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NCO adjustment in ADC12J4000EVM

MHC
Prodigy 70 points
Other Parts Discussed in Thread: ADC12J4000

1. I'm interested in monitoring the signal in NCO in order to synchronize it with other signals. Is there any way to do that?

2. Also, I'd like to change the values of NCO more than 8 frequencies, or bypass the NCO and feed other signals to the mixer of the DDC. Can I do that? If yes, how can I do?

  • 0
    TI__Guru* 91947 points

    MHC,

    We are looking into this.

    Regards,

    Jim

  • 0 in reply to jim s
    TI__Mastermind 44680 points

    Hi MHC

    The NCO (numerically controlled oscillator) is an internal digital representation of a sinewave, with adjustable frequency and starting phase offset. It is possible synchronize the NCO of multiple ADC12J4000 devices by doing the following:

    1) All ADC12J4000 devices have their internal LMFC properly aligned to a system wide SYSREF.

    2) The SYNC signal to all ADC12J4000 devices is de-asserted with acceptable setup and hold time with respect to the internal LMFC of the devices.

    Provided these 2 requirements are met, the NCO of all devices will start up using the configured frequency and phase settings with alignment across the system. Each Frequency/Phase pair has a dedicated phase accumulator so all 8 possible NCO settings are running in parallel with alignment to each other.

    Since the NCO is a rapidly changing digital representation of a sine it cannot be shared outside the ADC device, or received from an external source.

    Unfortunately there are only 8 NCOs available inside each ADC12J4000 device. The only ways to achieve more frequencies are to re-program the Frequency/Phase settings, or to use multiple ADC devices to sample the same signal.

    Best regards,

    Jim B