TS3420 2a, 1.25mhz synchronous buck converter 1/9 version: a12 sot - 2 6 general description TS3420 is a high efficiency monolithic synchronous buck regulator using a constant frequency, current mode architecture. the device is available in an adjusta ble version. supply current with no load is 200ua a nd drops to <1ua in shutdown. the 2.8v to 5.5v input voltage ra nge makes TS3420 ideally suited for single li-ion, two to three aa battery-powered applications. 100% duty cy cle provides low dropout operation, extending batte ry life in portable systems. switching frequency is internally set at 1.25mhz, allowing the use of small surface mount inductors and capacitors. the internal synchronous switch increases efficiency and decreases need of a n external schottky diode. low output voltages are easily supp orted with the 0.6v feedback reference voltage. features high efficiency: up to 96% 2.8v to 5.5v input voltage range output voltage from 0.6v to vin short circuit protection (scp) build in soft-start function 1.25mhz constant frequency operation up to 2a output current no schottky diode required in application 1ua shutdown current current mode operation for excellent line and load transient response application cellular phones digital still cameras portable electronics usb devices pin description name descript ion en power - off pin h normal operation l step-down operation stopped gnd ground pin sw switch output pin. connect external inductor here. minimize trace area at this pin to reduce emi. vcc ic power supply pin fb output feedback pin ordering information part no. package packing TS3420cx6 rfg sot-26 3kpcs/ 7 reel note: g denote for halogen free product application circuit pin definition : 1. en 2. ground 3. switching output 4. input 5. ground 6. feedback
TS3420 2a, 1.25mhz synchronous buck converter 2/9 version: a12 absolute maximum rating characteristics symbol rating unit vin pin voltage v in v ss - 0.3 to v ss + 6.5 v feedback pin voltage v fb v ss - 0.3 to v in + 0.3 v en pin voltage v en v ss - 0.3 to v in + 0.3 v switch pin voltage v sw v ss - 0.3 to v in + 0.3 v power dissipation pd ( t j -t a ) / ja mw storage temperature range t st -40 to +150 c operating temperature range t op -40 to +85 c junction temperature t j +125 c thermal resistance from junction to case jc 50 o c/w thermal resistance from junction to ambient ja 100 o c/w note: ja is measured with the pcb copper area of approximat ely 1 in 2 (multi-layer). electrical specifications (ta = 25 o c, v in =v run =3.6v unless otherwise noted) characteristics symbol conditions min typ max units input voltage range v in 2.8 -- 5.5 v v in uvlo threshold v in -- 2.2 -- v v in uvlo hysteresis v in(hys) -- 0.35 -- v feedback voltage v fb t a =25 0.588 0.6 0.612 v feedback bias current i fb v fb =0.65v -- -- 30 na quiescent current i ccq v fb =1v -- 200 350 ua shutdown supply current i sd v en =0v -- 0.1 1 ua switching current limit i limit 2.2 3 -- a line regulation v out /v out v in =2.5v to 5.5v -- 0.4 -- %/v load regulation v out /v out i out =0.01 to 2a -- 1 -- % oscillation frequency f osc i out =300ma 1.0 1.25 1.5 mhz r ds(on) of p-ch mosfet r dson v in =5v -- 120 - m ? feedback bias current i fb v fb =0.65v -- -- 30 na r ds(on) of n-ch mosfet r dson v in = 5v (note) -- 100 - m ? en pin logic input threshold voltage v enl -- -- 0.4 v v enh 1.5 -- --. en pin input current i en -- 0.1 1 ua thermal shutdown t ds -- 150 -- c thermal shutdown hysteresis t sh -- 30 -- c note: guaranteed by design
TS3420 2a, 1.25mhz synchronous buck converter 3/9 version: a12 block diagram fb en vin sw gnd over-temperature and short-circuit protection ref soft-star 0.6v + - - + icomp - + isense amp osc slope comp pwm logic - + izero comp non-overlap control reset set enable logic function description operation TS3420 is a monolithic switching mode step-down dc- dc converter. it utilizes internal mosfets to achie ve high efficiency and can generate very low output voltage by using internal reference at 0.6v. it operates a t a fixed switching frequency, and uses the slope compensated current mode architecture. this step-down dc-dc converter supplies minimum 2a output current at inp ut voltage range from 2.8v to 5.5v. current mode pwm control slope compensated current mode pwm control provides stable switching and cycle-by-cycle current limit for excellent load and line transient responses and pro tection of the internal main switch (p-ch mosfet) a nd synchronous rectifier (n-ch mosfet). during normal operation, the internal p-ch mosfet is turned on fo r a certain time to ramp the inductor current at each r ising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. the current comparator, i comp , limits the peak inductor current. when the main switch is off, the synchronous rectif ier will be turned on immediately and stay on until either the inductor current starts to reverse, as indicated by the current reversal comparator, i zero , or the beginning of the next clock cycle.
TS3420 2a, 1.25mhz synchronous buck converter 4/9 version: a12 application information setting the output voltage application circuit item shows the basic applicatio n circuit with ts3410 adjustable output version. th e external resistor sets the output voltage according to the f ollowing formula: inductor selection for most designs, the ts3410 operates with inductor s of 2.2h to 3.3h. low inductance values are phys ically smaller but require faster switching, which results in some efficiency loss. the inductor value can be derived from the following formula: where is inductor ripple current. large value induc tors lower ripple current and small value inductors result in high ripple currents. choose inductor ripple current app roximately 20% of the maximum load current 2a, ? il=400ma. for output voltages above 2.0v, when light-load eff iciency is important, the minimum recommended induc tor is 2.7h. for optimum voltage-positioning load transie nts, choose an inductor with dc series resistance i n the 50m ? to 150m ? range. for higher efficiency at heavy loads (above 200ma), or minimal load regulation (but some transient overshoot), the resistance should be kept below 100m ? . the dc current rating of the inductor should be at least equal to the maximum load current plus hal f the ripple current to prevent core saturation (20 00ma+200ma) input capacitor selection the input capacitor reduces the surge current drawn from the input and switching noise from the device . the input capacitor impedance at the switching frequency shal l be less than input source impedance to prevent hi gh frequency switching current passing to the input. a low esr input capacitor sized for maximum rms curr ent must be used. ceramic capacitors with x5r or x7r dielect rics are highly recommended because of their low es r and small temperature coefficients. a 10f ceramic capa citor for most applications is sufficient. output capacitor selection the output capacitor is required to be 10uf2 to ke ep the output voltage ripple small and to ensure re gulation loop stability. the output capacitor must have low imped ance at the switching frequency. ceramic capacitors with x5r or x7r dielectrics are recommended due to their low esr and high ripple current compensation capacitor selection the compensation capacitors for increasing phase ma rgin provide additional stability. it is required a nd more than 27pf. please refer to demo board schematic for desi gn. table 1: resistor select for output voltage setting vout r2 r1 1.2v 300k 300k 1.5v 300k 450k 1.8v 300k 600k 2.5v 150k 470k 3.3v 120k 540k table 2: inductor select for output voltage setting (v in =3.6v) vout 1.2v 1.5v 1.8v 2.5v inductor 2.7uh 2.7uh 2.7uh 2.2uh part number we-tpc 7440430027 7440430027 7440430027 7440430022 note: part type mh or m (www.we - online.com)
TS3420 2a, 1.25mhz synchronous buck converter 5/9 version: a12 electrical characteristics curve figure 1. output voltage vs. input voltage figure 2. load regulation (v out =3.3v) figure 3. quiescent current vs. input voltage figure 4. switching frequency vs. input voltage figure 5. output voltage vs. temperature figure 6. quiescent current vs. temperature
TS3420 2a, 1.25mhz synchronous buck converter 6/9 version: a12 electrical characteristics curve figure 7. frequency vs. temperature figure 8. efficiency vs. output current figure 9. v in = 5v, v out = 1.2v, no load figure 10. v in = 5v, v out = 1.2v, r load =0.5ohm figure 11. v in = 3.3v, v out = 1.2v, no load figure 12. v in = 5v, v out = 1.2v, r load =0.5ohm
TS3420 2a, 1.25mhz synchronous buck converter 7/9 version: a12 electrical characteristics curve figure 13. v in = 3.3v, v out = 1.2v, i out =0~2a figure 14. v in = 5v, v out = 1.2v, i out =0~2a
TS3420 2a, 1.25mhz synchronous buck converter 8/9 version: a12 sot-26 mechanical drawing arking diagram gg = device code y = year code 2 = 2012 3 = 2013 w = week code 01 ~ 26 (a~z) 27 ~ 52 (a~z) x = internal id code sot-26 dimension dim millimeters inches min typ max min typ max a 0.95 bsc 0.0374 bsc a1 1.9 bsc 0.0748 bsc b 2.60 2.80 3.00 0.1024 0.1102 0.1181 c 1.40 1.50 1.70 0.0551 0.0591 0.0669 d 2.80 2.90 3.10 0.1101 0.1142 0.1220 e 1.00 1.10 1.20 0.0394 0.0433 0.0472 f 0.00 -- 0.10 0.00 0.0039 g 0.35 0.40 0.50 0.0138 0.0157 0.0197 h 0.10 0.15 0.20 0.0039 0.0059 0.0079 i 0.30 -- 0.60 0.0118 -- 0.0236 j 5o -- 10o 5o -- 10o ggywx
TS3420 2a, 1.25mhz synchronous buck converter 9/9 version: a12 notice specifications of the products displayed herein are subject to change without notice. tsc or anyone on its behalf, assumes no responsibility or liability for any erro rs or inaccuracies. information contained herein is intended to provide a product description only. no license, express or implied, to any intellectual property rights is granted by this document. except as provided in tscs terms and co nditions of sale for such products, tsc assumes no liability wh atsoever, and disclaims any express or implied warr anty, relating to sale and/or use of tsc products includi ng liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, cop yright, or other intellectual property right. the products shown herein are not designed for use in medical, life-saving, or life-sustaining applica tions. customers using or selling these products for use i n such applications do so at their own risk and agr ee to fully indemnify tsc for any damages resulting from such i mproper use or sale.
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