LTC1643H Просмотр технического описания (PDF) - Linear Technology
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LTC1643H Datasheet PDF : 16 Pages
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LTC1643L/LTC1643L-1/LTC1643H
APPLICATIONS INFORMATION
MED 5V
MED 3.3V
12V
–12V
BD_SEL#
HEALTHY#
LONG GND
R2
0.007Ω Q1
1 1% 2 IRF7413
5V
R1
3
4
5A
0.005Ω
Q2
1 1% 2 IRF7413
3.3V
R11
1Ω†
5%
C6
0.1µF
R12 3Ω 5%
3
V(I/O)
D3* R8
12V 1.2k
5%
9
3VIN
1 12VIN
2 VEEIN
R9 2k 5% 5
ON
4
R3
10Ω
5%
10
11
3
13
3VSENSE GATE 3VOUT 5VIN
LTC1643L
12
5VSENSE
7.6A
R4
10Ω
R5
5%
100Ω
5%
14
5VOUT
16
12VOUT
15
VEEOUT
C1
0.047µF
12V
500mA
–12V
100mA
PRECHARGE OUT
V(I/O)
V(I/O)
R13
2k
D2*
6
FAULT
R10 2k 5%
5% 12V
7
C5
PWRGD
GND
0.1µF
8
TIMER
4
C2
1V ±20%
D1
IOUT = ±40mA 1N4148
C3
0.01µF R11
24Ω
5%
0.1µF
R6
130Ω
1%
R7
56.2Ω
1%
V(I/O)
LONG
3.3V
LT1117
OUT IN
ADJ
C4
1µF
PCI_RST#
I/O
DATA LINE EXAMPLE
DATA BUS
* BZX84C15 (SOT-23)
† VALUE MAY VARY FOR BACKPLANES WITHOUT BYPASS CAPACITANCE
LOCAL_PCI_RESET#
R14
10Ω, 5%
R13
10k
5%
LONG LONG
3.3V 5V
I/O 3.3V 5V
RESET#
PCI
BRIDGE
(21154)
1643 F07
Figure 7. Typical CompactPCI Application
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.
LTC1643L-1
The LTC1643L-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 12VOUT and VEEOUT pins are disabled.
The VEEIN pin can be connected to GND and the part will
still operate normally if a – 12VOUT output is not needed.
However, 12V is still required at the 12VIN pin for the part
to function. Refer to Figure 10 for a typical LTC1643L-1
application circuit.
Increasing 12V and – 12V Current Capability
The internal switches in the LTC1643 are designed for up
to 500mA loads on 12V and 200mA on – 12V. If more
current is needed, then the circuits in Figure 8 can be used.
13
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