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AIC3254: Mixer Amplifier power down

Miguel S
Intellectual 830 points

Hi all,

I have come across a problem with the power down of Mixer Amplifiers of AIC3254 codec.

In my application, I use LOL/LOR/MAR amplifiers.  As indicated in slaa473.pdf document, the power down sequence starts with the power down of HP/LO/MA (p1_r9_b5-0 = 000000b).  After this, I expected to have 0v at LOL and LOR pins, but I only have this when MAR volume is in the range [0,-19.2dB] (values of p1_r25 = 0x00 ..0x22).  If MAR volume is <-19.2dB (values of p1_r25 = 0x23..0x27), then the voltage at LOR is 0.9v (common mode voltage) and I have to do the power down in two steps: first power dow LOL/LOR and then power down MAR.  This is a problem in my application, which first powers down MAR and then LOL/LOR.

I have been able to recreate this problem with AIC3254EVM:

  • Generate a simple PPS project for AIC3254 8x4x Framework:

 

  • Modify SystemSettingsCode to route MAR to LOR and power up MAR.  To do this, it is only necessary to modify the last part of the script, DAC Channel Configuration, which finally is as follows (the changes are marked in bold):

;-----------------------------------------------------------------------------------

; DAC Channel Configuration

;-----------------------------------------------------------------------------------

reg[ 1][ 20] = 0x25 ; De-pop: 5 time constants, 6k resistance

reg[ 1][ 12] = 0x08 ; Route LDAC to HPL

reg[ 1][ 13] = 0x08 ; Route RDAC to HPR

reg[ 1][ 14] = 0x08 ; Route LDAC to LOL

reg[ 1][ 15] = 0x0A ; Route LDAC and MAR to LOR

reg[ 0][ 63] = 0xd4 ; Power up LDAC/RDAC w/ soft stepping

reg[ 1][ 25] = 0x27 ; Unmute MAR, -30.1dB

reg[ 1][ 16] = 0x00 ; Unmute HPL driver, 0dB Gain

reg[ 1][ 17] = 0x00 ; Unmute HPR driver, 0dB Gain

reg[ 1][ 18] = 0x00 ; Unmute LOL driver, 0dB Gain

reg[ 1][ 19] = 0x00 ; Unmute LOR driver, 0dB Gain

reg[ 1][ 9] = 0x3d ; Power up HPL/HPR and LOL/LOR drivers

reg[ 0][ 64] = 0x00 ; Unmute LDAC/RDAC

 

 

  • Download the project to AIC3254 EVM
  • At this point, the voltage at LOL and LOR is 0.9v (common mode voltage)
  • Write p1_r9_b5-0 = 000000b
  • Now, the voltage at LOL=0v but LOR=0.9v

 

 

Has anyone any ideas about what I could be doing wrong?

Best Regards,

  Miguel