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ADS1112 and ADS1115 - conversion time/I2C R/W delay

Alan Yeo
Prodigy 40 points
Other Parts Discussed in Thread: ADS1112, ADS1115

Together with a DAC, I am using the ADS1112 in a fast closed measurement loop. I need to read from only 1 channel (Ain0) as fast as possible. What is the minimum delay I should  set between I2C write to start conversion and I2C read ? The datasheet states 15samples/s in 16 bit ...is the conversion time 1/15s?

I plan to change to a faster converter ADS1115 which has 860samples/s rate....what is the min delay i should set? What is the conversion time for this converter?

  • 0
    TI__Guru** 113765 points

    Alan,

    Welcome to the forum!  I will assume that you want the 16 bit level of performance and will run the ADS1112 at the 15sps mode.  The typical value will be 1/15 of a second for conversion time, but the internal oscillator can vary from part to part by about 25%.  The datasheet shows minimum sample rate at 11sps to a maximum of 20sps.  You will need to use 11sps to be sure all possible parts will fit the criteria.  You would need to delay at least 90.09ms.

    The ADS1115 will be similar in that you need to consider internal oscillators that may vary from part to part.  The ADS1115 can vary +/- 10%, so if you have a nominal data rate of 860, the minimum will be 90% of 860 (774sps.)  This would require a minimum delay of 1.29us.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 40 points

    Hi Bob, thank you for your response. I need at least 16bit hence the choice of the above converters. last night, i tried with success, single shot conversion and a loop to check the RDRY bit to confirm end of conversion instead of a fixed delay loop.

    I believe you made a typo ...the ADS1115 min delay is 1.29 ms and not usec.

    Can you suggest some of your fastest i2C based data converters for me to consider.

    Best Regards.

  • 0 in reply to Alan Yeo
    TI__Guru** 113765 points

    Alan,

    You are correct, I made a typo in my previous post.  The ADS1115 family is the fastest 16 bit I2C device we currently have.  We have faster 12 bit devices. 

    Best regards,

    Bob B