Datasheet

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UC3724N UC3725N
1:2
PUA
33kW
3
+12V
1nF5kW 100nF
VMOTOR
TO MOTOR
UC1625
UC2625
UC3625
SLUS353C –NOVEMBER 2003–REVISED JUNE 2013 www.ti.com
Fast High-Side N-Channel Driver with Transformer Isolation
A small pulse transformer can provide excellent isolation between the UC3625 and a high-voltage N-Channel
MOSFET while also coupling gate drive power. In this circuit (shown in Figure 14), a UC3724 is used as a
transformer driver/encoder that duty-cycle modulates the transformer with a 150-kHz pulse train. The UC3725
rectifies this pulse train for gate drive power, demodulates the signal, and drives the gate with over 2-A peak
current.
Figure 14. Fast High-Side N-Channel Driver with Transformer Isolation
Both the UC3724 and the UC3725 can operate up to 500 kHz if the pulse transformer is selected appropriately.
To raise the operating frequency, either lower the timing resistor of the UC3724 (1 kΩ min), lower the timing
capacitor of the UC3724 (500 pF min) or both.
If there is significant capacitance between transformer primary and secondary, together with very high output
slew rate, then it may be necessary to add clamp diodes from the transformer primary to 12 V and ground.
General purpose small signal switching diodes such as 1N4148 are normally adequate.
The UC3725 also has provisions for MOSFET current limiting. Consult the UC3725 data sheet for more
information on implementing this.
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Product Folder Links: UC1625 UC2625 UC3625