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TCA9800: some questions about TCA9800, TCA9617B

Frank Xiao
Genius 12055 points
Part Number: TCA9800
Other Parts Discussed in Thread: TCA9617B,

Hi team,

My customer is using the TCA9800/TCA9617B  now. We have the questions below want to check with you. Thanks.

1.TCA9800 B side connect to CPU, A side connect to many slave device, whether it's ok?

2. For TCA9800, master A connect slave A, whether it's ok? As the picture below.

3.For TCA9617B  we have found the A side can be connected together. Whether B side can be connected together?

4. For TCA9800/ TCA9617B, whether we can connect the A side together, whether we can connect the Bside together? (in parallel)

Thanks.

  • 0
    TI__Guru 53555 points

    Hi Frank,

    1.TCA9800 B side connect to CPU, A side connect to many slave device, whether it's ok?

    This connection is fine. Please ensure that the low-level output voltage (VOL) for each device is compatible with the appropriate low-level input voltage (VIL). For example, TCA9800 B-side has a Vol of 0.26V. T Vil threshold of the CPU must be higher than this value.

    2. For TCA9800, master A connect slave A, whether it's ok? As the picture below.

    Yes, TCA9800 device can be wired with the A side in parallel such as depicted in Figure 31 of its datasheet.

    3.For TCA9617B  we have found the A side can be connected together. Whether B side can be connected together?

    TCA9617B does not allow parallel connections with other B terminals (or with similar device terminals with static or dynamic offset voltages). The A side of this device does support parallel connections such as in Figure 12 of the datasheet.

    4. For TCA9800/ TCA9617B, whether we can connect the A side together, whether we can connect the Bside together? (in parallel)

    These devices may not share a B-side connection with one other because they use incompatible methods of lockup avoidance (Integrated Current Source and Buffered Low). According to the VOL and VIL specifications for these devices, the A sides may be connected together in parallel. Also note there are cases where an A-side may not be compatible with a B-side (series connections). Let me know if you have a concern about a particular case.

    Regards,

    Eric

  • 0 in reply to Eric Schott1
    TI__Genius 12055 points

    Hi Eric,

    Thanks for your help. For TCA9800, whether the A side drive ability is better than B side? Thanks.

  • 0 in reply to Frank Xiao
    TI__Guru 53555 points

    Hi Frank,

    The A-side of this device has a lower Vol as well as faster rise/fall times. This side if often used for more sensitive components that require a low Vil. The B-side has different characteristics because of the integrated current source and current sensing capabilities.

    Regards,

    Eric

  • 0 in reply to Eric Schott1
    TI__Genius 12055 points

    Hi Eric,

    Thanks. Whether the A & B have drive current ability difference? Thanks.

  • 0 in reply to Frank Xiao
    TI__Guru 53555 points

    Hi Frank,

    The A-side of the device specifies its low-level output voltage while sinking 6mA (20mA Abs Max).

    Because TCA9800 does not require a pull-up resistor on the B-side, Iol is not specified on this side. Due to the need to sense current direction on this side of the device, the driver characteristics are different than the A side. No external sources of current may be present on the B-side of this device. Is this compatible with your current use-case?

    Regards,

    Eric