preliminary ts1935b 1.9a / 1.2mhz boost dc to dc converter 1/6 version: preliminary sot - 25 general description the ts1935b is a current mode step up converter int ended for small, low power applications. the conver ter input voltage ranging from 2.6v to 5.5v. the output volta ge can be set up to 27v. the frequency is 1.2mhz al lows the use of small external inductors and capacitors and provides fast transient response. internal soft sta rt results in small inrush current and extends battery life. inte rnal power mosfet with very low rds (on) provides h igh efficiency. the ts1935b automatically transits from pwm to pfm during light load condition further inc reasing efficiency. the converter also provides protection functions such as under-voltage lockout, current li mit and thermal shutdown. features 2.6v to 5.5 v operating input voltage range adjustable output voltage range up to 27v 1.2mhz fixed switching frequency internal soft-start function current limit and thermal shutdown protection under voltage lockout 1a shutdown current application white led current source digital still cameras portable electronics pdas and palm-top computers local boost regulator ordering information part no. package packing ts1935bcx5 rfg sot-25 3kpcs / 7 reel note: g denotes for halogen free absolute maximum rating parameter symbol limit unit input voltage v in gnd - 0.3 to gnd + 6.5 v en, v fb voltage v en , v fb gnd - 0.3 to v cc + 0.3 v sw voltage v sw 30 v ambient temperature range t a -40 to +85 o c junction temperature range t j -40 to +125 o c storage temperature range t stg -40 to +150 o c note: stress above the listed absolute maximum rating ma y cause permanent damage to the device thermal information parameter symbol maximum unit thermal resistance* (junction to case) ? jc 110 o c/w thermal resistance* (junction to ambient) ? ja 250 o c/w internal power dissipation p d (t j -t a )/ ? ja mw maximum junction temperature tj 150 o c lead solder temperature (260 o c) 5 s note: ? ja is measured with the pcb copper area of approximat ely 1 in2(multi-layer). pin definition : 1. sw 2. ground 3. fb 4. en 5. input
preliminary ts1935b 1.9a / 1.2mhz boost dc to dc converter 2/6 version: preliminary electrical specifications (ta = 25 o c, v in =5v, en=v in , i l =0a unless otherwise noted) characteristics symbol conditions min typ max units input voltage range v cc 2.6 -- 5.5 v under voltage lockout uvlo rising -- 2.35 2.60 v uvlo hysteresis -- -130 -- mv step-up voltage adjust range v out 3 -- 27 v operating quiescent current i ccq i out = 0ma, v fb =1.5v -- 150 250 a shutdown current i sd v en =0v -- 0.1 1 a feedback voltage v fb 1.213 1.238 1.263 v fb input leakage current i fb-lkg v fb = 1.3v -100 0.01 +100 na line regulation v in = 2.5 to 5.5v i out = 20ma -- 0.2 -- % load regulation v in = 5v i out = 1ma to 400ma - 0.2 -- % switching frequency f osc 900 1200 1500 khz maximum duty d max 82 87 - % n-channel mosfet current limit i lim duty=50% -- 1.9 -- a mosfet on-resistance (note 1) r ds(on) vcc=3v, i sw =1a -- 650 - m vcc=5v, i sw =1a -- 500 -- sw leakage current i swl v lx = 27v, v fb =1.5v -- -- 1 a en high-level input voltage v ih 1.0 -- -- v en low-level input voltage v il -- -- 0.4 v en hysteresis hys -- 200 - mv en input leakage current i en-lkg v en =gnd or vcc -- 0.01 0.1 a thermal shutdown t ds -- 150 -- c thermal shutdown hysteresis t sh -- 35 -- note 1: guaranteed by design pin description pin number pin name description 1 sw power switch output. sw is the drain of the internal mosfet switch. conn ect the power inductor and output rectifier to sw. sw can swing between gnd an d 27v. 2 gnd ground. tie directly to ground plan. 3 fb feedback input. fb voltage is 1.238v. connect a resistor divider to fb. 4 en regulator on/off control input. a high input at en turns on the converter, and a lo w input turns it off. when not used, connect en to the input source for a utomatic startup. the en pin cannot be left floating. 5 vcc input supply pin. must be locally bypassed.
preliminary ts1935b 1.9a / 1.2mhz boost dc to dc converter 3/6 version: preliminary block diagram vcc sw control and driver logic en soft start current sense slope compensation oscillator 1.2mhz fb error amplifier summing comparator thermal shutdown enable/ disable gnd n-mos uvlo vref 1.238v application circuit r1 54k vin=5v c1 10uf l1 4.7uh r2 470k vout=12v u1 ax5511 4 5 3 1 vcc en fb gnd sw c3 1nf c2 4.7uf d1 b240a r2 suggest 390k~820k on off 2 r3 r4 1m r1 r2 vout = 1.238v x (1 + ------- ) vin vout r3 2.6~3.6v 5v 120k 2.6~5.3v 7v 82k 2.6~5.5v 7.5~27v 0 ts1935b
preliminary ts1935b 1.9a / 1.2mhz boost dc to dc converter 4/6 version: preliminary application information setting the output voltage application circuit item shows the basic applicatio n circuit with ax5511 adjustable output version. th e external resistor sets the output voltage according to the f ollowing equation: ) r1 r2 +(1 1.238v = v out for most applications, r2 is a suggested a value by 390k~820k . place the resistor-divider as close to the ic as possible to reduce the noise sensitivity. under voltage lockout (uvlo) to avoid mis-operation of the device at low input v oltages an under voltage lockout is included that d isables the device, if the input voltage falls below (2.35v-130 mv). 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. for a lo wer output power requirement application, this value can be de creased. output capacitor selection the output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. the output capacitor must have low impedance at the swi tching frequency. ceramic capacitors with x5r or x7 r dielectrics are recommended due to their low esr an d high ripple current. a 4.7uf ceramic capacitors w orks for most of the applications. higher capacitor values c an be used to improve the load transient response. layout guide
preliminary ts1935b 1.9a / 1.2mhz boost dc to dc converter 5/6 version: preliminary sot-25 mechanical drawing sot-25 dimension dim millimeters inches min max min max. a+a1 0.09 1.25 0.0354 0.0492 b 0.30 0.50 0.0118 0.0197 c 0.09 0.25 0.0035 0.0098 d 2.70 3.10 0.1063 0.1220 e 1.40 1.80 0.0551 0.0709 e 1.90 bsc 0.0748 bsc h 2.40 3.00 0.09449 0.1181 l 0.35 bsc 0.0138 bsc ? 1 0o 10o 0o 10o s1 0.95 bsc 0.0374 bsc
preliminary ts1935b 1.9a / 1.2mhz boost dc to dc converter 6/6 version: preliminary 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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