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TXB0108: TXB0108 or TXS0108E or TXS0206 for SD card interface?

yukihiro
Prodigy 120 points
Part Number: TXB0108
Other Parts Discussed in Thread: TXS0108E, TXS0206, TXS0206A

Hi, now I am using TXB0108 between i.mx6-CPU and SD card interface for my prototype.

VCCB side is used for CPU (3.3V), VCCA side is used for SD card (battery backuped by approximately 3.4V)

In SD card specifications, class10 is enough for me.

I have two questions.

1.

Contrary to TXB0108 datsheet, VCCA is a little higher than VCCB by 0.1V.

But according to the application report below,

www.tij.co.jp/.../scea060.pdf

if the voltage difference is under 0.6V, it seems that any problems won't occur.

Is it OK for my how to use?

2.

Though TXB's drive strenght is too low, now my prototype began to run  in some way.

I am worried whether  I should keep to use TXB0108 for mass production.

But in the other device such as TXS0108E or TXS0206,

TXS0108E's internal pull up resisters are invalid when OE is low level and then TXS0206 is hard to mount for us due to its 0.4mm pitch BGA package.

Is it OK to use  TXB series for class10 SD card interface?

  • 0
    TI__Guru 62050 points
    Hello,

    welcome to e2e !

    I am glad that you have referred to the app note. There should not be any cause of concern having the Vcca = Vccb+0.1V. I would not advise having greater than 0.3V difference as there could be process/temperature shifts which can affect the diode behavior to start conducting and consuming increased current.

    TXS internal pull-up is disconnected when OE is asserted, will this be a problem? I believe that this is expected behavior where by default there is no voltage on the IO lines.

    TXS0206A is an application specific device built for SD card interface, I would suggest you consider using that because, in mass production, there is automatic mounting of the device onto the PCB instead of hand soldering.
  • 0 in reply to ShreyasRao
    Prodigy 120 points
    Hi ShreyasRao.
    Thank you for your reply.

    > will this be a problem?

    I am worried about the statement of SDA specification below.
    ---
    SD Specifications Part1 Physical Layer Specification Ver 6.00
    P226, P235
    To prevent bus floating, pull-up resistance(10K-100Kohm) is needed for SD card DATA line and CMD line.
    ---
    But it's okay I can put the pull-up resistance outside.

    With regard to TXS0206, 0.4mm pitch is too narrow so I am hesitating to use this device for increasing possible defect rate of mounting.

    By the way does TXS0206 need to keep VCCA < VCCB like TXS0108E or TXB0108?

    Regards,
    Yukihiro
  • 0 in reply to yukihiro
    TI__Guru 62050 points

    Yukihiro san,

    It is not a good idea for have floating inputs in general for the CMOS devices.
    With the TXS0206, there is no need of external pullup resistance as the IO will have a defined voltage with internal pullup resistance.
    There is no restriction for the TXS0206 regarding Vcca and Vccb biasing requirements to be less than or equal.
    I confirm this from the abs max and the recommended operating conditions of the datasheet.

    It is good information for us to know that there are restrictions on accepting the 0.4mm pitch devices. We are coming out with many devices with smaller pitch (0.35mm) as the needs of the industry for smaller devices in terms of area especially in the Personal electronics field.

  • 0 in reply to ShreyasRao
    Prodigy 120 points

    Hi ShreyasRao.

    Thank you for the TXS0206's helpful information.

    In terms of the first question,　Is it possible to use TXB0108 for class10 SD card interface ?

    Regards,

    yukihiro

    Oh in NEW FAQs,
    http://www.ti.com/lit/an/scea030b/scea030b.pdf
    It is said that TXB is designed for SD or SPI.
    Thank you, C.Ryan Land.
    Is TXB used widely in SD card interface?

    Regards,
    yukihiro

  • 0 in reply to yukihiro
    TI__Guru 62050 points
    Yukihiro san,

    Yes, you can use TXB for SD card interface.
    I see that there are some IOs which could be open drain and TXB is advised for PP interface.