LTC1559 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1559' PDF : 12 Pages View PDF
LTC4416/LTC4416-1
APPLICATIO S I FOR ATIO
Overvoltage
VFAIL
=
VETH
•
R2A +R2c||R2E
R2c||R2E
=
1.222V
•
221k+ 24.9k||187k
24.9k || 187k
=
13.51V
VRESTORE
=
VETH
•
R2A +R2c
R2c
=
1.222V
•
221k + 24.9k
24.9k
=
12.07V
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.
VIN
VTH2 WITH
HYSTERESIS
R2C
24.9k
GND
R2A R1A
221k 100k
LTC4416-1
H1
G1
R2E
187k
E1
V1
GND
VS
E2
V2
H2
G2
Q1 Q2
VOUT
TO
LOAD
4416 F07
Figure 7. LTC4416-1 Configured for Overvoltage Protection
Figure 9 contains a rapidly changing input voltage on a
much smaller time scale in comparison to Figure 8. The
LTC4416 will require the tE(OFF) time prior to the rapid pull-
up current being applied. The gate voltage will be pulled
high with IG(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:
tDELAY = tE(OFF) + tDIScHARGE
=
tE(OFF)
+
cGS • ∆V
IG(OFF)
20
VOUT
LTC4416
15
10
VOUT
LTC4416-1
VOUT
LTC4416-1
5 VIN
VOUT
LTC4416
0
0
20
40
60
80
TIME (ms)
4416 F08
Figure 8. Transient Response of the LTC4416 vs the LTC4416-1
Light Load with a Large Capacitor on VOUT
13.60
13.55
13.50
13.45
13.40
0
0
VIN
LTC4416
LTC4416-1
tE(OFF)
GATE DISCHARGE TIME
=
C
∆V
IG(OFF)
5 10 15 20 25 30 35 40
TIME (µs)
4416 F09
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.
4416fa
11
Share Link: 
