e-cmos corp. ( www.ecmos.com.tw ) page 1 of 8 4l05n rev. f002 38v 5a synchronous buck converter ec 93 0 3 application circuit general description the EC9303 is a monolithic synchronous buck regulator. the device integrates internal high side and external low side power mosfets, and provides 5a of continuous load current over a wide input voltage o f 8v to 38v. current mode control provides fast transien t response and cycle-by-cycle current limit. an internal soft-start prevents inrush current at t urn-on, this device available in sop8l-ep (exposed pad) package, provides a very compact solution with mini mal external components. features - wide 8v to 38v operating input range - integrated 80m power mosfet switches - output adjustable from vfb(1.0v) to 20v - up to 95% efficiency - internal soft-start. - stable with low esr ceramic output capacitors - fixed 160khz frequency - cycle-by-cycle over current protection - input under/over voltage lockout EC9303
e-cmos corp. ( www.ecmos.com.tw ) page 2 of 8 4l05n rev. f002 38v 5a synchronous buck converter ec 93 0 3 name description bs boot-strap pin. supply high side gate driver. decou ple this pin to lx pin with 0.1uf in power input pin. bypass in to gnd with a suitably l arge capacitor to eliminate noise on sw power switching output. sw is the switching node th at suppli es power to the output. lg gate drive for external low side n-mosfet.. pad ground (connect to gnd). fb feedback input. fb senses the output voltage to reg ulate that voltage. drive fb with a com p compensation node. comp is used to compensate the r egulation control loop. connect en enable control. pull high to turn on. do not float. vdd internal regulator pin pin assignment the package of EC9303 is sop8l-ep(exposed pad); the pin assignment is given by:
e-cmos corp. ( www.ecmos.com.tw ) page 3 of 8 4l05n rev. f002 38v 5a synchronous buck converter ec 93 0 3 ordering/ marking information EC9303nn xx x block diagram package type part number marking marking information sop 8l (exposed pad) EC9303nnmhr EC9303 lllll yyww 1. lllll last five number of lot no. 2. yyww date code mh sop 8(exposed pad) r tape & reel
e-cmos corp. ( www.ecmos.com.tw ) page 4 of 8 4l05n rev. f002 38v 5a synchronous buck converter ec 93 0 3 characteristics symb ol rating unit supply voltage v in C0.3 to +42 v switch node voltage v sw C 0.3 to v in + 0.3 v boost voltage v bs vsw C 0.3 to vsw + 6 v all other pins C0.3 to +6 v lead temperature 260 c storage temperature C65 to +150 c junction temperature t j 150 c output voltage v out vfb to 20 v ambient operating temperature C40 to +85 c thermal resistance from junction to jc 15 c/w thermal resistance from junction to ja 40 c/w absolute maximum ratings (at t a =25c) note: ja is measured with the pcb copper area of approximatel y 1 in 2 (multi-layer). that need connect to exposed pad. electrical characteristics (v in = 12v, t a = +25c, unless otherwise noted.) characteristics symbol conditions min typ max units input voltage range 8 - 38 v shutdown supply current i sd v en = 0v - 0.7 1.3 ma quiescent current i ccq v en = 5.0v; v fb = 1.05v - 0.7 1.5 ma feedback voltage v fb 8v v in 38v 0.98 1.00 1.02 v feedback overvoltage threshold ovp (fb) - 1.1x - v fb high-side switch on resistance (note) r ds(on)1 - 80 - m high-side switch leakage current v en = 0v, v sw = 0v - - 10 a high-side switch current limit minimum duty cycle 5.1 6.0 - a lg rise time t lxr c lx =1000pf - 40 - ns lg fall time t lxf c lx =1000pf - 40 - ns lg driver bias supply voltage - 5 - v oscillation frequency f osc1 - 160 - khz short circuit oscillation frequency f osc2 v fb =< 0.5v - 60 - khz
e-cmos corp. ( www.ecmos.com.tw ) page 5 of 8 4l05n rev. f002 38v 5a synchronous buck converter ec 93 0 3 maximum duty cycle d max - 90 - % minimum on time (note) t on(min) - 220 - ns en lockout threshold voltage enh (lock) - 2.5 - v en lockout hysterisis - 210 - mv input under voltage lockout threshold uvlo v in rising 6.5 7.0 7.5 v input under voltage lockout threshold hysteresis uvlo-hys - 800 - mv input over voltage lockout threshold ovlo vi n rising - 40 - v input over voltage lockout threshold ovlo-hys - 5 - v soft-start period - 3 - ms thermal shutdown t sd - 150 - c thermal shutdown hysterisis t sh - 30 - c note: guaranteed by design. function description the EC9303 is a synchronous rectified, current-mode , step-down regulator. it regulates input voltages from 8v to 38v down to an output voltage as low as v fb , and supplies up to 5a of load current. the EC9303 uses current-mode control to regulate th e output voltage. the output voltage is measured at fb through a resistive voltage divider and amplified through the internal tran conductance error amplifier. the vol tage at the comp pin is compared to the switch current measured inte rnally to control the output voltage. the converter uses internal n-channel mosfet switch es to step-down the input voltage to the regulated output voltage. since the high side mosfet requires a gate voltage greater than the input voltage, a boost ca pacitor connected between sw and bs is needed to drive the high side gate. the boost capacitor is charged from the internal 5v rail when sw is low. when the EC9303 fb pin exceeds 10% of the nominal r egulation voltage of v fb , the over voltage comparator is tripped and the comp pin is discharged to gnd, forc ing the high-side switch off. application information component selection setting the output voltage the output voltage is set using a resistive voltage divider from the output voltage to fb pin. the vol tage divider divides the output voltage down to the feedback voltage by the ratio. thus the output voltage is: for example, v fb =1.00v for a 5.0v output voltage, r2 is 10k , and r1 is 40k .
e-cmos corp. ( www.ecmos.com.tw ) page 6 of 8 4l05n rev. f002 38v 5a synchronous buck converter ec 93 0 3 vin <28v <35v inductor 47uh 33uh inductor selection the inductor is required to supply constant current to the output load while being driven by the switc hed input voltage. a larger value inductor will result in less ripple current that will result in lower ou tput ripple voltage. however, the larger value inductor will ha ve a larger physical size, higher series resistance , and/or lower saturation current. a good rule for determini ng the inductance to use is to allow the peak-to-pe ak ripple current in the inductor to be approximately 30% of the maximum switch current limit. the choice of which style inductor to use mainly de pends on the price vs. size requirements and any em i requirements. typical characteristics
e-cmos corp. ( www.ecmos.com.tw ) page 7 of 8 4l05n rev. f002 38v 5a synchronous buck converter ec 93 0 3
e-cmos corp. ( www.ecmos.com.tw ) page 8 of 8 4l05n rev. f002 38v 5a synchronous buck converter ec 93 0 3 package outlines
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