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High SPI interface with F28M35H52c controller

Govind K
Intellectual 510 points
Other Parts Discussed in Thread: F28M35H52C

Hello Friends,

I need to interface LDC1000 (Inductace to digital converter) with F28M35H52c controller. Details are below.

Interface: SPI , Speed: 4MHz, distance: 10 meters. 

How to extend these high speed SPI lines to controller to have a good noise immunity and better performance?? 

Is differentail signaling is required?? if yes, how ??

Please suggest design techniques . 

Thanks in advance. 

Regards,

Govind.

  • 0
    Guru 192875 points

    Hi Govind,

    Govind K said:

    Interface: SPI , Speed: 4MHz, distance: 10 meters. 

    How to extend these high speed SPI lines to controller to have a good noise immunity and better performance?? 

    Is differentail signaling is required?? if yes, how ??

    You can refer this note for extended SPI communication: http://www.ti.com/lit/an/slyt441/slyt441.pdf

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Intellectual 510 points

    Hello Gautam,

    Thanks for reply. Now i have to decide whether i really required a clock synchronization for my application??

    I have calculated max bus lenth as 16 meter at 4MHz master clock. Calculation method followed is explained below:

    SPI clock frequency f=4MHz, .=> T=250ns. that means, i have 125ns (250ns/2) time to get data from slave before next clock period starts.

    As per my sensor spec, it takes maximum 20ns to put data on SDI line of master.

    So i have 125-10=105ns time. 

    Assuming clock speed 0.5 feet per 1ns (please correct me if i am wrong), Maximum allowed SPI bus length is

    0.5*105=52.5 feet = 16 meters.

    My applicatin needs, maximum of 5 meter bus length. 

    Could you please check whether my approach is correct?? 

    Thanks in advacne.

    Regards,

    Govind.

  • 0 in reply to Govind K
    Guru 192875 points

    Govind K said:
    Could you please check whether my approach is correct?? 

    Seems alright.

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Intellectual 510 points

    Hello Gautam,

    Thanks for support. One final query on this topic.

    As per our discussion, propagation delay shouldn't be a problem for my application (3 to 5meters SPI bus length). 

    What about the noise immunity?? I am restricted to not to use 2nd SPI which is suggested in application note shared by you. So I can't use line drivers and receivers.

    Can you please suggest me on how to improve the noise immunity?? Also please share related material if you have.

    Clock speed: 4MHz, distance: 3 to 5 meters. 

    Thanks in advance.

    Regards,

    Govind

  • 0 in reply to Govind K
    Guru 192875 points

    Govind K said:

    What about the noise immunity?? I am restricted to not to use 2nd SPI which is suggested in application note shared by you. So I can't use line drivers and receivers.

    Can you please suggest me on how to improve the noise immunity?? Also please share related material if you have.

    Govind, there are lot of articles available online. I would like you to check them out. I can't point out only one or two, hence please refer online.

    Regards,

    Gautam