1/8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 aug. 04 , 2010 AX3020 200 khz, 1.5 a pwm buck dc/dc converter ? general description the AX3020 series are monolithic ic designed for a step - down dc/dc converter, and own the ability of driving a 1.5 a load without additional transistor. it saves board space. the external shutdown f unction 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 tempe rature operating from damage, and current limit is against over current operating of the output switch. if current limit function occurs and v fb is down below 0.5v, the switching frequency will be reduced. the AX3020 series operates at a switching frequen cy of 20 0khz thus allow smaller sized filter components than what would be needed with lower frequency switching regulators. other features include a guaranteed + 3 % tolerances on output voltage under specified input voltage and output load conditions, the chips are available in a standard 8 - lead sop package. ? features - output voltage: adjustable output version . - adjustable version output voltage range : 0.75 v to 22 v+ 3 % . - 20 0khz fixed switching frequency . - voltage mode non - synchronous pwm control . - thermal - shutdow n and current - limit protection . - on/off shutdown control input . - short circuit protect (scp). - operating voltage can be up to 2 4 v . - output load current: 1.5 a . - sop - 8l pb - free packages . - low power standby mode . - built - in switching transistor on chip . v?mw`r?y?b? w w w . g o f o t e c h . c o m
2/8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 aug. 04 , 2010 AX3020 ? b lock d i agram ? pin assignment the package of AX3020 is sop - 8l; the pin assignment is given by : name description v cc operating voltage input sw switching output fb output voltage feedback control en on/ off shutdown high on, low off v ss gnd pin ? order/marking information order information top marking 200 khz osc . start up + + _ + _ thermal shutdown control + driver comp . comp . vss sw en fb 200 mv 220 mv _ comp . v cc current limit + _ amp comp . current source bias 0 . 75 v reference 2 . 5 v regulator ( top view ) 1 2 3 4 8 7 6 5 vcc fb sop - 8 l en sw vss vss vss vss a x 3 0 2 0 package type s : sop - 8 l ax 3020 x x packing blank : tube a : taping logo y ax 3 part number id code : internal ww : 01 ~ 52 year : 10 = 2010 11 = 2011 0 2 0 y w w x v?mw`r?y?b? w w w . g o f o t e c h . c o m
3/8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 aug. 04 , 2010 AX3020 ? absolute maximum ratings characteristics symbol rating unit maximum supply voltage v cc +2 6 v on/off pin input voltage v en - 0.3 to v cc v feedback pin voltage v fb - 0.3 to 12 v output voltage to ground v out - 0.8 v power dissipation internally limited pd ( t j - t a ) / ja w storage temperature range t st - 65 to +150 c operating junction temperature range t j - 2 0 to +125 c operating supply voltage v op +4. 5 to +2 4 v thermal resistance from junction to case jc 2 0 c /w thermal resi stance from junction to ambient ja 55 c /w note : ja is measured with the pcb copper area (need connect to v ss pins) of appro ximately 1.5 in 2 ( multi - layer ) . ? electrical characteristics (unless otherwise specified, t a =25c, v cc =12v, v out =3.3v, i out = 0. 2 a) characteristics symbol conditions min typ max units feedback voltage v fb i out =0.2a 0.728 0.750 0.773 v quiescent current i q v fb = 1.2 v force driver off - 4 8 ma feedback bias current i fb i out =0.1a - - 10 - 50 na shutdown supply current i sd v en =0v - 2 10 ua oscillator frequency f osc 1 4 0 20 0 2 6 0 khz oscillator frequency of short circuit protect f scp when v fb <0.5v - 8 0 - khz max. duty cycle (on) dc v fb =1 . 2v force driver off - 0 - % min. duty cycle (off) v fb =0v force driver on - 100 - current limit i cl pear current, no outside circuit v fb =0v force driver on 1.8 - - a saturation voltage v sat i out =1.5a, no outside circuit v fb =0v force driver on - 1.2 1.5 v sw pin leakage current sw pin=0v i swl no outside circuit v fb =1.0v force driver off - - - 200 ua sw pin leakage current sw pin= - 0.8v v cc =24v force driver off - - 5 - ma en pin logic input threshold voltage v i h high (regu lator on) - 1. 2 2.0 v v i l low (regulator off) 0. 5 - en pin logic input current i h v en =2.5v (on) - 20 - ua en pin input current i l v en =0. 3 v (off) - - 5 - thermal shutdown temp t sd - 135 - c v?mw`r?y?b? w w w . g o f o t e c h . c o m
4/8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 aug. 04 , 2010 AX3020 ? a pplication c ircuit (1) adjustable output voltage version (2) en pin with delayed startup v out = v fb (1 + ) , v fb = 0. 75 v , r2 = 0. 75 k ~ 4 k table 1 resistor select for output voltage setting v out r2 r1 5 v 1.2 k 6.8 k 3.3 v 2 k 6.8 k 2.5 v 2 k 4.7 k 1 . 8v 2 k 3 k 1.5v 2 k 2 k 1 .3 v 2 k 1.5 k 1.2v 2 k 1.2 k l1 recommend value (v in =12v ,i out =1.5a,) v out 1.8 v 2.5v 3.3v 5v l1 value 22 u h 22 u h 33uh 33uh c 2 0 . 1 uf d 1 b 240 a l 1 33 uh c 3 330 uf c 1 220 uf u 1 ax 3020 1 2 3 4 5 6 7 8 vcc sw fb en vss vss vss vss vout = 5 v / 1 . 5 a vin = 12 v c 6 0 . 1 uf r 2 1 . 2 k r 1 6 . 8 k c 2 0 . 1 u f d 1 b 2 4 0 a l 1 3 3 u h c 3 3 3 0 u f c 1 2 2 0 u f u 1 a x 3 0 2 0 1 2 3 4 5 6 7 8 v c c s w f b e n v s s v s s v s s v s s v o u t = 5 v / 1 . 5 a v i n = 1 2 v o n / o f f c 6 0 . 1 u f r 2 1 . 2 k r 1 6 . 8 k c 4 0 . 1 u f r 3 1 0 0 k ? r2 r1 v?mw`r?y?b? w w w . g o f o t e c h . c o m
5/8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 aug. 04 , 2010 AX3020 ? function descriptions pin functions v cc this is the positive input s upply 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 needed by the regulator. v ss circuit ground. sw internal switch. the voltage at th is 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. feedback senses the regulated output voltage to complete the feedback loop. en allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply current to approximately 1 0 ua. pulling this pin below a threshold voltage of approximate ly 0.5 v shuts the regulator down, and pulling this pin above 2.0 v (up to a maximum of v cc ) turns the regulator o n . thermal considerations the sop - 8 l package needs a heat sink under most conditions. the size of the heat sink depends on the input voltage, the output voltage, the load current and the ambient temperature. the AX3020 junction temperature rises above ambient temperature for a 1.5 a load and different input and output voltages. for the best thermal performance, wide copper traces and generous am ounts of pcb copper (need connect to the v ss pins) should be used in the board layout , (one exception is the sw pin, which should not have large areas of copper.) large areas of copper provide the best transfer of heat (lower thermal resistance) to the sur rounding air, and moving air lowers the thermal resistance even further. v?mw`r?y?b? w w w . g o f o t e c h . c o m
6/8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 aug. 04 , 2010 AX3020 ? typical characteristics vfb vs vin iccq vs vin fosc vs vin fosc vs temperature vfb vs temperature iccq vs temperature vfb vs vin 0.71 0.72 0.73 0.74 0.75 0.76 0.77 4 6 8 10 12 14 16 18 20 22 24 26 vin(v) vfb(v) iccq vs vin 0.00 1.00 2.00 3.00 4.00 5.00 6.00 4 6 8 10 12 14 16 18 20 22 24 26 vin(v) iccq(ma) fosc vs vin 180 190 200 210 220 230 240 4 6 8 10 12 14 16 18 20 22 24 26 vin(v) fosc(khz) fosc vs temp 140 150 160 170 180 190 200 210 220 230 240 -20 0 20 40 60 80 100 120 temp ( vfb vs temp 0.745 0.748 0.751 0.754 0.757 0.760 0.763 -20 0 20 40 60 80 100 120 temp ( iccq vs temp 0.00 1.00 2.00 3.00 4.00 5.00 6.00 -20 0 20 40 60 80 100 120 temp ( v?mw`r?y?b? w w w . g o f o t e c h . c o m
7/8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 aug. 04 , 2010 AX3020 ? typical characteristics (continues) output ripple (v in =12v, v out = 3.3 v, i out = 1.5 a) power on test wave (v in =12v, v out =3.3v, i out =1.5a) load transient response (v in =12v, v out = 3.3 v, i out =0.1~ 1.5 a) en pin on test wave (v in =12v, v out =3.3v, i out =1.5a) efficiency (v in =12v, v out =5v) efficiency (v in = 12 v) vin=12v 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 0.0 0.5 1.0 1.5 iout(a) efficiency(%) vin=12v 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 0.0 0.5 1.0 1.5 iout(a) efficiency(%) vout=5v vout=3.3v vout=2.5v vout=1.8v vout=1.2v v?mw`r?y?b? w w w . g o f o t e c h . c o m
8/8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 3 aug. 04 , 2010 AX3020 ? package outlines symbol dimensions in millimeters dimensions in inches min. nom. max. min. nom. max. a - - 1.75 - - 0.069 a1 0.1 - 0.25 0.04 - 0.1 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 0 o - 8 o 0 o - 8 o mold flash shall not exceed 0.25mm per side jedec outline: ms-012 aa detail a l h e a a 2 a 1 e d 7 ( 4 x ) b y c detail a v?mw`r?y?b? w w w . g o f o t e c h . c o m
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