17 pwm control & pwm/pfm control step-down switching regulator-controllers s-8520/8521 series features the s-8520/8521 series consists of cmos step-down switching regulator-controllers with pwm-control (s-8520) and pwm/pfm- switched control (s-8521). the s-8520 series provides low-ripple power, high-efficiency, and excellent transient characteristics thanks to a pwm control circuit capable of varying the duty ratio linearly from 0% up to 100%. the series also contains an error amplifier circuit as well as a soft- start circuit that prevents overshoot at startup. the s-8521 series works with either pwm control or pfm control, and can switch from one to the other. it normally operates using pwm control with a duty ratio of 25% to 100%, but under a light load, it automatically switches to pfm control with a duty ratio of 25%. this series ensures high efficiency over a wide range of conditions, from standby mode to operation of peripheral equip- ment. they serve as ideal power supply units for portable devices when coupled with the sot-23-5 minipackage, providing such outstand- ing features as low current consumption. moreover, oscillation frequency, a 300khz type (e, f series) is also available. ? low current consumption: in operation : 60 m a max. (a & b series) 21 m a max. (c & d series) 100 m a max. (e & f series) when powered off : 0.5 m a max. ? input voltage : 2.5v to 16v (b & d & f series) 2.5v to 10v (a & c & e series) ? output voltage : selectable between 1.5v and 6.0v in steps of 0.1v. ? duty ratio : 0% to 100% pwm control (s-8520) 25% to 100% pwm/pfm-switched control (s-8521) ? the only peripheral components that can be used with this ic are a pch power mos fet or pnp transistor, a coil, a diode, and capacitors. (if a pnp transistor is used, a base resistance and a capacitor will also be required.) ? oscillation frequency: 180 khz type. (a & b series), 60 khz type. (c & d series), or 300 khz type. (e & f series). ? soft-start function: 8 msec type. (a & b series) or 12 msec type (c & d series) or 4.5 msec type (e & f series). ? with power-off function. ? with a built-in overload protection circuit. overload detection time: 4 msec type. (a series) or 14 msec type. (c series) or 2.6 msec type (e & f series). applications ? on-board power supplies of battery devices for portable tele- phones, electronic notebooks, pcas, and the like. ? power supplies for audio equipment, including portable cd play- ers and headphone stereo equipment. ? fixed voltage power supply for cameras, video equipment and communications equipment. ? power supplies for microcomputers. ? conversion from four nih or nicd cells or two lithium-ion cells to 3.3v/3v. ? conversion of ac adapter input to 5v/3v. product list s-8520a25mc-avk-t2 s-8520a30mc-avp-t2 s-8520a33mc-avs-t2 s-8520a50mc-awj-t2 2.5 3.0 3.3 5.0 s-8521a25mc-axk-t2 s-8521a30mc-axp-t2 S-8521A33MC-AXS-T2 s-8521a50mc-ayj-t2 s-8520b25mc-ark-t2 s-8520b30mc-arp-t2 s-8520b33mc-ars-t2 s-8520b50mc-asj-t2 s-8521b25mc-atk-t2 s-8521b30mc-atp-t2 s-8521b33mc-ats-t2 s-8521b50mc-auj-t2 item output voltage (v) s-8520axxmc series s-8521axxmc series s-8520bxxmc series s-8521bxxmc series a, b series (oscillation frequency 180khz) s-8520c25mc-brk-t2 s-8520c30mc-brp-t2 s-8520c33mc-brs-t2 s-8520c50mc-bsj-t2 2.5 3.0 3.3 5.0 s-8521c25mc-btk-t2 s-8521c30mc-btp-t2 s-8521c33mc-bts-t2 s-8521c50mc-buj-t2 s-8520d25mc-bvk-t2 s-8520d30mc-bvp-t2 s-8520d33mc-bvs-t2 s-8520d50mc-bwj-t2 s-8521d25mc-bxk-t2 s-8521d30mc-bxp-t2 s-8521d33mc-bxs-t2 s-8521d50mc-byj-t2 item output voltage (v) s-8520cxxmc series s-8521cxxmc series s-8520dxxmc series s-8521dxxmc series c, d series (oscillation frequency 60khz) s-8520e30mc-bjp-t2 s-8520e33mc-bjs-t2 s-8520e50mc-bkj-t2 3.0 3.3 5.0 s-8521e30mc-blp-t2 s-8521e33mc-bls-t2 s-8521e50mc-bmj-t2 s-8520f30mc-bnp-t2 s-8520f33mc-bns-t2 s-8520f50mc-boj-t2 s-8521f30mc-bpp-t2 s-8521f33mc-bps-t2 s-8521f50mc-bqj-t2 item output voltage (v) s-8520exxmc series s-8521exxmc series s-8520fxxmc series s-8521fxxmc series e, f series (oscillation frequency 300khz) some products described here in are under development. please contact us for samples. block diagram oscillation circuit vin + cin sd tr vin ext l vout cout + + - vss on/off note : the diode inside the ic is a parasitic diode pwm or pwm/pfm- switched control circuit reference voltage source with soft start on/off pin configurations sot-23-5 top view 1 4 3 5 2 pin no. 1 2 3 4 5 pin name on/off v ss v out ext v in function power-off terminal "h" : normal operation (step-down operation) "l" : step-down operation stopped (all circuit deactivated) gnd pin output voltage monitering terminal connection terminal for external transistor ic power supply terminal new
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