TCA4311A Hot Swappable 2-Wire Bus Buffers

1 Features

• 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
• Improved Noise Immunity
• 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 Applications

• Servers
• Routers (Telecom Switching Equipment)
• Base Stations
• Industrial Automation

3 Description

The TCA4311A 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 pre-charged to 1 V to minimize the current required to charge the parasitic capacitance of the chip.

When the I²C bus is idle, the TCA4311A can be put into shutdown mode by setting the EN pin low. When EN is high, the TCA4311A 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 TCA4311A has standard open-drain I/Os. The size of the pull-up resistors to the I/Os depends on the system, but each side of this buffer must have a pull-up 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.

1. For all available packages, see the orderable addendum at the end of the datasheet.

Device Images

Simplified Schematic