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TXS0108E Current Shink

Nhan Pham
Prodigy 170 points
Other Parts Discussed in Thread: TXS0108E, SN74LVC8T245

Hi,

The datasheet of the TXS0108E shown 'Io Continuous Output Current is +/- 50mA'. I assume any IO pin will capable of sourcing and sinking current up to +/-50mA. I found that it can source current that high, but current sink is only 5mA. Please help me to understand the data sheet spec. Thanks

Nhan Pham

  • 0
    Prodigy 30 points

    Could someone from TI please explain urgently.

    I have sample chips which seem to only be able to source and sink tiny currents <1mA (the datasheet specifies continuous +-50mA max (it does not say by 1shots during switching only) My application is extremely slow data rate. I may have damaged them by having thre ground floating during my initial test

  • 0 in reply to Hilton Moore
    Prodigy 170 points

    Don't rely on TI support. They never answered my question. I changed this part to SN74LVC8T245 for my design. The SN74LVC8T245 requires to have a direction control pin. My application is output only, so I tie DIR pin high permanently. Hope this will help. 

  • 0 in reply to Nhan Pham
    Prodigy 30 points

    Thanks, I'll probably add logic to obtain a direction signal and use MC74LVXC3245DT.

     

  • 0 in reply to Hilton Moore
    TI__Expert 6430 points

    Hi,

    '50mA' is short clamp current. The device cannot provide this value current under normal operation. Under normal operation, during low-to-high transition, TXS0108E can source more than 15mA current since 'one-shot' circuit is working. During high-to-low transition, TXS0108E can sink about 10mA current. For DC value, the source current will depend on power supply since source current is determined by power supply and internal 10k pull-up resistor and sink current will be less than 500uA whicn also depend power supply value.

    Thanks

     

     

  • 0 in reply to Wei Lang
    Prodigy 30 points

    Thank you for the good explination.

    You can close this query. (just one last thing please)

    I looked at the SN74LVC8T245 datasheet as an alternative.

    Is that chip able to source and sink significant current at DC condition. (I use 3v3 and 5V supplies)

    It states  Ioh and Iol max, but I am worried those are during transitions only?

    Can you tell me the estimated currents at DC please.

     

  • 0 in reply to Wei Lang
    Prodigy 170 points

    If the IC can not provide +/- 50mA continuously, the ABSOLUTE MAXIMUM RATINGS table should not listed "Continuous output current  of +/- 50mA" then.

  • 0 in reply to Nhan Pham
    TI__Expert 6430 points

     "Absolute maximum ratings" are stress ratings only, and parameters under normal operation are under "recommended operating conditions".

    Thanks

  • 0 in reply to Wei Lang
    Prodigy 170 points

    If the part can not provide up to +/- 50mA CONTINUOUSLY in a shorted load (R load = 0 ohm) condition, I can't think how can you over stress the part. Just like if I have a car that can not get up to 30 mph, but I tell my friend "don't drive it over 200 mph". It sounds silly isn't it?

  • 0
    Prodigy 130 points
    Marketing deception, because many hobbyists at first BUY, then test and thoroughly learn datasheet. There not big profit for TI but now I know how this company is lowering.