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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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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:
- What is the recommended maximum voltage that can be applied to any pin relative to VDDIO?
[JT] – 3.63V
- What is the Absolute Range of voltage that can be applied to the ADC?
[JT] – Absolute Range of voltage that can be applied is 0V to 3.63V
- What is the ADC Reference Voltage?
[JT] – The ADC Reference voltage is the Core Voltage which is always 1.2V
- How is power consumption affected by the input voltage range to the ADC?
[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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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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Hello Daisuke,
You should get close to 13 bits.
JT