kinetis k50 family TRIAMP to PGA to ADC, all internally.

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kinetis k50 family TRIAMP to PGA to ADC, all internally.

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hectorandrade
Contributor I

Hello, I would like to know if using a microcontroller from the kinetis k50 family it would be possible to do the following entirely within the microcontroller:

I need to measure light with a photodiode and convert that signal to voltage via the integrated transimpedance amplifier (TRIAMP). Since the light intensity will vary and I want to use the full scale of the ADC, I would then amplify this voltage signal with the integrated PGA (programmable gain amplifier) and then read this with the 16-bit SAR ADC. Please let me know if this would be possible without having to have external connections, since this would save valuable space on the PCB and reduce noise. 

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2 Replies

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xiangjun_rong
NXP TechSupport
NXP TechSupport

Hi, Hector,

As the Reference manual said, you can use the following diagram to test the photodiode current based on K50, the formula of the TRIAMP output voltage is Vout=Vdac+I*R1

Vout is the voltage of out_3V pin.

Vdac is the input voltage of inn_3v pin.

R1 is the external feedback resistor

I is the tested current

I is the tested current. You can select the appropriate R1 so that the Vout voltage  can reach up to ADC full scale, in this way, you can get low noise signal.

If you select small R1 and connect vdac to GND, and use on-chip OP amp to amplify it, you can to use TRIAMP0 module, and use OP1 to amplify it and use ADC to sample.

BR

Xiangjun Rong

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hectorandrade
Contributor I

Hi Xiangjun,

Thank you very much for your reply. That is the approach I will follow once I get my development board. It's too bad that it's not possible to connect the TRIAMP output directly to the PGA. This would reduce noise even further.

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