LTC1647-1/
LTC1647-2/LTC1647-3
22
1647fa
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
” LINEAR TECHNOLOGY CORPORATION 1999
LT 1010 REV A • PRINTED IN USA
RELATED PARTS
TYPICAL APPLICATION
PART NUMBER DESCRIPTION COMMENTS
LTC1421 2-Channel Hot Swap Controller 24-Pin, Operates from 3V to 12V and Supports –12V
LTC1422 Hot Swap Controller in SO-8 System Reset Output with Programmable Delay
LT1640AL/LT1640AH Negative Voltage Hot Swap Controller in SO-8 Operates from –10V to –80V
LT1641 High Voltage Hot Swap Controller in SO-8 Operates from 9V to 80V
LT1642 Fault Protected Hot Swap Controller Operates Up to 16.5V, Protected to 33V
LTC1643L/LTC1643H PCI-Bus Hot Swap Controller 3.3V, 5V and ±12V in Narrow 16-Pin SSOP
LT1645 2-Channel Hot Swap Controller Operates from 1.2V to 12V, Power Sequencing
Hot Swapping Two Supplies
Two separate supplies can be independently controlled by
using the LTC1647-3. In some applications, sequencing
between the two power supplies is a requirement. For
example, it may be necessary to ramp-up one supply first
before allowing the second supply to power-up, as well
as requiring that this same supply ramp-down last on
power-down. Figure 14’s circuit illustrates how to program
the delays between the two pass transistors using the
ON1 and ON2 pins (time events t1 to t4). t5 and t7 show
both channels being switched on simultaneously where
sequencing is not crucial.
Some applications require that both channels be gated
off if a fault occurs in one channel. This is accomplished
in Figure 14 by using a crisscross FAULT-to-SENSE
arrangement of R3/R4 and R7/R8. t6 and t9 illustrate the
circuit’s operation.
SENSE1
15 13
FAULT2
5V SUPPLY
V
OUT1
(5A)
FAULT
GND
ON2
ON1
5
ON2
4
FAULT1
3
ON1
2
GND
8
GATE1
LTC1647-3
C1
10nF
R2
10Ω
R1
0.01Ω
Q1
IRF7413
R3
100Ω
C
LOAD
+
V
CC1
SENSE2 GATE2V
CC2
1
14 1216
R8
100Ω
12V SUPPLY
V
OUT2
(2.5A)
C
LOAD
+
R5
10k
R6
10k
R4
4.7k
R7
12k
C3
10nF
*D1
DDZ23
*REQUIRED FOR V
CC
> 10V
Q2
IRF7413
R9
10Ω
R10
0.02Ω
CONNECTOR
V
R1
V
R10
V
ON1
V
ON2
V
OUT1
V
OUT2
t6
t9
1647-1/2/3 F14
t3t2
t1 t4 t5 t7 t8
Figure 14. Hot Swapping Two Supplies
