description the AMS1076 is a monolithic integrated step- down switch mode converter with an internal power mosfet. it achieves 1a continuous 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 condition protection includes cycle-by-cycle current limiting and thermal shutdown. the AMS1076 requires a minimum number of readily available standard external components. the AMS1076 is available in sot23-6 packages. features ? 1a output current ? 0.45 ? internal power mosfet switch ? stable with low esr output ceramic capacitors ? up to 92% efficiency ? 0.1 a shutdown mode ? fixed 1.4mhz frequency ? thermal shutdown ? cycle-by-cycle over current protection ? wide 4.5v to 18v operating input range ? output adjustable from 0.81v to 15v ? available in sot23-6 packages applications ? hand disk drive ? xdsl modems cable ? set-top box typical application AMS1076 sw fb bst gnd in en 1 6 3 2 4 5 v out 3.3v @ 1a cb 10nf d1 b230a v in 12v off on AMS1076 advanced monolithic systems http://www.ams-semitech.com 1 vout=0.81x(1+r1/r2) (v)
package reference bst gnd fb 1 2 3 6 5 4 sw in en top view sot23-6 absolute maxi mum ratings supply voltage v in .............................-0.3v~21v v sw .............................................-0.3v~vin+0.3v v bs ....................................................... v sw ~ 6v all other pins .................................?0.3v ~ +6v lead temperature ....................................260 advanced monolithic systems http://www.ams-semitech.com 2
electrical 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 1 8 v 0.790 0.810 0.830 v v fb = 0.8v 10 na feedback current i fb v fb = 2v 2 a switch-on resistance r ds(on) 0. 4 5
switch leakage v en = 0v, v sw = 0v 10 a current limit 1.8 a oscillator frequency f sw 1. 2 1.4 1.7 mhz fold-back frequency v fb = 0v 460 khz maximum duty cycle v fb = 0.6v 8 7 % minimum on-time t on 100 ns under voltage lockout threshold rising 2.5 2.8 3.1 v un d er volta g e lock o ut thres h old h y steres i s 150 mv en input low voltage 0.4 v en input high voltage 1.2 v v en = 2 v 2.1 en input current v en = 0v 0.1 a supply current (shutdown) v en = 0v 0.1 1 a supply current (quiescent) v en = 2v, v fb = 1v 0.8 1 ma thermal shutdown 1 6 0 c pin functions pin # name description 1 bst bootstrap. this capacitor is needed to drive t he power switch?s gate above the supply voltage. it is connected between sw and bs pins to form a fl oating supply across the power switch driver. 2 gnd ground. this pin is the voltage reference for t he regulated output voltage. for this reason care must be taken in its layout. this node should be pl aced 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 output 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 below 250mv. 4 en on/off control input. pull above 1.2v to turn the device on. 5 in supply voltage. the AMS1076 operates from a +4.5v to +1 8 v unregulated input. c1 is needed to prevent large voltage spikes from appearing at the input. 6 sw switch output. AMS1076 advanced monolithic systems http://www.ams-semitech.com 3
functional block diagram AMS1076 advanced monolithic systems http://www.ams-semitech.com 4 current sense amplifier regulator current limit comparator error amplifier otp lvp pwm comparator enable reference offset rsen
sot23-6 0.30 0.50 seating plane 0.95 bsc 0.90 1.30 1.45 max 0.00 0.15 top view front view side view 2.80 3.00 1.50 1.70 2.60 3.00 13 4 6 0.09 0.20 note: all dimensions are in millimeters . AMS1076 advanced monolithic systems http://www.ams-semitech.com 5
|
