Datasheet
LTC4416/LTC4416-1
11
4416fa
Overvoltage
V V
R A R C R E
R C R E
V
k
FAIL ETH
=
+
=
•
||
||
. •
2 2 2
2 2
1 222
221 ++
=
24 9 187
24 9 187
13 51
. ||
. ||
.
k k
k k
V
V V
R A R C
R C
V
k k
RESTORE ETH
=
+
=
+
•
. •
.
2 2
2
1 222
221 24 9
244 9
12 07
.
.
k
V=
The over and undervoltage lockout circuits are shown here
working in tandem. It is possible to configure the circuit
for either over or undervoltage lockout by using only one
of the voltage paths and eliminating the components from
the other. Refer to Figure 7 for an LTC4416-1 configured
for overvotlage protection. If the input does not go below
ground, transistor Q1 can be eliminated.
The LTC4416-1 should be used in this configuration rather
than the LTC4416 because the LTC4416-1 will turn-off
rapidly if an over or undervoltage condition is detected.
Refer to Figure 8 for a comparison of the transient response
of the two ICs using the circuit configuration of Figure 6.
The LTC4416 will not turn-off quickly in an overvoltage
or undervoltage condition because the “fast-off” feature
is not enabled. This will cause the output to travel beyond
the desired range.
APPLICATIO S I FOR ATIO
W UU
U
Figure 9 contains a rapidly changing input voltage on a
much smaller time scale in comparison to Figure 8. The
LTC4416 will require the t
E(OFF)
time prior to the rapid pull-
up current being applied. The gate voltage will be pulled
high with I
G(OFF)
which has a minimum current of 500µA.
The discharge time of the gate will be dependent on the
capacitance of the external FET and the initial gate-source
voltage of the circuit. The total time delay will equal:
t t t
t
C V
I
DELAY E OFF DISCHARGE
E OFF
GS
G
= +
= +
( )
( )
(
• ∆
OOFF)
Figure 8. Transient Response of the LTC4416 vs the LTC4416-1
Light Load with a Large Capacitor on V
OUT
Figure 9. Close Up of the Transient Response of the LTC4416-1
to a Rapidly Rising Input
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
Figure 7. LTC4416-1 Configured for Overvoltage Protection
LTC4416-1
H1
E1
GND
E2
H2
G1
V1
V
S
V2
G2
R2C
24.9k
GND
V
IN
R2E
187k
V
TH2
WITH
HYSTERESIS
V
OUT
TO
LOAD
4416 F07
R1A
100k
Q1 Q2
R2A
221k
5
0
0 20
V
IN
V
OUT
LTC4416-1
V
OUT
LTC4416
40
TIME (ms) 4416 F08
60 80
10
VOLTAGE (V)
15
20
V
OUT
LTC4416-1
V
OUT
LTC4416
13.40
13.45
LTC4416-1
GATE DISCHARGE TIME
= C
13.50
13.55
13.60
V
IN
LTC4416
0
0 10 20
TIME (µs) 4416 F09
305 15
t
E(OFF)
25 35 40
VOLTAGE (V)
∆V
I
G(OFF)
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