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TXB0104-Q1: Using TXB0104-Q1 for SWD(Serial Wire Debug) interface

Chase Jeong
Mastermind 9915 points

Part Number: TXB0104-Q1
Other Parts Discussed in Thread: TXB0604

Deat TI experts,

My customer made their PCB using TXB0104-Q1 for SWD(Serial Wire Debug) interface.

During the test, customer found that SWD is not connected properly even waveform seems fine.

Please check the waveform and schematic below.

Am I missing something? or TXB0104-Q1 is not suitable for SWD interface?

Please check this issue. Thanks.

Best regards,

Chase

  • 0
    TI__Guru 61061 points

    Hi Chase,

    The input edges appear to be quite noisy, is there any chance that can be cleaned up going into the device? (for example, the CLK edges on A2 distorted with ringing throughout the signal and bounces off GND). 

    Regards,

    Jack

  • 0 in reply to Jack Guan
    Mastermind 9915 points

    dear Jack,

    Thank you for your support.

    - Is there any chance that can be cleaned up going into the device? -> I think there is not, because they had no issues which customer used previous device (Nexperia)

    1. Do you think that A2 CLK noisy edges are one of the reason of not communicate?

    2. Do you have ideas to remove these noises by adding capacitor or something else?

    3. Is there any chances to get better by using another level shifter device?

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Guru 61061 points

    Hi Chase,

    1. Yes correct, the input CLK edges on A2 appear to be driving mid-rail for a low state/ ripples along the bus can be cleaned up better. 

    2. Customer can try to retest with the load disconnected at the output side. This would help to rule out if signal integrity is compromised due to excessive parasitic capacitances. 

    3. If the Q1 grade is not required here, the TXB0604 can be used as it was designed to drive signals over longer distances/ higher capacitive loads at the output. 

    Regards,

    Jack