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ADS1018-Q1: ADS1018-Q1:

Siddharth Sangam
Intellectual 640 points
Part Number: ADS1018-Q1
Other Parts Discussed in Thread: ADS1018, ADS1118

Hi ,

We are using ADS1018-Q1 in our design for analog to digital communication through SPI.
We are setting +/-0.512V as internal reference and our 5V power supply has 100mV ripple voltage capability.
In addition to this we have added 0.1uF MLCC capacitor (mentioned in datasheet) + 1uF MLCC capacitor at supply voltage. 

Need to know what will be the impact on communication and functionality because of 100mV ripple voltage and
also need to know what should be the precautions added in circuit to avoid uncertain noise issues.

with regards,
Siddharth Sangam.

  • 0
    TI__Guru* 93085 points

    Siddharth,


    I don't have any specific information or characterization data for the ADS1018 on power supply rejection. Any change in characteristics may depend on the frequency of the ripple along with the magnitude, which you've said is about 100mV.

    I don't think there would be any impact on the communication, but I would look to the ADS1118 for the power supply rejection from which the ADS1018 is based. For that device, the offset power supply rejection is 0.2LSB/V. This is rather small, especially considering that the ADS1118 is a 16-bit device and the ADS1018 is a 12-bit device. Additionally, even if the power supply is stable, and you're measuring the inputs that have this ripple as a common-mode signal, it would also be small because the common-mode rejection ration is anywhere from 90dB to 105dB depending on the FSR setting. Even at 50Hz and 60Hz, the CMRR is typically 105dB.

    Many of the numbers I've quoted come from DC measurements, so they might not be the same as ripple that has some higher frequency. If you are that concerned about the effect of ripple, then I would either add an LDO for the supply or test this on the EVM or your own circuit platform.


    Joseph Wu