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ADC12DJ3200: sampling data cannot reach full scale

Amy Luo
Expert 6895 points
Part Number: ADC12DJ3200

Hi team,

The customer uses jmode13 with 15bit effective bits. After 32-bit data is received, it is disassembled into I and Q channels with 15bit each:

The swing measured at the single end of AD input is 262mv, and the difference is 524mv. Set FS_RANGE to 2000, there will be no clipping, and the maximum value of the collected data is 10000 (far from 16384); Set FS_RANGE bit 0020 is theoretically out of range, but the maximum collected data is only 10200. What may be the reason?

The waveforms captured by the above two settings are ideal sine waves

The data to be checked is channel I. Will the amplitude of channel I or channel Q be 1/2 of the input signal after digital orthogonal down convert?

Best Regards,

Amy Luo

  • +1
    TI__Mastermind 20541 points

    Hi Amy,

    When using the digital down convertor mode on the ADC. The IQ mixing makes the output data 6dB lower. and to correct for it there is a 6dB digital gain that can be enabled to recover the signal amplitude. The digital gain can enabled by setting the register address 0x210 to the value of 0x01.

    Regards,

    Neeraj