BUS

MASTER

400 kHz

SDA

SCL

1.65 V

5 k

5 k

EN

SDAB

SCLB

SDAA

SCLA

VCCB VCCA

TCA980x

SDA

SCL

SLAVE

400 kHz

3.3 V

Copyright © 2017, Texas Instruments Incorporated

BUS

MASTER

400 kHz

SDA

SCL

1.2 V

5 k

5 k

EN

SDAA

SCLA

SDAB

SCLB

VCCA VCCB

TCA980x

SDA

SCL

SLAVE

400 kHz

3.3 V

Copyright © 2017, Texas Instruments Incorporated

19

TCA9803

www.ti.com

SCPS267B – MARCH 2017 – REVISED FEBRUARY 2020

Product Folder Links: TCA9803

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Typical Application (continued)

It is critical to note that there are no external sources of current allowed on the B-side ports, since this can affect

device operation as shown in the IEXT-I section.

Figure 19. Typical Level-Shifting Application Example (Master on A-side)

NOTE

Decoupling capacitors are not shown to keep the illustration simple. Decoupling capacitors

(1 µF and 0.1 µF) must be placed close to each power supply pin.

As shown in Figure 20, the I2C master can be on the B-side, and that it is ok to have VCCA > VCCB. The only

requirements are that no external source of current (pull-up resistor or current source) be on the B-pins of the

TCA980x, and that both VCCA/VCCB values are within the recommended range. As a note, since the EN pin is

referenced to the VCCA supply voltage, when the master is on the A-side, the system designer must ensure that

the enable pin voltage is pulled up to VCCA (either with an external or the internal pull-up resistor) to ensure that

the device is enabled.

Figure 20. Typical Level-Shifting Application Example (Master on B-side)

NOTE

Decoupling capacitors are not shown to keep the illustration simple. Decoupling capacitors

(1 µF and 0.1 µF) must be placed close to each power supply pin.