LT4356IDE-1#TRPBF Linear Technology, LT4356IDE-1#TRPBF Datasheet - Page 17

• Manufacturer Part Number: LT4356IDE-1#TRPBF
• Description: IC OVERVOLT PROT REG 12-DFN
• Manufacturer: Linear Technology

Specifications of LT4356IDE-1#TRPBF

• Voltage - Working: 4 ~ 80V
• Voltage - Clamping: 27V Adj
• Technology: Mixed Technology
• Number Of Circuits: 1
• Applications: Automotive
• Package / Case: 12-DFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power (watts): -
• Lead Free Status / Rohs Status: Compliant

Layout Considerations
To achieve accurate current sensing, Kelvin connection
to the current sense resistor (R
mended. The minimum trace width for 1oz copper foil is
0.02" per amp to ensure the trace stays at a reasonable
temperature. 0.03" per amp or wider is recommended.
Note that 1oz copper exhibits a sheet resistance of about
530μΩ/square. Small resistances can cause large errors in
high current applications. Noise immunity will be improved
signifi cantly by locating resistive dividers close to the pins
with short V
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 4.99k for R2.
The closest standard value for R1 is 59k.
APPLICATIONS INFORMATION
R2 =
R1 =
V
REG
=
OUT
250μA
(
1.25V
16V – 1.25V
1.25V • R1 + R2
CC
≤ 16V, current limit (I
and GND traces.
1.25V
= 5k
R2
(
CC
= 8V to 14V DC with transient up
)
• R2
)
= 16V
= 58.88k
SNS
LIM
in Figure 9) is recom-
) at 5A, low battery
OUT
to
Next calculate the sense resistor, R
C
The closest standard value for C
Finally, calculate R4 and R5 for the 6V low battery threshold
detection:
Choose 100k for R5.
Select 383k 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
R
C
R4 =
P =
6V =
t
OC
SNS
TMR
is then chosen for 1ms of early warning time:
=
14V • 50mV
1.25V • R4 + R5
(
=
=
6V – 1.25V
47nF • 0.85V
10mΩ
50mV
1ms • 5μA
I
45.5μA
LIM
100mV
1.25V
R5
(
=
LT4356-1/LT4356-2
= 70W
50mV
)
5A
• R5
= 50nF
= 0.878ms
)
= 380k
= 10mΩ
TMR
CC
SNS
= 14V.
is 47nF .
, value:
17
4356fa