ltc4357cms8-trpbf Linear Technology Corporation, ltc4357cms8-trpbf Datasheet - Page 8

• Manufacturer Part Number: ltc4357cms8-trpbf
• Description: Positive High Voltage Ideal Diode Controller
• Manufacturer: Linear Technology Corporation

LTC4357
APPLICATIONS INFORMATION
V
In the event of an input short, parasitic inductance between
the input supply of the LTC4357 and the load bypass
capacitor may cause V
operating voltage. This causes the turn-off time (t
increase.
To preserve the fast turn-off time, local output bypassing
of 39μF is suffi cient at voltages less than 30V. At higher
voltages, 100μF is adequate. As an alternative to local
bypassing, a 100Ω, 0.1μF RC hold-up circuit on the V
pin can be used, shown in Figure 2. In applications with
unusually large inductance or load current greater than
10A, use 100Ω and 1μF .
Design Example
The following design example demonstrates the calcula-
tions involved for selecting components in a 12V system
with 10A maximum load current (see Figure 3).
8
DD
12V
12V
V
V
IN
IN
Hold-Up Circuit
Figure 2. Two Methods of Protecting Against Collapse
of V
DD
From Input Short and Stray Inductance
IN
IN
Si4874DY
Si4874DY
LTC4357
LTC4357
GND
GND
GATE
GATE
DD
to glitch below its minimum
OUT
OUT
V
V
DD
DD
R1
100Ω
C1
0.1μF
4357 F02
C
39μF
BYPASS
OFF
) to
DD
First, calculate the R
the desired forward drop at full load. Assuming V
= 0.1V,
The Si4874DY offers a good solution, in an S8 package
with R
The maximum power dissipation in the MOSFET is:
With less than 39μF of local bypass, the recommended RC
values of 100Ω and 0.1μF were used in Figure 3.
Since BV
ing is unnecessary.
P = I
R
R
DS(ON)
DS(ON)
V
V
12V
12V
IN1
IN2
DS(ON)
LOAD
DSS
IN
IN
2
+ V
10m
= 10mΩ(max) and BV
V
I
• R
LOAD
DROP
Figure 3. 12V, 10A Diode-OR
IN
DS(ON)
Si4874DY
Si4874DY
LTC4357
LTC4357
is much less than 100V, output clamp-
GND
GND
GATE
GATE
=
DS(ON)
0.1V
10A
= (10A)
OUT
OUT
of the MOSFET to achieve
V
V
DD
DD
2
• 10mΩ = 1W
DSS
100Ω
100Ω
4357 F03
0.1μF
0.1μF
of 30V.
V
TO LOAD
OUT
DROP
4357fb