1/9 october 2002 n up to 450ma load currents n 200khz high-frequency current-mode pwm n 85% to 96% efficiencies n 33 m h or 100 m h pre-selected inductor value, no component design required n 0.8ma quiescent current n 0.3a shutdown supply current n adjustable output voltage n overcurrent, soft-start and undervoltage lockout protection n cycle-by-cycle current limiting n package available: dip-8 and so-8 description the st730a is a 5v output cmos, step-down switching regulator. the st730a accepts inputs between 5.2v and 11v and delivers 450ma. typical efficiencies are 85% to 96%. quiescent supply current is 0.8ma and only 0.3 m a in shutdown mode. the output does not exhibit frequency over this specified range. pulse-width modulation (pwm) current-mode control provides precise output regulation and excellent transient responses. output voltage accuracy is guaranteed to be 5% over line, load, and temperature varations. fixed-frequency switching and absence of subharmonic ruipple allows easy filtering of output ripple and noise, as well as the use of small external components. this regulators require only a single inductor value to work in most applications, so no inductor design is necessary. typical applications are: cellular phones & radios, portable instruments, portable communications equipments and computer peripherals. st730a 5v step-down, current-mode pwm dc-dc converters schematic diagram dip-8 so-8
st730a 2/9 absolute maximum ratings absolute maximum ratings are those values beyond which damage to the device may occur. functional operation under these conditi on is not implied. thermal data (*) this value depends from thermal design of pcb on which the device is mounted. ordering codes symbol parameter2 value unit v cc dc input voltage -0.3 to 12 v v lx switch pin voltage -0.3 to (v cc + 0.3) v v shdn shutdown voltage (shdn) -0.3 to (v cc + 0.3) v v s ,v c soft start (ss) and compensation capacitor (cc) pins voltage -0.3 to (v cc + 0.3) v i lx switching peak current 2a i ref reference current 2.5 ma p tot continuous power dissipation at t a =70c (dip-8) (so-8) 550 344 mw mw t stg storage temperature range -40 to +150 c t op operating junction temperature range (ac series) (ab series) 0 to +70 -40 to +85 c c symbol parameter so-8 dip-8 unit r thj-amb thermal resistance junction-ambient (*) 160 100 c/w type dip8 so-8 so-8 (t&r) st730ab st730abn ST730ABD ST730ABD-tr st730ac st730acn st730acd st730acd-tr
st730a 3/9 connection diagram (top view) pin description pin n symbol name and function 1 shdn shutdown control (active low): if connected to gnd the ic is in shutdown. connect to v cc for normal operation (on mode) 2 ref reference output voltage: (1.25v): bypass to gnd with a capacitor that does not exceed 47nf 3 ss soft start: a capacitor between ss and gnd provides soft-start and short-circuit protections. 4 cc compensation capacitor input: externally compensates the outer (voltage) feedback loop. connect to out with 330pf capacitor 5 out output voltage sense input: provides regulation of feedback sensing. connect to 5v output. 6 gnd ground 7 lx switch output. drain of internal p-channel power mosfet 8v cc supply voltage input. bypass to gnd with 1 m f ceramic capacitance and large value electrolytic capacitor in parallel. the 1 m f capacitor must be as close as possible to the gnd and v cc pins
st730a 4/9 electrical characteristics (v cc =5v, i o = 0ma, t a = t min to t max , unless otherwise specified.) typical application circuit symbol parameter test conditions min. typ. max. unit v cc input voltage 4 11 v v o output voltage v cc = 6 to 11v i o =0 to 450ma 4.75 5 5.25 v d v o line regulation v cc = 5.2 to 11v 0.15 %/v d v o load regulatio i o = 0 to 450ma 0.005 %/ma h power efficency i o =300ma 92 % i supply supply current on mode off mode, shdn =0 0.8 0.3 2.5 100 ma m a v ih shdn input high threshold 2 v v il shdn input low threshold 0.25 v i shdn shutdown input leakage current 1 m a v lock under voltage lockout v cc falling 2.7 3 v r ds(on) lx on resistance i lx =500ma 0.5 w i lx lx leakage current v cc = 12v v lx = 0v 1 m a v ref reference voltage t a = 25c 1.17 1.24 1.31 v d v ref temperature reference drift 50 ppm/c f osc switching frequency c series b series 180 160 200 220 280 khz r c compensation pin impedance 7500 w
st730a 5/9 typical performance characteristics (unless otherwise specified t j = 25c figure 1 : efficency vs output current figure 2 : supply current vs temperature figure 3 : oscillator frequency vs temperature figure 4 : oscillator frequency vs input voltage figure 5 : peak inductor current vs output current figure 6 : output voltage vs output current
st730a 6/9 figure 7 : switching waveforms, continuous conduction figure 8 : switching waveforms, discontinuous conduction figure 9 : line transient figure 10 : load transient v i = 6v to 11v , i o = 300 m a v i = 6v to 11v , i o = 300 m a
st730a 7/9 dim. mm. inch min. typ max. min. typ. max. a 3.3 0.130 a1 0.7 0.028 b 1.39 1.65 0.055 0.065 b1 0.91 1.04 0.036 0.041 b 0.5 0.020 b1 0.38 0.5 0.015 0.020 d 9.8 0.386 e 8.8 0.346 e 2.54 0.100 e3 7.62 0.300 e4 7.62 0.300 f 7.1 0.280 i 4.8 0.189 l 3.3 0.130 z 0.44 1.6 0.017 0.063 plastic dip-8 mechanical data p001f
st730a 8/9 dim. mm. inch min. typ max. min. typ. max. a 1.75 0.068 a1 0.1 0.25 0.003 0.009 a2 1.65 0.064 a3 0.65 0.85 0.025 0.033 b 0.35 0.48 0.013 0.018 b1 0.19 0.25 0.007 0.010 c 0.25 0.5 0.010 0.019 c1 45? (typ.) d 4.8 5.0 0.189 0.196 e 5.8 6.2 0.228 0.244 e 1.27 0.050 e3 3.81 0.150 f 3.8 4.0 0.149 0.157 l 0.4 1.27 0.015 0.050 m 0.6 0.023 s ? (max.) so-8 mechanical data 0016023 8
st730a 9/9 information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no res ponsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result f rom its use. no license is granted by implication or otherwise under any patent or patent rights of stmicroelectronics. specificati ons mentioned in this publication are subject to change without notice. this publication supersedes and replaces all information previously supplied. stmicroelectronics products are not authorized for use as critical components in life support devi ces or systems without express written approval of stmicroelectronics. ? the st logo is a registered trademark of stmicroelectronics ? 2002 stmicroelectronics - printed in italy - all rights reserved stmicroelectronics group of companies australia - brazil - canada - china - finland - france - germany - hong kong - india - israel - italy - japan - malaysia - malt a - morocco singapore - spain - sweden - switzerland - united kingdom - united states. ? http://www.st.com
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