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ISO7221A-Q1: Background or Revising the datasheet

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Replies: 3

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Part Number: ISO7221A-Q1


The datasheet was revised on the other day and some spec were degraded as attached.


Why were specs degraded?

I think that this degrading is an abnormal situation.

Best Regards,


  • Hi Kuramochi-san,

    Thank you for listing out some of the changes made to ISO7221A-Q1 datasheet. Please note that these are not degradation in specs, rather a more useful specifications that cover power supply variations. Please see below my inputs,

    1. Though the worst-case value for datarate is 1Mbps, it was stated to have a typical value of 1.5Mbps in earlier version of datasheet. Though this is still true and device will still support 1.5Mbps datarate under typical operating conditions (5V, 25C), this may not be very useful data as the actual applications won't be operated under typical operating conditions always. The actual applications can experience variations in VCC and temperature and hence 1.5Mbps doesn't stand as a good representative of device performance.
      1. Hence, we decided to provide you more useful datarate specification that covers both supply and temperature variation. i.e., 1Mbps is a more realistic datarate.
      2. Similarly, the typical values for tui are also removed as they are not representative actual applications.
    2. Propagation delay and PWD specs were earlier quoted by not considering any VCC variation which again is not a representative of actual application. Hence, ±10% VCC variation is assumed in quoting these specifications. When supply variation is considered, these parameters will increase in value as expected.
      1. If one operates the device with well regulated 5V power supply, they will see much lower max values even now.

    I hope this answers your question, thanks.

    Koteshwar Rao

  • In reply to Koteshwar Rao:


    Thank you for your quick response.

    I understand what you say.

    In this case, why were specifications not added but changed?

    Can we consider that previous specifications is also guaranteed actually?

    Best Regards,


  • In reply to Kuramochi Tadahiko:

    Hi Kuramochi-san,

    Even though the earlier specifications are all correct, customers might assume them to be wrong.

    For example consider let's consider propagation delay. Propagation delay was earlier quoted at VCC = 5V but when customer tests it in their lab or in customer product where if the VCC value is either lower or higher than 5V then they might see a propagation delay value which is larger than earlier datasheet value. This can make customer believe that device is not meeting datasheet values whereas the actual increase in propagation delay is due to VCC voltage variation and not datasheet violation.

    Hence, the specs were updated to reflect realistic values. Please note that the changes were done to existing specs and no new specs were added. Hence, there was no addition but an update of an existing specs itself.

    Koteshwar Rao