This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TXS0206: TXS0206 Latch Up?

Part Number: TXS0206

Hi All,

We have a TXS0206 issue ... in simple SD card buffer application.

Although our card can potentially have different VCCA/B, the supplies are connected in this case, so VCCA = VCCB = 3.3V

The A side signals are all LVCMOS33, and the SD card is 3.3V

WP is left unconnected.

If EN = 1, CD = pulled high, we can see CLKA propagated to CLKB correctly.

However, for the purposes of the issue, EN can be high or low. 

All is well, until CD is switched low, either when an SD card is inserted, or with a temporary jumper, at which point the part crowbars the supplies, and with no supply protection, kills the part. This happens regardless of whether CD is low at power-up, or if CD is switched low with power on.

On further investigation, and live part, a 27R resistor between CD and GND is pulled to 2.5V, i.e. sourcing ~100mA

This happens even if all the other signals are tristate.

We've looked at the obvious things (shorts, layout etc), and there appears to be nothing obvious.

The only visible issue (in relation to earlier posts), is that some of the signals (DAT1, DAT2) are unused and floating on both ports. I don't see why that would be an issue, given the on-chip pullups.

It's possible it's a manufacturing issue, but it occurs on multiple boards.

Has anyone else seen anything similar?

Thanks 

Julie

  • Hi Julie,
    I have notified the appropriate apps specialist. He should be back with you soon.
  • Hello Julie,

    We have not seen this issue before.
    Are both VCCA and VCCB connected to the same supply, or are they independent 3.3V supplies?
    If they are separate does it pull both down?

    When a known good part is populated and powered up with the CD pulled high, what is the resistance between the CD and VCCA pin? CD and VCCB Pin?

    If you are willing to share a snippet of your layout I could look that through as well.

    Best,
    Michael
  • Hi Michael,

    Thanks for the reply. I'm on vacation at the moment, so I can't immediately answer you on all points.

    I can say that VCCA and VCCB are ultimately the same supply, not independent. I say ultimately, because the SD module has a flexible cable that routes VCCA and VCCB independently, so the power nets are joined at the motherboard. It's a short flexi.

    I'll look into the other questions when I get back mid-week.

    Thanks

    Julie