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ADS7807: ADS78xx Errata

Part Number: ADS7807


Dear, All

Customer has questions about Errata of ADS78xx.
They thought that they read this Errata and occur only in the Serial data mode.
They are using the ADS7807 in Parallel data mode.
They shipped equipment using this device for over 5 years.
Until now, this kind of problem did not occur.
However, the phenomenon written in Errata this time occurred.
That is, even if the first R/C signal was turned on, the BUSY signal did not respond.
Their question is whether this Errata only covers the Serial data mode or includes Parallel data mode.
Please tell me.

Thanks, Masami M.

  • Hello,
    I am looking into this and will back to you soon
    Regards, Cynthia
  • Hi, Cynthia-san,

    Thanks for your support.
    I would like an early reply.

    Thanks, Masami M.

  • It seems that the errata applies when the device is being used in serial mode. The errata states that to enter the fault condition, EXT/INT is being held low. When using this device in paralllel this pin is pulled high.

    What state was CS when this occured? Could the customer provide a scope shot of this phenomenon? Did the customer change anything in the latest project from the previous work?

    If the costumer believes that they are experiencing simialiar issues and the errata needs to be expanded,  we will need to explore this to make sure all issues are covered.

    Regards, Cynthia

  • Hi, Cynthia-san,

    Sorry for the delay in response.
    I confirmed with the customer.

    From the conclusion it turned out that the phenomenon of their equipment is slightly different from the contents of Errata.
    As a result of their investigation, they found that the busy signal is operating normally at the first access from power on.
    However, the read data value at the time of the first access indicated an abnormal value.
    They set the reference value of the analog input to 1/2Vsd, but the first read data was 0x0001.
    They set this value as the error code.
    The second and subsequent read data was always normal.
    In the device where phenomena occurred, 22 abnormal data occurred out of 30 times.
    The device that has developed the phenomenon has been manufactured for less than 10 years ago, but it is a device manufactured in the last half of last year.
    We were able to deal with that in the same way as Errata.
    Please give me advice.

    Thanks, Masami M.

  • Hi, Cynthia-san,

    Thanks for your support.

    Customer confirmed again.
    They found that the first read data is not 0x0001.
    However, the first AD converted digital value outputted by the ADS7807 was outside the analog input voltage range.
    For this reason, the system converted to error code 0x0001.
    This phenomenon occurs only in the first access.
    Their reproducible environment will be removed at the end of May.
    Please contact them if you need something to confirm.

    Thanks, Masami M.
  • Thank you Masami-san

    I am glad they were able to find the root cause of their issue.
    Please let us know if the customer needs any support
    Regards, Cynthia
  • Hi, Cynthia-san,

    Thanks for your support.

    Please tell me.
    It is the same phenomenon as Errata when outputting outside value at the first access from ADS7807?
    Or is it another cause?

    Thanks, Masami M.

  • I do not believe this is the same as the Errata.
    The errata explains that the if in the fault condition the main issue is the internal serial clock output not allowed to go active. In the customer's situation, using in parallel, the internal serial clock output is not used and an external clock input is used instead.
    I would conclude that this issue is not the same as the errata.
    Regards Cynthia

  • Hi, Cynthia-san,

    Thank you for your answer.
    Please tell me.
    What is the reason why the read data value output from the ADS7807 greatly deviates from the analog input voltage only at the first access?

    Thanks, Masami M.

  • Masami-san,
    I cannot say definetly what is causing this behavior, but, from the infomration available, I suspect that the input voltage exceeding the input range might be what is causing this behavior. When bringing up the device from power down or reset care must be taken to ensure no input voltage exceeds the limits. If the customer would like, we can take this off line and talk about what actions to take to further look into the issue.
    Regards
    Cynthia