SLAAER9 May   2025 TAC5212

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Recording Path Mixers
    1. 2.1 Main ASI Mixer
      1. 2.1.1 Q-31 Formatting for Mixer Coefficients
      2. 2.1.2 Recording Path Main ASI Mixer: Example
    2. 2.2 Auxiliary ASI Mixer
      1. 2.2.1 Recording Path Auxiliary ASI Mixer - Example
    3. 2.3 ADC-to-DAC Loopback Mixer
    4. 2.4 TDM Transmission on DOUT
  6. 3Playback Path Mixers
    1. 3.1 Main ASI Mixer
      1. 3.1.1 Q-16 Formatting for Mixer Coefficients
      2. 3.1.2 Playback Path Main ASI Mixer - Example
    2. 3.2 Auxiliary ASI Mixer
      1. 3.2.1 Playback Path Auxiliary ASI Mixer - Example
    3. 3.3 Playback Path Side-Chain Mixer
      1. 3.3.1 Playback Path Side-Chain - Example
  7. 4Application: ADC Channel Summation to Improve TAC5212 Dynamic Range
  8. 5Application: Analog Input to Analog Output Signal Flow in TAC5412-Q1
  9. 6Summary
  10. 7References

2.3 ADC-to-DAC Loopback Mixer

As shown in Figure 2-6, the ADC-to-DAC loopback mixer mixes the output of the biquad filter path on all four recording signal chains and provides two separate digital outputs (A2D_LBx).


Loopback Mixer

Figure 2-6 Loopback Mixer

The mixer then outputs the resulting signal into the signal chain of the playback path at the side chain mixer.

The mixing is per Equation 3.

Equation 3. A 2 D _ L B x   =   a x × ( C H 1   s i g n a l )   +   b x × ( C H 2   s i g n a l )   +   c x × ( C H 3   s i g n a l )   +   d x × ( C H 4   s i g n a l )

The coefficients [ax, bx, cx, dx] are programmed as 32-bit signed values into the Page 10 registers which are described in Table 2-3. These coefficients are written in the 1.31 format described in Section 2.1.1.

Table 2-3 Page 10 Registers for Loopback Mixer
Register Address Register Register Description Reset Value Coefficient
0x48 ADC_LB_MIX1_CH1_BYT1[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 1 coefficient byte[31:24] 0x7F a1
0x49 ADC_LB_MIX1_CH1_BYT2[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 1 coefficient byte[23:16] 0xFF
0x4A ADC_LB_MIX1_CH1_BYT3[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 1 coefficient byte[15:8] 0xFF
0x4B ADC_LB_MIX1_CH1_BYT4[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 1 coefficient byte[7:0] 0xFF
0x4C ADC_LB_MIX1_CH2_BYT1[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 2 coefficient byte[31:24] 0x00 b1
0x4D ADC_LB_MIX1_CH2_BYT2[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 2 coefficient byte[23:16] 0x00
0x4E ADC_LB_MIX1_CH2_BYT3[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 2 coefficient byte[15:8] 0x00
0x4F ADC_LB_MIX1_CH2_BYT4[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 2 coefficient byte[7:0] 0x00
0x50 ADC_LB_MIX1_CH3_BYT1[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 3 coefficient byte[31:24] 0x00 c1
0x51 ADC_LB_MIX1_CH3_BYT2[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 3 coefficient byte[23:16] 0x00
0x52 ADC_LB_MIX1_CH3_BYT3[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 3 coefficient byte[15:8] 0x00
0x53 ADC_LB_MIX1_CH3_BYT4[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 3 coefficient byte[7:0] 0x00
0x54 ADC_LB_MIX1_CH4_BYT1[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 4 coefficient byte[31:24] 0x00 d1
0x55 ADC_LB_MIX1_CH4_BYT2[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 4 coefficient byte[23:16] 0x00
0x56 ADC_LB_MIX1_CH4_BYT3[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 4 coefficient byte[15:8] 0x00
0x57 ADC_LB_MIX1_CH4_BYT4[7:0] Digital loopback (ADC to DAC) mixer 1, ADC channel 4 coefficient byte[7:0] 0x00
0x58 ADC_LB_MIX2_CH1_BYT1[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 1 coefficient byte[31:24] 0x00 a2
0x59 ADC_LB_MIX2_CH1_BYT2[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 1 coefficient byte[23:16] 0x00
0x5A ADC_LB_MIX2_CH1_BYT3[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 1 coefficient byte[15:8] 0x00
0x5B ADC_LB_MIX2_CH1_BYT4[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 1 coefficient byte[7:0] 0x00
0x5C ADC_LB_MIX2_CH2_BYT1[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 2 coefficient byte[31:24] 0x7F b2
0x5D ADC_LB_MIX2_CH2_BYT2[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 2 coefficient byte[23:16] 0xFF
0x5E ADC_LB_MIX2_CH2_BYT3[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 2 coefficient byte[15:8] 0xFF
0x5F ADC_LB_MIX2_CH2_BYT4[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 2 coefficient byte[7:0] 0xFF
0x60 ADC_LB_MIX2_CH3_BYT1[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 3 coefficient byte[31:24] 0x00 c2
0x61 ADC_LB_MIX2_CH3_BYT2[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 3 coefficient byte[23:16] 0x00
0x62 ADC_LB_MIX2_CH3_BYT3[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 3 coefficient byte[15:8] 0x00
0x63 ADC_LB_MIX2_CH3_BYT4[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 3 coefficient byte[7:0] 0x00
0x64 ADC_LB_MIX2_CH4_BYT1[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 4 coefficient byte[31:24] 0x00 d2
0x65 ADC_LB_MIX2_CH4_BYT2[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 4 coefficient byte[23:16] 0x00
0x66 ADC_LB_MIX2_CH4_BYT3[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 4 coefficient byte[15:8] 0x00
0x67 ADC_LB_MIX2_CH4_BYT4[7:0] Digital loopback (ADC to DAC) mixer 2, ADC channel 4 coefficient byte[7:0] 0x00