LT4250H LINER [Linear Technology], LT4250H Datasheet - Page 9

• Manufacturer Part Number: LT4250H
• Description: Negative 48V Hot Swap Controller
• Manufacturer: LINER [Linear Technology]

APPLICATIONS
A circuit that automatically resets the circuit breaker after
a current fault is shown in Figure 10. 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
Resistor R8 turns off Q2. When a short occurs, the GATE
pin is pulled low and Q3 turns off. Node 2 starts to charge
V
20V/DIV
EE
I
5A/DIV
DRAIN
D
AND
(Q1)
Figure 8. Voltage Step on
Input Supply Waveforms
U
–48V RTN
* DIODES INC. SMAT70A
– 48V
INFORMATION
*
U
500 s/DIV
1N4148
D1
2N2222
Q2
100V
W
1 F
C4
5%
1M
R7
3
50V/DIV
NODE 2
Figure 10. Automatic Restart After Current Fault
2V/DIV
GATE
R8
510k
5%
ZVN3310
(SHORT PIN)
2
–48V RTN
Q3
U
549k
1%
R6
10k
1%
R9
16.5k
549k
1%
1%
R4
R5
EE
.
3
2
UV
OV
3
V
EE
1s/DIV
4
1
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
D1 clamps node 3 one diode drop below V
cycle is set to 10% to prevent Q1 from overheating.
0.02
–48V RTN
5%
R1
* DIODES INC. SMAT70A
– 48V
SENSE
2
(SHORT PIN)
Figure 9. Circuit for Input Steps with Small C2 (<10nF)
–48V RTN
*
4
5
6.49k
549k
C1
470nF
25V
10k
LT4250L
1%
1%
1%
R4
R5
R6
GATE
V
DD
8
6
IRF530
3
2
Q1
UV
OV
V
3
R2
10
5%
EE
4
1
1k, 5%
0.02
R3
5%
R1
SENSE
2
15nF
100V
C2
PWRGD
DRAIN
220
4
5
5%
LT4250L/LT4250H
R7
7
LT4250H
BAT85
1
V
C1
150nF
25V
DD
D1
8
+
GATE
4250 F10a
IRF530
C3
100 F
100V
6
Q1
R2
10
5%
5%
R3
1k
3.3nF
100V
C2
PWRGD
DRAIN
7
EE
1
. The duty
EE
. Diode
C3
0.1 F
100V
4250 F09
+
4250lhf
9
C4
22 F
100V