UCC2912

UCC3912

PROGRAMMABLE HOT SWAP POWER MANAGER

SLUS241D − MARCH 1994 - REVISED NOVEMBER 2003

7

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APPLICATION INFORMATION

For a resistive load of value RL, the value of COUT(max) can be estimated from:

C

OUT(max) [

28

103

CT

RL

n

1

1*

V

OUT

I

MAX

RL

The overcurrent comparator senses both the DAC output and a representation of the output current. When the

output current exceeds the programmed level the timing capacitor CT charges with 36 µA of current. If the fault

occurs for the time it takes for CT to charge up to 1.5 V, the fault latch is set and the output switch is opened.

The output remains opened until CT discharges to 0.5 V with a 1.2-µA current source. Once the 0.5 V is reached

the output is enabled and will either appear as a switch, if the fault is removed, or a current source if the fault

remains. If the over current condition is still present, then CT will begin charging, starting the cycle over, resulting

in approximately a 3% on time.

UDG-94019-1

Figure 3. UCC3912 On-Time Circuitry