advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 advanced ams4154 monolithic 2a output pwm buck converter systems rohs compliant features applications ? stable with low esr output ceramic capacitors ? battery chargers ? up to 99% on time ? portable (notebook) computers ? 2a output current ? industrial power supply ? wide operating input voltage range 5.5v to 32v ? point of regulation for hi gh performance electronics ? fixed 330 khz frequency ? consumer electronics ? thermal shutdown ? audio power amplifiers ? cycle-by-cycle over current protection ? distributed power systems ? under voltage lockout ? pre-regulator for linear regulators ? 5v reference output ? lcd tvs and lcd monitors ? adjustable output from 0.6v ? automotive electronics general description the ams4154 is a step-down converter for high voltage applications. current mode operation provides easier compensation and fast transient response. in ternal cycle-by-cycle current li miting and thermal shutdown provi des the necessary protection in faults situation. a 5v reference voltage is av ailable that can supply up to 2ma current. ordering information typical application pin connections output package ty pe temp. range voltage 8 lead soic adjustable AMS4154S -25c to 125c 8l soic so package (s) en comp f/b bst vin lx gnd 1 2 8 4 3 7 5 6 ref top view comp v ref gnd f/b lx bst en vin on off 10 f 470n l1 4.7 h 31.7k b220 10k 22 f 2.5v/2a 4.7n 3.9k
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4154 pin description ams4154 pin numbers name description 1 bst bootstrap. a capacitor is needed to dr ive the power switch?s dr ive above the supply voltage. it is connected between lx and bst pins to form a floating supply across the power switch driver. 2 vin supply voltage. the ams4154 operates from a+5.5v to +32v unregulated input. c1 is needed to prevent large voltage spikes from appearing at the input. 3 lx switch. this connects the inductor to vin through the internal power switch. 4 gnd ground. this pin is the ground for voltage reference and for the regulated output voltage. for this reason care must be taken in its layout. 5 fb feedback. an external resistor divider from the output to gnd, tapped to the fb pin sets the output voltage. 6 comp compensation. this node is the output of the transconductance error amplifier and the input to the current comparator. frequency compensation is done at this node by connecting a series r-c to ground. 7 en enable. a voltage greater than 2.5v enable s operation. for complete low current shutdown the en pin voltage needs to be less than 2.3v. 8 ref 5v reference voltage capable of supplying 1ma for other external circuits.
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4154 absolute maximum ratings input supply voltage -0.3v to +34v junction temperature +150 c sw voltage -1v to vin + 0.3v storage temperature -65 c to +150 c bs voltage v lx ? 0.3v to v lx + 6v lead temperature 260 c all other pins -0.3v to +6v electrical characteristics electrical characteristics at t a = 25 c and vin=12v (unless otherwise noted). parameter test conditions ams4154 min. typ. max. units feedback voltage 0.6v v in 32v, v comp < 2v 0.588 0.600 0.612 v su pp l y current v en = 5v, v fb = 1.4v 1.0 1.2 ma shutdown supply current v en = 0v 0.5 1 a current limit 2.5 3.6 4.9 a current sense to comp transconductance 3.5 a/v oscillation frequency 280 330 380 khz maximum duty cycle v fb = 1.0v 90 99 % minimum duty cycle v fb = 1.5v 0 % en threshold voltage v en rising, output on 2.5 2.6 2.8 v en threshold voltage v en falling , output off 2.2 2.3 v en threshold hysteresis 250 mv enable current v en = 0v 1.8 a thermal shutdown 160 oc 5v ref voltage i ref = 0 4.8 5.0 5.2 v ref load regulation ? i ref = 0 to 1ma 100 mv ref line regulation i ref = 100a, v in = 6.5 to 32v 30 mv
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4154 typical waveform
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4154 package dimensions inches (millimeters) unless otherwise noted. 8 lead soic plastic package (s) 0-8 typ 0.010-0.020 (0.254-0.508) s (so- 8 ) ams drw# 042293 x 45 0.016-0.050 (0.406-1.270) 0.008-0. 010 (0.203-0. 254) 0. 004-0.010 (0.101-0.254) 0.014-0. 019 (0. 355-0.483) 0.053-0.069 (1.346-1. 752) 0.050 (1.270) typ 0. 150-0.157** (3.810-3.988) 0.228-0.244 (5.791-6. 197) 0. 189-0.197* (4.801-5.004) 12 34 87 65 12 34 87 65 0.090 (2.28) 0.102 (2.59) 0.123 (3.12) 0.137 (3.48) 0.138 (3.50) 0.105(2.67) 0.213(5.41) 0.050(1.27) 0.024(0.61) 0.063(1.60) *dimension does not include mold flash. mold flash shall not exceed 0.006" (0.152mm) per side **dimension does not include interlead flash. interlead flash shall not exceed 0.010" (0.254mm) per side recommended layout pattern
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