LTC1422 Linear Technology, LTC1422 Datasheet - Page 16

• Manufacturer Part Number: LTC1422
• Description: Hot Swap Controller
• Manufacturer: Linear Technology

RELATED PARTS
PART NUMBER
LTC1421
LT1640L/LT1640H
LT1641
LT1642
LTC1643L/LTC1643H
LT1645
LTC1647
LTC1422
TYPICAL
Current Sensing with 48V Applications
In the LTC1422, the SENSE pin threshold is 50mV below
the V
nected to the V
resistor is connected to the negative terminal of the 48V
supply. The circuit in Figure 17 translates the current in the
sense resistor to a resistor connected to the LTC1422
SENSE pin.
The voltage drop across the current sense resistor R
is proportional to the load current I
across R
forced on R
16
48V
CC
+
–
FUSE
pin. Typically, the current sense resistor is con-
SENSE
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] FAX: [phone] www.linear-tech.com
MIRROR
APPLICATION
R1
36k
5%
R2
1.2k
5%
is buffered by the op amp follower and is
CC
pin, but in 48V applications the sense
.
C1
0.47 F
25V
DESCRIPTION
Hot Swap Controller
Negative Voltage Hot Swap Controller in SO-8
High Voltage Hot Swap Controller in SO-8
Fault Protected Hot Swap Controller
PCI-Bus Hot Swap Controller
2-Channel Hot Swap Controller
Dual Hot Swap Controller in SO-8 or SSOP-16
1
2
3
4
RESET
ON
TIMER
GND
LTC1422
U
LOAD
SENSE
1N755A
GATE
V
7.5V
FB
CC
D1
Figure 17. Switching 48V with Current Sensing
. The voltage drop
8
7
6
5
R5
15k
5%
I
I
VN2222L
MIRROR
MIRROR
Q2
SENSE
R
10
5%
R
39
5%
TRIP
MIRROR
The mirror current can be described as: I
R
trip resistor R
50mV across R
low (50mV = I
R
circuit can be used anywhere the current sense resistor is
not tied to V
C4
1 F
25V
SENSE
TRIP
). This example uses a 48V input but this translation
LT1006
/R
7
4
24-Pin Multiple Supplies
Operates from –10V to – 80V
Operates from 9V to 80V
Operates Up to 16.5V, Protected to 33V
3.3V, 5V and 12V in Narrow 16-Pin SSOP
Operates from 1.2V to 12V, Power Sequencing
Two ON Pins, Operates from 2.7V to 16.5V
MIRROR
OPAMP
+
–
COMMENTS
CC
3
2
MIRROR
.
TRIP
TRIP
. The mirror current flows through the
. When the mirror current generates
R6
1M
5%
R7
270k
5%
, the LTC1422 will latch the GATE pin
• R
TRIP
R4
10k
5%
1422fa LT/TP 0300 2K REV A • PRINTED IN USA
C2
0.1 F
25V
LINEAR TECHNOLOGY CORPORATION 1997
= I
0.22 F
100V
C5
LOAD
10
5%
R3
• R
100 F
100V
SENSE
MIRROR
C3
+
/R
Q1
IRF530
R
0.02
5%
1422 F17
SENSE
I
LOAD
= I
MIRROR
LOAD
LOAD
+
–
•
•