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AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 1 features ? high efficiency (95%) possible ? no schottky diode required ? 1a output current at 5v input 3.3v output ? oscillation frequency 1.0mhz ? built-in on/off function ? built-in short circuit protection ? low dropout operation: 100% duty cycle ? stand-by current max. 1 a ? input voltage: 2.5v ~5.5v applications ? power supply for portable devices general description the AT1361 provides complete control for a dc/dc converter optimized for high- p erformance microprocessor applications. it is operated on current mode architecture for excellent line and load transient response. 1mhz operation frequency is allowing the use of sm all surface mount inductor and capacitor. the intern al synchronous switch increases efficiency and el iminates the need for an external schottky diode. the AT1361 is a family of low-noise synchronous step-down dc/dc converters that is ideally suited for systems powered from a 1-cell li-ion battery or from a 3-cell to 4-cell nicd, nimh, or alkaline battery. it can also be used to usb-based power system. block dia g ram aimtron reserves the right without notice to change this circuitry and specifications.
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 2 pin configuration ordering information part number package marking AT1361x_ gre sot-25, green : date code with one bottom line * for more marking information, contact our sales representative directly pin description symbol pin no. descript run 1 on/off control gnd 2 power ground sw 3 switch node connection to inductor vin 4 power supply fb 5 output feedback
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 3 absolute maximum ratings: (ta=25c) rated value parameter condition min. max. unit power supply voltage ? -0.3 +6.0 v run,fb -0.3 vin v input pin voltage sw -0.3 vin+0.3 v p-channel switch source current (dc) ? - 1200 ma n-channel switch sink current (dc) ? - 1200 ma peak sw sink and source current ? - 1.5 a thermal resistance from junction to ambient ja sot-25 - 200 c /w operating temperature t a ? -35 +85 c storage temperature ? -55 +150 c hbm 2 kv esd susceptibility * 2 mm 200 v 1. stresses beyond those listed under ?absolute maximum ra tings? may cause permanent damage to the device. these are stress ratings only, and func tional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability . 2. device are esd sensitive. handling precaution r ecommended. the human body model is a 100pf capacitor discharged through a 1.5k ? resistor into each pin. recommended operating conditions (t a =+25 c ) values parameter symbol min. typ. max. unit power supply voltage v in 2.5 -- 5.5 ? operating temperature* t a -20 +25 +85 c operating junction temperature t j - - +150 c *using x5r or x7r input capacitors.
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 4 electrical characteristics (vin =5v, t a =+25c , unless otherwise noted. ) values parameter symbol condition min. typ. max. unit input supply range v in 2.5 -- 5.5 v input under-voltage lock out threshold v uvlo in rising -- 2.3 -- v uvlo hysteresis -- 0.1 -- v quiescent current * i s fb=0.6v,i load =0a active mode -- 70 100 a current in standby mode i st run=0v, vin=5.5v -- 0.5 1 a feedback voltage v fb 0.588 0.600 0.612 v feedback voltage line-regulation v fb-line v in = 2.5v to 5.5v -- 0.1 0.5 %/v feedback variation with temperature t a =-20c to +85c -- 0.5 1.0 % feedback current i fb -- -- 200 na peak inductor current* i pk vin=5v,vout=3.3v 1.2 1.8 -- a maximum output current* i o vin=5v 5%, vout=3.3v, l=4.7 h, t a =25 c 1 -- -- a fosc1 fb=0.6v 0.8 1.0 1.2 mhz oscillator frequency fosc2 fb=0v -- 200 -- khz r ds(on) of p-channel mosfet r pfet i sw =600ma -- 0.4 0.5 ? r ds(on) of n-channel mosfet r nfet i sw =-600ma -- 0.35 0.45 ? sw leakage current i lsw run=0v,sw=0v or 5v,vin=5v -- 0.1 1 a run high-level input voltage v run ? h v in =2.5v to 5.5v 1.5 -- -- v run low-level input voltage v run ? l v in =2.5v to 5.5v -- -- 0.3 v run leakage current i run -- 0.1 1 a l t v v i i i i on out in o o pk ? + = ? + = 2 ) ( 2 *
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 5 typical application circuit l1:sumida cdrh4d28-4r7 figure 1 .adjustable voltage regulator l1:sumida cdrh4d28-4r7 figure 2 . buck-boost regulator efficiency vs. load current 30 40 50 60 70 80 90 10 100 load current(ma) efficiency(% 7 */ 7 7 */ 7 7 */ 7
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 6 typical characteristics : quiescent current vs. input voltage input voltage(v) quisecent current(ua ) 7pvu7 reference voltage vs. input voltage input voltage(v) reference voltage(v) 7pvu7 oscillator frequency vs. i nput voltage input voltage(v) oscillator frequency(mhz ) 7pvu7 -pben" oscillator frequency vs. temperature 0.7 0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 temperature (
) oscillator frequency (mh z load=0.8a load=1a 7 */ 7 7 065 7 vout voltage vs. temperature temperature (
) vout voltage(v) vout voltage vs. temperature temperature (
) vout voltage(v)
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 7 typical characteristics : vout voltage vs. temperature temperature (
) vout voltage(v) vout voltage vs. temperature temperature (
) vout voltage(v) 7 */ 7 -pbe" -pbe" efficiency vs. load current 10 20 30 40 50 60 70 80 90 100 10 100 1000 load current(ma) efficiency(% 7*/7 70657 7*/7 70657 7*/7 70657 7*/7 70657 -v)43 efficiency vs. load current 10 20 30 40 50 60 70 80 90 100 10 100 1000 load current(ma) efficiency(%) 7*/7 70657 7*/7 70657 7*/7 70657 -v)43 efficiency vs. load current 10 20 30 40 50 60 70 80 90 100 10 100 1000 load current(ma) efficiency(% 70657 70657 70657 70657 -v)43
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 8 typical characteristics : power on/off ch1: v out ch2: v in ch3:sw ch4:i in v in =5v,v out =3.3v,load=1a, power on v in =5v,v out =3.3v,load=1a,power off en pin on/off ch1: v out ch2:en ch3:sw ch4:i in v in =5v,v out =3.3v,load=1a,en turn-on v in =5v,v out =3.3v,load=1a,en turn-off
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 9 transient response ch2:v out ch4:i out v in =5v,v out =3.3v,c2= 100pf i out =0ma to1a i out =50ma to 1a i out =100ma to 1a i out =200ma to1a ripple noise ? v in =5v,v out =3.3v,load=0a ? v in =5v,v out =3.3v,load=1a
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 10 application information short circuit protection function the AT1361 has short circuit prot ection(see the electrical char acteristics frequency item). when the output is shorted to ground, the fre quency of the oscillator is reduced to about 200khz. this frequency foldback ensures that the inductor current has more time to decay. it will prevent the inductor current and intern al p-mosfet current runaway to damage the device. the frequency will retu rn to the normal values when the short circuit condition is removed and the feedback voltage reaches 0.6v. capacitor selection in continuous mode, the source current of th e top mosfet is square wave of duty cycle. the primary function of the input capacitor is to provide a low impedance loop for the edges of pulsed current drawn by the AT1361. a lo ad step at the out put can induce ringing at the input vin. this ringing can couple to th e output and be mistaken as loop instability. the oscillation can be improved by add the capacitance of the input capacitor. a typical value is 4.7~22 f ceramic (x5r or x7r), poscap or aluminum polymer. these capacitors will provide good high frequenc y bypassing and their low esr will reduce resistive losses for higher efficiency. the input capacitor rms current varies with the input voltage and the output voltage. the equation for the maximum rms current in the input capacitor is: the output capacitor depends on the suitabl e ripple voltage. low ripple voltage corresponds to lower effective series resi stance (esr). the output ripple voltage is determined by: the output capacitor rms ri pple current is given by: ) 1 ( in o in o omax rms v v v v i i ? = ) 8 1 ( out l out fc esr i v + ? ? ? in out in out rms v f l v v v i ? = ) ( 3 2 1
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 11 when choosing the input and output ceramic capacitors, choose the x5r or x7r dielectric formulations. these dielectrics have the best temperature and voltage characteristics of all the ceramics for a given value and size. inductor selection the inductor is chosen based on the desired ripple current. large value inductors lower ripple current and small value inductors result in higher ripple current. always consider the losses associated with the dcr and its eff ect on the total converter efficiency when selecting an inductor. the inductor is sele cted to limit the ripple current to some predetermined value, typically 20~40% of th e full load current at the maximum input voltage. the formula of inductance value is as below: adjustable output voltage the AT1361 appears a 0.6v reference voltage at fb pin. the output voltage is set by a resistive divider which is according to the following formula: *r1=150k ? for stability consideration. ) ( 4 . 0 ~ 2 . 0 max out l i i = ? ? ? ? ? ? ? ? ? ? ? = in out l out v v i f v l 1 ) 1 2 1 ( 6 . 0 r r v v out + = gnd fb r1 r2 0.6v=v out =5.5v
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 12 the dissipation the power loss is given by: inductors surface mount inductance( h) manufacturer/part no. manufacturer website 4.7 sumida cdrh4d28-4r7 www.sumida.com 4.7 abc sh40284r7ysb www.atec-group.com capacitors surface mount capacitance( f) manufacturer/part no. manufacturer website 22 tdk c3216x5r0j226m www.tdk.com 47 tdk c3225x5r0j46m www.tdk.com 10 grm42-6x5r 106k6.3 www.murata.com 4.7 taiyo jmk212bj475mg www.t-yuden.com loss ja a max j p t t + = ) ( q in f r o d f r o in n on ds o p on ds o loss i v f t t i v f t t i v d r i d r i p + + + + + ? + = ? ? s s ) ( 2 ) ( 2 ) ( 2 1 ) ( 2 1 ) 1 (
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 13 pc board layout 1. the most critical aspect of the layout is the placement of the input capacitor c1. it must be placed as close as possible to the AT1361 to reduce the input ripple voltage. 2. power loops on the input and output of the convert er should be laid out with the shortest and widest traces possible. the longer and na rrower the trace, the higher resistance and inductance it will have. the length of traces in series with the capacitors increases its esr and esl and reduces their ef fectiveness at high frequency. 3. the fb pin should connect to feedback resistors directly. and the route should be away from the noise source, such as inductor of sw line. 4. grounding all components at the same point may effectively reduce the occurrence of loop.
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 14 package outline :sot-25 inches millimeters symbol min max min max notes a 0.035 0.057 0.90 1.45 - a1 0.000 0.006 0.00 0.15 - a2 0.035 0.051 0.90 1.30 - b 0.010 0.020 0.25 0.50 - c 0.003 0.008 0.08 0.20 - d 0.110 0.122 2.80 3.10 - e 0.102 0.118 2.60 3.00 - e1 0.059 0.069 1.50 1.75 - l 0.014 0.022 0.35 0.55 e 0.037ref 0.95ref e1 0.075ref 1.90ref r 0 0 10 0 0 0 10 0 -
AT1361 1mhz,1a synchronous buck converter 7f, no.9, park avenue ii, science-based indu strial park, hsinchu 300,taiw an, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 1/11/2008 rev:1.0 email: service@aimtron.com.tw 15 reflow profiles sn-pb eutectic assembly pb-free assembly profile feature large body pkg. thickness 2.5mm or pkg. volume 350mm 3 small body pkg. thickness <2.5mm or pkg. volume <350mm 3 large body pkg. thickness 2.5mm or pkg. volume 350mm 3 small body pkg. thickness 2.5mm or pkg. volume 350mm 3 average ramp-up rate (t l to t p ) 3 c/second max. 3 c/second max. preheat -temperature min(tsmin) -temperature max (tsmax) -time (min to max)(ts) 100 c 150 c 60-120 seconds 150 c 200 c 60-180 seconds ts m a x t o t l -ramp-up rate 3 c/second max. time maintained above: -temperature (t l ) -time (t l ) 183 c 60-150 seconds 217 c 60-150 seconds peak temperature(t p ) 225+0/-5 c 240+0/-5 c 245+0/-5 c 250+0/-5 c time within 5 c of actual peak temperature (t p ) 10-30 seconds 10-30 seconds 10-30 seconds 20-40 seconds ramp-down rate 6 c/second max. 3 c/second max. time 25 c to peak temperature 6 minutes max. 8 minutes max. * all temperatures refer to topside of the package, measured on the package body surface.

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