>> Knowles claims its world's lowest-power MEMS mic with a signal-to-noise (SNR) of 64.3 dB measures just 3.50 x 2.65 x 0.98 millimeters. (Source: Knowles)
It is fair to say that Knowles could be right. They are the industry leading mic MEMS maker. Though ST takes the bulk of the business because of its scale and business with Apple, Knowles does a lot of great works in this space.
I finally got an answer as to why they use PDM. Here's what they say:
"We selected the PDM interface based on our experience working with major OEMs around the world and the industry's adoption of PDM as the standard microphone interface. Within the analog-to-digital conversion, the PDM interface allows the microphone to contain the entire analog process with a digital output to the Codec or application processor. A digital output from the microphone enables the Codec and application processor to be more efficient in terms of size, scale, and power consumption. This also helps eliminates the need for a high power analog-to-digital converter between the microphone and the Codec or application processor."
Makes sense because I knew when we struggled in the industry to get pass the IPs Knowles has in MEMS micr. They have eaten the launch in this sector and will continue to stay on top unless they blow it. It is like in XL, there is one patent ST has in charge pump that enables you to ramp up voltage that makes everyone struggle.