LT4356CDE-1-PBF LINER [Linear Technology], LT4356CDE-1-PBF Datasheet - Page 14

• Manufacturer Part Number: LT4356CDE-1-PBF
• Description: Overvoltage Protection Regulator and Inrush Limiter
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
LT4356-1
Design Example
As a design example, take an application with the follow-
ing specifi cations: V
to 80V, V
detection at 6V, and 1ms of overvoltage early warning
(Figure 9).
First, calculate the resistive divider value to limit V
16V during an overvoltage event:
Set the current through R1 and R2 during the overvoltage
condition to 250μA.
Choose 4.99kΩ for R2.
The closest standard value for R1 is 59kΩ.
Next calculate the sense resistor, R
14
R2 =
R1 =
R
V
REG
SNS
=
OUT
250µA
(
=
1.25V
16V – 1.25V
1.25V • R1 + R2
50mV
I
≤ 16V, current limit (I
LIM
1.25V
= 5k
R2
(
=
CC
50mV
= 8V to 14V DC with transient up
)
5A
• R2
)
= 10m
= 16V
= 58.88k
LIM
SNS
) at 5A, low battery
, value:
OUT
to
C
The closest standard value for C
Finally, calculate R4 and R5 for the 6V low battery threshold
detection:
Choose 100kΩ for R5.
Select 383kΩ for R4.
The pass transistor, Q1, should be chosen to withstand
the output short condition with V
The total overcurrent fault time is:
The power dissipation on Q1 equals to:
These conditions are well within the Safe Operating Area
of IRLR2908.
TMR
C
R4 =
P =
6V =
t
OC
TMR
is then chosen for 1ms of early warning time:
=
14V • 50mV
1.25V • R4 + R5
(
=
6V – 1.25V
47nF • 0.85V
10m
1ms • 5µA
45.5μA
100mV
1.25V
R5
(
= 70W
)
• R5
= 50nF
= 0.878ms
)
= 380k
TMR
CC
= 14V.
is 47nF .
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