TCA9800 Datasheet, PDF (19/36 Pages) Texas Instruments – Level-Translating I2C Bus Buffer/Repeater

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TCA9800
SCPS264 – MARCH 2017
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 I_EXT-I section.
1.2 V
3.3 V
5k
SDA
BUS
SCL
MASTER
400 kHz
5k
VCCA VCCB
TCA980x
SDAA SDAB
SDA
SCLA SCLB
SCL
SLAVE
EN
400 kHz
Copyright © 2017, Texas Instruments Incorporated
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 V_CCA > V_CCB. 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 V_CCA/V_CCB 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 V_CCA (either with an external or the internal pull-up resistor) to ensure that
the device is enabled.
1.65 V
3.3 V
SDA
BUS
SCL
MASTER
400 kHz
5k
5k
VCCB VCCA
TCA980x
SDAB SDAA
SDA
SCLB SCLA
SCL
SLAVE
EN
400 kHz
Copyright © 2017, Texas Instruments Incorporated
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.
Copyright © 2017, Texas Instruments Incorporated
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