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LSF0204D: Leakage current rises 1.8V rail voltage?

Prodigy 670 points

Replies: 9

Views: 230

Part Number: LSF0204D

Hello,

My customer is trying to translate 1.8V and 3.3V with LSF0204DPWR.

VREFB = 3.3V and VREFA = 1.8V.

The customer observed issue that the 1.8V rail rises to 2.1V. 

My customer removed LSF0204DPWR and then the 1.8V rail returned to 1.8V.

1.8V is coming from TLV70018 which is powered by the 3.3V.

I guess this is due to leakage current from VrefB to VrefA.

How my customer improve his design?

Regards,

Itoh

  • There is leakage current of about 3 µA. I doubt that this is large enough to be a problem.

    But if that current is the problem, then a 470 kΩ resistor between 1.8 V and GND will help.

  • In reply to Clemens Ladisch:

    Hello Clemens-san,

    Thank you for the reply. Could you please review my customer's schematic?

    I'd like to send it to you via email.

    I cannot find your name from the directory, so could you please search my name and reach out to me?

    Regards,

    Itoh

  • In reply to Kazuki Itoh:

    I am not a TI employee.

  • In reply to Clemens Ladisch:

    Hi Clemens-san,

    Wow, thank you for your volunteer!

    100kΩ resistor between 1.8V and GND  worked.

    But my customer don't like this solution because it increases leakage.

    Do you happen to come up with other solution?

    Regards,

    Itoh

  • In reply to Kazuki Itoh:

    With LSF translators, the leakage current is unavoidable due to the architecture of the reference transistor:

    It should be possible to replace it with the TXS0104E. If automatic direction sensing and open-drain signals are not needed, a direction-controlled translator like the SN74AXC4T245 or SN74AXC4T774 would be a better solution.

  • In reply to Clemens Ladisch:

    Hi, 

    Is TXB0104 or TXS0104E capable of driving 6kΩ external pull-up resistor?

    Regards,

    Itoh

  • In reply to Kazuki Itoh:

    The TXB cannot drive more than 20 µA.

    The TXS uses passive switches, so the 6 kΩ pull-up will work if your other devices are capable of driving it. (And the TXS has internal pull-up resistors and does not need external ones.)

  • In reply to Clemens Ladisch:

    Hi Itoh-san,

    What communication protocol are they using? The TXB/TXS families don't like having pull-ups/pull-downs are the signal lines., especially ones as strong as 6 kohm. If its something like I2C and they can avoid using external pull-ups then I believe the TXS would be the best choice.

    Check out our new AXC family of Voltage Translators! 

    Watch the Introduction to AXC Family to find out more about the family.

  • In reply to Dylan Hubbard:

    Hi Dylan-san,

    I'd like to send the schematic to you offline. Please accept my friend request.

    Regards,

    Itoh