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TXS0102: TXS0102 Gives OUTPUT After 20 Seconds

Muhammet Serhan Özyigit
Prodigy 10 points
Part Number: TXS0102

Hi ;

I am using a TXS0102 level shifter in a MDIO line for shifting +1V8 CPU MDIO and +2V5 PHY MDIO.

But sometimes i am encountering accessing issues so i have checked the waveforms and I did not observe any problems. However, I saw that the +2V5  outputs of the TXS0102 started to give output approximately 20 seconds after the CPU started generating the clock, and the line remained at high during these 20 seconds.

What can cause this ? Also do i need to place pulup resistors in MDIO and MDCLK lines ?  How can i calculate the pull up values ? According to the datasheet maximum input clamp current is 50mA can low value pull ups exceed this current value and cause damage to the IC?

Thanks

  • 0
    TI__Mastermind 40216 points

    Hey Muhammet,

    It could be that the device is disabled during the first 20 seconds- what is driving the OE pin during this time? (Note the 4.7kohm pullup can be removed on the OE pin). Is there a particular power sequencing with VCCA/ VCCB in your system during boot up? Also note that external pullups are not recommended as the device contains internal 10kohm pullups. If pullups are absolutely required, it is suggested for them to be above >50kohms to not contend with the internal pullups. 

    Please also see Effects of pullup and pulldown resistors on TXS and TXB devices for more information.

    Regards,

    Jack