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How to measure ADC Latency from Analog In to I2S/TDM out

Carsten Thiele
Expert 7205 points

Hi Team,
 we have a general question about ADC latency in the Audio Signal Chain.
The document “Conversion latency in delta-sigma converters” www.ti.com/lit/an/slyt264/slyt264.pdf describes the latency in general very good.
We want to find out now the real latency in the system.
We want to measure the latency from Analog In to I2S/TDM Out. How could we accomplish such a measurement?
Does such a measurement make sense at all? I think these data need to come from the converter datasheet and actual setting (used filter, etc.) on the device itself.

Appreciate your feedback.

Thanks,
Best regards,
Carsten


  • 0
    TI__Guru 57800 points

    Hi, Carsten,

    Typically, our devices have the latency specified in the datasheet, in some documents it is called group delay, and in general is specified as a function of the sampling rate.  It may be possible to measure it in a system but it is complicated to get accurate data as it would depend on the equipment used. I have made some tests before by using a burst sine-wave with a very high amplitude difference as the ADC input while monitoring the I²S DOUT pin with an oscilloscope. Sometimes is possible to identify the DOUT bit toggling with respect to the input amplitude, giving an estimate about the latency of the ADC.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer