Datasheet
13
LTC1643AL
LTC1643AL-1/LTC1643AH
1643afb
APPLICATIONS INFORMATION
WUU
U
circuit, PCI bridge chip and the LOCAL_PCI_RESET# logic
circuitry. The BD_SEL# signal is connected to the ON pin
while the PWRGD pin is connected to the HEALTHY#
signal. The HEATHLY# signal is combined with the
PCI_RESET# signal to generate the LOCAL_PCI_RESET#
signal. Capacitors C6 and C7 provide chip bypassing on
the 12V and –12V inputs. Diode D2 protects the part from
voltage surges below –13.2V on the –12V supply.
The 1V precharge voltage for the data bus lines is gener-
ated by an LT1117 low dropout regulator. The output of the
LT1117 is set to 1.8V, then the voltage is dropped by a
1N4148 diode to generate 1V. The precharge circuit is
capable of sourcing and sinking 40mA.
R1
0.005Ω
1%
V(I/O)
V(I/O)
V(I/O)V(I/O)
Q2
IRF7413
Q1
IRF7413
R2
0.007Ω
1%
R3
10Ω
5%
R4
10Ω
5%
R5
100Ω
5%
C1
0.047µF
5V
5A
MED 5V
MED 3.3V
BD_SEL#
LONG GND
PCI_RST#
I/O
3.3V
7.6A
–12V
100mA
12V
500mA
PRECHARGE OUT
1V ±20%
I
OUT
= ±40mA
R9 2k 5%
R12 3Ω 5%
R10 2k 5%
R8
1.2k
5%
LOCAL_PCI_RESET#
DATA LINE EXAMPLE
DATA BUS
R14
10Ω, 5%
11 3 13 12 14
16
15
4
8
109
5
6
3V
IN
1
2
12V
–12V
12V
IN
V
EEIN
ON
FAULT
3V
SENSE
5V
SENSE
3V
OUT
LTC1643AL
5V
OUT
12V
OUT
V
EEOUT
TIMER
5V
IN
GATE
HEALTHY#
7
PWRGD
1643A F07
C2
0.1µF
GND
CompactPCI CONNECTOR
C6
0.1µF
C5
0.1µF
C3
0.01µF
C4
1µF
D1
1N4148
R13
10k
5%
RESET#
LONG
3.3V
LONG
3.3V
LONG
5V
3.3V
PCI
BRIDGE
(21154)
5V
OUT
IN
ADJ
LT1117
R11
24Ω
5%
R6
130Ω
1%
R7
56.2Ω
1%
I/O
R13
2k
5%
R11
10Ω
†
5%
D2*
12V
D3*
12V
* BZX84C15 (SOT-23)
†
VALUE MAY VARY FOR BACKPLANES WITHOUT BYPASS CAPACITANCE
43
21
43
21
Figure 7. Typical CompactPCI Application
LTC1643AL-1
The LTC1643AL-1 is designed for CompactPCI designs
where the ±12V supplies are not being used on the board
or the supplies are not well regulated. The power good
comparators on the 12V
OUT
and V
EEOUT
pins are disabled.
The V
EEIN
pin can be connected to GND and the part will
still operate normally if a –12V
OUT
output is not needed.
However, 12V is still required at the 12V
IN
pin for the part
to function. Refer to Figure 10 for a typical LTC1643AL-1
application circuit.