AD6654 NCO Hopping

We are using AD6654 in our Digital Receiver Boards for the Radar and Satellite communication applications.


We have one requirement with on the fly NCO register change depending upon the change in the IF frequency.

We are using two channels of a DDC.

One is used for acquiring the DDC data for finding the current frequency value by using CFFT method.

Once we know the current frequency, we want to tune second channel of the DDC with the corresponding NCO value.


We are resetting the AD6654 and programming both the channels by putting AD6654 in the sleep mode, the NCO is getting programmed to desired value.

After this we detect the change in the IF frequency, we try to change NCO of second channel on the fly.

We are following the method mentioned in the AD6654 data sheet Rev  0 under CHIP SYNCHRONIZATION - Hop with Soft Sync.

However we are not able to see any change in the NCO frequency in the second channels and it continues with the original value programmed after power on.


Request you to let me know if there is any change in the procedure mentioned in the AD6654 data sheet Rev  0 under CHIP SYNCHRONIZATION - Hop with Soft Sync and what is exact method to change the NCO value on the fly.

On another subject, we are starting a new design with 8 DSP (ADSP21587/SC587) , 8 DDCs, 8 DDCs.

This is to replace the existing ADSPTS201,AD9856 and AD6654 based design.


We are looking for replacement of AD6654 with new chip with better features.

Although we have FPGA based DDC design, It has some limitations.

Please suggest a good replacement for AD6654 which can support for at least next 8 to 10 years (My retirement!)

  • 0
    •  Analog Employees 
    on Feb 23, 2017 1:36 AM over 4 years ago

    Hi Maria,

    To get a Frequency hop to work you must initiate a SYNC (soft or pin) and the HOP hold-off counter must be >1. Please confirm these conditions are met.

    The AD6654 was released some 12 yrs ago and was quite a unique integrated Wideband IF to Baseband Receiver product for its time. Since then, FPGA cores and Standardized DDC Code Reference Designs have evolved, become more affordable, and mainstream to the point where newer ADC's and FPGA's typically offer a more flexible alternative to using a dedicated 12yr old DDC ASIC.


    The AD6654 component is still available for sale to support existing legacy designs, but is no longer being recommended for new designs. The AD6654 evaluation boards and associated evaluation software tools previously available for customer sampling, design-in prototyping, and evaluation have been discontinued and out of production for >5 years.


    If you like I can contact you privately to obtain more details about your application requirements. This information may allow me to recommend newer ADI integrated receiver alternatives to the AD6654.


    Best Regards,