LT1640AH LINER [Linear Technology], LT1640AH Datasheet - Page 10

• Manufacturer Part Number: LT1640AH
• Description: Negative Voltage Hot Swap Controller
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
LT1640AL/LT1640AH
Under some conditions, a short circuit at the output can
cause the input supply to dip below the UV threshold,
resetting the circuit breaker immediately.
The LT1640A then cycles on and off repeatedly until the
short is removed. This can be minimized by adding a
deglitching delay to the UV pin with a capacitor from UV to
V
resistors at UV, allowing the input supply to recover before
the UV pin resets the circuit breaker.
A circuit that automatically resets the circuit breaker after
a current fault is shown in Figure 9.
10
EE
. This capacitor forms an RC time constant with the
* DIODES INC. SMAT70A
– 48V
GND
*
U
1N4148
U
D1
2N2222
Q2
100V
1 F
C4
1M
5%
R7
3
W
R8
510k
5%
ZVN3310
Figure 9. Automatic Restart After Current Fault
2
Q3
GND
U
9.09k
562k
10k
1%
1%
1%
R4
R5
R6
(SHORT PIN)
3
2
UV
OV
3
V
EE
4
1
0.02
5%
R1
Transistors Q2 and Q3 along with R7, R8, C4 and D1 form
a programmable one-shot circuit. Before a short occurs,
the GATE pin is pulled high and Q3 is turned on, pulling
node 2 to V
occurs, the GATE pin is pulled low and Q3 turns off. Node
2 starts to charge C4 and Q2 turns on, pulling the UV pin
low and resetting the circuit breaker. As soon as C4 is fully
charged, R8 turns off Q2, UV goes high and the GATE
starts to ramp up. Q3 turns back on and quickly pulls node
2 back to V
below V
overheating.
SENSE
2
4
5
EE
. The duty cycle is set to 10% to prevent Q1 from
LT1640AL
C1
150nF
25V
EE
GATE
EE
V
DD
. Diode D1 clamps node 3 one diode drop
. Resistor R8 turns off Q2. When a short
8
6
IRF530
Q1
R2
10
5%
1640A F09b
18k
5%
R3
3.3nF
100V
C2
PWRGD
DRAIN
7
1
+
1640A F09a
C3
100 F
100V