1/ 10 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 1 ju l.27, 2010 ax66 38 dual 7 00ma ldo regulator with enable function ? general description the ax 6638a/b/c is an efficient, precise dual-channel cmos ldo regulator optimized for ultra-low-quiescent applications. regulators output1 and output2 are capable of sourcing 700ma of output current. the regulators are stable with output capacitors as low as 1f, including current limit, thermal shutdown protection, fast transient response, low dropout voltage, high output accuracy, current limiting protection, and high ripple rejection ratio. the ax 6638a/b/c contains internal pull high enable function that allows the output of regulator to be turned off. the ax 6638a/b/c regulators are available in used to252- 5l pb -free package. ? features - input voltage range : 3.4v to 5.5v - low quiescent current is 50ua/per channel (typ.) - fast transient response - tight load and line regulation - current limit and thermal shutdown protection - only low - esr ceramic capacitors required for stability - available in the to252 - 5l pb - free package ? b lock d iagram cur rent limit1 - + vo ut1 gnd error amp bandgap t hermal shutdown enabl e en cur rent limit2 - + error amp vo ut2 vi n 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. 1 ju l.27, 20 10 ax66 38 ? pin assignment the package of ax 6638a/b/ c is to252 - 5l ; the pin assignment is given by : name description vin channel1/2 input voltage en channel1/2 shutdown control pin, the pin is internal pull high. vout1 channel 1 output voltage vout2 channel 2 output voltage gnd common ground ? order/marking information order information top marking ? absolute maximum ratings (at t a =25 c ) characteristics symbol rating unit v in pin voltage v in 6 v output voltage v o ut1 /v out2 gnd - 0.3 to v in + 0.3 v enable voltage v en gnd - 0.3 to v in + 0.3 v power dissipation pd i nternal limited w storage temperature range t st - 65 to +150 c operating junction temperature range t op j - 4 0 to + 125 c junction temperature t j - 4 0 t o +1 50 c thermal resistance from junction to case jc 1 0 c /w thermal resistance from junction to ambient ja 30 c /w note: ja is measured with the pcb copper area of approximately 1 in 2 (multi - layer). that need connect to tap pad. to 252 - 5 l 1 out 1 4 out 2 3 gnd 2 vin 5 en ( top view ) ( side view ) metal tab gnd ax 6638 xx x d 5 : to 252 - 5 l output voltage package packing blank : tube a : taping a : v out 1 = 3 . 3 v , v out 2 = 1 . 8 v x b : v out 1 = 3 . 3 v , v out 2 = 1 . 5 v c : v out 1 = 3 . 3 v , v out 2 = 1 . 2 v a : ax 6638 a b : ax 6638 b c : ax 6638 c logo y ax 6 part number id code : internal ww : 01 ~ 52 year : 10 = 2010 11 = 2011 6 3 8 y w w x x functional code 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. 1 ju l.27, 20 10 ax66 38 ? electrical characteristics (v in = 5v, t a =25 c (unless otherw ise no ted ) characteristics symbol conditions min typ max units input voltage (note1) v in i out1 /2 =30ma 3.4 - 5.5 v quiescent current i q i out1/2 =0ma, v in =5v - 100 160 ua enable input threshold v enh 2.0 - - v v enl - - 0.8 shutdown current i sd i out1, 2 =0ma, v in =5v, v en =0v - 4 8 a temperature shutdown t sd1,2 - 1 5 0 - oc temperature shutdown hysterisis t sdr1,2 - 4 0 - oc regulator1 output voltage accuracy v out1 i out1 =30ma 3.234 3.3 3.366 v output voltage temperature stability i out1 =10ma (note 4) - 1 - % dropout voltage v dr op1 i out1 =7 00ma, v out1 =v out1 - 2% - 4 00 500 mv line regulation v line1 v in = 4 v to 5.5v, i out 1 = 30ma - 0.1 0.2 %/v load regulation v load i out1 =1m~ 7 00ma - 10 4 0 mv current limit i limit1 v in = 5.0v 8 00 - - ma short circuit current i short1 v out1 < 0. 25 *v out1 - 5 00 - ma ripple rejection psrr1 i out1 =30ma, f=100hz - - 60 - db regulator2 output voltage accuracy v out2 i out2 =30ma (AX6638a) 1.764 1.8 1.836 v i out2 =30ma (AX6638b) 1.470 1.5 1.530 i out2 =30ma (AX6638c) 1.176 1.2 1.224 output voltage temperature stability i out2 =10ma - 1 - % dropout voltage v drop2 i out2 =700ma, v out2 =v out2 - 2% v out2 =1.8v - 700 1000 mv v out2 =1.5v - 1000 1300 v out2 =1.2v - 1300 1600 line regulation v line1 v in = 3.4 v to 5.5v, i out2 = 30ma - 0.1 0.2 %/v load regulation (note 3) v load i out2 =1m~ 7 00ma - 10 30 mv current limit (note 2) i limit2 v in = 5.0v 800 - - ma short circuit current i short2 v out2 < 0.25 *v out2 - 5 00 - ma ripple rejection psrr2 i out2 =30ma, f=100hz - - 60 - db note1 : the device is not guaran teed to function outside its operating conditions. note 2 : current limit is measured at constant junction temperature by using pulsed testing with a low on time. note 3 : regulation is measured at constant junction temperature by using pulsed testing with a low on time. note4: guaranteed by design. 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. 1 ju l.27, 20 10 ax66 38 ? application circuit ? function descriptions the ax 6638a/b/c is a highly accurate, dual, low noise, cmos ldo voltage regulators with enable function. the output voltage for each regulator is set independently by fuse trimming. as illustrated in function block diagram, it consists of a reference, error amplifier, a p-channel pass transistor, an on/off control logic and an internal feedback voltage divider. the band gap reference is connected to the error amplifier, which compares the reference with the feedback voltage and amplifies the voltage difference. if the feedback voltage is lower than the reference voltage, the pass- transistor gate is pulled lower, which allows more current to p ass to the vout pin and increases the output voltage. if the feedback voltage is too high, the pass transistor gate is pulled up to decrease the output voltage. the output voltage is feed back through an internal resistive divider connected to vout pin. additional blocks include an output current limiter, thermal sensor, and shutdown logic. enable function en pin start and stop the corresponding two outputs. th is pin is internal pull high. when the en pin is switched to the power off level, the operation of all internal circuit stops, the build-in p-channel mosfet output transistor between pins vin and vout is switched off, allowing current consumption to be drastically reduced. dropout voltage a regulators minimum input -output voltage differential, or dropout voltage, determines the lowest usable supply voltage. the ax 6638a/b/c use a p- channel mosfet pass transistor, its dropout voltage is function of drain- to -source on-resistance r ds (on) multiplied by the load current. current limit each channel of ax 6638a/b/c includes a fold back current limiter. it monitors and controls the pass transistors gate voltage, estimates the output current, and limits the output current minimum 8 00 ma. vin vout 1 gnd c 1 v in c 2 ax 6638 a / b / c 1 uf 1 uf out 1 v vout 2 en c 4 1 uf out 2 v 2 1 4 5 3 on off v dropout = v in - v out = r ds ( on ) * i out 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. 1 ju l.27, 20 10 ax66 38 thermal shutdo wn protection thermal shutdown protection limits total power dissipation of ax 6638a/b/c. when the junction temperature exceeds t j = +150c, a thermal sensor turns off the pass transistor, allowing the ic to cool down. the thermal sensor turns the pass transistor on again after the junction temperature cools down by 40c, resulting in a pulsed output during continuous thermal shutdown conditions. thermal shutdown protection is designed to protect the ax 6638a/b/c in the event of fault conditions. for continuous operation, the absolute maximum operating junction temperature rating of t j = +125c should not be exceeded. ? application information like any low-dropout regulator, the ax 6638a/b/c requires input and output decoupling capacitors. the device is specifically designed for portable applications requiring minimum board space and smallest components. these capacitors must be correctly selected for good performance (see capacitor characteristics section). please note that linear regulators with a low dropout voltage have high internal loop gains which require care in guarding against oscillation caused by insufficient decoupling capacitance. input capacitor an input capacitance of 1 f is required between input pin and ground directly (the amount of the capacitance may be increased without limit). the input capacitor must be located less than 1cm from the device to assure input stability. a lower esr capacitor allows the use of less capacitance, while higher esr type (like aluminum electrolytic) requires more capacitance. capacitor types (aluminum, ceramic and tantalum) can be mixed in parallel, but the total equivalent input capacitance/ esr must be defined as above to stable operatio n. there are no requirements for the esr on the input capacitor, but tolerance and temperature coefficient must be considered when selecting the capacitor to ensure the capacitance will be 1 f over the entire operating temperature range. output capacitor the ax 6638a/b/c is designed specifically to work with very small ceramic output capacitors. a ceramic capacitor (temperature characteristics x7r, x5r) in 1 f is suitable for the ax 6638a/b/c application. the recommended minimum capacitance for the device is 1 f, x5r or x7r dielectric ceramic, between vout and gnd for stability, but it may be increased without limit. higher capacitance values help to improve transient. the output capacitor's esr is critical because it forms a zero to provide phase lead which is required for loop stability. 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. 1 ju l.27, 20 10 ax66 38 thermal considerations the ax 6638a/b/c series can deliver a current of up to 700ma/channel over the full operating junction temperature range. however, the maximum output current must be debated at higher ambient temperature to ensure the junction temperature does not exceed 125 c. with all possible conditions, the junction temperature must be within the range specified under operating conditions. power dissipation can be calculated based on the output current and the voltage drop across regulator. p d = (v in - v out ) i out + v in i gnd the final operating junction temperature for any set of conditions can be estimated by the following thermal equation: p d (max) = (t j (max) - t a ) / ja where t j (max) is the maximum junction temperature of the die (125c) and t a is the maximum ambient temperature. the junction to ambient thermal resistance ( ja ) to252- 5l package at recommended minimum footprint is 30 c /w that is connect 1 in 2 pcb copper area to exposed pad. 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. 1 ju l.27, 20 10 ax66 38 ? typical characteristics 0 20 40 60 80 100 120 140 160 180 200 3.5 4 4.5 5 5.5 vin (v) quiescent current (ua) vin vs quiescent current AX6638a iout1/2=0a 0 200 400 600 800 1000 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 iout1/2 (a) dropout voltage (mv) dropout voltage AX6638a channel 1 channel 2 3.20 3.22 3.24 3.26 3.28 3.30 3.32 3.34 3.36 3.38 3.40 3.5 4 4.5 5 5.5 vin (v) vout1 (v) vin vs vout1 (channel 1) AX6638a iout1=30ma 1.70 1.72 1.74 1.76 1.78 1.80 1.82 1.84 1.86 1.88 1.90 3 3.5 4 4.5 5 5.5 vin (v) vout2 (v) vin vs vout2 (channel 2) AX6638a iout1=30ma 3.20 3.22 3.24 3.26 3.28 3.30 3.32 3.34 3.36 3.38 3.40 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 iout1 (a) vout1 (v) iout vs vout1 (channel 1) AX6638a vin=5v 1.70 1.72 1.74 1.76 1.78 1.80 1.82 1.84 1.86 1.88 1.90 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 iout2 (a) vout2 (v) iout vs vout2 (channel 2) AX6638a vin=5v 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. 1 ju l.27, 20 10 ax66 38 ? typical characteristics (continuous) 3.10 3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50 ??: ??: ?: ?: ?: ?: ??: ??: temperature vout1 (v) temperature vs vout1 (channel1) AX6638a vin=5v iout1=10ma 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 ??: ??: ?: ?: ?: ?: ??: ??: temperature vout2 (v) temperature vs vout2 (channel2) AX6638a vin=5v iout2=10ma 0 200 400 600 800 1000 ??: ??: ?: ?: ?: ?: ??: ??: temperature dropout voltage (mv) AX6638a iout1=700ma iout2=700ma temperature vs dropout voltage channel1 channel2 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. 1 ju l.27, 20 10 ax66 38 ? typical characteristics (continuous) power on test (channel1) power on test (channel2) enable C on test (channel 1) enable C on test (channel 2) load transient (channel 1) load transient (channel 2) 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. 1 ju l.27, 20 10 ax66 38 ? p ackage o utlines symbol dimensions in millimeters dimensions in inches min. nom. max. min. nom. max. a 6.35 6.6 6.73 0.250 0.260 0.265 b 5.21 5.33 5.46 0.205 0.210 0.215 c 6.86 7.24 7.62 0.270 0.285 0.300 d 2.67 ref 0.105 ref p 1.27 ref 0.050 ref h 2.18 2.29 2.39 0.086 0.090 0.094 j 0.46 0.51 0.58 0.018 0.020 0.023 k 0.00 0.08 0.13 0.000 0.003 0.005 l 1.40 1.60 1.78 0.055 0.063 0.070 m 5.33 5.46 5.59 0.210 0.215 0.220 b 0.38 0.56 0.71 0.015 0.022 0.028 b1 0.38 0.53 0.66 0.015 0.021 0.026 mold flash shall not exceed 0.005inch per side b a b b 1 m d h j 5 . 8 1 1 . 0 5 . 8 2 . 0 1 . 27 land pattern recommendation ( unit : mm ) 7 . 2 0 . 6 p ( typ .) c k l v?mw`r?y?b? w w w . g o f o t e c h . c o m
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