LTC1422C View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
LTC1422C Datasheet PDF : 16 Pages
| |||
LTC1422
TYPICAL APPLICATION
Current Sensing with 48V Applications
In the LTC1422, the SENSE pin threshold is 50mV below
the VCC pin. Typically, the current sense resistor is con-
nected to the VCC pin, but in 48V applications the sense
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 mirror current can be described as: IMIRROR = ILOAD •
RSENSE/RMIRROR. The mirror current flows through the
trip resistor RTRIP. When the mirror current generates
50mV across RTRIP, the LTC1422 will latch the GATE pin
low (50mV = IMIRROR • RTRIP = ILOAD • RSENSE/RMIRROR •
RTRIP). This example uses a 48V input but this translation
circuit can be used anywhere the current sense resistor is
not tied to VCC.
The voltage drop across the current sense resistor RSENSE
is proportional to the load current ILOAD. The voltage drop
across RSENSE is buffered by the op amp follower and is
forced on RMIRROR.
+
R5
R1
15k
36k
5%
LTC1422
5%
1 RESET VCC 8
RTRIP
10Ω
2 ON SENSE 7
5%
3 TIMER GATE 6
C5
0.22µF
100V
C3 +
100µF
100V
LOAD
–
R4
R3
10k
10Ω
5%
5%
Q1
IRF530
R2
1.2k
4 GND
FB 5
R6
1M
5%
IMIRROR
5%
C2
+
C1
C4
0.1µF
48V
–
0.47µF
D1
25V
7.5V
1µF
R7
25V
25V
270k
1N755A
7
3
5%
FUSE
Q2
VN2222L
IMIRROR
RMIRROR
39Ω
5%
LT1006
2
4
OPAMP
RSENSE
0.02Ω
5%
ILOAD
1422 F17
Figure 17. Switching 48V with Current Sensing
RELATED PARTS
PART NUMBER
LTC1421
LT1640L/LT1640H
LT1641
LT1642
LTC1643L/LTC1643H
LT1645
LTC1647
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
16 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX:(408)434-0507 q www.linear-tech.com
COMMENTS
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
1422fa LT/TP 0300 2K REV A • PRINTED IN USA
© LINEAR TECHNOLOGY CORPORATION 1997
Share Link: 