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ADS127L11: sample value get doubled when motor started

lin lu
Prodigy 10 points
Part Number: ADS127L11

Tool/software:

this project using ADS127L11 to sample motor voltage(380V)  and its starting voltage;

the set up is:

reference voltage： 2.5V

INP_RNG: 1(2x input range)

START_MODE :  Start/stop control mode (Using GPIO to control)

before the motor start  or after the motor start, the sample value is exactly right,   but if we first start sampling the start the motor,  the moment the motor start, the sample value double.

for example,  normal sample value is between 0.8-1.2(sine wave),  when motor start, the value become as 1.6-2.4.  and it remains so until we reset MCU;  unpower the ads127l11 can not solve this issue;

thanks!

  • 0
    TI__Mastermind 46380 points

    Hello Lin Lu,

    Welcome to the TI E2E community.

    You have some sort of transient voltage causing either the ADC or the MCU to go into an unknown state.  You may need to add over-voltage protection on the ADC inputs or add additional filtering to the ADC inputs to prevent this incorrect behavior.

    Have you confirmed that the output of the ADS127L11 is incorrect?  Please capture the SPI data frame using an oscilloscope or logic analyzer and provide a picture.

    /DRDY, /CS, SDO, SDI, and SCLK would be helpful.

     

    Also, provide a picture of the ADC schematic, showing how the 380V input to the ADS127L11 input.

    Regards,
    Keith Nicholas
    Precision ADC Applications