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TLV320AIC3204: Minimum AGC attack/delay time calculations

Matthew Kipper
Intellectual 460 points
Part Number: TLV320AIC3204

Hi, I'm having troubles interpreting a calculation from the TLV320AIC3204 Application Reference Guide (SLAA557). 

The document outlines a few registers that can be used to control the attack and decay times of each each channel's AGC:

  • Page 0 / Register 89: Left Channel Attack Time
  • Page 0 / Register 90: Left Channel Decay Time
  • Page 0 / Register 97: Right Channel Attack Time
  • Page 0 / Register 98: Right Channel Decay Time

For these registers, the upper 5 bits specify the times as follows:

Attack Time = [1,63] * 32 ADC Word Clocks

Decay Time = [1,63] * 512 ADC Word Clocks

This is clear enough, but I'm unclear on the 3 LSBs of these registers, which specify the Scale Factor. I don't see any other references to this value in the document, so I'm unclear on what it does exactly. Are the attack times above multiplied by this factor? Are they divided by it? Is there some other calculation that uses this factor?

Thanks

  • 0
    TI__Guru* 84915 points
    Hi, Matthew,

    This scale factor is used to multiply the attack or delay time of the specific register. Please take a look at the example below for clarification.

    The Page 0 / Register 89 will be used for this example. Sampling rate (Word Clock): 44.1KHz.

    If bits D7-D3 are configured as 0 0000 and bits D2-D0 = 000, the current left channel AGC attack time would be 1*32 ADC Word Clocks = 0.725624ms and the scale factor would be '1'. This means that the attack time will be 0.725624ms (factor is 1, so there are no changes on the attack time). However, if bits D2-D0 = 001, the scale factor would be '2'. The current attack time would be multiplied by 2. So, the result will be 1.45125ms.

    Basically, the attack or delay times of the registers that you mentioned are multiplied by the respective scale factor.

    I hope this was clear. Please let me know if you have additional questions or comments.

    Best regards,
    Luis Fernando Rodríguez S.