TCA9800 Datasheet, PDF (12/36 Pages) Texas Instruments – Level-Translating I2C Bus Buffer/Repeater

TCA9800
SCPS264 – MARCH 2017
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9.3 Feature Description
9.3.1 Integrated Current Source
The TCA980x family has an integrated current source on the B side. By using an integrated current source, the
device is able to measure current to determine if an external device is pulling down on the bus or not. This
innovative detection method removes the need for a static voltage offset on the B side.
9.3.2 Ultra-Low Power Consumption
The TCA980x family features ultra low power consumption, to help maximum battery life, or cut down on power
dissipation in sensitive applications.
9.3.3 No Static-Voltage Offset
The TCA980x family has no static-voltage offset, which are commonly used in buffered translators to prevent a
device lock-up situation where the buffer's own output low could trip the input low threshold. The removal of the
static voltage offset is significant because it allows the device to have low a low V_OL on the B side, which helps
prevents communication issues that arise from connecting a static-voltage offset output device to an input with
an input low threshold which is below the static voltage V_OL.
9.3.4 Active-High Repeater Enable Input
The TCA980x has an active-high enable (EN) input with an internal pull-up to VCCA, which allows the user to
select when the repeater is active. This can be used to isolate a badly behaved slave on power-up reset. The EN
input must change state only when the global bus and repeater port are in an idle state, to prevent system or
communication failures.
9.3.5 Powered Off High Impedance I²C Bus Pins on A-Side
The SCLA and SDAA pins enters a high impedance state when either VCCA or VCCB fall below their UVLO
voltages. These pins are safe to continue having I²C communication on, even when the device is disabled or has
no power.
The SCLB and SDAB pins remain powered by their current source (I_CS), even when VCCA is below UVLO.
When VCCB falls below UVLO, the current source turns off, and a weak pull-up is connected to prevent the B-
pins from floating. This is intended behavior, because no external pull-up resistors are to be used on the SDAB
or SCLB pins. This behavior prevents the bus pins from floating, and allows it to follow VCCB.
9.3.6 Powered-Off Back-Power Protection for I²C Bus Pins
All I²C bus pins has protection circuitry to prevent current from flowing to the VCC pins from the I²C bus pins.
9.3.7 Clock Stretching and Multiple Master Arbitration Support
The TCA980x family supports clock stretching and multiple master arbitration methods, and helps to minimize
overshoot during these hand offs between master and slave (or multiple masters).
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