LTC1646
W
BLOCK DIAGRA
5V
5V
3V
3V
3V
5V
IN
SENSE
SENSE
9
IN
OUT
OUT
GATE
10
12
11
8
7
5
V
GG
5V
3V
OUT
OUT
13µA
+–
+
+
+ –
55mV
55mV
+–
+ –
Q2
Q3
–
–
Q1
200µA
+
–
+
–
150mV
150mV
+–
+ –
2.5V
UVL
2.5V
UVL
C
P3
+
OFF/ON 15
–
FAULT
3
REF
Q7
Q6
C
P4
+
–
PWRGD
4
LOGIC
1
RESETOUT
REF
Q4
RESETIN 16
5V
in
5µA
+
–
1V
TIMER
2
Q5
1646 BD
6
14
13
PRECHARGE
GND
DRIVE
U
W
U U
APPLICATIO S I FOR ATIO
Hot Circuit Insertion
The LTC1646 is specifically designed for CPCI applica-
tions where the chip resides on the plug-in board.
When a circuit board is inserted into a live CompactPCI
(CPCI)slot, thesupplybypasscapacitorsontheboardcan
draw huge supply transient currents from the CPCI power
bus as they charge up. The transient currents can cause
glitches on the power bus, causing other boards in the
system to reset.
LTC1646 Feature Summary
1. Allows safe board insertion and removal from a CPCI
backplane.
2. Controls 5V and 3.3V CPCI supplies.
TheLTC1646isdesignedtoturnaboard’ssupplyvoltages
on and off in a controlled manner, allowing the board to be
safely inserted or removed from a live CPCI slot without
glitching the system power supplies. The chip also pro-
tectsthesuppliesfromshorts,prechargesthebusI/Opins
during insertion and extraction and monitors the supply
voltages.
3. Current limit during power-up: the supplies are allowed
to power up in current limit. This allows the chip to
power up boards with widely varying capacitive loads
without tripping the circuit breaker. The maximum
allowable power-up time is programmable using the
TIMER pin and an external capacitor.
1646fa
9
Linear [ Linear ]
