1 Features

• Stable continuous conduction mode (CCM)

operation with internal slope compensation

• Fixed-frequency operation of 65kHz or 100kHz

• Secondary-side regulation (SSR) with opto-coupler

• Frequency foldback and burst mode for improved

light-load efficiency

• Frequency dithering for improved EMI

performance

• Gate source/sink capability: 300mA/500mA

• Internal 4ms soft-start

• Robust protection features:

– Over-voltage and Under-voltage lockout

– Output over-power protection (OPP)

– Output short-circuit (OSC) protection

– Output over-voltage (OVP) protection

– Cycle-by-cycle peak over-current limit

– External over-temperature, over-voltage

protection (OTP, OVP) and brownout detection

on FLT pin

– Internal thermal shutdown

2 Applications

• Isolated offline AC/DC power supply

• Appliances

– Battery pack and charger

– Small home appliances

– Major appliance

• Grid Infrastructure

– Electricity meter

– String inverter

– Micro-inverter

• Power Delivery

– Server PSU with 12V output

3 Description

UCC28750 is a highly-integrated current-mode,

continuous-conduction-capable, PWM controller

optimized for high performance, low standby

power, and cost effective offline flyback converter

applications using an opto-coupler. During light-load

conditions the device enters frequency foldback and

burst modes, improving light-load efficiency. The

burst-mode algorithm used in UCC28750 controls

the minimum effective switching frequency to prevent

audible noise during light-load conditions. Frequency

dithering improves EMI performance, and is active

in normal, frequency foldback, and power boost

operations.

UCC28750 provides protection features that enable

a robust converter design with minimal external

components. Output over-power protection (OPP) and

cycle-by-cycle over-current limit protect the load and

power-stage components from electrical stress. Overvoltage

and under-voltage lockout (OVLO and UVLO)

prevent switching in unwanted input conditions.

The FLT pin provides line brown-out sensing and

protection, or external over-temperature and overvoltage

protection, depending on the device variant.

The FLT pin is also used to disable the device

through external control by pulling the pin to ground,

regardless of the device variant.