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TXS0104E: TXS0104E for LED on/off control

Arthur Huang
Expert 6065 points
Part Number: TXS0104E
Other Parts Discussed in Thread: SN74AVC4T245, SN74LVC07A, SN74LVC2T45, SN74LVC8T245, SN74AHCT125, CD74HCT125

Hi Team,

customer is adopted TXS0104E device for LED on/off control as below schematic, please help to advise if it's ok or not? Thanks.

Regards,

Arthur

  • 0
    TI__Mastermind 27015 points
    Hello Arthur,

    I would not recommend trying to drive LEDs with the TXS0104. The DC drive strength of the TXS0104 is only around 20uA so it is not strong enough to drive the output of an LED. I would recommend that you use an LVC4T245 instead as it can provide several mA of drive current to power the LEDs.
  • 0 in reply to aozer
    TI__Expert 6065 points

    Hi Aozer,

    I don't find the LVC4T245 product information, only SN74AVC4T245. available on TI home page.

    After looked up the SN74AVC4T245, I found its maximum continuous output current is same as the TXS0104E as 50mA.

    Any comments from you is very appreciated.

    Regards,

    Arthur

  • 0
    Guru 285580 points

    The TXS devices (S = "switch") are designed for open-drain buses; they use a pass transistor and have no drive strength by themselves.

    A TXS output cannot source current; it can sink current if the device driving its input can handle that current plus the current through the pull-up resistors. Assuming that the GPIO outputs are not too weak, this circuit will work fine.

    (See A Guide to Voltage Translation With TXS-Type Translators (SCEA044).)

    And neither the auto-direction sensing nor the one-shot edge speedup are needed for driving a bunch of LEDs. I would consider a simple open-collector driver with 5 V-tolerant outputs, such as the SN74LVC07A.

  • 0 in reply to Clemens Ladisch
    TI__Expert 6065 points
    Hi Clemens,

    Thanks for your feedback. We will propose this SN74LVC07A to customer. However, since the SN74LVC07A is for 6 channels, while customer only needs 4 channels, so do you think the SN74AVC4T245 is an another option or not? Please advise. Thanks.

    Regards,
    Arthur
  • 0 in reply to Arthur Huang
    TI__Mastermind 27015 points

    Hello,

    The SN74AVC4T245 will not operate at 5V, only up to 3.6V.

    Sorry, I was mistaken about the LVC4T245, we do not have a 4 bit LVC translator. You could use two 2-bit  SN74LVC2T45 translators, or a single 8-bit SN74LVC8T245. 

  • 0 in reply to Arthur Huang
    TI__Guru 59070 points
    Arthur ,

    There are various quad buffer gates you could consider like the sn74AHCT125 which operates at 5v and TTL input compatible.(Vih =2V).
    also , CD74HCT125 is another option.
  • 0 in reply to Arthur Huang
    Guru 285580 points

    since the SN74LVC07A is for 6 channels, while customer only needs 4 channels

    It does not have more pins than the TXS0104E (but of course a different pinout).
    Just tie the unused inputs to VCC (or use two outputs in parallel to get even higher drive strength).

    sn74AHCT125 ... CD74HCT125

    The circuit looks as if it wants more than 8 mA drive strength (although it uses the same resistance for LEDs with different forward voltages).