lt4254cgn-trpbf Linear Technology Corporation, lt4254cgn-trpbf Datasheet - Page 9

• Manufacturer Part Number: lt4254cgn-trpbf
• Description: Positive High Voltage Hot Swap Controller With Open-circuit Detect
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
TEST CIRCUIT
Hot Circuit Insertion
When circuit boards are inserted into a live backplane, the
supply bypass capacitors on the boards draw high peak
currents from the backplane power bus as they charge.
The transient currents can permanently damage the con-
nector pins and glitch the system supply, causing other
boards in the system to reset.
The LT4254 is designed to turn on a board’s supply
voltage in a controlled manner, allowing the board to be
safely inserted or removed from a live backplane. The
TI I G DIAGRA S
W U
GATE
UV
4V
Figure 2. UV to GATE Timing
V
U
OUT
t
PLHUV
+2V
U
W
V
CC
W
– SENSE
GATE
3.6V
Figure 4. SENSE to GATE Timing
4254 F02
V
OUT
U
–
t
PHLUV
+
50mV
+2V
3V
V
PWRGD
OPEN
FB
OV
UV
CC
t
PHLSENSE
Figure 1
GND
SENSE
RETRY
TIMER
GATE
device also provides undervoltage and overvoltage as well
as overcurrent protection while a power good output
signal indicates when the output supply voltage is ready
with a high output.
Power-Up Sequence
An external N-channel MOSFET pass transistor (Q1) is
placed in the power path to control the power up of the
supply voltage (Figure 5). Resistor R5 provides current
detection and capacitor C1 controls the GATE slew rate.
V
CC
3V
4254 TC
PWRGD
24V
+ –
FB
+ –
Figure 3. V
100pF
4.45V
4254 F04
1V
t
PLHFB
OUT
to PWRGD Timing
4V
LT4254
4254 F03
1V
t
PHLFB
4254fb
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