Rev 1.4a

Copyright

© 1996

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SHUTDOWN OPTIONS

1. Use an external transistor or open-collector comparator to pull

down on the Comp terminal. This will set the PWM latch turning

off both outputs. If the shutdown signal is momentary, pulse-

by-pulse protection can be accomplished as the PWM latch will

be reset with each clock pulse.

2. The same results can be accomplished by pulling down on the

Soft-Start terminal with the difference that on this pin, shutdown

will not affect the amplifier compensation network but must

discharge any Soft-Start capacitor.

3. Apply a positive-going signal to the Shutdown terminal. This

will provide most rapid shutdown of the outputs but will not

immediately set the PWM latch if there is a Soft-Start capacitor.

This capacitor will discharge but with a current of approxi-

mately twice the charging current.

4. The shutdown terminal can be used to set the PWM latch on

a pulse-by-pulse basis if there is no external capacitance on

Soft-Start terminal. Slow turn-on may still be accomplished by

applying an external capacitor, blocking diode, and charging

resistor to the comp terminal. (See SG1524 Application Note).

SG1525A/1527A LAB TEST FIXTURE