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Read problem of ADS7830

Taichi Noda
Expert 1350 points
Other Parts Discussed in Thread: ADS7830

Hi,All

Please let me ask you a question about ADS7830 because I was asked it by my customer.

When they read a sampling value without wait time as following upper diagram,

read value is always higher than true value by 2 or 3 LSB.

But when they read a sampling value with more than 25usec as following lower diagram,

read value is correct value.

Is there a rule about wait time?

According to a datasheet P3,conversion time is written 5usec so they  tried it ,but the results were wrong.

It seems that clock frequency to SCL is lower,read value is closer to correct value.

Is there a relation between read value and clock frequency?

Best regards.

Taichi.

 

  • 0
    Expert 1350 points

    Hi,all

    Please let me change a previous question to a simple question.

    If they insert a wait time between command byte and read -addressing byte,is there a problem?

    My customer said that datasheet P16 is written "In HS mode,there is not enough time for a single converthesion to complete betweenthe reception for repeated START condition and the read-addressing byte,so the ADS7830 stretches the clock after the read-addressing byte has been fully received,holding it LOW until the conversion is complete" so they was thinking that wait time is no need,but in the case of no wait time,sampling value is higher than correct value by 2 or 3 LSB.

    Best regards.

     

  • 0 in reply to Taichi Noda
    Expert 1350 points

    Hi,all

    This problem was caused by customers's circumstance.

    I'm sorry for all the fuss.

    Best regards.

    Taichi