FAN103 PDF – Primary-Side-Regulation PWM Controller

This post explains for the PWM Controller.

The Part Number is FAN103.

The function of this semiconductor is Primary-Side-Regulation PWM Controller.

The package is SOP-8 Pin type

Manufacturer: Fairchild Semiconductor

Preview images :

FAN103 pdf


This third-generation Primary-Side-Regulation (PSR) and highly integrated PWM controller provides several features to enhance the performance of low-power flyback converters. The proprietary topology, TURECURRENT™, of FAN103 enables precise CC regulation and simplified circuit for battery charger applications. A low-cost, smaller and lighter charger results as compared to a conventional design or a linear transformer.

A Primary-Side-Regulation (PSR) PWM Controller is an integrated circuit (IC) used in power supply applications. It is designed to regulate the output voltage on the primary side of the power supply without the need for a secondary-side feedback circuitry.

In a typical power supply system, the output voltage is regulated using feedback information obtained from the secondary side of the transformer. However, in a PSR configuration, the controller operates by modulating the duty cycle of the primary-side switching transistor based on the primary current or other primary-side parameters. This eliminates the need for an optocoupler or other secondary-side feedback components.


FAN103 pinout datasheet


1. Low Standby Power Under 30mW
2. High Voltage Startup
3. Fewest External Component Counts
4. Constant-Voltage (CV) and Constant-Current (CC) Control without Secondary-Feedback Circuitry
5. Green-Mode Function: Linearly-Decreasing PWM Frequency
6. Fixed PWM Frequency at 50kHz with Frequency Hopping to Solve EMI Problem
7. Cable Compensation in CV Mode
8. Peak-Current-Mode Control in CV Mode
9. Cycle-by-Cycle Current Limiting
10. VDD Over-Voltage Protection with Auto Restart
11. VDD Under-Voltage Lockout (UVLO)
12. Gate Output Maximum Voltage Clamped at 15V

FAN103 PDF Datasheet