TCA4311A Datasheet, PDF (14/22 Pages) Texas Instruments – HOT SWAPPABLE 2-WIRE BUS BUFFERS

TCA4311A
SCPS226 – JANUARY 2011
www.ti.com
Figure 13 shows the TCA4311A 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 EN. An RC product of 10 ms provides a filter to
prevent the TCA4311A from becoming activated until the transients associated with live insertion have settled.
Backplane
Backplane
Connector
V_CC
R1 R2
10 k 10 k
SDA
SCL
I/O Periperal Card 1
R3
100 k
EN
SDAIN
SCLIN
C2 0.1 µF
V_CC
TCA4311
GND
C1
0.01 µF
SDAOUT
SCLOUT
READY
R4
R5 R6
10 k 10 k 10k
CARD_SDA
CARD_SCL
I/O Peripheral Card 2
R7
100 k
EN
SDAIN
SCLIN
C4 0.1µF
V_CC
TCA4311
GND
C3
0.01 µF
SDAOUT
SCLOUT
READY
R8
R9 R10
10 k 10 k 10 k
CARD2_SDA
CARD2_SCL
•
•
•
Figure 13. Inserting Multiple I/O Cards into a Live Backplane Using the TCA4311A in a PCI System
Repeater/Bus Extender Application
Users who wish to connect two 2-wire systems separated by a distance can do so by connecting two TCA4311A
back-to-back, as shown in Figure 14. The I²C specification allows for 400 pF 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
specifications are to be met. The strong pullup and pulldown impedances of the TCA4311A are capable of
meeting rise- and fall-time specifications for one nanofarad of capacitance, thus allowing much more interconnect
distance. In this situation, the differential ground voltage between the two systems may limit the allowed distance,
because a valid logic low voltage with respect to the ground at one end of the system may violate the allowed
V_OL specification with respect to the ground at the other end. In addition, the connection circuitry offset voltages
of the back-to-back TCA4311A add together, directly contributing to the same problem.
14
Submit Documentation Feedback
Product Folder Link(s): TCA4311A
Copyright © 2011, Texas Instruments Incorporated