cinderblock
Member
Hey all,
I'm looking at using an analog output MEMS microphone for a new project. I'm not finding good definitive examples of how to properly hook them up.
I've found plenty of the guides for single ended inputs using electret microphones; decoupling the output and biasing it to Vmax/2. This however seems to be unnecessary as these MEMS microphones take in power and claim to have an internal amplifier.
I'm specifically planning to use a SPV1840LR5H-B but I'm open to other options with a bottom port.
So, my question is, do I just connect the output of the microphone to an ADC on the Teensy? If not, what should I do?
I have a couple concerns about this:
1. Don't we have to protect the ADC inputs on Teensy from going above ~1.2V?
2. What voltage do I use for microphone VDD? Teensy's 3.3V? Or a 1.8V supply? (Will microphone output be proportional to VDD?)
3. The datasheet for SPV1840LR5H-B says it has a "DC Output" of 1.1V with VDD at 1.5V. If we have a +/- swing from there, as I'm not finding a pk-pk voltage rating, I'm guessing we'd go over the 1.2V limit. I've seen other microphones with a DC Output around 0.6V. Does this mean I need a different mic?
4. The datasheet shows an example amplifier circuit with a decoupling capacitor and referencing VREF. Is VREF VCC/2? Or ADC max (1.2V)? Or 0.6V?
Thanks for looking. Cheers!
I'm looking at using an analog output MEMS microphone for a new project. I'm not finding good definitive examples of how to properly hook them up.
I've found plenty of the guides for single ended inputs using electret microphones; decoupling the output and biasing it to Vmax/2. This however seems to be unnecessary as these MEMS microphones take in power and claim to have an internal amplifier.
I'm specifically planning to use a SPV1840LR5H-B but I'm open to other options with a bottom port.
So, my question is, do I just connect the output of the microphone to an ADC on the Teensy? If not, what should I do?
I have a couple concerns about this:
1. Don't we have to protect the ADC inputs on Teensy from going above ~1.2V?
2. What voltage do I use for microphone VDD? Teensy's 3.3V? Or a 1.8V supply? (Will microphone output be proportional to VDD?)
3. The datasheet for SPV1840LR5H-B says it has a "DC Output" of 1.1V with VDD at 1.5V. If we have a +/- swing from there, as I'm not finding a pk-pk voltage rating, I'm guessing we'd go over the 1.2V limit. I've seen other microphones with a DC Output around 0.6V. Does this mean I need a different mic?
4. The datasheet shows an example amplifier circuit with a decoupling capacitor and referencing VREF. Is VREF VCC/2? Or ADC max (1.2V)? Or 0.6V?
Thanks for looking. Cheers!