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TCA9406DCUR Datasheet, PDF (9/21 Pages) Texas Instruments – 2-BIT BIDIRECTIONAL 1MHz, I2C BUS AND SMBUS VOLTAGE-LEVEL TRANSLATOR WITH 8kV HBM ESD
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Application Notes
TCA9406
SCPS221B – OCTOBER 2010 – REVISED JUNE 2013
PRINCIPLES OF OPERATION
Figure 1. Typical Design Example
The TCA9406 has a VCC isolation feature known as Ioff partial power down and backdrive protection. If a cable is
connected, and the connected external system is still powered own, the system can be put into standby mode by
shutting down the power rail. In this state, the TCA9406 has a leakage current of approximately 2 µA caused by
current flow from powered-on system.
Power Up, Power Down
One advantage of the TCA9406 translator is that either power supply can be ramped up first. Another advantage
is that either power supply can be set to 0 V, and the outputs are in high-impedance state.
The recommended power up sequence is:
1. Apply power to the first VCC and apply the second VCC
2. Drive the OE input high to enable the device
The recommended power down sequence is:
1. Drive OE input low to disable the device
2. Switch Off the power from either VCC and remove power from other VCC.
Enable/Disable
The TCA9406 has an OE input that is used to disable the device by setting OE low, which place all I/Os in the
high-impedance state. The control OE is referenced to the VCCA supply. A pulldown resistor tying OE to ground
should be used to ensure that bus contention, excessive currents, or oscillations do not occur during power up
and power down. The value of resistor is based upon the current sinking capability of the device.
Integrated Pullup Resistors on the I/Os (A-Ports/B-Ports)
Each A-port I/O has an internal 10-kΩ pullup resistor to VCCA, and each B-port I/O has an internal 10-kΩ pullup
resistor to VCCB. If a smaller value of pullup resistor is required, an external resistor must be added from the I/O
to VCCA or VCCB (in parallel with the internal 10-kΩ resistors). Adding lower value pull-up resistors may effect VOL
levels. The internal pullups of the TCA9406 are disabled when the OE pin is low.
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