Datasheet
LT4356-1/LT4356-2
16
4356fb
For more information www.linear.com/LT4356-1
ApplicAtions inForMAtion
Shutdown
The LT4356 can be shut down to a low current mode when
the voltage at the SHDN pin goes below the shutdown
threshold of 0.6V. The quiescent current drops to 7µA for
the LT4356-1 and 60µA for the LT4356-2 which leaves the
auxiliary amplifier on.
The SHDN pin can be pulled up to V
CC
or below GND by
up to 60V without damaging the pin. Leaving the pin open
allows an internal current source to pull it up and turn
on the part while clamping the pin to 2.5V. The leakage
current at the pin should be limited to no more than 1µA
if no pull up device is used to help turn it on.
Supply Transient Protection
The LT4356 is guaranteed to be safe from damage with
supply voltages up to 100V. Nevertheless, voltage tran
-
sients above 100V may cause permanent damage. During
a short-circuit condition, the large change in current flowing
through power supply traces and associated wiring can
cause inductive voltage transients which could exceed
100V. To minimize the voltage transients, the power trace
parasitic inductance should be minimized by using wide
traces. A small surge suppressor, D2, in Figure 9, at the
input will clamp the voltage spikes.
A total bulk capacitance of at least 22µF low ESR electro
-
lytic is required close to the source pin of MOSFET Q1. In
addition, the bulk capacitance should be at least 10 times
larger than the total ceramic bypassing capacitor on the
input of the DC/DC converter.
Figure 8. Overvoltage Regulator with P-Channel MOSFET
Reverse Input Protection
Figure 9. Overvoltage Regulator with Low-Battery Detection
C
TMR
0.1µF
R
SNS
10mΩ
Q1
IRLR2908
Q2
Si4435
V
IN
12V
V
OUT
12V, 3A
CLAMPED
AT 16V
4356 F08
LT4356S
GND TMR
10 1
OUTSNS
35
SHDN
7
A
OUT
11
IN
+
12
V
CC
6
EN
FLT
FB
9
8
2
R2
4.99k
R1
59k
GATE
4
R6
10k
D1
1N5245
15V
R3
10Ω
D2*
SMAJ58CA
*DIODES INC.
C
TMR
47nF
*SANYO 25CE22GA
R3
10Ω
R
SNS
10mΩ
Q1
IRLR2908
D2
SMAJ58A
V
IN
4356 F09
LT4356S
GND TMR
OUTGATESNS
IN
+
SHDN
A
OUT
FAULT
EN
FLTUNDERVOLTAGE
FB
C
L
*
22µF
DC-DC
CONVERTER
GND
SHDN
V
CC
R2
4.99k
R4
383k
R5
100k
R1
59k
10 1
345
7
12
V
CC
6
11
2
9
8
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