TCA4311A Datasheet, PDF (13/22 Pages) Texas Instruments – HOT SWAPPABLE 2-WIRE BUS BUFFERS

TCA4311A
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APPLICATION INFORMATION
SCPS226 – JANUARY 2011
Live Insertion and Capacitance Buffering Application
Figure 12 through Figure 13 illustrate the usage of the TCA4311A in applications that take advantage of both its
hot swap controlling and capacitance buffering features. In all of 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 TCA4311A on the edge of each card,
however, isolates the card capacitance from the backplane. For a given I/O card, the TCA4311A drives the
capacitance of everything on the card and the backplane must drive only the capacitance of the TCA4311A,
which is less than 10 pF.
Figure 12 shows the TCA4311A in a CompactPCI™ configuration. Connect V_CC and EN to the output of one of
the CompactPCI power supply Hot Swap circuits. Use a pullup resistor to EN 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.
V_CC
BD_SEL
SDA
SCL
Backplane
R1 R2
10 k 10 k
Backplane
Connector
Power Supply
Hot Swap
I/O Peripheral Card 1
R3
10 k
Card
Enable/Disable
EN
V_CC
SDAIN
TCA4311
SCLIN
GND
C1
0.01 µF
SDAOUT
SCLOUT
READY
R4
R5 R6
10 k 10 k 10 k
CARD_SDA
CARD_SCL
Power Supply
Hot Swap
I/O Peripheral Card 2
R7
10 k _Card
Enable/Disable
EN
V_CC
SDAIN
TCA4311
SCLIN
GND
C3
0.01 µF
SDAOUT
SCLOUT
READY
R8
R9 R10
10 k 10 k 10 k
CARD2_SDA
CARD2_SCL
Power Supply
Hot Swap
I/O Peripheral Card N
R11
10 k
Card
Enable/Disable
EN
V_CC
SDAIN
TCA4311
SCLIN
GND
C5
0.01 µF
SDAOUT
SCLOUT
READY
R12 R13 R14
10 k 10 k 10 k
CARDN_SDA
CARDN_SCL
Figure 12. Inserting Multiple I/O Cards into a Live Backplane Using the TCA4311A in a CompactPCI
System
Copyright © 2011, Texas Instruments Incorporated
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