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The datasheet of the microphone mentions:

Source termination resistors are used to match the impedance of the source and the trace.
The component values of the termination resistors depend on the properties of the trace they are on; typical values range from 50 to 100 Ohms.

I am new to electronic design could not understand this, as I haven't calculated trace impedance before.

What does "the impedance of the source" mean? Do I have to match the pin impedance of the ESP32 for clock and data pins to the trace of clock pin and data pin on the microphone?

Also, I am planning to attach this PCB at 6-inch distance from the PCB where the ESP32 is attached. I was planning to attach together both PCBs with wire solder on pads. Now do I also need to calculate the impedance of these wires?

Velvet
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Moaz Azam
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  • it helped a lot thank you. my confusion is that esp32 pins has their own impedance which are very high could not find their exact value do i need to consider that also? – Moaz Azam Dec 19 '23 at 05:58
  • If this were a very long cable you should look up the pin's source impedance and choose a resistor that sums with it to match the trace impedance. However for a few inches and an audio clock signal your probably don't need to do this and instead could put a somewhat higher resistor (~100 ohms) to limit the rise time rather than match the impedance. This will stretch out your rising edges but your clock is so low that won't be a problem. – user1850479 Dec 19 '23 at 12:58

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