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TCA9803

SCPS267B – MARCH 2017 – REVISED FEBRUARY 2020

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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 VOL 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 VOL.

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. When enable is a logic LOW while VCCB is powered on, the internal current source on

B side is still enabled. The enable pin does not disable the internal current source.

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 (ICS), 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).