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TCA9406: How can output be driven if the part is driving it?

Ray Vincent Aranzaso
Genius 13535 points
Part Number: TCA9406
Other Parts Discussed in Thread: TCA9416

Hi,

Good Day. I have a customer who is working with TCA9406. Please see below his query for your reference. Thank you very much.

The datasheet says that the user must wait for the one-shot to stop driving the output before applying an input in the opposite direction. My question : what if the signal is transitioning from high to low, then, how strongly does the IC drive the output? Is the user expected to overdrive this? What am I missing? Thanks

Best Regards,

Ray Vincent

  • 0
    Guru 243870 points

    The one-shot works only for low-to-high transitions (because only those are slow in an open-drain system).

    At all other times, this device is a passive switch. During a high-to-low transition, the signal is driven only by your external device.

  • 0
    TI__Mastermind 49270 points

    Hi Ray,

    To add a little bit more to Clemen's answer, the TCA9406's rise time accelerator when triggered will stay on for about ~30ns and will only turn off after this timer is finished. The rise time accelerator's threshold trigger is a voltage threshold at about 30% of VccA. Ideally you should not drive low while the rise time accelerator is turned on otherwise there can be contention. 

    I would also like to point out we have our new TCA9416 which is a lower voltage supported version of TCA9406 with no Vcc rules and includes a fall time accelerator to help drive heavy capacitive loads for lower voltage open driven drivers (low voltage usually means weaker drivers/RDSON).

    -Bobby