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advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 advanced ams4106 monolithic 5a synchronus pwm buck converter systems rohs compliant features applications ? internal mosfet driver with integrated high side ? lcd tvs and lcd monitors ? uses external low side mosfet ? computer peripherals ? adjustable output voltage dawn to 0.600v ? portable (notebook) computers ? external clock synchronization ? industrial power supply ? built in start/stop uvlo ? point of regulation for hi gh performance electronics ? over current and thermal protection ? consumer electronics ? shutdown supply current < 1ua ? audio power amplifiers ? frequency range 100khz to 750khz general description the ams4106 is a medium output current synchronous buck converter. the high side device is integrated into the device. the ams4106 provides an adaptive gate drive for the external fet. for low current operation this can be replaced with a schottky diode allowing asynchronous operation. the part has either a fixed internal present pwm frequency of 250 khz, or externally adjustable up to 600 khz, allowing smalle r inductors where efficiency is less critical and faster transient response is needed. the part uses current mode control for simple compensation an d ease of use with low esr capacitors. it uses a programmable soft start to reduce inrush current and allow large output capacitors to be used where very low ripple is required. the part ha s enable pin with virtual zero power in shutdown mode. a power good is provided with open collector to facilitate power ready functions. the part is available in soic 16 thermally enhanced packages. ordering information typical application pin connections output package type temp. voltage 16 lead soic range adjustable AMS4106S -25oc to 125oc 16 lead soic (s) 1 2 16 4 3 15 13 14 lx v in f set enable fdr pgnd 5 6 12 8 7 11 9 10 gnd bst comp ss pwrgd vpwr vpwr f/b lx lx top view
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4106 pin description ams4106 pin numbers name description 1 pwrgd power good output. open collector output. a low on the pin indicates that the output is less than the desired output voltage. there is an internal rising filter on the output of the pwrgd comparator. 2 ss soft start pin connect a capacitor to gnd, to slow the start up. 3 gnd analog ground-internally connected to the sensitive analog ground circuitry. 4, 5 vpwr input supply voltage, 4.5 v to 20 v. must bypass with a low esr 10? f ceramic capacitor. 6 v in input supply voltage, 4.5 v to 20 v powers up the internal circuitry. must bypass with a low esr 10? f ceramic capacitor. 7 comp error amplifier output. connect freque ncy compensation network from comp to gnd. 8 f/b input pin of the error comparator. 9 f set external frequency set 100 khz-750khz. 10 enable logic enable/disable device function. 11 bst boost voltage for the output stage drive. connect a capacitor between lx pin and boost. 12, 13, 14 lx phase node- connect to external fet and external l-c filter. 15 pgnd power ground-noisy internal ground-return currents from the fdr driver output return through the pgnd 16 fdr gate drive for low side mosfet. connect gate of n-channel mosfet.
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4106 absolute maximum ratings v in -0.3v to 30v lx internally limited f/b -0.3 to 8.0v fdr (st eady state current) 500 ma en -0.3v to 8.0v comp 3 ma fset -0.3v to 4.0v fdr (steady state current) 100 ma ss -0.3v to 4.0v lx (steady state current) 500 ma bst vi (ph) + 8.0v comp 3 ma fdr -0.3v to 8.5v ss pwrgd 10 ma pwrgd 0.3v to 30v agnd to pgnd 0.3v comp 0.3v to 30v esd 2kv lx -1.5v to 30v junction temperature +150c lead temperature1,6 mm for 10 sec. 26 0c storage temperature -65c to +150c stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any ot her conditions beyond those indicated under recommended operatin g conditions is not implied. exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. electrical characteristics electrical characteristics at t j = 25 c and vin=12v (unless otherwise noted) parameter test conditions ams4106 min. typ. max. units supply current i q quiescent current operating current, lx pin open, no external low side mosfet, 3 12 ma shutdown, en= 0v 0.5 a start threshold voltage 4.32 4.49 v stop threshold voltage 3.69 3.97 v vin hysteresis 350 mv reference system accuracy t j = 25 o c 0.588 0.600 0.612 v reference voltage t j = 125 o c 0.600 v oscillator (rt pin) f set open 200 250 300 f set to gnd khz internally set pwm switching frequency f set to vcc khz error amplifier f/b and comp pins error amplifier sink current running 60 85 a error amplifier source current running 1.0 98 a error amplifier source current start-up 20 a
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4106 electrical characteristics (continued) electrical characteristics at t j = -40 c to 125 c and vin = 4.5v (unless otherwise noted) parameter test conditions ams4106 min. typ. max. units soft start (ss) 2.22 a f = 250 khz 4.6 internal soft start (10% to 90%) f = 500 khz 2.3 ms power good (pwrgd pin) power good threshold rising voltage 95% f = 250 khz 4 rising edge delay f = 500 khz 2 ms output saturation voltage i sink = 1 ma, vin > 4.5 v 0.05 v output saturation voltage i sink = 1 a, vin = 0 v 0.075 v pwr gd open collector leakage voltage on pwrgd = 6 v 2 a current limit current limit vin = 12 6.1 6.5 7.5 a current limit hiccup time f = 500 khz 4.5 ms thermal shutdown thermal shutdown trip point 145 c thermal shutdown hysteresis (1) 10 c low side external fet drive vin = 4.5v, capacitive load = 1000 pf 15 turn on rise time, (10%/90%) (1) vin = 8 v, capacitive load = 1000 pf 12 ns deadtime (1) vin = 12 v 60 ns vin = 4.5 v sink/ source 7.5 driver on resistance vin = 12 v sink/ source 5 ? output power mo sfets (lx pin) lx node voltage when disabled dc conditions and no load, en = 0 v 0.5 v vin = 4.5 v, idc = 100 ma 1.13 1.42 voltage drop, low side fet and diode vin = 12 v, idc = 100 ma 1.08 1.38 v vin = 4.5 v, bst-lx = 4.5 v, i o = 0.5 a 60 r ds (on) high side power switch vin = 12 v, bst-lx = 8 v, i o = 0.5 a 40 m ? (1) specified by design, not production tested.
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4106 typical performance characteristics line regulation 0.598 0.5985 0.599 0.5995 0.6 0.6005 0.601 0.6015 0.602 5 7 9 1113151719 supply feedback voltage series1 load rulation 0.59 0.595 0.6 0.605 0.61 0123456 amps feedback voltage series1 frequency stability 250 252 254 256 258 260 262 264 266 268 270 5101520 supply voltage frequency series1 250khz 3.3v output efficiency 79 80 81 82 83 84 85 86 87 0246 amp s % 12v efficiency 18v efficiency 5v output efficiency 0.79 0.8 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 0123456 output current 12v eff 18v eeff
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4106 typical performance characteristics ( continued) fig.1 fig.2 normal operating waveform, with internal frequency, power good threshold ~95%, 2.5a load sta rt up. 12v input and 2a load. fig.3 fig.4 power good at light load start up <10ma shutdown fig.5 fig.6 trailing edge non overlap leading edge non ove rlap
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4106 typical performance characteristics ( continued) fig.7 fig.8 load transient test performance 0.5a to 4a/10 s supply current through transient event (0.5 -4a) scale 100mv division, current/ fall time 10 s current scale is 0.5a per division fig. 9 fig. 10 output ripple at 3a load supply ripple current at 4 a (200ma per division) fig. 11 fig. 12 start up current with 2a load input current during start up and shut down. current is 200ma per division.
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4106 detail description and guidelines start up from enable when the enable is low the part is completely shut down with th e nano-amps only of leakage current. when the enable is taken above the turn on threshold it powers up part. there are 2 soft start mechanisms in operation during start up, error amplifier and external. for small output capacita nce (ceramic only solutions), the compensation ca n be used for soft start, and the soft star t pin is left open. for situation requiring slower soft start or wher e large output capacitors are used a separate soft start pin is used. this charges the external capacitor with around 2.2 a current allowing small ceramic capacitors to be used. when power good senses the output is almost at its final value the error amplifie r current is turned on to its normal running current overridin g the startup current. enable connected to vin the part initiates its soft start described above at uvlo threshold of around 4.75v. pwm frequency the default it internally set to 250 khz with the fset pin left open. adding a resistor to ground switches it into the external set mode. a 68k resistor to ground gives approximately 250 khz pwm frequency. care should be taken to keep the resistor close to the part as pick-up on this pin can cause jitter. over-current shutdown if over-current is sensed the part shuts down and initiates the soft start sequence providing a hiccup function. this means tha t shorting the output is non destructive and will run a low supply current. when the output shuts down the low-side fet is turned off giving a tri-state output. this helps prevent negative output voltages being generated in an overload condition where the l oad significantly reduces (due to system reset etc) as a result of the output voltage failing. power good is held low during over current. synchronous operation with an external fet fitted between phase and ground the parts enters synchronous operation. gate time is adaptively controlled allowing large freedom in the choice of output fet. for highest performance the lowe st gate charge fet typically will give the best overall efficiency. the gate drive features a medium drive capability of around 0.5-1a removing the need series gate resistors for most applications . due to the fast switching on the phase node it is important that the fet is placed very close to the part with very short paths for both ground and the phase node. large parasitic inductance can cause large negative spikes on the switch output causing jitter and in se vere circumstances potential circuit malfunction. asynchronous operation a schotty diode can be used in place of the fet for certain a pplications, no other changes are required to accommodate this mode. the gate drive pin should be left open. this is at the ex pense of full load efficiency especially at low output voltage. transient performance is also reduced. for applications when light load hi gher efficiency is required asyn chronous operation is preferred. for applications requiring hot switching asynchronous operation is preferred preventing unwanted dips on the output supply. duty cycle considerations for low input output ratios greater than 50% duty cycle the maximum output should be de-rated to reduce package heating and thermal shutdown. for high input output ratios the maximum frequency is determined by the minimum useable duty cycle, for this part it is around 120ns, shorter duty cycles could cause jitter or pulse skippi ng. for a 0.8v output and a switching frequency of 500khz a maximum input voltage of around 14v can be accommodated at light load rising to about 20v at 4a. bootstrap circuit to allow operation over a very large range the devices uses an internal boost regulator and internal boost diode. the boost capacitor supplies the output bias current re quirements. the regulator is set to the minimum voltage required to give operation at full output current. it is important that the capacitor is large enough to supply the current for the full on time for large du ty 1f is recommended for short duty cycle<10% 100nf is suitable. using a 1f boost capacitor for all applications has no detrimental effect. the voltage across the capacitor is small (a round 3v) so small ceramic case sizes can be used.
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4106 detail description and guidelines (continued) reference circuit a high precision bandgap is used giving a low tc and good supply rejection. the output is attenuated to give a reference voltage of 0.600v making it suitable for very low output voltage applications. compensation the converter is of the current mode to pology considered simplifying the selecti on of compensation components. for most voltages this simple formula is a good starting point ccomp = 15e-9/vout for l = 10e-6 and cout = 44e-6 ccomp is proportional to the output inductors and output capacitor rcomp = 18e3/vout output capacitor cout, is a function of the maximum current and ripple required. multiple capacitors may be required to give the optimum ripple and transient response. the stability is not that critical for varying cout, however to prev ent ocp during fast load transients ccomp, has to be increa sed in proportion to cout. the current gain of the output stage is approximately 6a/volt the running transconductan ce output current is sourcing current 95 a sinking current 85 a this equates to about 600e-6 mohs for best transient response each application is unique and these components should only be used as a starting point.
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4106 application example testing condition for above circuit supply working range 6-20v maximum 5a input voltage @23v gate drive voltage max 8v nominal frequency 258 khz gate and output wave form. small kick on gate drive present at 20v in 5v/4a output
advanced monolithic systems, inc. www.advanced-monolithic.com phone (925) 443-0722 fax (925) 443-0723 ams4106 package dimensions inches (millimeters) unless otherwise noted. 16 lead soic package (s) 0-8 typ 0.010-0.020 (0.254-0.508) s (so-16 ) ams drw# 0702021 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) 0.013-0.020 (0.33-0.51) 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) 0.386-0.393* (9.80-10.0) *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

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