LTC4300A-1/LTC4300A-2
12
4300a12fa
the figure. In addition, make sure that the V
CC
bypassing
on the backplane is large compared to the 0.01μF bypass
capacitor on the card. Establishing early power V
CC
ensures that the 1V precharge voltage is present at the
SDAIN and SCLIN pins before they make contact. Con-
nect V
CC2
to the output of one of the CompactPCI power
supply Hot Swap circuits. V
CC2
is monitored by a filtered
UVLO circuit. With the V
CC2
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.
Figure 5 shows the LTC4300A-1 in a PCI application,
where all of the pins have the same length. In this case,
connect an RC series circuit on the I/O card between V
CC
and ENABLE. An RC product of 10ms provides a filter to
prevent the LTC4300A-1 from becoming activated until
the transients associated with live insertion have settled.
Figure 5. Inserting Multiple I/O Cards into a Live Backplane Using the LTC4300A-1 in a PCI System
Figure 6 shows the LTC4300A-2 in an application where the
user has a custom connector with pins of three different
lengths available. Making V
CC2
the shortest pin ensures
that all other pins are firmly connected before V
CC2
receives
any voltage. A filtered UVLO circuit on V
CC2
ensures that
the V
CC2
pin is firmly connected before the LTC4300A-2
connects the backplane to the card.
Repeater/Bus Extender Application
Users who wish to connect two 2-wire systems separated
by a distance can do so by connecting two LTC4300A-1s
back-to-back, as shown in Figure 7. The I
2
C specification
allows for 400pF maximum bus capacitance, severely
limiting the length of the bus. The SMBus specification
places no restriction on bus capacitance, but the limited
impedances of devices connected to the bus require
systems to remain small if rise- and fall-time specifica-
tions are to be met. The strong pull-up and pull-down
impedances of the LTC4300A-1 are capable of meeting
R3
100k
ENABLE
SDAIN
SCLIN
V
CC
GND
SDAOUT
SCLOUT
READY
ENABLE
SDAIN
SCLIN
V
CC
GND
SDAOUT
SCLOUT
READY
4300a12 F05
R9
10k
R8
10k
R10
10k
I/O PERIPHERAL CARD 2
U2
LTC4300A-1
CARD2_SCL
CARD2_SDA
R5
10k
R4
10k
I/O PERIPHERAL CARD 1
U1
LTC4300A-1
C2 0.1μF
R7
100k
C4 0.1μF
CARD_SCL
CARD_SDA
R1
10k
V
CC
R2
10k
BACKPLANE
BACKPLANE
CONNECTOR
SDA
SCL
C1
0.01μF
C3
0.01μF
R6
10k
t
t
t
APPLICATIONS INFORMATION
