Power Management ICs

PWM Control & PWM/PFM Control Step-Down Switching Regulator (DC-DC Converter ICs) S-8520/8521 Series

The S-8520/8521 series consists of CMOS step-down switching regulator (DC-DC Converter ICs)-controllers with PWM-control (S-8520) and PWM/PFM-switched control (S-8521). These devices contain a reference voltage source, oscillation circuit, error amplifier, and other components.
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 equipment.
With the addition of an external Pch Power MOS FET or PNP transistor, a coil, capacitors, and a diode connected externally, these ICs can function as step-down switching regulators (DC-DC Converter ICs). They serve as ideal power supply units for portable devices when coupled with the SOT-23-5 minipackage, providing such outstanding features as low current consumption. Since this series can accommodate an input voltage of up to 16V, it is also ideal when operating via an AC adapter.
we offer a simulation software as a support tool for circuit design where switching regulator (DC-DC Converter ICs) is used.


Low current consumption
In operation:
60 µA max.,21 µA max. (C & D series),100 µA max. (E & F series)
When powered off:0.5 µA max.
Input voltage
2.5 V to 16 V (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 typ. (A & B series), 60 kHz typ. (C & D series), or 300 kHz typ. (E, F series).
Soft-start function
8 msec. typ. (A & B series) 12 msec. typ.(C & D series), or 4.5 msec. typ. (E, F series).
With a power-off function.
With a built-in overload protection circuit.
Overload detection time: 4 msec. typ. (A series), 14 msec. typ. (C series) or 2.6 msec. typ.(E, F series).
Lead-free products


  • On-board power supplies of battery devices for portable telephones, electronic notebooks, PDAs, and the like
  • Power supplies for audio equipment, including portable CD players 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

Standard Circuit

Standard Circuit