Teensy 3.5 3.3V Pin

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Xeyow

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Hello,

I have a Teensy 3.5 that is powered from a USB cable (so it`s powered by 5V). I know that it has an internal LDO that converts 5V to 3.3V.

I am currently working on a project, a transimpedance amplifier for a photodiode to measure the LED illuminance. The output of the op-amp will be connected to one Analog pins of the Teensy. As we all know, this output MUST BE 3.3V maximum (because the pins are 3.3V tolerant), and this can be achieved by powering the op-amp at 3.3V and GND.

My question is:

Can i use the pin between 12 and 24 (the 3.3V pin) to power the op-amp? From the datasheet, i can see that the op-amp draws a maximum of 0.5mA.

9324f74ab3b000e9a1e6278471200736_original.png

(the pin i`m talking about is the one with a yellow square)
 
Xeyow said:
Hello,

I have a Teensy 3.5 that is powered from a USB cable (so it`s powered by 5V). I know that it has an internal LDO that converts 5V to 3.3V.

I am currently working on a project, a transimpedance amplifier for a photodiode to measure the LED illuminance. The output of the op-amp will be connected to one Analog pins of the Teensy. As we all know, this output MUST BE 3.3V maximum (because the pins are 3.3V tolerant), and this can be achieved by powering the op-amp at 3.3V and GND.

My question is:

Can i use the pin between 12 and 24 (the 3.3V pin) to power the op-amp? From the datasheet, i can see that the op-amp draws a maximum of 0.5mA.


(the pin i`m talking about is the one with a yellow square)
Click to expand...

Yes, all 3.3V pins are the same (total 250 mA)
However, IMO, if there is other digital devices driven by teensy (e,g SDCard) the stability may not be good enough for Analog circuits
 
I`m not using any external digital drivers.

I use 10 pwm pins, and 11 adcs. The control circuit for the leds is powered from an external 5V power supply.

The only circuit that needs 3V3 is the transimpedance amplifier.

And from what you say, i can easily use the 3V3 pin from the teensy to power up this little circuit, right?
 
Try it out. If the analog quality is not good enough, you may need to use an external LDO.
 
@ Xeyow - a more meaningful test is to build up as much of the other hardware as you can and use a resistive divider to measure approximately half 3.3V. Exactly what doesn't matter but take a bunch of samples and record standard deviation and possible worst case deviation. Possibly try disabling/powering down any element you think might be producing noise.

This will give you some data for your hardware, your code and your RF enviroment to make decisions with.
 
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