UCC2913

UCC3913

SLUS274A – JANUARY 1999 – REVISED APRIL 2003

9

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APPLICATION INFORMATION

TIMING DIAGRAM

Io(nom)

0A

2.5V

0.5V

0V

0V

VSS

t

t

t

Output

Current

Voltage

(w/respect to VSS)

Output

Voltage

(w/respect to GND)

TIME

DESCRIPTION

TIME

DESCRIPTION

t0

Safe condition. Output current is nominal, output voltage is at the negative rail, VSS.

t1

Fault control reached. Output current reaches the programmed fault value. CT begins to charge at approximately

36-

µA.

t2

Maximum current reached. Output current reaches the programmed maximum level and becomes a constant current

with value IMAX.

t3

Fault occurs. CT has charged to 2.5V. Fault output goes high. The FET turns off allowing no output current to flow.

VOUT floats up to ground.

t4

Retry. CT has discharged to 0.5 V, but fault current is still exceeded, CT begins charging again, FET is on, VOUT pulled

down to VSS.

t5

t5 = t3. Illustrates 3% duty cycle.

t6

t6 = t4

t7

Output short circuit. If VOUT is short circuited to ground, CT charges at a higher rate depending upon the values for

VSS and RPL.

t8

Fault occurs. Output is still short circuited, but the occurrence of a fault turns the FET off so no current is conducted.

t9

t9 = t4. Output short circuit released, still in fault mode.

t10

t10 = t0. Fault released. Safe condition. Return to normal operaton of the circuit breaker.