Overview

The CX7528 is a current-mode PWM control chip with a built-in high-voltage power MOSFET, suitable for applications with power up to 25W. It operates at a fixed switching frequency in PWM mode, which is precisely set internally. Under no-load or light-load conditions, the operating frequency is adjusted internally by the chip. The chip can operate in green mode to reduce losses under light load and improve overall efficiency. It requires very low current during startup and operation, allowing the use of a large resistor in the startup circuit to further reduce standby power consumption.

The chip includes a built-in slope compensation circuit to avoid sub-harmonic oscillation when operating at a large duty cycle, improving system stability.

CX7528 features a built-in leading-edge blanking time to eliminate the impact of the reverse recovery current of the diode in the snubber circuit on the IC.

CX7528 adopts frequency jitter technology, which can effectively improve the system's EMI performance. The system's burst frequency is set above the audio frequency (22KHz), avoiding audible noise during operation.

CX7528 incorporates multiple protection features, including cycle-by-cycle current limiting (OCP), VDD over-voltage protection (OVP), VDD over-voltage clamp & under-voltage lockout (UVLO), over-temperature protection (OTP), etc. The soft driver structure helps improve the system's EMI characteristics.

Features

-  Standby power consumption less than 75mW for full voltage range (90Vac-265Vac) input

-  Built-in soft start to reduce Vds stress on the MOSFET

-  Frequency jitter function for improved EMI performance

-  Burst mode operation to improve light load efficiency and reduce standby power consumption

-  Fixed 65KHz switching frequency

-  Built-in synchronous slope compensation

-  Low startup current and low operating current

-  Built-in leading-edge blanking (LEB) function

-  Built-in overload protection (OLP)

-  Cycle-by-cycle current limiting (OCP)

-  VDD over-voltage protection, under-voltage lockout (UVLO), VDD voltage clamping

-  Secondary side output diode short circuit protection

-  Over-temperature protection (OTP)

-  ASOP6 package

Applications

-  Chargers

-  Power adapters for PDAs, digital cameras, camcorders

-  Set-top box power supplies

-  Open-frame switching power supplies

-  PC auxiliary power