AD9951: Amplitude is lower than expected

Dear Technical Support Team,

I didn't get expected amplitude with AD9951.

ASF is 0x3FFF(Fullscale).

   Expected Amplitude: 250mV (25Ω x 10mA(FS) )

   Actual Amplitude: 160mV


See attached schematic and waveform.

If you have any advice. please let me know.

PDF

Best Regards,

ttd

  • 0
    •  Analog Employees 
    on Sep 10, 2021 2:36 PM

    Based on your circuit configuration, at pin 1 of the transformer (U4), I calculate 150mVpp centered at 1.425V. This agrees closely with your measurements.

    Be aware that your configuration differs from that of the recommended configuration as per the Evaluation Board (EVB) schematic. Specifically, the EVB schematic uses the center-tapped side of the transformer as the connection to the AD9951 output with the center tap connected to VCC (1.8V in your case). I would recommend reversing the orientation of the transformer.

    Also, by reversing the transformer connection, you can use Application Note AN-912 to determine the expected output signal levels.