 s-8521e30m c-blp-t2 s-8521f30mc-bpp-t2 3.1 s-8521d31mc-bxq-t2 s- 8521e31mc-blq-t2 s-8521f31mc-bpq-t2 3.2 s-8521d32mc-bxr-t2 s-8521e32mc-blr-t2 s-8521f32mc-bpr-t2 3.3 s-8521d33mc-bxs-t2 s-8521e33m c-bls-t2 s-8521f33mc-bps-t2 3.4 s-8521d34mc-bxt-t2 s-8521e34mc-blt-t2 s-8521f34mc-bpt-t2 3.5 s-8521d35mc-bxu-t2 s-8521e35mc-blu-t2 s-8521f35mc-bpu-t2 3.6 s-8521d36mc-bxv-t2 s-8521e36m c-blv-t2 s-8521f36mc-bpv-t2 3.7 ? s-8521e37mc-blw-t2 s-8521f37mc-bpw-t2 3.8 ? s-8521e38mc-blx-t2 s-8521f38mc-bpx-t2 3.9 ? s-8521e39mc-bly-t2 s-8521f39mc-bpy-t2 4.0 s-8521d40mc-bxz-t2 s-8521e40mc-blz-t2 s-8521f40mc-bpz-t2 4.1 ? s-8521e41mc-bma-t2 s-8521f41mc-bqa-t2 4.2 ? s-8521e42mc-bmb-t2 s-8521f42mc-bqb-t2 4.3 ? s-8521e43mc-bmc-t2 s-8521f43mc-bqc-t2 4.4 ? s-8521e44mc-bmd-t2 s-8521f44mc-bqd-t2 4.5 ? s-8521e45mc-bme-t2 s-8521f45mc-bqe-t2 4.6 ? s-8521e46mc-bmf-t2 s-8521f46mc-bqf-t2 4.7 ? s-8521e47mc-bmg-t2 s-8521f47mc-bqg-t2 4.8 ? s-8521e48mc-bmh-t2 s-8521f48mc-bqh-t2 4.9 ? s-8521e49mc-bmi-t2 s-8521f49mc-bqi-t2 5.0 s-8521d50mc-byj-t2 s-8521e50mc-bmj-t2 s-8521f50mc-bqj-t2 5.1 ? s-8521e51mc-bmk-t2 s-8521f51mc-bqk-t2 5.2 ? s-8521e52mc-bml-t2 s-8521f52mc-bql-t2 5.3 ? s-8521e53mc-bmm-t2 s-8521f53mc-bqm-t2 5.4 ? s-8521e54mc-bmn-t2 s-8521f54mc-bqn-t2 5.5 ? s-8521e55mc-bmo-t2 s-8521f55mc-bqo-t2 5.6 ? s-8521e56mc-bmp-t2 s-8521f56mc-bqp-t2 5.7 ? s-8521e57mc-bmq-t2 s-8521f57mc-bqq-t2 5.8 ? s-8521e58mc-bmr-t2 s-8521f58mc-bqr-t2 5.9 ? s-8521e59mc-bms-t2 s-8521f59mc-bqs-t2 6.0 ? s-8521e60mc-bmt-t2 s-8521f60mc-bqt-t2 remark please contact the sii marketing department fo r the availability of product samples other than those specified above.
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 8 seiko instruments inc. pin configuration table 3 pin no. pin name pin description 1 off / on shutdown pin ?h?: normal operation (step-down operation) ?l?: step-down operation stopped (all circuits deactivated) 2 vss gnd pin 3 vout output voltage monitoring pin 4 ext connection pin for external transistor sot-23-5 top view 5 4 3 2 1 5 vin ic power supply pin figure 3 absolute maximum ratings table 4 (ta = 25 c unless otherwise specified) item symbol absolute maximum ratings unit vin pin voltage v in a, c, e types v ss ? 0.3 to v ss + 12 v b, d, f types v ss ? 0.3 to v ss + 18 vout pin voltage v out a, c, e types v ss ? 0.3 to v ss + 12 b, d, f types v ss ? 0.3 to v ss + 18 off / on pin voltage off / on v a, c, e types v ss ? 0.3 to v ss + 12 b, d, f types v ss ? 0.3 to v ss + 18 ext pin voltage v ext v ss ? 0.3 to v in + 0.3 ext pin current i ext 50 ma power dissipation p d 250 mw operating ambient temperature topr ? 40 to + 85 c storage temperature tstg ? 40 to + 125 caution the absolute maximum ratings are rated values exceeding which the product could suffer physical damage. these values must therefore not be exceeded under any conditions.
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 9 electrical characteristics 1. a type, b type table 5 (ta = 25 c unless otherwise specified) parameter symbol condition min. typ. max. unit test circuit output voltage *1 v out(e) ? v out(s) 0.976 v out(s) v out(s) 1.024 v 3 input voltage v in ? a type 2.5 ? 10.0 2 b type 2.5 ? 16.0 current consumption 1 i ss1 v out = v out(s) 1.2 ? 35 60 a current consumption during shutdown i sss off / on v = 0 v ? ? 0.5 ext pin output current i exth v ext = v in ? 0.4 v s-8520/21x15 to 24 ? 2.3 ? 4.5 ? ma ? s-8520/21x25 to 34 ? 3.7 ? 7.0 ? s-8520/21x35 to 44 ? 5.3 ? 9.3 ? s-8520/21x45 to 54 ? 6.7 ? 11.3 ? s-8520/21x55 to 60 ? 8.0 ? 13.3 ? i extl v ext = 0.4 v s-8520/21x15 to 24 + 4.3 + 8.4 ? s-8520/21x25 to 34 + 7.0 + 13.2 ? s-8520/21x35 to 44 + 9.9 + 17.5 ? s-8520/21x45 to 54 + 12.6 + 21.4 ? s-8520/21x55 to 60 + 15.0 + 25.1 ? line regulation v out1 v out(s) 2.0 v v in = 2.5 to 2.94 v ? 30 60 mv 3 v out(s) > 2.0 v v in = v out(s) 1.2 to 1.4 ? 30 60 load regulation v out2 load current = 10 a to i out 1.25 ? 30 60 output voltage temperature coefficient ta v out ? ? ta =? 40 c to + 85 c ? v out(s) 5e ? 5 ? v/ c oscillation frequency f osc v out(s) 2.4 v 144 180 216 khz measured waveform at ext pin. v out(s) 2.5 v 153 180 207 pwm/pfm control switching duty ratio (s-8521 series) pfmduty no load, measured waveform at ext pin. 15 25 40 % v sh judged oscillation at ext pin 1.8 ? ? v 2 off / on pin input voltage v sl judged oscillation stop at ext pin ? ? 0.3 i sh ? ? 0.1 ? 0.1 a 1 off / on pin input leakage current i sl ? ? 0.1 ? 0.1 soft start time t ss ? 4.0 8.0 16.0 ms 3 overload detection time (a type) t pro duration from the time v out is reduced to 0 v to the time the ext pin obtains v in . 2.0 4.0 8.0 2 efficiency effi ? ? 93 ? % 3 external parts coil: sumida corporation cd54 (47 h) diode: matsushita electric industr ial co., ltd. ma720 (shottky type) capacitor: matsushita electric industrial co., ltd. te (16 v, 22 f tantalum type) transistor: toshiba corporation 2sa1213y base resistance (r b ): 0.68 k ? base capacitor (c b ): 2200 pf (ceramic type) the recommended components are connected to the ic, unless otherwise indicated. v in = v out(s) 1.2 v (v in = 2.5 v if v out(s) 2.0 v), i out = 120 ma the off / on pin is connected to vin pin. *1 . v out(s) : specified output voltage value, v out(e) : actual output voltage value
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 10 seiko instruments inc. 2. c type, d type table 6 (ta = 25 c unless otherwise specified) parameter symbol condition min. typ. max. unit test circuit output voltage *1 v out(e) ? v out(s) 0.976 v out(s) v out(s) 1.024 v 3 input voltage v in ? c type 2.5 ? 10.0 2 d type 2.5 ? 16.0 current consumption 1 i ss1 v out = v out(s) 1.2 ? 10 21 a current consumption during shutdown i sss off / on v = 0 v ? ? 0.5 ext pin output current i exth v ext = v in ? 0.4 v s-8520/21x15 to 24 ? 2.3 ? 4.5 ? ma ? s-8520/21x25 to 34 ? 3.7 ? 7.0 ? s-8520/21x35 to 44 ? 5.3 ? 9.3 ? s-8520/21x45 to 54 ? 6.7 ? 11.3 ? s-8520/21x55 to 60 ? 8.0 ? 13.3 ? i extl v ext = 0.4 v s-8520/21x15 to 24 + 4.3 + 8.4 ? s-8520/21x25 to 34 + 7.0 + 13.2 ? s-8520/21x35 to 44 + 9.9 + 17.5 ? s-8520/21x45 to 54 + 12.6 + 21.4 ? s-8520/21x55 to 60 + 15.0 + 25.1 ? line regulation v out1 v out(s) 2.0 v v in = 2.5 to 2.94 v ? 30 60 mv 3 v out(s) > 2.0 v v in = v out(s) 1.2 to 1.4 ? 30 60 load regulation v out2 load current = 10 a to i out 1.25 ? 30 60 output voltage temperature coefficient ta v out ? ? ta =? 40 c to + 85 c ? v out(s) 5e ? 5 ? v/ c oscillation frequency f osc v out(s) 2.4 v 45 60 75 khz measured waveform at ext pin. v out(s) 2.5 v 48 60 72 pwm/pfm control switching duty ratio (s-8521 series) pfmduty no load, measured waveform at ext pin 15 25 40 % v sh judged oscillation at ext pin 1.8 ? ? v 2 off / on pin input voltage v sl judged oscillation stop at ext pin ? ? 0.3 i sh ? ? 0.1 ? 0.1 a 1 off / on pin input leakage current i sl ? ? 0.1 ? 0.1 soft start time t ss ? 6.0 12.0 24.0 ms 3 overload detection time (c type) t pro duration from the time v out is reduced to 0 v to the time the ext pin obtains v in . 7.0 14.0 28.0 2 efficiency effi ? ? 93 ? % 3 external parts coil: sumida corporation cd54 (47 h) diode: matsushita electric industr ial co., ltd. ma720 (shottky type) capacitor: matsushita electric industrial co., ltd. te (16 v, 22 f tantalum type) transistor: toshiba corporation 2sa1213y base resistance (r b ): 0.68 k ? base capacitor (c b ): 2200 pf (ceramic type) the recommended components are connected to the ic, unless otherwise indicated. v in = v out(s) 1.2 v (v in = 2.5 v if v out(s) 2.0 v), i out = 120 ma the off / on pin is connected to vin pin. *1 . v out(s) : specified output voltage value, v out(e) : actual output voltage value
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 11 3. e type, f type table 7 (ta = 25 c unless otherwise specified) parameter symbol condition min. typ. max. unit test circuit output voltage *1 v out(e) ? v out(s) 0.976 v out(s) v out(s) 1.024 v 3 input voltage v in ? e type 2.5 ? 10.0 2 f type 2.5 ? 16.0 current consumption 1 i ss1 v out = v out(s) 1.2 ? 60 100 a current consumption during shutdown i sss off / on v = 0 v ? ? 0.5 ext pin output current i exth v ext = v in ? 0.4 v s-8520/21x15 to 24 ? 2.3 ? 4.5 ? ma ? s-8520/21x25 to 34 ? 3.7 ? 7.0 ? s-8520/21x35 to 44 ? 5.3 ? 9.3 ? s-8520/21x45 to 54 ? 6.7 ? 11.3 ? s-8520/21x55 to 60 ? 8.0 ? 13.3 ? i extl v ext = 0.4 v s-8520/21x15 to 24 + 4.3 + 8.4 ? s-8520/21x25 to 34 + 7.0 + 13.2 ? s-8520/21x35 to 44 + 9.9 + 17.5 ? s-8520/21x45 to 54 + 12.6 + 21.4 ? s-8520/21x55 to 60 + 15.0 + 25.1 ? line regulation v out1 v out(s) 2.0 v v in = 2.5 to 2.94 v ? 30 60 mv 3 v out(s) > 2.0 v v in = v out(s) 1.2 to 1.4 ? 30 60 load regulation v out2 load current = 10 a to i out 1.25 ? 30 60 output voltage temperature coefficient ta v out ? ? ta =? 40 c to + 85 c ? v out(s) 5e ? 5 ? v/ c oscillation frequency f osc v out(s) 2.4 v 225 300 375 khz measured waveform at ext pin. v out(s) 2.5 v 240 300 360 pwm/pfm control switching duty ratio (s-8521 series) pfmduty no load, measured waveform at ext pin 15 25 40 % v sh judged oscillation at ext pin 1.8 ? ? v 2 off / on pin input voltage v sl judged oscillation stop at ext pin ? ? 0.3 i sh ? ? 0.1 ? 0.1 a 1 off / on pin input leakage current i sl ? ? 0.1 ? 0.1 soft start time t ss ? 2.0 4.5 9.2 ms 3 overload detection time (e type) t pro duration from the time v out is reduced to 0 v to the time the ext pin obtains v in . 1.3 2.6 4.5 2 efficiency effi ? ? 90 ? % 3 external parts coil: sumida corporation cd54 (47 h) diode: matsushita electric industr ial co., ltd. ma720 (shottky type) capacitor: matsushita electric industrial co., ltd. te (16 v, 22 f tantalum type) transistor: toshiba corporation 2sa1213y base resistance (r b ): 0.68 k ? base capacitor (c b ): 2200 pf (ceramic type) the recommended components are connected to the ic, unless otherwise indicated. v in = v out(s) 1.2 v (v in = 2.5 v if v out(s) 2.0 v), i out = 120 ma the off / on pin is connected to vin pin. *1 . v out(s) : specified output voltage value, v out(e) : actual output voltage value
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 12 seiko instruments inc. test circuits 1. ext vss off / on vout open open vin a figure 4 2. vss off / on vin ? + vout ext oscillosco p e a figure 5 3. vss off / on 0.68 k ? 2200 pf vin ? v + vout ext ? + figure 6
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 13 operation 1. step-down dc-dc converter 1-1. pwm control (s-8520 series) the s-8520 series consists of dc-dc converters that employ a pulse-width modulation (pwm) system. this series is characterized by its low current consumption. in conventional pfm system dc-dc converters, pulses are skipped when they are operated with a low output load current, causing variations in the ripple frequency of the output volt age and an increase in the ripple voltage. both of these effects constitute inherent drawbacks to those converters. in converters of the s-8520 series, the pulse width va ries in a range from 0 to 100 %, according to the load current, and yet ripple voltage produced by the sw itching can easily be removed through a filter because the switching frequency remains constant. t herefore, these converters provide a low-ripple power over broad ranges of input voltage and load current. 1-2. pwm/pfm switching control (s-8521 series) the s-8521 series consists of dc- dc converters capable of automatic ally switching the pulse-wide modulation system (pwm) over to the pulse-frequency modulation sy stem (pfm), and vice versa, according to the load current. this series of converters features low current consumption. in a region of high output load currents, the s-8521 series converters function with pwm control, where the pulse-width duty varies from 25 to 100 %. this function helps keep the ripple power low. for certain low output load currents, the converters are switched over to pfm control, whereby pulses having their pulse-width duty fixed at 25 % ar e skipped depending on the quantity of the load current, and are output to a switching transistor. this caus es the oscillation circuit to produce intermittent oscillation. as a result, current consumpti on is reduced and efficiency losses are prevented under low loads. especially for output load currents in the region of 100 a, these dc-dc converters can operat e at extremely high efficiency. 2. off on/ pin (shutdown pin) this pin deactivates or activates the step-down operation. when the off / on pin is set to "l", the v in voltage appears through the ext pin, prodding the switching transistor to go off. all the internal circuits stop working, and substantial savings in current consumption are thus achieved. the off / on pin is configured as shown in figure 7 . since pull-up or pull-down is not performed internally, please avoid operating the pin in a floating st ate. also, try to refrain from applying a voltage of 0.3 to 1.8 v to the pin, lest the cu rrent consumption increase. when this off / on pin is not used, leave it coupled to the vin pin. table 8 off / on pin cr oscillation circuit output voltage ?h? activated set value ?l? deactivated v ss off / on vin vss figure 7
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 14 seiko instruments inc. 3. soft start function the s-8520/8521 series comes with a built-in soft star t circuit. this circuit enables the output voltage (v out ) to rise gradually over the specified soft start ti me (t), when the power is switched on or when the off / on pin remains at the "h" level. this pr events the output voltage from overshooting. however, the soft start function of this ic is not able to perfectly prevent a rush current from flowing to the load. (refer to figure 8. ) since this rush current depends on the input voltage and load conditions, we recommend that you evaluate it by testi ng performance with the actual equipment. (v in : 0 4.0 v) t [1 ms/div] v out [1 v/div] rush current [0.5 a/div] 0 a 1.5 a 3 v power switched on 0 v figure 8 waveforms of output voltage and rush current at soft start (ex. s-8520a33mc) 4. overload protection circuit (a, c, e types) the a, c and e types of the s-8520/8521 series come with a built-in overload protection circuit. if the output voltage falls because of an overload, the maximum duty state (100 %) will continue. if this 100 % duty state lasts longer than the prescribed overload detection time (t pro ), the overload protection circuit will hold the ext pin at "h," thereby protec ting the switching transistor and inductor. when the overload protection circuit is functioning, the referenc e voltage circuit will be activated by means of a soft start in the ic, and the reference voltage will rise slowly from 0 v. the reference voltage and the feedback voltage obtained by dividing the output voltage are compared to each other. so long as the reference voltage is lower, the ext pin will be held at "h" to keep the oscillation inactive. if the reference voltage keeps rising and exceeds the f eedback voltage, the oscillation will resume. if the load is heavy when the oscillation is restarted, and the ext pin holds the "l" level longer than the specified overload detection time (t pro ), the overload protection circui t will operate again, and the ic will enter intermittent operation mode, in which it r epeats the actions described abov e. once the overload state is eliminated, the ic resumes normal operation. waveforms at ext pin protection circuit on [t ss 0.3] overload detection time (t pro ) figure 9 waveforms appearing at ext pin as the overload protection circuit operates
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 15 5. 100 % duty cycle the s-8520/8521 series operates with a maximum dut y cycle of 100 %. when a b, d and f types products not provided with an overload protection circui t is used, the switching transistor can be kept on to supply current to the load continually, even in ca ses where the input voltage falls below the preset output voltage value. the output voltage delivered under these circumstances is one that results from subtracting, from the input voltage, the voltage dr op caused by the dc resistance of the inductance and the on-resistance of the switching transistor. if an a, c and e types products provided with an overload protection circuit is used, this protection circuit will function when the 100 % duty state has lasted l onger than the preset overload detection time (t pro ), causing the ic to enter intermittent operation mode. under these conditions, the ic will not be able to supply current to the load continually, unlike the case described in the preceding paragraph. selection of series products and associated external components 1. method for selecting series products the s-8520/8521 series is classified into 12 types, a ccording to the way the control systems (pwm control and pwm/pfm switching control), the diffe rent oscillation frequencies, and the inclusion or exclusion of an overload protection circuit are comb ined one with another. please select the type that best suits your needs by taking advantage of the features of each type described below. 1-1. control systems two different control systems are available: pwm control system (s-8520 series) and pwm/pfm switching control system (s-8521 series). if particular importance is attached to the operat ion efficiency while the load is on standby -- for example, in an application where the load current heavily varies from that in standby state as the load starts operating -- a high efficiency will be obtai ned in standby mode by selecting the pwm/pfm switching control system (s-8521 series). moreover, for applications where switching noise poses a serious problem, the pwm control system (s-8520 series), in which the switching frequency does not vary with the load current, is preferable because it can eliminate ripple voltages easily using a filter. 1-2. oscillation frequencies three oscillation frequencies--180 khz (a, b types), 60 khz (c, d types), and 300 khz (e, f types) -- are available. because of their high oscillation frequency and low ripple voltage the a, b, e and f types offer excellent transient response characteristics. the products in these series allow the use of small- sized inductors since the peak current remains smalle r in the same load current than with products of the other series. in addition, they can also be us ed with small output capacitors. these outstanding features make the a, b, e and f types ideal pr oducts for downsizing the associated equipment. on the other hand, the c and d types, having a lowe r oscillation frequency, are characterized by a small self-consumption of current and excellent effi ciency under light loads. in particular, the d type, which employs a pwm/pfm switching control syst em, enables the operation efficiency to be improved drastically when the output l oad current is approximately 100 a. (refer to ? reference data ?.)
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 16 seiko instruments inc. 1-3. overload protection circuit products can be chosen either with an overload protection circuit (a, c, e types) or without one (b, d, f types). products with an overload protection circuit (a, c, e types) enter intermittent operation mode when the overload protection circuit operates to accommodate overloads or load short-circuiting. this protects the switching elements and inductors. nonet heless, in an application where the load needs to be fed continually with a current by taking advantage of the 100 % duty cycle st ate, even if the input voltage falls below the output voltage value, a b, d, f types product will have to be used. choose whichever product best handles the condi tions of your application. in making the selection, please keep in mind that the upper limit of the operating voltage range is either 10 v (a, c, e types) or 16 v (b, d, f types), depending on whether the product comes with an overload protection circuit built in. table 9 provides a rough guide for selecting a pr oduct type depending on the requirements of the application. choose the product that gives you the largest number of circles (o). table 9 s-8520 series s-8521 series a b c d e f a b c d e f an overload protection circuit is required the input voltage range exceeds 10 v the efficiency under light loads (load current 1 ma) is an important factor to be operated with a medium load current (200 ma class) to be operated with a high load current (1 a class) it is important to have a low-ripple voltage importance is attached to the downsizing of external components remark the symbol " " denotes an indispensable condition, while the symbol " " indicates that the corresponding series has superiori ty in that aspect. the symbol " " indicates particularly high superiority.
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 17 2. inductor the inductance value greatly affe cts the maximum output current (i out ) and the efficiency ( ). as the l-value is reduced gradually, the peak current (i pk ) increases, to finally reach the maximum output current (i out ) when the l-value has fallen to a certain point. if the l-value is made even smaller, i out will begin decreasing because the current dr ive capacity of the switching tr ansistor becomes insufficient. conversely, as the l-value is augment ed, the loss due to the peak current (i pk ) in the switching transistor will decrease until the efficiency is maximized at a ce rtain l-value. if the l-value is made even larger, the loss due to the series resistance of the coil will increase to the detriment of the efficiency. if the l-value is increased in an s-8520/8521 series product, the output voltage may turn unstable in some cases, depending on the conditions of the input voltage, output voltage, and the load current. perform thorough evaluations under the conditions of ac tual service and decide on an optimum l-value. in many applications, selecting a value of a, b, c and d types 47 h, e and f types 22 h will allow a s-8520/8521 series product to yield its best c haracteristics in a well-balanced manner. when choosing an inductor, pay attention to its allow able current, since a current applied in excess of the allowable value will cause the inductor to produce magnetic saturation, leading to a marked decline in efficiency. therefore, select an inductor in which the peak current (i pk ) will not surpass its allowable current at any moment. the peak current (i pk ) is represented by the following equat ion in continuous operation mode: ) v v ( l f 2 ) v v ( ) v v ( i i f in osc out in f out out pk + ? + + = where f osc is the oscillation frequency, l the inductance value of the coil, and v f the forward voltage of the diode. 3. diode the diode to be externally coupled to the ic s hould be a type that meets the following conditions: ? its forward voltage is low (s chottky barrier diode recommended). ? its switching speed is high (50 ns max.). ? its reverse direction voltage is higher than v in . ? its current rating is higher than i pk . 4. capacitors (c in , c out ) the capacitor inserted on the input side (c in ) serves to lower the power impedance and to average the input current for better efficiency. select the c in value according to the impedance of the power supplied. as a rough rule of thumb, you should use a value of 47 f to 100 f, although the actual value will depend on the impedance of the power in use and the load current value. for the output side capacitor (c out ), select one of large capacitance with low esr (equivalent series resistance) for smoothing the ripple voltage. however, notice that a capacitor with extremely low esr (say, below 0.3 ? ), such as a ceramic capacitor, could make the output voltage unstable, depending on the input voltage and load current conditions. instead, a tantalum electrolytic capacitor is recommended. a capacitance value from 47 f to 100 f can serve as a rough yardstick for this selection.
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 18 seiko instruments inc. 5. external switching transistor the s-8520/8521 series can be operated with an external switching transistor of the enhancement (pch) mos fet type or bipolar (pnp) typ. 5-1. enhancement mos fet type the ext pin of the s-8520/8521 series is capable of directly driving a pch power mos fet with a gate capacity of some 1000 pf. when a pch power mos fet is c hosen, because it has a higher switching speed than a pnp type bipolar transistor and because power losses due to the presence of a base current are avoided, efficiency will be 2 to 3 % higher than when ot her types of transistor are employed. the important parameters to be kept in mind in se lecting a pch power mos fet include the threshold voltage, breakdown voltage between gate and source , breakdown voltage between drain and source, total gate capacity, on-resistanc e, and the current rating. the ext pin swings from voltage v in over to voltage v ss . if the input voltage is low, a mos fet with a low threshold voltage has to be used so that the mos fet will come on as required. if, conversely, the input voltage is high, select a mos fet whos e gate-source breakdown voltage is higher than the input voltage by at least several volts. immediately after the power is turned on, or when the power is turned off (that is, when the step-down operation is terminated), the input voltage will be im posed across the drain and the source of the mos fet. therefore, the transistor needs to have a dr ain-source breakdown voltage that is also several volts higher than the input voltage. the total gate capacity and the on-resistance affect the efficiency. the power loss for charging and discharging the gate capacity by switching operation will increase, when the total gate capacity becomes larger and t he input voltage rises higher. therefore the gate capacity affects the efficiency of power in a low l oad current region. if the efficiency under light loads is a matter of particular concern, select a mos fet with a small total gate capacity. in regions where the load current is high, the effi ciency is affected by power losses caused due to the on-resistance of the mos fet. therefore, if the efficiency under heavy loads is particularly important for your application, choose a mos fe t with as low an on-resistance as possible. as for the current rating, select a mos fet whos e maximum continuous drain current rating is higher than the peak current (i pk ). for reference purpose, some efficiency data has been included in this document. for applications with an input voltage range of 10 v or less, data was obtained by using tm6201 of toyoda industries corporation. irf7606, a standard of international rectifier corporation, was used for applications with an input voltage range over 10 v. (refer to " reference data ".)
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 19 5-2. bipolar pnp type figure 10 shows a sample circuit diagram using to shiba corporation 2sa1213-y for the bipolar transistor (pnp). the driving capacity for incr easing the output current by means of a bipolar transistor is determined by the h fe value and the r b value of that bipolar transistor. v in ext vin r b c b toshiba corporation 2sa1213-y figure 10 the r b -value is given by the following equation: extl b in b i 4 . 0 i 7 . 0 v r ? ? = find the necessary base current ib using the h fe value of bipolar transistor by the equation, fe pk b h i i = , and select a smaller r b value. a small r b value will certainly contribute to increasing the output current, but it will also adversely affect the efficiency. moreover, in practice, a current may flow as the pulses or a voltage drop may take place due to the wiring resistance or some other reason. determine an optimum value through experimentation. in addition, if speed-up capacitor (c b ) is inserted in parallel with resistance r b , as shown in figure 10 , the switching loss will be reduced, leading to a higher efficiency. select a c b value by using the following equation as a guide: 7 . 0 f r 2 1 c osc b b however, the practically reasonable c b value differs depending upon the characteristics of the bipolar transistor. optimize the c b value based on the experiment result.
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 20 seiko instruments inc. standard circuits 1. using a bipolar transistor vss vout + v in c in l sd c out off / on reference voltage source with soft start vin tr c b r b ext off / on v + + ? pwm control or pwm/pfm switching cotrol circuit oscillation circuit figure 11 2. using a pch mos fet transistor vss vout l sd c out + + ? vin t r + ext v in c in off / on off / on v oscillation circuit reference voltage source with soft start pwm control or pwm/pfm switching control circuit figure 12 caution the above connection diagram and c onstant will not guarantees successful operation. perform through evaluation using the actual application to set the constant.
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 21 power dissipation of the package 200 100 50 100 150 power dissipation (p d ) [mw] temperature (ta) [ c] 0 0 figure 13 power dissipation of package (before mounting) precautions ? mount the external capacitors, the diode and the coil as close as possible to the ic, and secure grounding at a single location. ? characteristics ripple voltage and spike noise occur in ic containing switching regulators. moreover, rush current flows at the time of a power supply inje ction. because these largely depend on the coil, the capacitor and impedance of power s upply used, fully check them using an actually mounted model. ? the overload protection circuit of this ic performs the protective function by detecting the maximum duty time (100 %). in choosing the components, make sure that over currents generated by short-circuits in the load, etc., will not surpass the allowable dissi pation of the switching transistor and inductor. ? do not apply an electrostatic discharge to this ic that exceeds the performance ratings of the built-in electrostatic protection circuit. ? make sure that dissipation of the switching transis tor (especially at a high temperature) does not exceed the allowable dissipation of the package. ? sii claims no responsibility for any and all disputes aris ing out of or in connection with any infringement of the products including this ic upon patents owned by a third party.
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 22 seiko instruments inc. application circuits 1. external adjustment of output voltage the s-8520/8521 series allows you to adjust the output voltage or to set the output voltage to a value over the preset output voltage range (6 v) of the pr oducts of this series, when external resistances (r a and r b ), and capacitor (c c ) are added, as illustrated in figure 14 . moreover, a temperature gradient can be obtained by inserting a thermistor or other element in series with r a and r b . s-8520/8521series c c r a r b d1 vout ? + vin out ext ? + reference voltage source with soft start + ? r 2 r 1 off / on vss oscillation circuit pwm control or pwm/pfm switching control circuit figure 14 the s-8520/8521 series have an internal impedance of r 1 and r 2 between the vout pin and the vss pin, as shown in figure 14 . therefore, the output voltage (out) is determined by the output voltage value (v out ) of the s-8520/8521 series, and the ratio of the parallel resi stance value of external resistance (r b ) and internal resistances (r 1 + r 2 ) of the ic, to external resistance (r a ). the output voltage is expr essed by the following equation: out = v out + v out r a (r b // *1 (r 1 + r 2 )) the voltage accuracy of the out set by resistances (r a and r b ) is not only affected by the ic's output voltage accuracy (v out 2.4 %), but also by the absolute pr ecision of external resistances (r a and r b ) in use and the absolute value deviations of internal resistances (r 1 and r 2 ) in the ic. let us designate the maximum deviations of the absolute value of r a and r b by r a max and r b max, respectively, the minimum deviations by r a min and r b min, respectively, and the maximum and minimum deviations of the absolute value of r 1 and r 2 in the ic by (r 1 + r 2 ) max and (r 1 + r 2 ) min, respectively. then, the minimum deviation value outmin and the maximum deviation value outmax of the out are expressed by the following equations: out min. = v out 0.976 + v out 0.976 r a min. (r b max//(r 1 + r 2 ) max.) out max. = v out 1.024 + v out 1.024 r a max. (r b min//(r 1 + r 2 ) min.) the voltage accuracy of the out cannot be made higher than the output voltage accuracy (v out 2.4 %) of the ic itself, without adjusting the r a and r b involved. the closer the voltage value of the output out and the output voltage value (v out ) of the ic are brought to one other, the more the output voltage remains immune to deviations in the absolute accuracy of r a and r b and the absolute value of r 1 and r 2 in the ic. in particular, to suppress the influence of deviations in r 1 and r 2 in the ic, a major contributor to deviations in the out, the r a and r b must be limited to a much smaller value than that of r 1 and r 2 in the ic.
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 23 on the other hand, a reactive current flows through r a and r b . this reactive current must be reduced to a negligible value with respect to the load current in the actual use of the ic so that the efficiency characteristics will not be degraded. th is requires that the value of r a and r b be made sufficiently large. however, too large a value (more than 1 m ? ) for the r a and r b would make the ic vulnerable to external noise. check the influence of this value on actual equipment. there is a tradeoff between the voltage accuracy of the out and the reactive current. this should be taken into consideration based on the requi rements of the intended application. deviations in the absolute value of the internal resistances (r 1 and r 2 ) in the ic vary with the output voltage of the s-8520/8521 series, and are broadly classified as follows: table 10 output voltage deviations in the absolute value of r 1 and r 2 in the ic 1.5 v to 2.0 v 5.16 m ? to 28.9 m ? 2.1 v to 2.5 v 4.44 m ? to 27.0 m ? 2.6 v to 3.3 v 3.60 m ? to 23.3 m ? 3.4 v to 4.9 v 2.44 m ? to 19.5 m ? 5.0 v to 6.0 v 2.45 m ? to 15.6 m ? when a value of r 1 + r 2 given by the equation indicated below is taken in calculating the voltage value of the output out, a median voltage devia tion will be obtained for the out. r 1 + r 2 = 2 (1 maximum deviation in absolute value of r 1 and r 2 + 1 minimum deviation in absolute value of r 1 and r 2 ) moreover, add a capacitor (c c ) in parallel to the external resistance (r a ) in order to avoid output oscillations and other types of instability. (refer to figure 14 .) make sure that c c is larger than the value given by the following equation: c c (f) 1 (2 r a ( ? ) 7.5 khz) if a large c c value is selected, a longer soft start time than the one set up in the ic will be set. ? sii is equipped with a tool that allows you to automat ically calculate the necessa ry resistance values of r a and r b from the required voltage accuracy of the out. sii will be pleased to assist its customers in determining the r a and r b values. should such assistance be desired, please inquire. ? moreover, sii also has ample information on which peripheral components are suitable for use with this ic and data concerning the deviations in the ic's characteristics. we are ready to help our customers with the design of application circuits. pl ease contact the sii components sales dept. *1. // shows the combined resistance in parallel. caution the above connection diagram and c onstant will not guarantees successful operation. perform through evaluation using the actual application to set the constant.
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 24 seiko instruments inc. typical characteristics 1. current consumption (i ss1 )-input voltage (v in ) 0 5 10 15 20 ta = 25 c ta = 85 c i ss1 [ a] (f osc = 60 khz ) 2 4 6 8 10 12 14 16 v in [v] ta =? 40 c 0 10 20 30 40 2 4 6 8 10 12 14 16 v in [v] i ss1 [ a] ta =? 40 c ta = 85 c ta = 25 c (f osc = 180 khz) 0 10 20 30 40 50 60 2 4 6 8 10 12 14 16 v in [v] i ss1 [ a] (f osc = 300 khz) ta =? 40 c ta = 25 ta = 85 c 2. oscillation frequency (f osc )-input voltage (v in ) 40 45 50 55 60 65 70 75 80 2 4 6 8 10 12 14 16 v in [v] f osc [khz] (f osc = 60 khz) ta = 25 c ta = 85 c ta =? 40 c 140 150 160 170 180 190 200 210 220 2 4 6 8 10 12 14 16 v in [v] f osc [khz] ( fosc = 180 khz ) ta = 25 c ta = 85 c ta =? 40 c 240 260 280 300 320 340 360 2 4 6 8 10 12 14 16 v in [v] f osc [khz] (f osc = 300 khz) ta =? 40 ta = 25 c ta = 85 c
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 25 3. ext pin output current ?h? (i exth )-input voltage (v in ) 4. ext pin output current ?l? (i extl )-input voltage (v in ) 2 4 6 8 10 12 14 16 v in [v] i exth [ma] ta =? 40 c ta = 85 c ta = 25 c ? 60 ? 50 ? 40 ? 30 ? 20 ? 10 0 0 10 20 30 40 50 60 2 4 6 8 10 12 14 16 v in [v] i extl [ma] ta =? 40 c ta = 85 c ta = 25 c 5. soft start time (t ss )-input voltage (v in ) 0 5 10 15 20 25 2 4 6 8 10 12 14 16 v in [v] t ss [ms] (f osc = 60 khz) ta =? 40 c ta = 85 c ta = 25 c 0 5 10 15 20 25 2 4 6 8 10 12 14 16 v in [v] t ss [ms] (f osc = 180 khz) ta =? 40 c ta = 85 c ta = 25 c 0 2 4 6 8 10 2 4 6 8 10 12 14 16 v in [v] t ss [ ms ] (f osc = 300 khz) ta = 25 c ta = 85 c ta =? 40 c
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 26 seiko instruments inc. 6. overload detection time (t pro )- input voltage (v in ) 6 10 14 18 22 26 30 2 4 6 8 10 12 14 16 (f osc = 60 khz) t p ro [ms] ta =? 40 c v in [v] ta = 25 c ta = 85 c 2 3 4 5 6 7 8 2 4 6 8 10 12 14 16 v in [v] t pro [ms] ta =? 40 c ta = 85 c ta = 25 c (f osc = 180 khz) 1 2 3 4 2 4 6 8 10 12 14 16 v in [v] t p ro [ms] (f osc = 300 khz) ta = 85 c ta = 25 c ta =? 40 c 7. off on/ pin input voltage ?h? (v sh )-input voltage (v in ) 8. off on/ pin input voltage ?l? (v sl )-input voltage (v in ) 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2 4 6 8 10 12 14 16 v in [v] v sh [v] ta =? 40 c ta = 25 c ta = 85 c 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 2 4 6 8 10 12 14 16 v in [v] v sl [v] ta =? 40 c ta = 85 c ta = 25 c
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 27 9. output voltage (v out )-input voltage(v in ) s-8521b30mc s-8521b50mc ( ta = 25c ) 2.98 2.99 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 2 4 6 8 10 12 14 16 v in [v] v out [v] i out = 100 ma i out = 500 ma i out = 0.1 ma ( ta = 25c ) 4.98 4.99 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 2 4 6 8 10 12 14 16 v in [v] v out [v] i out = 100 ma i out = 500 ma i out = 0.1 ma s-8521f33mc s-8521f50mc ( ta = 25c ) 3.28 3.29 3.30 3.31 3.32 3.33 3.34 3.35 3.36 3.37 3.38 2 4 6 8 10 12 14 16 v in [v] v out [v] i out = 0.1 ma i out = 100 ma i out = 500 ma ( ta = 25c ) 4.97 4.98 4.99 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 2 4 6 8 10 12 14 16 v in [v] v out [v] i out = 0.1 ma i out = 100 ma i out = 500 ma
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 28 seiko instruments inc. transient response characteristics 1. power on (i out = no load) s-8520/8521c30mc (v in = 0 3.6 v) t [2 ms/div] v in [2.5 v/div] v out [1 v/div] 0 v 3 v 0 v 10 v (v in = 0 9.0 v) t [2 ms/div] v in [2.5 v/div] v out [1 v/div] 0 v 3 v 0 v 10 v s-8520/8521a30mc (v in = 0 3.6 v) t [1 ms/div] v in [2.5 v/div] v out [1 v/div] 0 v 3 v 0 v 10 v (v in = 0 9.0 v) t [1 ms/div] v in [2.5 v/div] v out [1 v/div)] 0 v 3 v 0 v 10 v s-8520/8521e33mc (v in = 0 4.0 v) t [1 ms/div] v in [2.5 v/div] v out [1 v/div] 0 v 3 v 0 v 10 v (v in = 0 9.0 v) t [1 ms/div] v in [2.5 v/div] v out [1 v/div] 0 v 3 v 0 v 10 v
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 29 2. off on/ pin response ( off on/ v = 0 v 1.8 v, i out = no load) s-8520/8521c30mc (v in = 3.6 v) t [2 ms/div] off / on v [1 v/div] v out [1 v/div] 0 v 3 v 0 v 3 v (v in = 9.0 v) t [2 ms/div] v out [1 v/div] 0 v 3 v 0 v 3 v off / on v [1 v/div] s-8520/8521a30mc (v in = 3.6 v) t [1 ms/div] v out [1 v/div] 0 v 3 v 0 v 3 v off / on v [1 v/div] (v in = 9.0 v) t [1 ms/div] v out [1 v/div] 0 v 3 v 0 v 3 v off / on v [1 v/div] s-8520/8521e33mc (v in = 4.0 v) t [1 ms/div] v out [1 v/div] 0 v 3 v 0 v 3 v off / on v [1 v/div] (v in = 9.0 v) t [1 ms/div] v out [1 v/div] 0 v 3 v 0 v 3 v off / on v [1 v/div]
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 30 seiko instruments inc. 3. supply voltage variation (v in = 4 v 9 v, 9 v 4 v) s-8520/8521c30mc (i out = 10 ma) t [0.5 ms/div] v in [2.5 v/div] v out [0.2 v/div] 0 v 10 v (i out = 500 ma) t [ 0.5 ms/div ] v in [2.5 v/div] v out [0.2 v/div] 0 v 10 v s-8520/8521a30mc (i out = 10ma) t [0.5 ms/div] v in [2.5 v/div] v out [0.2 v/div] 0 v 10 v (i out = 500 ma) t [ 0.5 ms/div ] v in [2.5 v/div] v out [0.2 v/div] 0 v 10 v s-8520/8521e33mc (i out = 10 ma) t [0.5 ms/div] v in [2.5 v/div] v out [0.2 v/div] 0 v 10 v (i out = 500 ma) t [ 0.5 ms/div ] v in [2.5 v/div] v out [0.2 v/div] 0 v 10 v
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 31 4. load variation s-8520/8521c30mc (v in = 3.6 v, i out = 0.1 ma 500 ma) t [0.1 ms/div] i out v out [0.1 v/div] 0.1 ma 500 ma (v in = 3.6 v, i out = 500 ma 0.1 ma) t [5 ms/div] i out v out [0.1 v/div] 0.1 ma 500 ma s-8520/8521a30mc (v in = 3.6 v, i out = 0.1 ma 500 ma) t [0.1 ms/div] i out v out [0.1 v/div] 0.1 ma 500 ma (v in = 3.6 v, i out = 500 ma 0.1 ma) t [10 ms/div] i out v out [0.1 v/div] 0.1 ma 500 ma s-8520/8521e33mc (v in = 4.0 v, i out = 0.1 ma 500 ma) t [ 0.1 ms/div ) i out v out [0.1 v/div] 0.1 ma 500 ma (v in = 4.0 v, i out = 500 ma 0.1 ma) t [ 5 ms/div ] i out v out [0.1 v/div] 0.1 ma 500 ma
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 32 seiko instruments inc. reference data this reference data is intended to help you select per ipheral components to be externally connected to the ic. therefore, this information provides recommendat ions on external components selected with a view to accommodating a wide variety of ic applications. charac teristic data is duly indicated in the table below. table 10 external parts for efficiency data no. product name output voltage inductor transistor diode output capacitor application (1) s-8520b30mc 3.0 v cd105/47 h tm6201 ma737 47 f i out 1 a, v in 10 v (2) s-8520f33mc 3.3 v d62f/22 h ma720 22 f i out 0.5 a, v in 10 v (3) cdh113/22 h irf7606 ma737 i out 1 a, v in 16 v (4) s-8521d30mc 3.0 v cd54/47 f tm6201 ma720 47 f2 i out 0.5 a, v in 10 v, with e quipment standby mode (5) irf7606 i out 0.5 a, v in 16 v, with e quipment standby mode (6) s-8521b30mc cd105/47 h tm6201 ma737 47 f i out 1 a, v in 10 v, with e quipment standby mode (7) irf7606 i out 1 a, v in 16 v, with e quipment standby mode (8) s-8521f33mc 3.3 v d62f/22 h tm6201 ma720 22 f i out 0.5 a, v in 10 v, with e quipment standby mode (9) cdh113/22 h irf7606 ma737 i out 1 a, v in 16 v, with e quipment standby mode (10) s-8520b50mc 5.0 v cd54/47 f tm6201 ma720 47 f i out 0.5 a, v in 10 v (11) cd105/47 h irf7606 ma737 i out 1 a, v in 16 v (12) s-8520f50mc d62f/22 h tm6201 ma720 22 f i out 0.5 a, v in 10 v (13) cdh113/22 h irf7606 ma737 i out 1 a, v in 16 v (14) s-8521d50mc cd54/47 f tm6201 ma720 47 f2 i out 0.5 a, v in 10 v, with e quipment standby mode (15) cd105/47 h irf7606 ma737 i out 1 a, v in 16 v, with e quipment standby mode (16) s-8521b50mc cd54/47 f tm6201 ma720 47 f i out 0.5 a, v in 10 v, with e quipment standby mode (17) cd105/47 h irf7606 ma737 i out 1 a, v in 16 v, with e quipment standby mode (18) s-8521f50mc d62f/22 h tm6201 ma720 22 f i out 0.5 a, v in 10 v, with e quipment standby mode (19) cdh113/22 h irf7606 ma737 i out 1 a, v in 16 v, with e quipment standby mode
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 33 table 11 external parts for ripple data no. product name output voltage inductor transistor r b c b diode output capacitor (20) s-8520d30mc 3.0 v cd105/47 h 2sa1213y 680 ? 2200 pf ma720 47 f2 (21) s-8521d30mc (22) s-8520b30mc 22 f2 (23) s-8521b30mc (24) s-8520f33mc 3.3 v cdh113/22 h irf7606 ? ? ma737 22 f (25) s-8521f33mc ? ? (26) s-8520d50mc 5.0 v cd105/47 h 2sa1213y 680 ? 2200 pf ma720 47 f2 (27) s-8521d50mc (28) s-8520b50mc 22 f2 (29) s-8521b50mc (30) s-8520f50mc cdh113/22 h irf7606 ? ? ma737 22 f (31) s-8521f50mc ? ? table 12 performance data component product name manufacturer name ?l? value dc resistance maximum allowable current diameter height inductor cd54 sumida corporation 47 h 0.37 ? 0.72 a 5.8 mm 4.5 mm cd105 0.17 ? 1.28 a 10.0 mm 5.4 mm cdh113 22 h 0.09 ? 1.44 a 11.0 mm 3.7 mm d62f toko ink. 0.25 ? 0.70 a 6.0 mm 2.7 mm diode ma720 matsushita electric industrial co., ltd. forward current 500 ma (at v f = 0.55 v) ma737 forward current 1.5 a (at v f = 0.5 v) output capacity f93 nichicon corporation ? te matsushita electric industrial co., ltd. ? external transistor (bipolar pnp) 2sa1213y toshiba corporation v ceo 50 v max., i c ? 2 a max., h fe 120 to 240, sot-89-3 package external transistor (mos fet) tm6201 toyota industries corporation v gs 12 v max., i d ? 2 a max., v th ? 0.7 v min., c iss 320 pf typ., r on 0.25 ? max. (v gs =? 4.5 v), sot-89-3 package irf7606 international rectifier corporation v gs 20 v max., i d ? 2.4 a max., v th ? 1 v min., c iss 470 pf typ., r on 0.15 ? max. (v gs =? 4.5 v), micro 8 package
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 34 seiko instruments inc. 1. efficiency characteristics: output current (i out )-efficiency (effi) s-8520b30mc (cd105/47 h, tm6201) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 3.6 v v in = 9.0 v s-8520f33mc (d62f/22 h, tm6201) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 9 v v in = 6 v v in = 4 v (cdh113/22 h, irf7606) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 14 v v in = 9 v v in = 6 v v in = 4 v s-8521d30mc (cd54/47 h, tm6201) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 3.6 v v in = 9.0 v (cd54/47 h, irf7606) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 3.6 v v in = 9.0 v s-8521b30mc (cd105/47 h, tm6201) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 3.6 v v in = 9.0 v (cd105/47 h, ifr7606) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 3.6 v v in = 9.0 v
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 35 s-8521f33mc (d62f/22 h, tm6201) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 9 v v in = 6 v v in = 4 v (cdh113/22 h, irf7606) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 14 v v in = 9 v v in = 6 v v in = 4 v s-8520b50mc (cd54/47 h, tm6201) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 6.0 v v in = 9.0 v (cd105/47 h, irf7606) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 14 v v in = 9 v v in = 6 v s-8520f50mc (d62f/22 h, tm6201) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 9 v v in = 6 v (cdh113/22 h, irf7606) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 14 v v in = 9 v v in = 6 v s-8521d50mc (cd54/47 h, tm6201) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 6.0 v v in = 9.0 v (cd105/47 h, irf7606) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 14 v v in = 9 v v in = 6 v
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 36 seiko instruments inc. s-8521b50mc (cd54/47 h, tm6201) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 6.0 v v in = 9.0 v (cd105/47 h, irf7606) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 9 v v in = 6 v v in = 14 v s-8521f50mc (d62f/22 h, tm6201) 50 60 70 80 90 100 0.01 0.1 1 10 100 1000 i out [ma] effi [%] v in = 9 v v in = 6 v (cdh113/22 h, irf7606) 50 60 70 80 90 100 i out [ma] effi [%] v in = 14 v v in = 9 v v in = 6 v 0.01 0.1 1 10 100 1000
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 37 2. ripple voltage characteristics: ripple voltage (v rip )-input voltage (v in ) (l: cd105/47 f, tr: 2sa1213, sbd: ma720) s-8520d30mc s-8521d30mc (c out = 47 f 2) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 500 ma i out = 100 ma i out = 0.1 ma (c out = 47 f 2) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 0.1 ma i out = 500 ma i out = 100 ma s-8520b30mc s-8521b30mc (c out = 22 f 2) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 0.1 ma i out = 100 ma i out = 500 ma (c out = 22 f 2) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 0.1 ma i out = 500 ma i out = 100 ma s-8520f33mc s-8521f33mc (c out = 22 f) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 500 ma i out = 100 ma i out = 0.1 ma (c out = 22 f) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 500 ma i out = 100 ma i out = 0.1 ma s-8520d50mc s-8521d50mc (c out = 47 f 2) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 0.1 ma i out = 100 ma i out = 500 ma (c out = 47 f 2) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 500 ma i out = 100 ma i out = 0.1 ma
pwm control, pwm/pfm switching control step-down switching regulator s-8520/8521 series rev.7.4 _20 38 seiko instruments inc. s-8520b50mc s-8521b50mc (c out = 22 f 2) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 500 ma i out = 100 ma i out = 0.1 ma (c out = 22 f 2) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 0.1 ma i out = 500 ma i out = 100 ma s-8520f50mc s-8521f50mc (c out = 22 f) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 500 ma i out = 100 ma i out = 0.1 ma (c out = 22 f) 0 40 80 120 160 200 240 2 4 6 8 10 12 14 16 v in [v] v rip [mv] i out = 0.1 ma i out = 100 ma i out = 500 ma
pwm control, pwm/pfm switching control step-down switching regulator rev.7.4 _20 s-8520/8521 series seiko instruments inc. 39 3. pwm/pfm switching characteristics: input voltage (v in )-output current (i out ) s-8521d30mc s-8521b30mc 2 6 10 14 1 10 100 1000 i out [ma] v in [v] 2 6 10 14 1 10 100 1000 i out [ma] v in [v] s-8521f33mc s-8521d510mc 2 6 10 14 1 10 100 1000 i out [ma] v in [v] 2 6 10 14 1 10 100 1000 i out [ma] v in [v] s-8521b50mc s-8521f50mc 2 6 10 14 1 10 100 1000 i out [ma] v in [v] 2 6 10 14 1 10 100 1000 i out [ma] v in [v]

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the information described herein is subject to change without notice. seiko instruments inc. is not responsible for any problems caused by circuits or diagrams described herein whose related industrial properties, patents, or other rights belong to third parties. the application circuit examples explain typical applications of the products, and do not guarantee the success of any specific mass-production design. when the products described herein are regulated products subject to the wassenaar arrangement or other agreements, they may not be exported without authorization from the appropriate governmental authority. use of the information described herein for other purposes and/or reproduction or copying without the express permission of seiko instruments inc. is strictly prohibited. the products described herein cannot be used as part of any device or equipment affecting the human body, such as exercise equipment, medical equipment, security systems, gas equipment, or any apparatus installed in airplanes and other vehicles, without prior written permission of seiko instruments inc. although seiko instruments inc. exerts the greatest possible effort to ensure high quality and reliability, the failure or malfunction of semiconductor products may occur. the user of these products should therefore give thorough consideration to safety design, including redundancy, fire-prevention measures, and malfunction prevention, to prevent any accidents, fires, or community damage that may ensue.

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