Power Management ICs

PWM Control & PWM/PFM Control High Frequency Step-Down Switching Regulator (DC-DC Converter ICs) S-8540/8541 Series

The S-8540/8541 series is a family of CMOS step-down switching regulator (DC-DC Converter ICs) controllers with PWM control (S-8540) and PWM/PFM switchover control (S-8541). These devices consist of a reference voltage source, oscillation circuit, an error amplifier, phase compensation circuit, PWM control circuit, current limit circuit. A high efficiency and large current switching regulator (DC-DC Converter ICs) is realized with the help of small external components due to the high oscillation frequency, 300 kHz and 600 kHz.
The S-8540 provides low-ripple voltage, high efficiency, and excellent transient characteristics which come form the PMW control circuit capable of varying the duty ratio linearly from 0% to 100%, the optimized error amplifier, and the phase compensation circuit.
The S-8541 operates under PWM control when the duty ratio is 29% or higher and operates under PFM control when the duty ratio is less than 29% to ensure high efficiency over all load range.
These controllers serve as ideal main power supply units for portable devices due to the high oscillation frequencies together with the small 8-pin MSOP package.


Oscillation frequency
600 kHz (A & B series), 300 kHz (C & D series)
Output voltage
1.5V to 6.0V in steps of 0.1V (A & C series)
Output voltage precision
Feed back type for output voltage (FB)
External components
a transistor, a coil, a diode, and capacitors.
Built-in PWM/PFM switchover control circuit (S-8541)
Duty ratio: 29% (PFM control),
29 to 100% (PWM control)
Current limit circuit
Current is set by an external resistor RSENSE.
Time is set by an capacitor CSS and a resistor RSS.
Shutdown function
Lead-free products


  • Power supplies for PDAs, electric organizers, and portable devices
  • Power supplies for audio equipment such as portable CD players and headphone stereos
  • Main or sub power supplies for notebook computers and peripheral equipment

Standard Circuit

Standard Circuit