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I want to use Infineon IM69D120 microphones [1][2] in an array (about eight of them), and I am confused as to how exactly (with which components) should the MEMS microphones be supplied.

I chose USB as the power source which is something like 5V+-10%, thus it is necessary to get from that to a lower, stable voltage without creating noise. The microphones require supply voltage (Vdd) in the range of 1.62V to 3.6V, but I do not know which voltage is optimal for performance (This is the first question?). Although the microphones include voltage regulators they can only reject about 0.1V if I understand the specifications correctly.

Should I use a voltage regulator/reference (What is the difference between voltage regulator and voltage reference? EDIT: answered here: Voltage regulator vs. voltage reference) between the USB power supply and the microphones? If yes, what kind? Digikey has about five categories [0] just for linear voltage regulators. EDIT: If I need precision regulation, it seems I could use a reference like some of these: https://www.digikey.com/product-detail/en/linear-technology-analog-devices/LT6658BIMSE-2.5-PBF/LT6658BIMSE-2.5-PBF-ND/6200413, https://www.digikey.com/product-detail/en/linear-technology-analog-devices/LT6658BIMSE-3-PBF/LT6658BIMSE-3-PBF-ND/8031573. They provide 20mA which is enough because I think I only need about 8mA for 8 microphones.

Should I use a DC-DC converter to drop the voltage a bit between the USB power supply and the voltage regulator? If so, which kind?

As this is for microphones none of the components should create acoustical noise.

Another relevant document is [3], which says a resistor or ferrite may be used with the power supply to filter out high-frequency noise, but is that necessary if a regulator is already being used? If yes, what kind of resistor or ferrite should be used?

Regarding the question of what will I use for processing the PDM, I plan to make two variants; one with FPGA and one with a 200-500MHz microcontroller/microprocessor. But I do not think it is necessarily a good idea to power the microphones from the same regulator which supplies the processor/FPGA. Because, as far as I understand, that would mean some noise from processor/FPGA operation would be created in the microphones' power supply, and the microphones (I think) need a more stable voltage than a processor/FPGA.

[0] https://www.digikey.com/products/en

[1] https://www.infineon.com/dgdl/Infineon-IM69D120-DS-v01_00-EN.pdf?fileId=5546d462602a9dc801607a0e41a01a2b

[2] https://www.infineon.com/cms/en/product/sensor/mems-microphones/im69d120/

[3] https://www.infineon.com/dgdl/Infineon-AN558_MEMS_Electrical_Implementation-AN-v01_00-EN.pdf?fileId=5546d46261764359016199fad0e62021

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    \$\begingroup\$ Sounds like you should use a RC tilter that feeds into an LDO. The RC is to remove any high-frequency trash; values like 10 ohms and100uF will progressively attenuated above 1milliSec timeconstant (160Hz). \$\endgroup\$ – analogsystemsrf Feb 28 at 13:06
  • \$\begingroup\$ The link you provided isn't helpful. Perhaps that was an editing mistake? Please update the link to point to the Infineon datasheet for your microphones. \$\endgroup\$ – Elliot Alderson Feb 28 at 14:12
  • \$\begingroup\$ @ElliotAlderson, linked to datasheet. \$\endgroup\$ – user2373145 Feb 28 at 16:10
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    \$\begingroup\$ What voltage do you need to use for the digital signals coming from the microphones - what does the rest of the system look like? You may already have/need a 3.3V supply in it. \$\endgroup\$ – pjc50 Feb 28 at 16:43
  • \$\begingroup\$ Where do you get the impression that the built in regulator can only handle 0.1V of noise? I don't see it. \$\endgroup\$ – JRE Feb 28 at 16:54

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