Digital microphone interface circuit for voice recognition and including the same

An electronic device which includes an audio processing block for voice recognition in a low-power mode, comprising:

• a first digital microphone and a second digital microphone configured to receive a voice signal from a user and convert the received voice signal into a first pulse density modulation (PDM) signal and a second PDM signal, respectively;
• a first digital microphone (DMIC) interface circuit configured to receive the first PDM signal, to convert the first PDM signal into a first pulse code modulation (PCM) signal, and to tune a maxscale gain of the first PCM signal based on a distance information between a user and the electronic device acquired in advance of receiving the first PDM signal;
• a second DMIC interface circuit configured to receive the second PDM signal, to convert the second PDM signal into a second PCM signal, and to tune a maxscale gain of the second PCM signal based on additional distance information different from the distance information acquired in advance of the first PDM signal,
• wherein tuning the maxscale gain includes setting a gain so that a maximum signal amplitude is at a level just below where distortion or failure of voice recognition would occur, and
• wherein the first DMIC interface circuit includes:
• a first PDM-PCM converting block configured to convert the first PDM signal into the first PCM signal;
• a first maxscale gain tuning block configured to tune a maxscale gain of the first PCM signal received from the first PDM-PCM converting block based on the distance information acquired in advance of the first PDM signal;
• a first anti-aliasing block configured to perform filtering for acquiring voice data of a target frequency band associated with a first PCM signal output from the first maxscale gain tuning block, and
• wherein the second DMIC interface circuit includes:
• a second PDM-PCM converting block configured to convert the second PDM signal into the second PCM signal;
• a second maxscale gain tuning block configured to tune a maxscale gain of the second PCM signal received from the second PDM-PCM converting block based on the additional distance information;
• and
• a second anti-aliasing block configured to perform filtering for acquiring voice data of a target frequency band associated with a second PCM signal output from the second maxscale gain tuning block;
• and
• a main processor including a voice recognition module configured to perform voice recognition based on the first PCM signal output from the first DMIC interface circuit and the second PCM signal output from the second DMIC interface circuit.

A method for voice recognition of an electronic device which includes a digital microphone (DMIC), a DMIC interface circuit, and a sensor, the method comprising:

• acquiring, by the sensor, a distance information between a user and the electronic device indicating a physical distance between the user and the electronic device;
• subsequently converting, by the digital microphone, a voice from the user into a pulse density modulation (PDM) signal;
• subsequently converting, by the DMIC interface circuit, the PDM signal into a pulse code modulation (PCM) signal;
• tuning, by the DMIC interface circuit, a maxscale gain of the converted PCM
• signal based on the acquired distance information;
• performing, by the DMIC interface circuit, filtering for acquiring voice data of a target frequency band associated with the tuned PCM signal;
• and
• executing, by a voice recognition module, voice recognition based on the filtered PCM signal,
• wherein tuning the maxscale gain includes setting a gain so that a maximum signal amplitude is at a level just below where distortion or failure of voice recognition would occur.