Datasheet

LTC4211
32
4211fb
APPLICATIONS INFORMATION
1
V
CC
ON
TIMER
GATE
RESET
FILTER
>V
REF
– 80mV
FAULT
V
OUT
GATE
V
OUT
23 5672A 4 8 A B C
SLOW COMPARATOR ARMED
IF OVERVOLTAGE GOES
AWAY, SECOND CYCLE
CONTINUES
OVERVOLTAGE
IF ANY FAULT HAPPENS
AFTER THIS POINT, THE
CIRCUIT BREAKER TRIPS
AND FAULT LATCHES LOW
OVERVOLTAGE CIRCUIT BREAKER
TRIPS, GATE PULLS DOWN AND
FAULT LATCHES LOW
FAULT IS PULLED LOW (BUT NOT LATCHED)
DUE TO A START-UP OVERVOLTAGE PROBLEM
POWER GOOD
V
FB
> V
REF
POWER BAD
V
FB
< V
REF
FPD
4211 F24
>V
REF
FAULT
LATCHED LOW
Low Side (Output) Overvoltage Protection
A Zener diode can be used in a similar fashion to detect/
protect the system against a supply overvoltage condition
on the load (or low) side of the pass transistor. In this
case, the Zener diode is connected from the load to the
LTC4211’s FILTER pin, as shown in Figure 25. An additional
diode, D1, prevents the FILTER pin from pulling low during
an output short-circuit. Figure 26 illustrates the timing
diagram for a low side output overvoltage condition. In
this example, V
CC
starts up in an overvoltage condition
but the LTC4211 can only sense the overvoltage supply
condition at Time Point 6 when the GATE pin has ramped
up. At Time Point 6, V
FILTER
is greater than 1.236V, the
circuit breaker is tripped, the GATE pin voltage is pulled
to ground and FAULT is asserted low and latched.
Figure 24. High Side Overvoltage Protection