• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 32 subscribers
  • Views 147 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

SN65HVD63: How to choose AC coupling capacitor

Yishan Chen
Intellectual 1030 points
Part Number: SN65HVD63

Tool/software:

Hi,

Customer have asked me one question about the RXIN AC capacitor value.

I want to know why the capacitance is 220nF, Could it be 100nF,X7R,1608 package capacitor?

Thank you

Yishan Chen

  • 0
    TI__Guru 60540 points

    Yishan,

    The device was designed/tested/validated around the 220nF cap. It also affects the passband filter. Please use the 220nF as recommended by the datasheet.

    -Bobby

  • 0 in reply to BOBBY
    TI__Intellectual 1030 points

    Hi Bobby,

    Thank you for your answer.

    But customer is tested in 100nF, would it have some potential risks?

    Besides, could you tell me how this affects the pass band filter?

    Best Regards,

    Yishan Chen

  • 0 in reply to Yishan Chen
    TI__Guru 60540 points
    Yishan Chen said:
    But customer is tested in 100nF, would it have some potential risks?

    I did run a simulation using simple RC circuits. The difference in attenuation when driving through the cap into a 50 ohm load was only 1%. This was using the 2.176MHz carrier frequency. I don't necessarily think the carrier transmission is that heavily affected by changing the coupling capacitor. 

    The data wave signal did see a bit more distortion when I used a lower data rate (9600bps). 

    Yishan Chen said:
    Besides, could you tell me how this affects the pass band filter?

    Unfortunately this device is quite old. I don't think we will be able to locate the files to find out what the internal receiver band pass filter looks like. 

    -Bobby