Can ADAU1777 support dual ANC?
Hi,
My customer wants to use ADAU1777 with qualcomm QCC3026 to do TWS ANC earbud. They a few questions:
1. Can use ADAU1777 to realize both Hybrid ANC and CVC ANC simultaneously?
-->Base on my understanding, ADAU1777 has 4 analog mic inputs, which should be able to support dual ANC (using 3 mics in total). Kindly please help to double confirm.
2. Serial port support from 192KHz down to 8KHz. But in the datasheet never mention how to achieve it. The only place is Table27 showing 48KHz, 96KHz and 192KHz. Therefore, is it able to support 44.1KHz or 16KHz? And how to implement?
3. They send me the schematic for verification. I did 1st layer checking and suggested:
they should add pull up resistors of 2.0KΩ on the SCL& SDA lines
change the decoupling cap value to 1uF at MICBIASx pin. If 20Hz to 20KHz, will increase the decoupling cap value to 4.7uF
Thank you very much and hope to hear from you soon!
BR,
Keddy Yang
Integrated/Special Purpose A/D Converters
adau1777
Audio CODECs
Hello Keddy,
For question #1, I am not certain of all the details of the algorithm since I am not an ANC expert. We generally cannot help too much with the actual algorithm. The part does have the capability for four mics and can process 32 IIR filters per sample period. So I think it will do what you desire. The best thing is to obtain an evaluation board and program your algorithm to be certain. The microphones can be all analog, all digital or two digital and two analog for the four total inputs to the core.
Question 2:
You can use a crystal that is slightly lower frequency for the master clock. Often 12.288MHz is used since it is 256 x fs when the base fs is 48kHz. So you can use a crystal that is 256 x 44.1kHz and that would give you the 44.1kHz/88.2kHz etc., sample rates when it is divided down from the crystal. However, this part does have a fractional PLL so you could program the PLL to operate with the correct internal clock rate to obtain the 44.1kHz fs based frequencies.
I do want to point out that one of the benefits of this part is that there are ASRCs on the serial ports. When you operate as a master then the internal clock rates are what you have to choose from. When you operate the serial ports as a slave then the ASRC will simply convert the serial port rate to the internal sample rate! You have to do nothing. It is all automatic. So it will follow whatever rate you feed into it. Should you want to change the rate you can simply change the clocks coming in and it will mute, relock and follow the new rate. So you can run between 192kHz and 8kHz fs and all rates in-between.
For your third question, I would have to look at the schematics to comment on them.
Dave T
Dear Dave,
Thank you very much!
Subbu has helped me to review the schematic. Thank you once again for your advice!
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