DESCRIPTION 

 The  UC3873 is a high performance current mode PWM

controller ideally suited for low standby power. Low VDD startup

current make the power reliable on startup design and a large

value resistor could be used in the startup circuit to minimize the

standby power. At no load condition, the IC operates in

power-saving mode for lower standby power, decreasing frequency

for Higher conversion efficiency at light load condition.  

The  UC3873 contains protection with automatic recovery

including OLP (over load protection), programming OTP (over

temperature protection), OVP (over voltage protection), UVLO (VDD

over voltage clamp and under voltage lockout).To protect the

power MOSFET, Gate-drive output is fixed up to 15V max. The

UC3873 contains protection OCP (cycle-by-cycle current limiting).

The internal slope compensation  improves system stability at

high PWM duty cycle output. Leading-edge blanking on current

sense input removes the signal glitch, which offering minimal

external component count in the design. Excellent EMI

performance is achieved with UTC proprietary frequency hopping

technique (ZL201020615247.1) together with soft driver control.

Audio noise is eliminated due to switch frequency more than 20kHz

during operation.

The UC3873 has such applications as: battery charger, power

adaptor, set-top box power supplies, ink jet printers, open-frame SMPS.   

FEATURES

 * UTC proprietary frequency hopping technology for Improved EMI

performance. 

* Power-saving mode for high light-load and standby efficiency

* Soft Start  

* Dynamic peak current limiting for constant output power

* Built-in synchronized slope compensation

* OLP,OVP and VDD clamp for higher security

* Programming OTP for higher security

* Fixed switch frequency 65kHz

* Gate output voltage clamped at 15V

* Low start-up current

* Cycle-by-cycle Current Limiting

* Under voltage lockout (UVLO)

* Few external components required