Hardware/Mezzanine/audio AD-DA

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Audio AD/DA mezzanine board

Audio AD-DA Mezzanine

This board has been developed as a low-cost replacement of the high-speed AD-DA board. It features:

  • two 24-bit, 192 kHz WM8782 stereo ADCs
  • two 24-bit, 192 kHz WM8759 stereo DACs

Power supply

The supply from the connector is used to power the TL064 op amps. They can be powered between ±3.5 V and ±18V.

A TPS54227 DC/DC converter generates 6.5 V from the power supply and is followed by a 5 V regulator.

Hence, the minimal power supply range is about ±7 V.

Input range

The board input signals are brought to a first stage of differential op-amp circuits with:

  • R15 = R17 = R16 = R18 = R36 = R38 = R37 = R39
  • gain1 = R17 / R8 = R15 / R10 = R18 / R12 = R16 / R14 = R38 / R29 = R36 / R31 = R39 / R33 = R37 / R35
  • pos_offset / pos_supply = R17 / R7 = R18 / R11 = R38 / R28 = R39 / R32
  • neg_offset / neg_supply = R17 / R10 = R18 / R13 = R38 / R30 = R39 / R34

The ADC inputs range from 0 V to 5V.

The output of this first circuit is decoupled and brought to a second stage built around the in-circuit op-amp of the ADC. The gain of the second stage is:

  • gain2 = R23 / R21 = R24 / R22 = R44 / R42 = R45 / R43

Output range

The DAC output signals are brought to differential op-amp circuits with:

  • R15 = R17 = R16 = R18 = R36 = R38 = R37 = R39
  • gain1 = R17 / R8 = R15 / R10 = R18 / R12 = R16 / R14 = R38 / R29 = R36 / R31 = R39 / R33 = R37 / R35
  • pos_offset / pos_supply = R17 / R7 = R18 / R11 = R38 / R28 = R39 / R32
  • neg_offset / neg_supply = R17 / R10 = R18 / R13 = R38 / R30 = R39 / R34

The DAC outputs range from 0 V to 5V.

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