UNISONIC TECHNOLOGIES CO., LTD
UC3873B
LINEAR INTEGRATED CIRCUIT
LOW COST POWER-SAVING
MODE PWM CONTROLLER
FOR FLYBACK CONVERTERS
4
5
6
DESCRIPTION
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2
The UC3873B is a high performance current mode PWM
1
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.
SOT-26
The UC3873B 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 16V max. The UC3873B 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 UC3873B 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 * Programming OTP for higher security
performance.
* Fixed switch frequency 100kHz
* Gate output voltage clamped at 15V
* Low start-up current
* 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
* -500/+500mA gate driver
* Cycle-by-cycle Current Limiting
* Under voltage lockout (UVLO)
* Few external components required
ORDERING INFORMATION
Ordering Number
Package
SOT-26
Packing
Lead Free
Halogen Free
UC3873BG-AG6-R
UC3873BL-AG6-R
Tape Reel
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