Datasheet

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SLUS274A – JANUARY 1999 – REVISED APRIL 2003
9
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APPLICATION INFORMATION
TIMING DIAGRAM
I OUT
I MAX
I FAULT
Io(nom)
0A
V
CT
2.5V
0.5V
0V
0V
V
OUT
VSS
t
0
t1 t2 t3 t4 t5 t6 t7 t8 t9 t10
t
t
t
Output
Current
C
T
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, V
OUT
pulled
down to VSS.
t5 t5 = t3. Illustrates 3% duty cycle.
t6 t6 = t4
t7
Output short circuit. If V
OUT
is short circuited to ground, CT charges at a higher rate depending upon the values for
VSS and R
PL
.
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.