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ADS1262: ADS1262 adc count stability problem

christy jude
Prodigy 110 points

Part Number: ADS1262

Hi

We are using ADS1262  ADC  module for our application.In our application we have the input voltage 1 mV to  2V.

And we are using mV source to test the module .For our test we give the 3mV .when reading the count from ADC module(32 bit) the  nearly 1000000 counts were jumped from mean value.and also i tested the adc count by truncating last 8 bits and 16 bits.

Please help me in this issue and how to stabilize the ADC count, and we have bought 50 nos module for our production.so please consider this as critical issue.

we are configured the module by default module settings and PGA - 32V.

the results given below and attached the graph also

the count value jump from mean value.the readings are given below

3mv --- count is  87475544   (for 32 bit count ),

highest count  from mean value  -  88201325

Lowest count  from  men value    -  86626213

1575112  counts jumping from lowest to highest.

3mv --- count is  340791   (for 32 bit count  last LSB were truncated ( adc_count >> 8),

highest count  from mean value  -   343045

Lowest count  from  men value    -  336827 

6000 counts jumping from lowest to highest.

3mV --- count is    1349  (  (for 32 bit count  16bits were truncated ( adc_count >> 16)

highest count  from mean value    -   1357

Lowest count  from  mean value    -  1338 

nearly 19  counts jumping from lowest to highest.

88201325
  • 0
    TI__Mastermind 44820 points
    Hi Christy,

    Assuming the ADS1262's default data rate (20 SPS w/ FIR filter), internal 2.5V reference, and a PGA gain of 32 V/V; a 1,500,000 code peak-to-peak noise corresponds to about 55uVpp. The ADS1262's noise performance in this configuration should be around 0.167uVpp...

    To confirm the source of the noise, would you try shorting the ADC inputs and measuring the shorted input noise? You can configure the INPMUX register such that AINCOM is selected for both the positive and negative inputs and then enable the VBIAS bit in the POWER register to set the common-mode voltage at mid-supply.

    If you find that the shorted input noise is close to the 0.167uVpp datasheet specification (about 5,000 codes PP), then you can conclude that the noise is coming from the input signal source. However, if the noise performance is still poor, then usually the next most likely issues are with power supply or ground noise (from the PCB layout).

    Best regards,
    Chris
  • 0 in reply to Christopher Hall
    Prodigy 110 points

    Hi

    Thanks for your immediate response

    I tested the ADC module as per you mentioned.For this test,I used the 5V dc adapter and see the result,I have attached the graph for your reference

    From the result,we conclude that there is noise in power supply circuit .

    please suggest me, what type of power supply that can be used for ADS1262 circuit?

  • 0 in reply to christy jude
    TI__Mastermind 44820 points

    Hi Christy,

    Generally, most any low-noise LDO should be okay for this type of application. On the ADS1262EVM we used the REG104GA-5 (33uVrms) and we're able to get good noise performance.

    Keep in mind that the power supply decoupling and layout are equally important for creating a clean supply rail. Section 12 in the ADS1262 data sheet provides some layout guidelines to help get the full performance capabilities of this device.

    Best regards,
    Chris