Full-bridge PWM controller for high-density power conversion
The UC3875DWP is a full-bridge PWM controller from Texas Instruments designed for offline and DC-DC converters where transformer-coupled isolation and high efficiency are required. Its 1 MHz switching frequency allows the use of smaller magnetics and output capacitors, shrinking the power stage footprint. The controller integrates frequency control, soft-start, and synchronization for multi-phase or paralleled converter designs.
1 MHz switching — what it means for the transformer and filter
At 1 MHz, the UC3875DWP drives the primary-side switches of a full-bridge topology. The 100% duty cycle capability supports the full-bridge phase-shifted modulation scheme.
Supply range and start-up behaviour
The controller operates from a 9.5 V to 20 V supply and has a start-up threshold of 10.75 V, meaning the bias rail must reach 10.75 V before the PWM outputs begin switching. Below that, the IC stays in undervoltage lockout. This matters for the auxiliary winding design: the bias winding needs to deliver at least 10.75 V during start-up and stay within 9.5 V to 20 V during steady-state operation.
Protection and control features
Current limiting fault protection is built in. Soft-start limits inrush during power-up, and the sync input lets multiple units operate at a common frequency.
Package and mounting
Housed in a 28-SOIC wide-body package (7.50 mm width), surface-mount for automated assembly. The 28-SOIC footprint is standard for this controller family, making PCB layout straightforward with existing land patterns.
Lifecycle and sourcing
The UC3875DWP is listed as Active on the Texas Instruments product line. No end-of-life notice or last-time-buy window is in effect.