1 Features

1• Operating Power-Supply Voltage Range of 2.7-V

to 5.5-V

• Supports Bidirectional Data Transfer of I2C Bus

Signals

• SDA and SCL Lines Are Buffered Which

Increases Fanout

• 1-V Precharge on All SDA and SCL Lines

Prevents Corruption During Live Board Insertion

and Removal From Backplane

• SDA and SCL Input Lines Are Isolated From

Outputs

• Accommodates Standard Mode and Fast Mode

I2C Devices

• 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 I2C Pins

• Open-Drain I2C 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)

2 Description

The TCA4311 is a hot swappable I2C 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 I2C 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 I2C devices in

addition to SMBus devices. Standard Mode I2C

devices only specify 3 mA in a generic I2C system

where Standard Mode devices and multiple masters

are possible. Under certain conditions, high

termination currents can be used.