Datasheet

8
LTC1643AL
LTC1643AL-1/LTC1643AH
1643afb
BLOCK DIAGRAM
W
+
–
+
–
+
–
+
–
LOGIC
9.5V
UVL
5V
OUT
+
–
3V
OUT
12V
IN
62µA
200µA
Q5
ON/ON
FAULT
22µA
3V
SENSEGATE
5V
IN
5V
SENSE
12V
IN
12V
OUT
V
EEIN
V
EEOUT
TIMER
GND
12V
IN
3V
IN
5V
OUT
3V
OUT
2.5V
UVL
2.5V
UVL
REF
REF
REF
LTC1643AH/LTC1643AL
ONLY
LTC1643AH/LTC1643AL
ONLY
Q2
Q8
REF
1643A BD
C
P3
+
–
+
–
+
–
C
P4
C
P5
C
P7
Q3
Q4
5
13
1 16 4 2 15 8
12 11 10 9 3 14
6
7
PWRGD
Q7
Q1
Q9
Q10
Q6
APPLICATIONS INFORMATION
WUU
U
Hot Circuit Insertion
When a circuit board is inserted into a live PCI slot, the
supply bypass capacitors on the board can draw huge
transient currents from the PCI power bus as they charge
up. The transient currents can cause permanent damage
to the connector pins and cause glitches on the power bus,
causing other boards in the system to reset.
The LTC1643A 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 PCI slot
without glitching the system power supplies. The chip
also protects the PCI supplies from shorts and monitors
the supply voltages.
The LTC1643AH is designed for motherboard applica-
tions, while the LTC1643AL/LTC1643AL-1 are designed
for CompactPCI applications where the chip resides on
the plug-in board.
V
EEOUT
(Pin 15): –12V Supply Output. A 1.2Ω switch is
connected between V
EEIN
and V
EEOUT
. V
EEOUT
must
exceed –10.8V before the PWRGD signal can go high on
the LTC1643AH and LTC1643AL.
PIN FUNCTIONS
UUU
12V
OUT
(Pin 16): 12V Supply Output. A 0.5Ω switch is
connected between 12V
IN
and 12V
OUT
. 12V
OUT
must
exceed 11.4V before the PWRGD signal can go high on the
LTC1643AH and LTC1643AL.