• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 20 subscribers
  • Views 401 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TXS02612: SD card cannot be recognized at CLK50MHz

Shinichi Inoue
Guru 21701 points
Part Number: TXS02612

Dear Specialists,

My customer is considering TXS02612 and has a question.

I would be grateful if you could advise.

--- 

We have a question about TXS02612RTW.

We are currently developing products (COM Express board, COM Express carrier board) that implement TXS02612RTW.
TXS02612RTW is used for voltage level conversion between CPU (1.8V series) and SD Card socket (3.3V series), and is mounted on the COM Express board side.
(Could you please see the block diagram in the attachment).

When I inserted the SD Card into the SD Card socket and checked the operation, the CPU did not recognize the SD Card, so I debugged and measured the waveform.
As a result, it was found that the CMD waveform was distorted and reflected noise was generated when the clock frequency was operating at 50 MHz.
(Could you please see the waveform in the attachment).

When the clock frequency was lowered to about 1MHz, the CPU recognized the SD Card and confirmed that the waveform was not distorted.

Could you please let us know about the possible reasons for these and how to fix with them (such as the placement position of parts and the regulation of wiring length)?

As reference information, the wiring length is as follows.
CPU <-> TXS02612RTW: About 20mm
TXS02612RTW <-> COMe Connector wiring length: about 100 mm
COMe Connector <-> SD Card socket wiring length: about 150mm

QA_TXS02612RTW_20220707A.xlsx

---

I appreciate your great help in advance.

Best regards,

Shinichi

  • +1
    TI__Guru 51686 points

    Hi Shinichi,

    Thanks for the detailed information provided. The schematics with how the pins are configured would also help give some feedback.

    However, please see section 3 and 4 for the referenced AppNote explaining the possible reasons for your observation.

    For the bi-directional signal; I would recommend considering the below while keeping the traces and capacitive loading as minimal as possible due to transmission line effects.

    • Cables/connectors do not work well with the device. Taking the connectors out (if possible) would help with the signal integrity while also minimizing the trace length.
    • Adding some series resistors to match the impedance of your the transmission line would also help.
    • Keeping the output impedance of the external driver less than 50 ohms should also help.
    • Also, keeping the total capacitive loading (from signal trace to connector, to signal trace, to connector, to signal trace, to SD Socket), <70 pF would be very significant for the signal.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    Guru 21701 points

    Hi Michael,

    Thank you for your reply.

    I understand it should be taken care of trace and capacitive load.

    I'll share these information with the customer.

    When the customer have an additional question, I consult you again.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi