AD9284 default mode problem


Posted on Feb 5, 2014

Using AD9284 with the interface of adl5380 demodulator. I tried to work in default mode of AD9284. I have checked I and Q outputs of demodulator and everything was fine there. When i checked digital outputs of AD9284, I could not see the desired output. So, AD9284 seem to be not working properly. Second, there is not an Reference voltage interface in between demodulator and ADC.


AD9284 default mode problem
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Actually output of the demodulator is connected to the ADC through a capacitor and I think that this type of a usage should be OK. Still, I am not sure that this may cause some serious problems. it sounds like you shouldn`t have an issue with the common mode voltage on the output of the ADL5380 if you have DC blocking caps. Do you have the common mode voltage (CMV) connection for the AD9284 It should be connected similar to the below schematic. Perhaps you could send me an IM with your schematic so I could take a look and review it. Thank you for your support. I think i may have interface problem between demodulator and adc. Interface is at attachment. I did not use Vcm voltage in my interface circuit. I just connected it to ground by a decoupling capacitor. If you are just using the topology you have shown in your last reply, it does not appear that you have provided the common mode voltage to the ADC inputs. In order to operate correctly, the 0. 9V common mode voltage needs to be applied to the Vin+ and Vin- inputs. You have the option of using a voltage divider topology in the circuit between the ADL5380 and the ADC, but you have tradeoffs to consider on the performance (see page 22 of the ADL5380 datasheet). In order to keep insertion loss down and have an easier translation to the 0. 9V for the ADC, the lower common mode output voltage of the ADL5380 would work best, but this has the tradeoffs listed on page 22 of the...




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