• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 34 subscribers
  • Views 606 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

TCA9617B: Under shoot issue B side Clock and data signals...

TCA9617B: VOL compatibility issue

Manjunatha Nagamma
Prodigy 140 points
Part Number: TCA9617B
Other Parts Discussed in Thread: INA228, TCA9800, TCA9803, TCA9509

Hi,

We are using TCA9617B as bus repeater. We have 7 devices on B side and these are IN228 current sensors.

The SCLB output of TCA9617B is specified to maintain a static offset voltage of 0.5V while driving LOW which is understandable as per datasheet.

But the INA228 device specifies a VIL max of 0.4V.

How can we make sure INA228 device detects the LOW level signal driven by TCA9617B on SCLB / SDAB correctly?

Regards,

Manjunatha 

  • 0
    TI__Mastermind 26836 points

    Manjunatha,

    The TCA9617B implements a buffered low on the B side, which is required for proper operation, as you observed. The A-side does not used a buffered low. Since the VIL of the INA228 is 0.4 V max, you would not be able to guarantee recognition of the buffered low from the TCA9617B B-side.

    There are a few ways this can be addressed depending on the application. One device I recommend evaluating is the TCA9800 (or the TCA980x series), which does not used a buffered low but has the same pinout. Alternatively, you could still use a buffered-low device like the TCA9617B, but use the A-side of the device for the INA228 communication. This, however, would require rerouting of the board and is why my recommendations are application-dependent.

    Please let me know if you have any additional questions or concerns.

    Best,

    Danny

  • 0
    Guru 318920 points

    What supply voltage are you using? At 3.3 V or below, it might be possible to use the TCA9803 instead.

  • 0 in reply to Danny Bacic
    Prodigy 140 points

    Danny,

    Thanks for the  quick response. I looked at TCA980x device. But it appears to have some strict requirements on current sinking at B port to keep low VOH.

    Is there a better solution that could work without requiring us to change the current design? 

    Hi Clemens,

    The VCCA and VCCB are operated at 3..3V. 

    Regards,

    Manjunatha

  • 0 in reply to Manjunatha Nagamma
    TI__Mastermind 26836 points

    Manjunatha,

    A change will need to be made. The buffered output low on the B-side of the TCA9617B is built into the device as part of its operation, and there is no way to alter the device itself or to use software to change this for the TCA9617B.

    If you are able to look at other devices, I'd recommend evaluating the TCA9509. This is similar to the TCA980x series, but the current-sensing side is on the A-side rather than the B-side. The VOL values are below 0.4 V for both sides.

    Best,

    Danny

  • 0 in reply to Danny Bacic
    Prodigy 140 points

    Hi Danny,

    Understood. Thanks for your support.

    Regards,

    Manjunatha