LTC4253CGN Linear Technology, LTC4253CGN Datasheet - Page 12

• Manufacturer Part Number: LTC4253CGN
• Description: IC HOT SWAP CONTRLR -48V 16-SSOP
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LTC4253CGN

• Applications: General Purpose
• Internal Switch(s): No
• Voltage - Supply: 11.2 V ~ 14.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP (0.150", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

operaTion
LTC4253/LTC4253A
Hot Circuit Insertion
When circuit boards are inserted into a live backplane,
the supply bypass capacitors can draw huge transient
currents from the power bus as they charge. The flow
of current damages the connector pins and glitches the
power bus, causing other boards in the system to reset.
The LTC4253/LTC4253A are designed to turn on a circuit
board supply in a controlled manner, allowing insertion or
removal without glitches or connector damage.
Initial Start-Up
The LTC4253/LTC4253A reside on a removable circuit
board and control the path between the connector and load
12
–48RTN
(LONG PIN)
–48RTN
(SHORT PIN)
–48V
(LONG PIN)
4.75k
38.3k
432k
1%
1%
1%
R3
R2
R1
47k
R9
C1
10nF
0.1µF
C
C
RESET
PUSH
SS
SQ
68nF
Figure 2. –48V/2.5A Application with a Wider Operating Range
C
0.33µF
UV
OV
RESET
SS
SQTIMER
TIMER
T
–48RTN
Figure 1. Basic LTC4253/LTC4253A Hot Swap Topology
BACKPLANE
–48V
V
IN
LTC4253
R
2.5k
15k(1/4W)/6
V
IN
EE
PWRGD1
PWRGD2
PWRGD3
D
DDZ13B*
SENSE
DRAIN
IN
GATE
EN3
EN2
††
PLUG-IN BOARD
LTC4253A
LTC4253
C
1µF
IN
R
D
R
10
C
1M
C
18nF
C
R4
5.6k
+
Q1
IRF530S
R
0.02
†
S
or power conversion circuitry with an external MOSFET
switch (see Figure 1). Both inrush control and short-circuit
protection are provided by the MOSFET.
A detailed schematic is shown in Figure 2. – 48V and
–48RTN receive power through the longest connector pins
and are the first to connect when the board is inserted.
The GATE pin holds the MOSFET off during this time. UV/
OV determines whether or not the MOSFET should be
turned on based upon internal high accuracy thresholds
and an external divider. UV/OV does double duty by also
monitoring whether or not the connector is seated. The top
of the divider detects –48RTN by way of a short connector
pin that is the last to mate during the insertion sequence.
C
LOAD
EN2
R5
5.6k
+
–
CONVERTER
ISOLATED
MODULE
DC/DC
V
IN
V
†
†
IN
+
–
R6
5.6k
LOW
VOLTAGE
CIRCUITRY
100µF
R7
†
C
4253 F01
L
+
POWER
MODULE 1
OUTPUT
EN3
EN
MODULE 1
POWER
*DIODES, INC.
†
††
MOC207
RECOMMENDED FOR HARSH ENVIRONMENTS.
V
†
IN
MODULE 2
EN
MODULE 2
OUTPUT
POWER
POWER
R8
4253 F02
MODULE 3
EN
425353afd
POWER