• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 46 subscribers
  • Views 1039 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.

ADS7952-Q1: Lock up of SPI

Chris Brune
Prodigy 30 points
Part Number: ADS7952-Q1
Other Parts Discussed in Thread: TMS320F28375S, ADS7952

Hello,

I am using the ADS7952 with a TI DSP (TMS320F28375S) in an inverter application.  Everything works correctly most of the time.  I am able to read the ADC values correctly in Manual mode.

When our inverter enables it does create more electrical noise in the system.

What I am experiencing is that the ADS7952 seems to lockup and not respond to the SPI port anymore.  It does not do this every time, just occasionally.

I have confirmed on a scope that the DSP is producing CS/SCLK/MOSI signals when in this locked up condition.  The SDO/MISO signal from the ADS7952 is just stuck low when in this locked up condition.

If I recycle power to the chip it starts operating normally again.

Wondering if there were any ideas on what might cause this and if there are perhaps some critical layout issues that should be looked at?

If the ADS7952 were to get some bad data sent to it would it cause it to lock up or get into a mode that wouldn't respond?

Is there some particular sensitivity to noise?

Thanks!

  • 0
    TI__Mastermind 21685 points
    Chris,
    I will look into this and get back to you.
    Thanks,
    Vishy
  • 0 in reply to Vishy Viswanathan
    TI__Mastermind 21685 points
    Chris,

    >>>>When our inverter enables it does create more electrical noise in the system.
    >>>>Wondering if there were any ideas on what might cause this and if there are perhaps some critical layout issues that should be looked at?

    Is it possible the ADC input is exposed to a sudden voltage surge? The maximum rating for input is -0.3V to VA+0.3V. Input signal beyond this range can make products behave unexpectedly or cause damage. Please check following app note for different methods to protect against overvoltage condition on exposed input pins

    www.ti.com/.../sbaa227.pdf

    Thanks,
    Vishy
  • 0 in reply to Vishy Viswanathan
    Prodigy 30 points
    Vishy,
    Although I agree with your suggestion I do not believe that it is addressing quite the issue that I have. That is are you suggesting that if an analog input is too high that the part would get into a mode where the CS input is ignored and the SDO output does not produce data?

    Do you know of any circumstance that would cause the CS input to be ignored and the SDO output to have no data?

    Regards,
    Chris
  • 0 in reply to Chris Brune
    TI__Mastermind 21685 points
    Chris,

    When inputs exceed this specification the internal esd protection diodes start conducting and a high current through the device can cause malfunction and damage. This condition applies to supply, VREF, and ADC input pins. Please see
    e2e.ti.com/.../567373

    Please monitor pin voltages at VA, REFP, VBD, and ADC input pins that are exposed and see if you come across anything unusual when inverter is enabled. Also, if you share with us your schematic/layout (we can do this offline if needed), we can review and give us our inputs.

    Thanks,
    Vishy