Audio Codec (ADAU1961) Specification detail

Dear Team,

    I have some clarification about using this audio codec IC (ADAU1961).

    For my project, audio codec is required for handling handset (for both microphone and earphone). Handset specification are given below.

    Whether any pre-amplifier circuit is required for connecting microphone to this audio codec chip. I referred your evaluation board user guide "UG-119-ADAU1961 EVALU". In this evaluation schematic LINE IN are connected between audio codec and audio jack pins (As two nos of separate differential input and one stereo single ended input). Here I planned to use handset microphone which works based on moving coil technology. Kindly suggest for ADC front end design for this microphone input.

    Similarly, audio output is connected to the handset earphone. Also suggest any amplifiers with filter are required for this handset earphone connection.

Handset Specification:

Microphone

Sensitivity at 1000Hz
Relative to 1V/2.8Pa
(With 300 Ohm Load)

> -56dB

Impedance at 1000Hz

300 Ohms ± 20%

Distortion (300 to 3000Hz)

6%

Frequency Response

Refer below Figure

Earphone

Sensitivity at 1000Hz

104 to 112 dB SPL
REL 20uPa at 1mW
Input to Earphone

Impedance at 1000Hz

300 Ohms ± 20%

Distortion (300 to 3000Hz)

5%

Frequency Response 3500 to 9000 Hz

110dB SPL

Frequency Response 300 to 3000 Hz

Refer below Figure

Schematic for Headset connection

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  • 0
    •  Analog Employees 
    on Feb 6, 2019 5:10 PM

    Hello Boosun,

    It is unusual to find an actual dynamic microphone on a headset. They are usually electret condensers that require power and have a built in amplifier. So the PGA gain in the 1961 is plenty for those microphones. For a dynamic mic with a low impedance it is best to use an external preamplifier. the SSM2019 might be a good choice but it is an older part. You may be able to use a simple Op-Amp design for your application but I think it is best to use an external amplifier to get around 20 to 40dB of gain. The PGA in the 1961 can give you more if needed.

    Since the headset wiring uses ground for the shields and for one side of the speaker, you will have to operate with a ground referenced headphone output. So the cap coupled design will be needed. Page 34 of the datasheet discusses the ground reference headphone output. You can drive the headphone earpiece directly from this part unless you need unusually high output levels. The 300 ohms impedance is not very low so I think it will be fine to drive it directly from the codec.

    Dave T

Reply
  • 0
    •  Analog Employees 
    on Feb 6, 2019 5:10 PM

    Hello Boosun,

    It is unusual to find an actual dynamic microphone on a headset. They are usually electret condensers that require power and have a built in amplifier. So the PGA gain in the 1961 is plenty for those microphones. For a dynamic mic with a low impedance it is best to use an external preamplifier. the SSM2019 might be a good choice but it is an older part. You may be able to use a simple Op-Amp design for your application but I think it is best to use an external amplifier to get around 20 to 40dB of gain. The PGA in the 1961 can give you more if needed.

    Since the headset wiring uses ground for the shields and for one side of the speaker, you will have to operate with a ground referenced headphone output. So the cap coupled design will be needed. Page 34 of the datasheet discusses the ground reference headphone output. You can drive the headphone earpiece directly from this part unless you need unusually high output levels. The 300 ohms impedance is not very low so I think it will be fine to drive it directly from the codec.

    Dave T

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