Total delay of AD1934

Dear support team,

I want to know total delay of AD1934.

In datasheet, Group delay of DAC interporation filter is 42us@192kHz.

Is it total delay?

If no, please teach me total delay(Analog input to output register, not include shift time of I2S)

Best regards,

Takepiro

  • Dea support team,

    Sorry , I misstake

    >If no, please teach me total delay(Analog input to output register, not include shift time of I2S)

    If no, please teach me total delay(input register to Analog output, not include shift time of I2S)

    Best regards,

    Takepiro

    •  Analog Employees 
    on Feb 28, 2019 7:36 PM

    Hello takepiro,

    Since there is no DSP core in this DAC there is no need for resyncing to other clock domains so it is really simple. After the data shifts in during one sample period (this is the I2S time) at the end of the frame the data is shifted out and into the filter. Once the filter has processed the sample it is transferred to the DAC for output. So the Group delay you see in the datasheet for the filter is the number you need.

    My calculations show that at 192kHz the new sample will take 8.064 samples to reach the DAC.I am guessing that the 42ns specification was rounded out. The best way to calculate this is using the filter's sampling rate. The oversampling rate at the 192kHz setting is 8x fs. So this is a sampling rate of 1.536MHz. The filter is a 64 tap filter so it will take 64 samples at the 1.536MHz sampling rate to reach the end so that would be 41.6ns.

    If you need a DAC with even less delay we do have the ADAU1962A family of parts. The standard settings is exactly the same group delay but there is a low latency setting for the 192kHz fs. In this mode the group delay is 10ns. The tradeoff is that the filter will have more out-of-band noise and require more filtering externally.

    Dave T