GATE

REFERENCE

GENERATOR

VIN

10.75V/9.25V

VREF

GND

INTERNAL

BIAS

4.75V

TO SOFT -

START

LOGIC

UC1875-SP

www.ti.com

SLUSAQ9

– DECEMBER 2011

APPLICATION INFORMATION

Undervoltage Lockout Section

reference generator will be off, the fault latch is reset, the soft-start pin is discharged, and the outputs are actively

held low. When VIN exceeds the upper UVLO threshold, the reference generator turns on. All else remains in the

shut-down mode until the output of the reference, VREF, exceeds 4.75 V.

Figure 3. Undervoltage Circuit

The high frequency oscillator may be either free-running or externally synchronized. For free-running operation,

the frequency is set via an external resistor and capacitor to ground from the FREQSET pin.

Figure 4. Simplified Oscillator Schematic

Copyright

© 2011, Texas Instruments Incorporated

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Product Folder Link(s): UC1875-SP