LTC1646
BLOCK DIAGRA
5V
IN
12
5V
SENSE
11
5V
OUT
+–
55mV
+
–
Q1
+–
+
150mV
+–
–
2.5V
UVL
OFF/ON 15
FAULT 3
Q7
C
P4
PWRGD 4
LOGIC
Q6
REF
RESETIN 16
5V
in
5µA
TIMER 2
Q5
APPLICATIO S I FOR ATIO
Hot Circuit Insertion
When a circuit board is inserted into a live CompactPCI
(CPCI) slot, the supply bypass capacitors on the board can
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.
The LTC1646 is designed to turn a board’s supply voltages
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-
tects the supplies from shorts, precharges the bus I/O pins
during insertion and extraction and monitors the supply
voltages.
U
W
W
GATE
10
V
GG
13µA
3V
OUT
3V
SENSE
9
3V
IN
8
3V
OUT
5V
OUT
7
5
+
–
–+
55mV
200µA
–+
+
150mV
Q2
Q3
–
–+
2.5V
UVL
C
P3
+
–
+
–
REF
Q4
1 RESETOUT
+
–
1V
6
GND
14
DRIVE
13
PRECHARGE
1646 BD
U
U
The LTC1646 is specifically designed for CPCI applica-
tions where the chip resides on the plug-in board.
LTC1646 Feature Summary
1. Allows safe board insertion and removal from a CPCI
backplane.
2. Controls 5V and 3.3V CPCI supplies.
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
LINER [ LINEAR TECHNOLOGY ]
