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SCPS173 – DECEMBER 2008
HOT SWAPPABLE 2-WIRE BUS BUFFERS
1
FEATURES
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•
•
•
•
•
•
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Applications Include Hot Board Insertion and
Bus Extension
Low I
CC
Chip Disable of <1
µA
READY Open-Drain Output
Supports Clock Stretching, Arbitration, and
Synchronization
Powered-Off High-Impedance I
2
C Pins
Open-Drain I
2
C Pins
Latch-Up Performance Exceeds 100 mA Per
JESD 78, Class II
ESD Protection Exceeds JESD 22
– 8000-V Human-Body Model (A114-A)
– 200-V Machine Model (A115-A)
– 1000-V Charged-Device Model (C101)
•
Operating Power-Supply Voltage Range of
2.7-V to 5.5-V
•
Supports Bidirectional Data Transfer of I
2
C
Bus Signals
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SDA and SCL Lines Are Buffered Which
Increases Fanout
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1-V Precharge on All SDA and SCL Lines
Prevents Corruption During Live Board
Insertion and Removal From Backplane
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SDA and SCL Input Lines Are Isolated From
Outputs
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Accommodates Standard Mode and Fast Mode
I
2
C Devices
2
D OR DGK PACKAGES
(TOP VIEW)
EN
SCLOUT
SCLIN
GND
1
2
3
4
8
7
6
5
V
CC
SDAOUT
SDAIN
READY
DESCRIPTION/ORDERING INFORMATION
The TCA4311 is a hot swappable I
2
C bus buffer that supports I/O card insertion into a live backplane without
corruption of the data and clock busses. Control circuitry prevents the backplane from being connected to the
card until a stop command or bus idle occurs on the backplane without bus contention on the card. When the
connection is made, this device provides bidirectional buffering, keeping the backplane and card capacitances
isolated. During insertion, the SDA and SCL lines are precharged to 1 V to minimize the current required to
charge the parasitic capacitance of the chip.
When the I
2
C bus is idle, the TCA4311 can be put into shutdown mode by setting the EN pin low. When EN is
high, the TCA4311 resumes normal operation. It also includes an open drain READY output pin, which indicates
that the backplane and card sides are connected together. When READY is high, the SDAIN and SCLIN are
connected to SDAOUT and SCLOUT. When the two sides are disconnected, READY is low.
Both the backplane and card may be powered with supply voltages ranging from 2.7 V to 5.5 V, with no
restrictions on which supply voltage is higher.
The TCA4311 has standard open-drain I/Os. The size of the pullup resistors to the I/Os depends on the system,
but each side of this buffer must have a pullup resistor. The device is designed to work with Standard Mode and
Fast Mode I
2
C devices in addition to SMBus devices. Standard Mode I
2
C devices only specify 3 mA in a generic
I
2
C system where Standard Mode devices and multiple masters are possible. Under certain conditions, high
termination currents can be used.
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
CompactPCI is a trademark of PCI Industrial Computer Manufacturers Group.
Copyright © 2008, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
TI [ TEXAS INSTRUMENTS ]
