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UC3973 Datasheet Preview

UC3973 Datasheet

PWM CONTROLLER

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UNISONIC TECHNOLOGIES CO., LTD
UC3973
LINEAR INTEGRATED CIRCUIT
LOW COST POWER-SAVING
MODE PWM CONTROLLER
FOR FLYBACK CONVERTERS
DESCRIPTION
The UC3973 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 UC3973 contains protection with automatic recovery
including OLP (over load protection), programming OTP (over
SOP-8
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 UC3973 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 UC3973 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
ORDERING INFORMATION
Ordering Number
UC3973G-S08-R
Package
SOT-8
Packing
Tape Reel
www.unisonic.com.tw
Copyright © 2015 Unisonic Technologies Co., Ltd
1 of 10
QW-R103-086.B




UTC

UC3973 Datasheet Preview

UC3973 Datasheet

PWM CONTROLLER

No Preview Available !

UC3973
MARKING
PIN CONFIGURATION
LINEAR INTEGRATED CIRCUIT
PIN DESCRIPTION
PIN NO.
1
2
3
4
5
6
7
8
PIN NAME
GND
FB
VIN
NC
RT
SENSE
VDD
GATE
PIN TYPE
P
I
I
-
I
I
P
O
DESCRIPTION
Ground.
Feedback input pin. The PWM duty cycle is determined by voltage level
into this pin and SENSE pin input.
Connected through a start up resistor to line voltage for VCC ON
No Connection
Connected through a NTC resistor to GND for OTP.
Current sense input pin. Connected to MOSFET current sensing resistor
node.
Power supply.
The totem-pole output driver for driving the power MOSFET.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
2 of 10
QW-R103-086.B


Part Number UC3973
Description PWM CONTROLLER
Maker UTC
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