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TXS0206 VilB and VihB With SD card

Joe S
Prodigy 70 points
Other Parts Discussed in Thread: TXS02612, TXS0206

We are looking at using the TXS0206 or TXS02612 in a 1.8V CPU <-> 3.3V SDcard translation.  

I do not have access to the complete SD card specifications, but I have found the datasheets for a few SD cards and they all seem to agree.

Voh @100uA = .75* VCC = 2.475V

Vol @ 100uA = .125 * VCC = .4125V

The TXS0206 has the following input requirements on the B inputs.

Vih = VCC - .2V = 3.1V
Vil = .15V

From the above it appears that SD cards will not be able to trigger logic high and low on the B inputs of the TXS0206.  Since this chip is designed specifically for use with SD cards I feel that I am missing something in the operation of the part.

Can you describe how the SD card outputs can meet the require logic thresholds of the TXS0206?

  • 0
    TI__Guru 62270 points
    Hi Joe ,

    I will move this into voltage translation forum for appropriate support .
  • 0
    TI__Genius 16510 points
    Hello Joe,

    After looking into this more, I will agree with you on some points.

    This device does not appear to meet the VIL and VIH requirements of the SD card specifications you have right out of the box.

    It is possible to lower the VIH by using a pull-down resistor, which is listed in the datasheet. FOr example, with a 10k resistor, it will bring the VIH to 0.714*Vcc = 2.36V.

    VIL is fixed so that we can guarantee a VOL of 0.55. If the device receiving the signal on the other end of the TXS0206 can handle a higher VOL, then VIL can be raised as well.

    Another possible option for you is to look at the SN74AVCA406E
  • 0 in reply to Jonathan Valdez
    Prodigy 70 points

    Unfortunately our processor(Freescale T4240) does not have the direction pins needed on the SD card interface to use the SN74AVCA406E. So we will be forced to use a bidirectional translator.

    A follow up question would be. Do you have any bidirectional translators for SD card use that meet the input requirements of a SD card?

  • 0 in reply to Joe S
    TI__Guru 62270 points

    Hi Joe ,

    There are devices from TI which are dual supply and come with DIR pin for direction control.

    You can consider this device as an example . There are 8 or 16 bit options too .

    LSF can also be considered which is bidirectional translator but without direction control.