ts3406 600ma / 1.5mhz synchronous buck converter 1/7 version: c12 sot - 25 general description the ts3406 is a high efficiency monolithic synchron ous buck regulator using a 1.5mhz constant frequenc y, current mode architecture. the device is available in an adjustable version. supply current with no lo ad is 300a and drops to <1a in shutdown. the 2.5v to 5.5v inp ut voltage range makes the ts3406 ideally suited fo r single li-ion battery-powered applications. 100% duty cycl e provides low dropout operation, switching frequen cy is internally set at 1.5mhz, allowing the use of small surface mount inductors and capacitors. the intern al synchronous switch increases efficiency and elimina tes the need for an external schottky diode. low ou tput voltages are easily supported with the 0.6v feedbac k reference voltage. the ts3406 can supply 600ma of load current at vcc=3v. features high efficiency: up to 96% 2.5v to 5.5v input voltage range short circuit protection (scp) 1.5mhz constant frequency operation low dropout operation: 100% duty cycle 0.6v reference allows low output voltages 600ma output current at vcc=3v low quiescent current: 300ua 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 description en power-off pin h normal operation l step-down operation stopped (all circuits deactivated) 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 ts3406cx5 rf sot-25 3kpcs/ 7 reel application circuit pin definition : 1. en 2. ground 3. switching output 4. input 5. feedback
ts3406 600ma / 1.5mhz synchronous buck converter 2/7 version: c12 absolute maximum rating characteristics symbol rating unit v in pin voltage v in gnd - 0.3 to gnd + 6 v feedback pin voltage v fb gnd - 0.3 to v in + 0.3 v run pin voltage v run gnd - 0.3 to v in + 0.3 v switch pin voltage v sw gnd - 0.3 to v in + 0.3 v peak sw sink & source current i psw 1.5 a operating supply voltage v op +2.5 to +5.5 v power dissipation p d (t j -t a ) / ja mw storage temperature range t st -40 to +150 o c operating temperature range t op -40 to +85 o c junction temperature t j +125 o c thermal resistance from junction to case jc 110 o c/w thermal resistance from junction to ambient ja 250 o c/w note1: ja is measured with the pcb copper area of approximat ely 1 in 2 (multi-layer). that need connect to gnd pin of the ts3406. electrical specifications (ta = 25 o c, v in =v run =3.6v unless otherwise noted) characteristics symbol conditions min typ max units feedback voltage v fb t a =25 ,i out =50ma 0.588 0.6 0.612 v quiescent current i ccq v fb =0.5v -- 270 400 ua feedback bias current i fb v fb =0.65v -- -- 30 na shutdown supply current i sd v run =0v -- 0.08 1 ua maximum output current i out(max) v cc =3v 0.6 -- -- a current limit i limit v cc =3v 0.85 1.2 -- a line regulation v out /v out v cc = 2.5v~5.5v -- 0.5 1 % load regulation v out /v out i out = 0.01 to 0.6a -- 0.4 0.6 % oscillation frequency f osc sw pin 1.2 1.5 1.8 mhz frequency of scp f osc1 sw pin -- 300 -- khz r ds(on) of p-ch mosfet r dson i sw = 300ma -- 0.30 0.50 ? r ds(on) of n-ch mosfet r dson i sw = -300ma -- 0.20 0.45 ? efficiency e ffi v out =1.8v,i out = 0.5a -- 89 -- % run threshold v run 0.3 0.45 1.3 v run pin input current i run -- 0.1 1 ua note2: 100% production test at +25c. specification s over the temperature range are guaranteed by desi gn and characterization.
ts3406 600ma / 1.5mhz synchronous buck converter 3/7 version: c12 block diagram function description operation ts3406 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 600ma output current at vcc = 3v with input voltage range from 2.5v 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 responses and protection of the internal main switch (p-ch mosfet) and synchro nous rectifier (n-ch mosfet). during normal operation, t he internal p-ch mosfet is turned on for a certain time to ramp the inductor current at each rising edge of th e internal oscillator, and switched off when the pe ak inductor current is above the error voltage. the current com parator, icomp, limits the peak inductor current. w hen the main switch is off, the synchronous rectifier will be tu rned on immediately and stay on until either the in ductor current starts to reverse, as indicated by the current reve rsal comparator, izero, or the beginning of the nex t clock cycle. the ovdet comparator controls output transient over shoots by turning the main switch off and keeping i t off until the fault is no longer present. idle mode operation at very light loads, the ts3406 automatically enter s idle mode. in the idle mode, the inductor current may reach zero or reverse on each pulse. the pwm control loop will automatically skip pulses to maintain output regulation. the bottom mosfet is turned off by the current reve rsal comparator, izero and the switch voltage will ring. this is discontinuous mode operation, and is normal beha vior for the switching regulator. when the input vo ltage decreases toward the value of the output voltage, t he ts3406 allows the main switch to remain on for m ore than one switching cycle and increases the duty cycle un til it reaches 100%. the output voltage then is the input voltage minus the voltage drop across the main switch and t he inductor. at low input supply voltage, the rds(o n) of the p- ch mosfet increases, and the efficiency of the conv erter decreases. caution must be exercised to ensur e the heat dissipated not to exceed the maximum junction temperature of the ic.
ts3406 600ma / 1.5mhz synchronous buck converter 4/7 version: c12 function description (continue) maximum load current the ts3406 will operate with input supply voltage a s low as 2.5v, however, the maximum load current de creases at lower input due to large ir drop on the main swi tch and synchronous rectifier. the slope compensati on signal reduces the peak inductor current as a function of the duty cycle to prevent sub-harmonic oscillations at duty cycles greater than 50%. conversely the current limit incr eases as the duty cycle decreases. application information setting the output voltage application circuit item shows the basic applicatio n circuit with ts3406 adjustable output version. th e external resistor sets the output voltage according to the f ollowing equation: inductor selection for most designs, the ts3406 operates with inductor s of 1h to 4.7h. low inductance values are physic ally smaller but require faster switching, which results in some efficiency loss. the inductor value can be derived from the following equation: 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 35% of the maximum load current 600ma, ? il=210ma. for output voltages above 2.0v, when light-load eff iciency is important, the minimum recommended induc tor is 2.2h. 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 (60 0ma+105ma). 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 4.7f ceramic cap acitor for most applications is sufficient. 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 300k 950k table 2: inductor select for output voltage setting (vcc-3.6v) vout 1.2v 1.5v 1.8v 2.5v inductor 2.2uh 2.2uh 2.2uh 2.2uh part number we-tpc 7440430027 7440430027 7440430027 7440430022 note: part type mh or m (www.we-online.com)
ts3406 600ma / 1.5mhz synchronous buck converter 5/7 version: c12 application information (continue) 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. compensation capacitor selection the compensation capacitors for increasing phase ma rgin provide additional stability. it is required a nd more than 22p, refer to demo board schematic, the optimum val ues for c4 is 47pf.
ts3406 600ma / 1.5mhz synchronous buck converter 6/7 version: c12 sot-25 mechanical drawing marking diagram g8 = device code y = year code w = week code 01~26=a~z 27~52=a~z x = internal id code 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 g8ywx
ts3406 600ma / 1.5mhz synchronous buck converter 7/7 version: c12 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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