description the AMS1073 is a monolithic step-down switch mode converter with a b uilt-in power mosfet. it achieves 1.2a peak output current over a wide input supply range with excellent load and line regulation. current mode operation provides fast transient response and eases loop stabilization. fault con dition protection includes cycle-by-cycle current limiting and therm al shutdown. the AMS1073 requires a minimum numbe r of readily available standar d extern al components. the AMS1073 is available in sot23-6 packages. features ? 1.2a peak output current ? 0.35 ? internal power mosfet switch ? stable with low esr output ceramic capacitors ? up to 92% efficiency ? 0.1 a shutd own mode ? fixed 1.4mhz frequency ? thermal shutdown ? cycle-by-cycle over current protection ? wide 4.5v to 24v operating input range ? output adjustable from 0.81v to 15v ? available in sot23-6 packages applications ? distributed power systems ? battery ch arger ? pre-regulator for linear regulators ? wled driv ers typical application AMS1073 sw fb bst gnd in en 1 6 3 2 4 5 v out 3.3v @ 1.2a d1 b230a v in 12v off on c1 10uf c2 10nf l1 4.7uh r1 49.9k r2 16.2k 22uf c3
ordering information part number package top marking free air temperature (t a ) AMS1073 sot23-6 -40 qc to +85 qc package reference bst gnd fb 1 2 3 6 5 4 sw in en top view absolute maxi mum ratings (1) supply voltage v in ............................ -0.3v~ 26v v sw ............................................ -0.3v~vin+ 0.3 v v bs ....................................................... v sw + 6v all other pins ..................................-0.3v to +6v continuous power dissipation (t a = +25c) (2) sot23-6 .............................................. 0.568w junction temperature ...............................150 qc lead temperature ....................................260 qc storage temperature............... -65 qc to +150 qc recommended operating conditions (3) supply voltage v in ...........................4.5v to 24v output voltage v out .......................0.81v to 15v ambient temperature ................ -40 qc to +85 qc max input current into the en pin............. 300 a thermal resistance (4) ja jc sot23-6 ..............................220.... 110.. qc/w notes: 1) exceeding these ratings may damage the device. 2) the maximum allowable power dissipation is a function of the maximum junction temperature t j (max), the junction-to- ambient thermal resistance ja , and the ambient temperature t a . the maximum allowable continuous power dissipation at any ambient temperature is calculated by p d (max)=(t j (max)- t a )/ ja . exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. internal thermal shutdown circuitry protects the device from permanent damage. 3) the device function is not guaranteed outside of the recommended operating conditions. 4) measured on jesd51-7, 4-layer pcb..
electri cal characteristics v in = 12v, t a = +25 q c, unless otherwise noted. parameters symbol condition min typ max units feedback voltage v fb 4.5v d v in d 24v 0.790 0.810 0.830 v feedback current i fb v fb = 0.8v 0.1 a s witch-on r esistance (5) r ds(on) 0.35
switch leakage v en = 0v, v sw = 0v 10 a current limit (5) 1.8 a oscillator frequency f sw v fb = 0.6v 1.2 1.4 1.7 mhz fold-back frequency v fb = 0v 460 khz maximum duty cycle v fb = 0.6v 87 % minimum on-time (5) t on 100 ns under voltage lockout threshold rising 2.5 2.8 3.1 v under voltage lockout threshold hysteresis 150 mv en input low voltage 0.4 v en input hig h voltage 1.2 v v en = 2v 2.1 en input current v en = 0v 0.1 a supply current (shutdown) i s v en = 0v 0.1 1.0 a supply current (quiescent) i q v en = 2v, v fb = 1v 0.8 1.0 ma therm al shutdown (5) 150 c note: 5) guaranteed by design. pin functions pin # name des cription 1 bst bootstrap. a capacitor is connected between sw and bs pins to form a floating sup ply across the power switch driver. this capacitor is nee ded to drive the power switch?s gate above the sup ply voltage. 2 gnd ground. this pin is the voltage reference for the regulated output voltage. for this reaso n care must be taken in its layout. this node should be placed outside of the d1 to c1 ground path to prevent switching current spikes from inducing voltage noise into the part. 3 fb feedback. an external resistor divider from t he outp ut to gnd, tapped to the fb pin sets the output voltage. to prevent current limit run aw ay during a short circuit fault condition, the frequency foldback comparator lowers the osc illator frequency when the fb voltage is b elow 250mv. 4 en on/off control input. pull en above 1.2v to turn the device on. for automat ic enable, connect a 100k
resistor between this pin and vin pin. 5 in supply voltage.the AMS1073 operates from a +4.5v to +24v unregulated input.c1 is needed to prevent large voltage spikes from appearing at the input. 6 sw switch output.
5in en fb gnd sw bst 4 3 2 1 6 regulator oscillator 1.4mhz/460khz ramp generator driver current sense amplifier error amplifier current limit comparator pwm comparator d x20 m1 regulator reference ea -- + -- + -- + s r r q -- + 27pf 1pf functional block diagram
typical application circuits v in notes: 1) d3 can be installed if v in < 5v 2) d2 can be installed if v out < 5v 3) no need for both d2 and d3 v out 3.3v c2 10nf d1 u1 d2 1n4148 (optional) AMS1073 fb sw bs gnd en in 1 5 4 6 3 off on 1.4mhz, 3.3v output at 1a step-dow n convert er v out (v) r1 (k ? ? resistor selection for common output voltages vout=0.81x(1+r1/r2) c1 l1 10uf 22uf c3 4.7uh r1 49.9k r2 16.2k d3 1n4148 (optional)
sot23-6 millimeter symbol min nor max a - - 1.35 a1 0.04 - 0.15 a2 1.00 1.10 1.20 a3 0.55 0.65 0.75 d 2.72 2.92 3.12 e 2.60 2.80 3.0 e1 1.40 1.60 1.80 e 0.95bsc e1 1.90bsc l 0.30 - 0.60 0 - 8
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