I'd really like to use the Cmedia CM118B USB audio chip - it's dual ADC and DAC, so supports stereo speakers/headphones and stereo mic over USB. However, the datasheet lacks any application schematics whatsoever. The datasheet explains the function of each pin, but without being clear on how it's supposed to be wired up, leaving a lot of guesswork.

For example, pin 27 is "Microphone Input for Right Channel," with a complementary "Microphone Bias Voltage Supply for Right Channel (3V)" on pin 26. That is the full extent of the data on how to hook up the mic. Similarly with the headphone output, there is a left and right line out channel, and a 1.75v output for line out bias, no further info. If anyone has any experience of Cmedia chips I'd be thankful for any pointers.

CM118B datasheet

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    \$\begingroup\$ Step 1: buy a million chips. Step 2: C-Media support will help you. \$\endgroup\$
    – CL.
    Dec 7, 2019 at 18:46

1 Answer 1


In absence of specific reference designs for this IC in the documentation I'm using elements from CM108 design and Cmedia's FAQ. Will see how this plays out in prototype.

CM118 based codec


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