nrf52 microphone : SAADC, PDM or I2S ?

[ThierryC]

I'm starting a new design on nRF52 and I need to connect a microphone on it. Reading the datasheets and questions here, I found there's 3 solutions for the type of microphone and interface to nRF52 :

• Analog microphone connected to SAADC
• Digital microphone with PDM output
• Digital microphone with I2C

Does anyone have experienced these 3 interfaces and is there some advantages for one or the other (ie for power consumption, cpu time consumption, etc...) ?

Look to me that we have twice the current using PDM (1.4 mA) compared to SAADC (700 uA). Didn't find current consumption for I2S.

[Sigurd]

Hi,

• Analog microphone: The current consumption for a typical analog microphone is about 100µA to 250µA. An analog microphone is also more prone to picking up RF interference (E.g. Bluetooth), so you could get some noise distortion, and it should ideally be placed away from the antenna.
• Digital microphone: The current consumption for a typical digital microphone(PDM/I2S) is about 600µA to 1000µA. Digital microphones are often used in applications where analog audio signals may be susceptible to interference. Since the connections are digital, they are less prone to RF interference. You typical get better audio quality from the digital microphone compared to the analog, with less noise/distortion in the audio signal, but they use more current.

If you go for a digital microphone, I would recommend using PDM, this is used in e.g. The nRFready Smart Remote 3 for nRF52 Series. Here 2 PDM microphones are used (MP34DB02).