TXS0102: Use TXS0102 to drive LED current

Ben Kuo

Part Number: TXS0102
Other Parts Discussed in Thread: SN74AVC2T45, SN74LVC2T45, SN74LV1T34, SN74AVC2T244, SN74LV1T32, SN74LVC2G04

Dear expert,

I have a circuit on hand and would like to get your feedback about it.

In my opinion, this cannot work. Because the internal pull high resistor is 10K-ohm. So only can drive 0.33mA.

Can I use LSF family to replace TXS in this application? Thanks!

over 8 years ago

0 Clemens Ladisch over 8 years ago

Guru 325520 points

Yes, the TXS has almost no drive strength for high-level signals (because it is intended for open-drain signals).

LSF devices have the same problem (although you could choose stronger pull-up resistors).

But in this application, a bidirectional level shifter is not needed. Simply use one SN74AVC2T244, SN74AVC2T45, SN74LVC2T45, or two SN74LV1T34‍s.

Or, even simpler, use two level-shifting OR gates (SN74LV1T32).

0 Michael J Schultis over 8 years ago in reply to Clemens Ladisch

TI__Mastermind 25225 points

Hello Ben,

I agree with Clemens on this one. Any of his recommendations would work with SN74LV1T32 being the simplest.

Best,
Michael

0 Ben Kuo over 8 years ago in reply to Michael J Schultis

TI__Expert 7670 points

Hi Clemens and Michael,

Thanks for your reply. One more question about this application.
Did TI have some app note or document which is talking about driving bi-direction LED via logic IC?

-Ben

0 Emrys Maier over 8 years ago in reply to Ben Kuo

TI__Guru* 97666 points

There's isn't an application report, however it seems like a very simple solution. This is how I would do it:

Something like an SN74LVC2G04 should do the trick. In this case, one of the LEDs will always be on.

0 Ben Kuo over 8 years ago in reply to Emrys Maier

TI__Expert 7670 points

Dear Expert,

In my opinion, below circuit can work normally to swap between blue and white LED.

Is there any risk on my circuit? Thanks!

-Ben

0 Emrys Maier over 8 years ago in reply to Ben Kuo

TI__Guru* 97666 points

Hi Ben,
This will work fine. If SYS_WHITE_LED and SYS_BLUE_LED are different, then one of the LED's will turn on. If they are the same, the LEDs will be off.

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TXS0102: Use TXS0102 to drive LED current