1/ 10 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 4 aug. 04 , 20 10 ax30 1 1 50k hz, 2 a pwm buck dc/dc converter ? general description the AX3011 series are monolithic ic designed for a step - down dc/dc converter, and own the ability of driving a 2.5a load without additional transistor. it saves board space. the external shutdown function can be controlled by logic level and then come into standby mode. the internal compensation makes feedback control having good line and load regulation without external design. regarding protected function, thermal shutdown is to prevent over temp er ature operating from damage; current limit is against over current operating of the output switch that set by outside resistance . if current limit function occurs and v fb is down below 0. 3 v, the switching frequency will be reduced to 10 khz; and over vol tage protection (ovp) that can avoid high v out voltage to damage circuit and capacitor. the chip is available in sop-8l-ep package which features small size as sop-8l with an exposed pad to reduce the junction- to -case resistance. ? features - operating voltage can be up to 40v . - maximum a djustable output voltage up to 38 v . - t ypical switching frequency is 50k hz. - voltage mode non - synchronous pwm converter . - thermal - shutdown and current - limit protection . - short circuit protect (scp). - external current limit setting. - o ver voltage protect (ovp) sense and output . - output load current: 2 a . - low power standby mode . - built - in switching transistor on chip . - sop - 8l- ep pb - free package s. v?mw`r?y?b? w w w . g o f o t e c h . c o m
2/ 10 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 4 aug. 04 , 20 10 ax30 1 1 ? block diagram ? pin assignment the package of AX3011 is sop - 8 l - ep ; the pin assignment is given by : name description v cc operating voltage input ocset add an external resistor to set max switch output current v ss gnd pin fb output voltage feedback control sw switch pin. connect exte rnal inductor and diode here. ovp ovp output pin. comp compensation pin sense over voltage sense input ? order /marking information order information top marking 50 khz osc . start - up + + _ + _ thermal shutdown control + driver comp . comp . vss sw fb 2 . 0 a switch _ comp . v cc current limit + _ amp comp . current source bias 1 . 25 v reference 2 . 5 v regulator ocset comp + _ 1 . 155 v ovp comp . sense ( t o p v i e w ) 1 2 3 4 8 7 6 5 o c s e t s w s o p - 8 l - e p v s s f b c o m p v c c o v p v s s s e n s e a x 3 0 1 1 x x p a c k a g e t y p e e s : e p - s o p - 8 l p a c k i n g b l a n k : t u b e a : t a p i n g x logo y ax 3 part number id code : internal ww : 01 ~ 52 year : 10 = 2010 11 = 2011 0 1 1 y w w x v?mw`r?y?b? w w w . g o f o t e c h . c o m
3/ 10 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 4 aug. 04 , 20 10 ax30 1 1 ? absolute maximum ratings char acteristics symbol rating unit maximum supply voltage v cc + 4 5 v comp pin input voltage v comp - 0.3 to 6 v feedback pin voltage v fb - 0.3 to 12 v sense pin voltage v sense - 0.3 to 12 v ocset pin input voltage v ocset - 0.3 to vcc v sw pin voltage v sw - 0 .3 to v cc v ovp pin voltage v o vp - 0.3 to vcc v power dissipation internally limited pd ( t j - t a ) / ja w storage temperature range t st - 65 to +150 c operating temperature range t op - 40 to +125 c thermal resistance from junction to case jc 15 c /w thermal resistance from junction to ambient ja 40 c /w note: ja is measured with the pcb copper a rea (need connect to exposed pad ) of approximately 3 in 2 ( multi - layer ) . ? electrical characteristics (unless otherwise specified, t a =25c, v cc =12v, v out =5v, i load = 0.2a) characteristics symbol conditions min typ max units operating supply voltage v cc 4. 5 - 40 v feedback voltage v fb 1.143 1.155 1.167 v feedback bias current i fb v fb =1.5v - - 10 - na line regulation v cc =10~40v - 0.1 0.2 % load regulation i out =0~2a - 0.1 0.2 % quiescent current i ccq v fb =2v force driver off - 3 6 ma oscillator frequen cy f osc 45 50 55 khz oscillator frequency of short circuit protect f scp v fb <0.3v - 10 - khz max. duty cycle (on) dc v fb =0v force driver on - 100 - % min. duty cycle (off) v fb =12v force driver off - 0 - saturation voltage v sat i out =2a, no outside cir cuit v fb =0v force driver on - 1.0 1.2 v sense voltage v sense 1.205 1.23 1.255 v v?mw`r?y?b? w w w . g o f o t e c h . c o m
4/ 10 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 4 aug. 04 , 20 10 ax30 1 1 ? electrical characteristics (continues) (unless otherwise specified, t a =25c, v cc =12v, v out =5v, i load = 0.2a) ovp voltage v ovp v sense =1.5v, i ovp =3ma - 0.35 0.5 v sw pin leakage current sw pin=0v i swl no outside circuit v fb =2v force driver off - - - 200 ua sw pin leakage current sw pin= - 0.8v v cc =40v force driver off - - 5 - ma thermal shutdown temp t sd - 15 5 - c thermal shutdown hysteresis t sh - 35 - c ? application circuit v out = v fb (1 + ) , v fb = 1.155 v , r2 = 0.7 k ~ 1.8 k ? function descriptions v cc this is the positive input supply for the ic switching regulator. a suitable input bypass capacitor must be presented at this pin to minimize voltage transients and to supply the switching currents neede d by the regulator. v ss circuit ground. c 2 0 . 1 uf d 1 b 340 a l 1 1 2 c 3 470 uf c 1 220 uf u 1 vcc sw fb sense ovp vout = 5 . 0 v / 2 a vin = 12 ~ 40 v c 4 0 . 1 uf r 2 1 . 5 k r 1 5 k ocset r 3 3 . 9 k vss comp c 5 47 nf 4 . 7 k ax 3011 r 4 10 k c 7 100 uf c 8 0 . 1 uf r 7 r 6 1 2 3 4 5 6 7 8 100 uh r 5 c 9 1 nf r 8 5 k 1 . 5 k 5 k ? r2 r1 v?mw`r?y?b? w w w . g o f o t e c h . c o m
5/ 10 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 4 aug. 04 , 20 10 ax30 1 1 sw internal switch. the voltage at this pin switches between (+ v cc C v sat ) and approximately C 0.5v, w ith a duty cycle of approximately v out / v cc . to minimize coupling to sensitive circuitry, the pc board copper area connected to this pin should be minimized. f b sense the regulated output voltage to complete the feedback loop. ocset the current limit threshold is setting by the external resistor (r3) connecting from v cc supply to ocset pin . normally, the cu rrent limit setting more than i out 0.8a, please refer the table for setting the minimum current limit value : r3 () current limit (a) 1.5k 1.22 1.8k 1.44 2.2k 1.78 2.7k 2.14 3k 2.34 3.3k 2.56 3.9k 2.98 ovp the ovp p in must pull high a 10k res istance, i f v sense >1.2 3 v , the ovp is happened that ovp can be pull high , system can be control the output pmos off and internal driver off . sense the over voltage sense p in , i f v sense >1.2 3 v , the ovp is happened that it can turn - off the driver. y ou can set v out ovp voltage by outside resistances ( r6 and r7). comp the compensation pin. the comp pin connects r5 and c5 to fb pin , the c 5 use 47n f and r5 use 4.7k for all condition. v?mw`r?y?b? w w w . g o f o t e c h . c o m
6/ 10 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 4 aug. 04 , 20 10 ax30 1 1 ? application information setting the output voltage application circuit item shows the basic application circuit with adjustable output version. the external resistor sets the output voltage according to the following equation: table 1 resistor select for output voltage setting v out r2 r1 5.0v 1.5 k 5 k 3.27v 1.2 k 2.2 k inductor selection for most designs, the operates with inductors of 82 h to 100h for AX3011. the inductor value can be derived from the following equation: where is inductor ripple current. large value inductors lower ripple current and small value inductors result in high ripple currents. choose inductor ripple current approximately 20 % of the maximum load current 2a, i l =0.4 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+ 0.2a ). please refer the recommend table for setting the inductor value: l1 recomm end value ( v in =12v , i out = 2 a ,) v out 3.3v 5v l1 value 82 uh 100 uh ? ? ? ? ? ? ? ? ? r r v v out ? ? f i v v v v l osc l in out in out ? ? ? ? ? ? v?mw`r?y?b? w w w . g o f o t e c h . c o m
7/ 10 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 4 aug. 04 , 20 10 ax30 1 1 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 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 maximum rms current must be used. a 22 0f low esr capacitor for most applications is sufficient. output capacitor selection the output capacitor is required to filter the out put and provide regulator loop stability. t he important capacitor parameters are; the 100khz equivalent series resistance (esr), the rms ripples current rating, voltage rating, and capacitance value. for the output capacitor, the esr value is the most impo rtant parameter. the esr can be calculated from the following formula. = 0.4a x 13 0m= 52mv 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 may b e needed to provide the low esr values required for low output ripple voltage. it is recommended to replace this low esr capacitor by using a 470 f low esr values < 130m . thermal considerations the sop - 8 l - ep package needs a heat sink under most cond itions. the heat sink connect exposed pad of AX3011 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. the AX3011 junction temperature rise above ambient temperat ure for a 2a load by different input and output voltages. esr i v l ripple ? ? ? v?mw`r?y?b? w w w . g o f o t e c h . c o m
8/ 10 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 4 aug. 04 , 20 10 ax30 1 1 ? typical characteristics 5.000 5.005 5.010 5.015 5.020 5.025 5.030 5.035 5.040 5.045 5.050 5 10 15 20 25 30 35 40 vin vs vout vin (v) vout (v) load=0.3a 5.000 5.002 5.004 5.006 5.008 5.010 5.012 5.014 5.016 5.018 5.020 0 0.5 1 1.5 2 load vs vout load (a) vout (v) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 200 400 600 800 1000 1200 1400 1600 1800 2000 load vs saturation voltage load (ma) saturation voltage (v) vin=12v 0 0.5 1 1.5 2 2.5 3 3.5 4 5 10 15 20 25 30 35 40 vin vs current limit vin (v) current limit (a) r3=3.9k vout=3.3v 0 10 20 30 40 50 60 70 80 90 100 0.5 0.8 1.1 1.4 1.7 2 efficiency test load (a) efficiency (%) vin=40v,vout=5v vin=12v,vout=3.3v vin=12v,vout=5v vin=40v,vout=12v 1.14 1.143 1.146 1.149 1.152 1.155 1.158 1.161 1.164 1.167 1.17 -40 -25 0 25 50 75 100 125 temperature vs vfb temperature ( v?mw`r?y?b? w w w . g o f o t e c h . c o m
9/ 10 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 4 aug. 04 , 20 10 ax30 1 1 ? typical characteristics (continues) load transient (vin=12v, vout=5v, load=0.1~2a) load transient (vin=40v, vout=5v, load=0.1~2a) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 -40 -25 0 25 50 75 100 125 temperature vs satureation voltage temperature ( 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 -40 -25 0 25 50 75 100 125 temperature vs current limit temperature ( v?mw`r?y?b? w w w . g o f o t e c h . c o m
10/10 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 4 aug. 04 , 20 10 ax30 1 1 ? package outlines symbol dimensions 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? w w w . g o f o t e c h . c o m
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