ADAU1701 Madness Frequency Responce +-30dB

Hello,

If your design includes the active DAC filter from the ADAU1701 Datasheet:

C8 as shown is way too large to achieve a cutoff frequency above the full audio range. Most likely it should be 470 pF.

Best regards,

Bob

Hello

Thx for answer

I check all parts in filter - 470pf+4k7 + 150pf +604 Ohm 1% + 3n3

its all 1206 smd - problem is something else

Oops, the datasheet error was fixed in its Revision C. Your measured curve shows a 6 dB/octave loss throughout the audio range. It's hard to imagine a possible cause.

Check to be sure that your ADAU1701 Pin 30 ('reserved") is tied low -- recently eepmc discovered effects including apparent fs/4 operation when this pin is allowed high.

How are you booting your -1701? If for example via uC, perhaps the exported SigmaStudio code has been incorrectly copied. Fortunately your test project is simple enough that the code can be examined manually (see below).

Have you changed any default settings in the 1701 Register Controls tab?

I attached the exported TxBuffer contents. The project runs OK on the stock -1701 eval board.

KJBob

Thank you for your help!

I found error - it was in 150pf capacitors in DAC filter.

Chinas "friend" sold 800nf instead 150pf - change to 150pf ceramic and everything fine now

One more thank to you!

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