SG3525

Overview

The SG3525 is a voltage-mode pulse width modulator integrated circuit designed for switching power supply applications. It operates within an input voltage range of 8 V to 35 V and features a +5.1 V reference trimmed to ±1%. The oscillator frequency range spans from 100 Hz to 500 kHz, with synchronization capabilities via a dedicated terminal. Key electrical characteristics include adjustable dead-time control, internal soft-start circuitry, and input undervoltage lockout with hysteresis. The output stage utilizes a totem-pole design capable of sourcing or sinking over 200 mA, employing NOR logic for the OFF state.

Feature Summary

• Dual source/sink output drivers with high current capability
• Internal soft-start circuitry requiring only an external timing capacitor
• Pulse-by-pulse shutdown and latching PWM to prevent multiple pulses
• Adjustable dead-time control via a single resistor

Applications

• DC-DC converters
• DC-AC inverters
• Motor control circuits
• Battery chargers

Procurement Notes

Verify the specific manufacturer suffix (e.g., AN, A) as performance specifications such as maximum switching frequency and operating temperature ranges may vary between vendors like ON Semiconductor, STMicroelectronics, or others. Confirm package type compatibility, typically DIP-16 or SO-16, against the target PCB footprint. Ensure the component grade matches the application requirements, distinguishing between commercial, industrial, or military variants if specified in the datasheet.

Selection Notes

Select the SG3525 variant based on the required operating temperature range and maximum switching frequency. Verify that the output drive current meets the gate charge requirements of the connected power MOSFETs. Consider the need for external synchronization by checking the availability of the sync terminal. Evaluate the undervoltage lockout threshold and hysteresis to ensure stable operation under varying input voltage conditions.

Part Context

The SG3525 series is a widely used voltage-mode PWM controller originally developed by Silicon General. It serves as a standard solution for designing efficient switching power supplies. The device integrates essential functions such as error amplification, oscillator control, and output driving into a single package, reducing the external component count compared to discrete solutions. Its versatility supports various topologies including buck, boost, and flyback configurations.

Replacement Considerations

The SG2525A is a confirmed substitute part number offering similar functionality. Verify pinout compatibility and electrical parameter alignment before substitution.