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Anonymous
Not applicable

I'd like to measure fine value through ADC.

I'm using adc_SetInputRange(ADC_RANGE_0_3P6V) and adc_readSampleRaw();

Sample frequency should be default. (I don't call adc_setAdcSampleFrequency()).

(1) What is noise-free resolution?

ENOB in above configuration looks 13bits.

The noise-free resolution will be lower number of bits I think.

(2) What is accuracy of reference voltage?

I don't input external known voltage as reference input.

And this also affects ADC result.

Is it +/-5%, +/-2% or less value like +/-0.1%?

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1 Solution
Anonymous
Not applicable

Hello Daisuke,

You should get close to 13 bits.

JT

View solution in original post

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3 Replies
Anonymous
Not applicable

Hello Daisuke,

1.  The most that we can achieve is really 13 ENOB @ 5.859KHz, going down to 10 ENOB @ 187 KHz

2.  The A/D result is +/- 2%

Here is a related post: BCM20732S ADC Configuration

Here is also other info compiled about ADC:

 

GPIO and ADC Voltage Range Questions:

 

  1. What is the recommended maximum voltage that can be applied to any pin relative to VDDIO?
    1. [JT] – 3.63V

  2. What is the Absolute Range of voltage that can be applied to the ADC?
    1. [JT] – Absolute Range of voltage that can be applied is 0V to 3.63V

  3. What is the ADC Reference Voltage?
    1. [JT] – The ADC Reference voltage is the Core Voltage which is always 1.2V

  4. How is power consumption affected by the input voltage range to the ADC?
    1. [JT] – The voltage is clamped at the low end by the Core Voltage and at the high end by the VDDIO Voltage

Thanks

JT

  

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Anonymous
Not applicable

Thank you for your answer j.t.

Let me check this again.

By (2), ADC result has +/- 2% error even if the ENOB is 13bits@5.859kHz.

It means when I use internal voltage as reference, the ENOB of absolute value will be ~5bits?

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Anonymous
Not applicable

Hello Daisuke,

You should get close to 13 bits.

JT

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