Datasheet

LTC4300A-1/LTC4300A-2
11
4300a12fa
APPLICATIONS INFORMATION
these applications, note that if the I/O cards were plugged
directly into the backplane, all of the backplane and card
capacitances would add directly together, making rise-
and fall-time requirements difficult to meet. Placing a
LTC4300A on the edge of each card, however, isolates the
card capacitance from the backplane. For a given I/O card,
the LTC4300A drives the capacitance of everything on the
card and the backplane must drive only the capacitance
of the LTC4300A, which is less than 10pF.
Figure 3 shows the LTC4300A-1 in a CompactPCI configu-
ration. Connect V
CC
and ENABLE to the output of one of
the CompactPCI power supply Hot Swap circuits. Use a
pull-up resistor to ENABLE for a card side enable/disable.
V
CC
is monitored by a filtered UVLO circuit. With the V
CC
voltage powering up after all other pins have established
connection, the UVLO circuit ensures that the backplane
and card data and clock busses are not connected until
the transients associated with live insertion have settled.
Owing to their small capacitance, the SDAIN and SCLIN
pins cause minimal disturbance on the backplane busses
when they make contact with the connector.
Figure 4 shows the LTC4300A-2 in a CompactPCI con-
figuration. The LTC4300A-2 receives its V
CC
voltage from
one of the long “early power” pins. Because this power is
not switched, add a 5Ω to 10Ω resistor between the V
CC
pins of the connector and the LTC4300A-2, as shown in
Figure 4. Inserting Multiple I/O Cards into a Live Backplane Using the LTC4300A-2 in a CompactPCI System
C1
0.01μF
C3
0.01μF
C5
0.01μF
R13
10k
R12
10k
R14
10k
I/O PERIPHERAL CARD N
V
CC
SDAIN
SCLIN
U3
LTC4300A-2
V
CC2
GND
CARDN_SCL
CARDN_SDA
SDAOUT
SCLOUT
ACC
V
CC
SDAIN
SCLIN
V
CC2
GND
SDAOUT
SCLOUT
ACC
V
CC
SDAIN
SCLIN
V
CC2
GND
SDAOUT
SCLOUT
ACC
4300a12 F04
ttt
R9
10k
R8
10k
R10
10k
I/O PERIPHERAL CARD 2
U2
LTC4300A-2
CARD2_SCL
CARD2_SDA
R5
10k
R4
10k
R6
10k
I/O PERIPHERAL CARD 1
U1
LTC4300A-2
C2 0.01μF
5.1Ω
CARD_SCL
CARD_SDA
V
CC2
BACKPLANE
BACKPLANE
CONNECTOR
SDA
SCL
V
CC
BD_SEL
STAGGERED CONNECTORSTAGGERED CONNECTORSTAGGERED CONNECTOR
POWER SUPPLY
HOT SWAP
C4 0.01μF
5.1Ω
POWER SUPPLY
HOT SWAP
C6 0.01μF
5.1Ω
POWER SUPPLY
HOT SWAP
R1
10k
R2
10k