Part Number: PCM4220
Other Parts Discussed in Thread: PCM4222
Hi team,
We meet some issues regarding THD+N of this part.
In datasheet, it shows THD+N is -10xdB at 997Hz, -1dB input and -9xdB at 997Hz, -20dB input no matter which sample rate is used.
But we cannot get this extraordinary good THD+N during my experiment. Here is my rough setup and procedure.
- Audio source : AP515, 1kHz, 100mV~2V sinusoidal with a differential buffer which is wired as the config in Figure 45(page 25) in PCM4220 datasheet.
- Already check the AP source is good by lookback test(-9xdB~-10xdB)
- Catch the signal just before PCM4220 input to know THD+N of ADC input signal. The results are still -9xdB~-103dB.
- Decode I2S to get rawdata using Saleae and make .wav file by using this rawdata and Octave code(similar to Matlab)
- Play this .wav file in AP and perform loopback test. The results are -6xdB~-8xdB.
Can you help us to figure out which part may be a problem?
If you need more details, please let us know.
Besides, do we have ADC EVB which it is for audio application and THD+N<-100dB?
Maybe it can also help us to verify our setup and figure out what the problem is.
Regards,
Roy
