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ADS1282 always indicates input over-range

su tao
Prodigy 30 points
Other Parts Discussed in Thread: ADS1282

Hi all,

I'm using the ADS1282 in my prototype board. The MFLAG (Modulator Over-Range Detection) signal always outputs high.

Power supply: DVDD=+3.3V, AVDD=+2.5V, AVSS=-2.5V. Voltage reference: VREFP=+2.5V, VREFN=-2.5V. Anolog inputs AIN1P and AIN1N are short-connected for test.

According to the configuration guide in the datasheet, a nRESET signal is needed after power-on. But immediately the MFLAG turns high, which puzzels me a lot. After that the registers can be read or write normally, but when reading the conversion results (either by Read Data Continuous or Read Data By Command Mode), the output data is always 0x7FFFFF.

Best regards

Su Tao

  • 0
    Prodigy 30 points

    Here full-scale = 5V. Registers read through SPI interface to DSP, so I'm sure they're in there default states. MUX[2:0]=000b for channel 1, PGA=000b for Gain=1. I'v tried to set MUX[2:0]=010b for input internal short via 400Ω, or use channel 2, but still MFAGL=1.

    Reset timing. Externally trigged by the rising edge of nRESET, and MFLAG goes high. After about 63ms nDRDY indicates data availbale.

    Thanks for any comment,

    Su Tao

  • 0
    Prodigy 30 points

    The problem is solved. I'v made a silly mistake, replaced R1/R2 with 0Ω, thus CAPP/CAPN short connected to VREFP/VREFN, and modulator input truly over-ranged. Now I can read the data.

    Su Tao

  • 0 in reply to su tao
    TI__Mastermind 44640 points

    Su Tao,

    I'm glad you found the issue! Thanks for the update.

    Best regards,
    Chris