LTC4253AIGN#TR Linear Technology, LTC4253AIGN#TR Datasheet - Page 11

• Manufacturer Part Number: LTC4253AIGN#TR
• Description: MS-Hot Swap/High Voltage, Neg. 48V Hot Swap With 1% UV, Sequencer
• Manufacturer: Linear Technology

Specifications of LTC4253AIGN#TR

• Family Name: LTC4253A
• Package Type: SSOP N
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 3.99mm
• Product Height (mm): 1.5mm
• Mounting: Surface Mount
• Pin Count: 16
• Lead Free Status / Rohs Status: Not Compliant

OPERATIO
Hot Circuit Insertion
When circuit boards are inserted into a live backplane, the
supply bypass capacitors can draw huge transient cur-
rents 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
–48RTN
(LONG PIN)
–48RTN
(SHORT PIN)
–48V
(LONG PIN)
4.75k
38.3k
432k
1%
1%
1%
R3
R2
R1
47k
U
R9
C1
10nF
0.1µF
C
RESET
C
PUSH
SS
SQ
68nF
Figure 2. – 48V/2.5A Application with a Wider Operating Range
C
0.33µF
–48RTN
UV
OV
RESET
SS
SQTIMER
TIMER
T
BACKPLANE
Figure 1. Basic LTC4253/LTC4253A Hot Swap Topology
–48V
LTC4253
V
V
EE
IN
PWRGD1
PWRGD2
PWRGD3
R
2.5k
15k(1/4W)/6
IN
DRAIN
SENSE
GATE
EN3
EN2
PLUG-IN BOARD
LTC4253A
LTC4253
C
1µF
IN
R
D
R
10Ω
C
1M
C
18nF
C
R4
5.6k
+
Q1
IRF530S
R
0.02Ω
†
C
S
load or power conversion circuitry with an external MOS-
FET 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.
LOAD
EN2
+
–
CONVERTER
R5
5.6k
ISOLATED
MODULE
DC/DC
V
IN
V
†
†
IN
+
–
LOW
VOLTAGE
CIRCUITRY
R6
5.6k
LTC4253/LTC4253A
100µF
R7
4253 F01
†
C
L
+
POWER
MODULE 1
OUTPUT
EN3
MODULE 1
EN
POWER
V
†
IN
†
MOC207
MODULE 2
EN
MODULE 2
OUTPUT
POWER
POWER
R8
4253 F02
11
MODULE 3
EN
425353afc
POWER