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Using txs0108e between am335x and wl1271 for sdio voltage level translation

Shi Zhaohui
Prodigy 80 points
Other Parts Discussed in Thread: TXS0108E, WL1271, TWL1200, WL1835

Hi,all.

I referenced to AM335x Starter Kit for my design. But I changed MMC1 pins, powering from  VDDSHV5(3.3V). So I use txs0108e to translate voltage level between am335x(3.3V) and wl1271(1.8V). 

Attached is my schematic. Please check if this circuit is correct or not. And what else should I pay attention to when using txs0108e?

Thanks.

  • 0
    TI__Expert 4705 points

    Hi, Zhaohui,

    Based on the schematic, the connection is OK and no issue. 

    Just some further thinkings here.

    1. Since it is for SD card, do you care about the power consumption when in disable status? if so, suggest put the EN can be controlled, which means connect it to one GPIO while have a pull down resistor.

    2. Another thinking is to make sure all the IO are in high-z status when power on by put the EN to low,because when powering up, we can not make sure the IO staus are what you want. in the datasheet, we have below suggestion.

     "To ensure the high-impedance state during power up or power down, OE should be tied to GND through a
    pulldown resistor; the minimum value of the resistor is determined by the current-sourcing capability of the driver."

    But if you don't care the IO status when powering up, you can keep your schematic without changes.

    3. Also the TXS0108E has the internal pull up resistor to VCC when it is in the enable status, when IO is"high", the value is 4Kohm, when IO is "Low", the value is 40Kohm. So, you don't need to add the external pull up resistors. But if you want to have the default high status for the IO when disable status. 

    Those thinkings are just for your reference. any unclear, please let me know.

    BR

    Junjie

  • 0 in reply to Junjie Mai
    Prodigy 80 points

    Hi, Junjie, 

    Thank you for your replaying.

    According to an application note from LS Research, which is attached bellow, all SDIO I/Os except SDIO_D3 of wl1271, are open drain.

    According to the datasheet of txs0108e,

    Max Data Rates

    – 60 Mbps(Push Pull)

    – 2 Mbps(Open Drain)

    So can the data rates meet the requirement of SDIO interface?(The max SDIO clock rate of wl1271 is 25MHz). 

    Thanks.

  • 0 in reply to Shi Zhaohui
    TI__Expert 4705 points

    Hi, Zhaohui,

    Actually, we have one level shifter which is TWL1200, it is designed for WL1271/3 to implement the level translation and worked well.

    You can see in the datasheet for TWL1200, it has the same structure and datarate with TXS0108E.

    So there should be no problem. I am also checking this concern with WL1271 group, if any update, will let you know.

    BR

    Junjie

  • 0 in reply to Junjie Mai
    Prodigy 80 points

    Hi, Junjie, 

    Thank you for your help. 

    Looking forward for the replaying from WL1271 group.

    Thanks.

    Zhaohui

  • 0 in reply to Junjie Mai
    Prodigy 80 points

    Hi, Junjie, 

    Is there any update from WL1271?Thanks.

    Regards.

    Zhaohui

  • 0 in reply to Shi Zhaohui
    TI__Expert 4705 points

    Hi, Zhaohui,

    Here is the current feedback I have. so based on that you can see TXS0108E is in our their reference design.

    " For all our reference design we use http://www.ti.com/product/TXS0108E as the level snifter from 3.3V to 1.8V and vice verse. 

    Indeed for WL7 the max SDIO clock is 24MHz .Am not familiar with the 2Mbps limitation mentioned and it is not quoted on the spec refereed. can not advise on LS change but recommend to keep the reference LS which has proven performance both from voltage and transient switching time (also at high speed IO toggle)

    "

    BR
    Junjie

  • 0
    Intellectual 375 points

    Hi

    refering to current discussion about the use of level translator. 

    attached schematic for the verification. incase of TWL1200 connection to WL1835 mod. 

    pls. confirm the connection diagram.