ADAU1467 ASRC
Have noted that its possible to use sample rates higher that 192k as input to the asrc, for example 384k. Have tested it on the adau1467 eval board. The ASRC0_RATIO register 0xF582 correctly responds that the ratio is 8 (384/48). When I read the data sheet I realized that it does not say that asrc is limited to 192k, so my question is - what is the supported upper limit of the asrc? Can we safely downsample from 384k with good audio quality? Unfortunately our audio test equipment does only support max 192k.
Best,
Alexander.
Audio Signal Processors
adau1467
SigmaDSP Audio Processors
asrc
Hello Alexander,
Here is my initial look at this but this is not a definitive answer. I will have to ask several other engineers about this. Is this going into a product that will be operating over wide temperatures or a high number of units produced?
First thing I quickly checked is that the max bit rate for the bitclock input of the serial port is 24.576MHz so if the 384kHz fs is I2S with 32 bit slot size per channel then it will just make that specification. 64 x fs.
The rest of the specifications are setup for a 192Mhz max. It may be only because we have set that as the max. I am not sure if we ever tested and characterized it at a higher rate. The DSP core can actually run at 384kHz and we have tested that but I am not 100% certain about the entire serial port.
The ASRC will most likely be fine. We have similar ASRCs in other parts that run up to 768kHz so I feel you should be fine.
So according to the datasheet the answer is no. Remember that the specifications are meant to cover the full temperature range and silicon skews and still maintain a safety timing margin. So one part at room temperature may work fine but we have to allow for all the variables for the operation of the part.
I will let you know what I hear back from other engineers.
Dave T
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