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1/ 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 pwm control 3 a step - down converter ? general description a x3117 /a /b consists of step - down switching regulator with pw m control. the devi ce include s a reference voltage source, oscillation circuit, error amplifier, internal pmos and etc. AX3117 /a /b provides low- ripple power, high efficiency, and excellent transient characteristics. the pwm control circuit is able to the duty ratio linearly forms 0 up to 100%. an over current protect ion and short circuit protect ion function s are built outside that it can set b y a resistance. a n external compensation is easily to system stable; the low esr output capacitor can be used. with the addition of an internal p - channel power mos, a coil, capacitors, and a diode connected externally, these ics can function as step - down s witching regulators. they serve as ideal power supply units for portable devices when coupled with the sop - 8l- ep package, providing such outstanding features as low current consumption. since this converter can accommodate an input voltage up to 40 v, it is also suitable for the operation via an ac adapter. ? features - input v oltage 8 v to 40 v - duty ratio 0% to 100% pwm control - oscillation frequency 10 0 k / 3 0 0k hz - thermal shutdown function. - short circuit protect (scp) . - built - in internal sw p - channel mos. - current mo de non - synchronous pwm converter - external current limit setting. - under v oltage lockout. - over v oltage protection. - line - compensation built in. - sop - 8l- ep pb - free package. v?mw`r?y?b? www.gofotech.com
2/ 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 ? b lock d iagram ? pin assignment the package of AX3117 /a /b is sop - 8l - ep; the pin assignment is given by : name description en/ct shutdown and auto restart control pin gnd gnd pin vgate driver gate clamping pin. the pin must connect a 0.1uf capacitor to vin vcc operating voltage in put comp compensation pin sw switch pin. connect external inductor and diode here sense1 current sense input1 sense2 current sense input2 fb feedback pin ? order/marking information order information top marking o s c . + + _ t h e r m a l s h u t d o w n c o n t r o l + d r i v e r c o m p . s w _ c o m p . c u r r e n t l i m i t + _ a m p c u r r e n t s o u r c e b i a s 1 . 2 3 v r e f e r e n c e 2 . 5 v r e g u l a t o r s e n s e 1 1 . 0 0 v 1 4 0 m v + _ a m p + _ a m p 0 . 4 v s c p o v p l i n e c o m p e n s a t i o n v g a t e v c c g n d f b s e n s e 2 5 . 8 0 v s t a r t - u p a n d a u t o r e s t a r t c o n t r o l e n / c t ( t o p v i e w ) 1 2 3 4 8 7 6 5 e n / c t g n d s o p - 8 l - e p v c c v g a t e f b s e n s e 2 s w s w s e n s e 1 p a c k a g e t y p e e s : s o p - 8 l - e p a x 3 1 1 7 x x x x p a c k i n g b l a n k : t u b e a : t a p i n g f r e q u e n c y / l i n e c o m p . b l a n k : 1 0 0 k h z / 3 2 0 m v a : 3 0 0 k h z / 3 2 0 m v b : 1 0 0 k h z / 1 5 0 m v a x 3 l o g o p a r t n u m b e r i d c o d e : i n t e r n a l w w : 0 1 ~ 5 2 y e a r : 1 1 = 2 0 1 1 1 2 = 2 0 1 2 y y w w x 1 1 7 x b l a n k : a x 3 1 1 7 a : a x 3 1 1 7 a b : a x 3 1 1 7 b v?mw`r?y?b? www.gofotech.com
3/ 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 ? a bsolute m aximum r atings (at t a = 25 c ) characteristics symbol rating unit v in pin voltage v in gnd - 0.3 to gnd + 4 5 v feedback pin voltage v fb gnd - 0.3 to v in v sense 1/2 , en/ct pin voltage gnd - 0.3 to 6 v switch pin volta ge v sw gnd - 0.3 to v in + 0.3 v power dissipation pd (t j C t a )/ ja w storage temperature range t st - 40 to +1 65 c operating temperature range t op - 3 0 to +1 30 c operating supply voltage v op + 7.5 to + 40 v output current i out 0 to 3 a thermal resistanc e from junction to case jc 15 c /w thermal resi stance from junction to ambient ja 40 c /w note : e ja is m easured with the pcb copper are (need connect to exposed pad ) of approximately 1 in 2 (multi - layer) . ? e lectrical c haracteristics (v in =12v, t a =25 c , un less otherwise specified) characteristics symbol conditions min typ max units feedback voltage v fb i out =10ma 0.98 1 .0 0 1.0 2 v under voltage lockout u vlo falling - 5.8 - v uvlo hysteresis - - 1.6 - v ovp detect voltage v ovp internal define - 6 - v lin e regulation - v in =10 ~ 40v , i out =10ma - 0.5 1 % load regulation - i out =0~ 2 a , r se n se = 50 m ax31117/a +270 +320 +370 mv a x3117b + 100 + 150 + 200 quiescent current i ccq v fb = 1.5v, force driver off. - 5 8 ma oscillator frequency f osc i out = 0.5a AX3117/b 70 100 130 khz AX3117a 240 300 360 khz max. duty cycle (on) dc f orce driver on v fb = 0.6v - 100 - % min. duty cycle (off) f orce driver off v fb = 1.5v - 0 - % internal mosfet r dson r dson v in =12v, i out = 2a - 1 0 0 1 5 0 m sense voltage v sense v sense1 - v sense2 130 1 40 150 mv sense voltage hysteresis v sense - h - 50 - mv en/ct pin logic i nput threshold voltage v en shutdown mode - 0.3 v v ct auto restart, v fb <0.4v 0.5 - 1.5 en/ct pin current i en/ct - c charge current - - 26 - ua en/ct pin current i en/ct - d discharge current - 1. 8 - ua thermal shutdown temp t sd - 1 5 0 - c thermal shutdow n hysteresis t sh - 4 0 - c v?mw`r?y?b? www.gofotech.com
4/ 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 ? a pplication c ircuit l1 recommend value (v in =10 ~3 6 v ,v out = 5 v) version ax3 117 /b ax3 117a l1 value (h) 66u 33u ? f unction d escriptions sense1/2 the current limit sense pin, if v sense1 - v sense2 R 140mv, the over current is happened that it can turn - off driver cycle by cycle. en/ct the pin is enable/shutdown and auto restart control functions. w hen system is normal operating, this pin is enable/shutdown function. pulling this pin below a threshol d voltage of under 0. 3 v shuts the regulator o ff , and pulling this pin from 0.5v to 1.5 v turns the regulator on. however when v out is short (v fb <0.4v), the auto restart function can be started that restart the regulator cycle by cycle. t he cycle time is set by outside capacitor (c 10 ). please refer the below waveform and formula, the t2 cycle is regulator off time and t1 cycle is current limit time. t he charge - current is 26 ua and discharge - current is 1. 8 ua. vcc=10~36v vout=5.0v/1.15a c2 open u1 AX3117/a/b 1 2 3 4 5 6 7 8 en/ct vss vgate vcc sw sense1 sense2 fb c7 0.1uf c1 33nf c10 0.1uf l1 c4 0.1uf d1 b340a r1 100mr c5 470uf r7 1k c8 0.1uf c9 470uf r3 4k ) 1 r 2 r + 1 ( v 0 . 1 = v out v?mw`r?y?b? www.gofotech.com
5/ 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 under voltage lockout (uvlo) to avoid error-operation of the device at low input voltages an under voltage lockout is included that disables the device, if the input voltage lower than 5.8 v. current limit protection the current limit is set by outside resistance (r s ense ), when the sense1 - sense2 voltage larger than 140mv, the current limit is happened that driver can be turned off until the drop is small than 9 0 mv. the current limit set according to the following equation: the maximum output current table is shown as below; please refer the table to design. r sense () current limit (a) 50m 2.3 75m 1.5 3 100m 1. 15 inductor selection for most designs, the different frequency can be reducing the inductor value; please refer the table below . l1 recommend value (v in =10 ~3 6 v ,v out = 5 v) version AX3117 a AX3117 /b l1 value (h) 22~47u 66~100u v e n / c t t i m e t 1 t 2 t i m e i i n ( a ) 0 . 5 v 1 . 5 v 0 c u r r e n t l i m i t .) sec ( u 8 . 1 1 10 c = 2 t .) sec ( u 26 1 10 c = 1 t sense r 2 ) mv 0 mv 140 ( + mv 140 = (a) limit current 5 - v?mw`r?y?b? www.gofotech.com
6/ 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 where is inductor ripple current. large value inductors lower ripple current and small value inductors result in high ripple currents. choose inductor rippl e current approximately 20% of the maximum load current 2 a, i l = 0.6 a. the dc current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation ( 2 a+ 0.3 a). input capacitor selection this capacitor should be located close to the ic using short leads and the voltage rating should be approximately 1.5 times of the maximum input voltage. the rms current rating requirement for the input capacitor of a buck regulator is approximately 1 / 2 the dc load current. a low esr input capacitor sized for maxim um rms current must be used. a 220~ 470f low esr capacitor for most applications is sufficient. output capacitor selection the output capacitor is required to filter the output and provide regulator loop stability. the important capacitor parameters are; the 100 khz equivalent series resistance (esr), the rms ripples current rating, voltage rating, and capacitance value. for the output capacitor, the esr value is the most important parameter. the esr can be calculated from the following formula. = 0. 6 a x 80m= 48 mv an aluminum electrolytic capacitor s esr value is related to the capacitance and its voltage rating. in most case, higher voltage electrolytic capacitors have lower esr values. most of the time, capacitors with much higher voltage ratings ma y be needed to provide the low esr values required for low output ripple voltage. system stability is depending on output capacitors esr, correct to choose output capacitors esr is very important. it is recommended to using a 220~470f, the esr values ra nge is 40~130m. thermal considerations the sop - 8 l - ep package needs a heat sink under most conditions. the heat sink connect exposed pad of AX3117 /a /b to obtain best effect. the size of the heat sink depends on the input voltage, the output voltage, the load current and the ambient temperature. esr i v l ripple ? ? ? v?mw`r?y?b? www.gofotech.com
7/ 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 ? typical characteristics v?mw`r?y?b? www.gofotech.com
8/ 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 ? typical characteristics (continuous) v?mw`r?y?b? www.gofotech.com
9/ 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 ? typical characteristics (continuous) v?mw`r?y?b? www.gofotech.com
10/ 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 ? typical characteristics (cont inuous) v in =12v , v out =5v , i out =1.2a , cen=0.1u v in =32v , v out =5v , i out =1.2a , cen=0.1u t hermal s hut d own r elease v in =32v , v out =5v , i out =1.5a s hort r elease v in =32v , v out =5v , i out =1a v?mw`r?y?b? www.gofotech.com
11 / 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 ? typical characteristics (continuous) AX3117/ a line compensation (r sense =50m), i out =2a line compensation (r sense =50m), i out =1a AX3117b line compensation (r sense =50m), i out =2a line compensation (r sense =50m), i out =1a v?mw`r?y?b? www.gofotech.com
12/ 12 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 jun. 09 , 20 12 AX3117 ? p ackage o utlines symbol d imensions in millimeters dimensions in inches min. nom. max. min. nom. max. a - - 1.75 - - 0.069 a1 0 - 0.15 0 - 0.06 a2 1.25 - - 0.049 - - c 0.1 0.2 0.25 0.0075 0.008 0.01 d 4.7 4.9 5.1 0.185 0.193 0.2 e 3.7 3.9 4.1 0.146 0.154 0.161 h 5.8 6 6.2 0.228 0.236 0.244 l 0.4 - 1.27 0.015 - 0.05 b 0.31 0.41 0.51 0.012 0.016 0.02 e 1.27 bsc 0.050 bsc y - - 0.1 - - 0.004 x - 2.34 - - 0.092 - y - 2.34 - - 0.092 - 0 o - 8 o 0 o - 8 o mold flash shall not exceed 0.25mm per side jedec outline: ms - 012 ba detail a l h e a a 2 a 1 e d 7 ( 4 x ) b y c detail a y x expose pad v?mw`r?y?b? www.gofotech.com

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