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THVD1550: Some problems about TIDA-01401

Robin Yu
Intellectual 2190 points
Part Number: THVD1550
Other Parts Discussed in Thread: TIDA-01401,

Hi team,

My customer has some problems about TIDA-01401 as below.

1.About the description in Page 7.

(1)using R42//R43 with 470pF  as a low pass filter to improve the immunity?

(2)using R42+R43 with 220pF as a low pass filter to improve the immunity?

(3)Both (1)+(2) are used or just one of them is enough?

(4)Why 220pF and 470pF are used in this case, how to calculate, determined by cutoff frequency? R42/43 is 59Ohm, it is for terminal impedance match?

2.About EFT test result of Fig.23 and Fig.25.

It seems the result of Fig.25 is worse after using the same transceiver. Does it mean our TIDA board is worse than the unknown encoder? How to understand?

If customer want to improve the EFT performance, what method could be used?

Thanks.

Robin

  • 0
    TI__Mastermind 25705 points

    Robin,

    About the implementation of common noise filter, you can use either one of the circuit to add the capacitor. In either way, the termination resistors R42/R43 (to match the cable impedance) are recommended. R38 and R46 are fail-safe biasing. You can find the related app note here.

    www.ti.com/.../slyt514.pdf

    The common noise filter works like the decoupling cap from Vcc to GND. The capacitor tries to keep the DC common mode voltage. You can find some discussion in this article.

    can-newsletter.org/.../c190a7e99e71c41e1bf4692d5da58cd1.pdf

    Since I don't have much information about the unknown encoder, it's hard to pin down what makes the difference in EFT performance. The main purpose of the testing was comparing THVD1550 and competitor's device in the same system. In general, if a customer wants good EFT performance, TX should use the device like THVD1550 that is optimized for EFT in design. RX is less critical but needs to be robust as well. The power design and bus filter can also have impact here.

    Regards,

    Hao