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| US1651 Datasheet, PDF (6/7 Pages) Unisonic Technologies – PRIMARY-SIDE REGULATION PWM POWER SWITCH | |||
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US1651
Preliminary
CMOS IC
ï® OPERATION DESCRIPTION (Cont.)
Adjustable Drive Capability
The internal power MOSFET in UTC US1651 is driven by a dedicated gate driver for power switch control. Too
weak the gate drive strength results in higher conduction and switch loss of MOSFET while too strong gate drive
compromises EMI. A good tradeoff is achieved through the built-in totem pole gate design with right output strength
control. The gate drive strength can be adjusted externally by a resistor connected between VDD and VDDG, The low
idle loss and good EMI system design is possible with this dedicated control scheme.
Protection Control
Good power supply system reliability is achieved with its comprehensive protection features including VDD
over-voltage protection, VDD Clamp, GATE Clamp, Power on soft start, Cycle-by-cycle current limiting, short circuit
protection, leading edge blanking, OTP and UVLO, etc.
VDD is supplied by transformer auxiliary winding output. The output of UTC US1651 is shutdown when VDD drops
below VTH(OFF) and the power converter enters power on start-up sequence thereafter.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
6 of 7
QW-R129-005.a
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