Calculate ADC value for 3.3V as max input

Question

Hi, 
 I want to measure ADC for 3.3V 
 Using formula 
 RESULT = [V(P) – V(N) ] * GAIN/REFERENCE * 2 (RESOLUTION - m) 
 Rearranging eqn: 
 Vin = ( RESULT*REFERENCE)/(2 (RESOLUTION - m) *GAIN) Considering Result = Resolution (Received max value on ADC) REFERENCE = 0.6 Gain = 1/6 or 1/5 Vin = 3.6 or 3 
 
 What I get is the result for input as either 3.6V or 3V. How do I measure adc for 3.3V? 
 
 Regards

Øyvind · Accepted Answer

Hello, 
 Vin = ( RESULT*REFERENCE)/(2 (RESOLUTION - m) *GAIN) 
 Can you give me an example of the numbers you are using, in this formula? 
 According to the Product Specification , the resolution is " output resolution in bits, as configured in register RESOLUTION ". See this case for more information about measuring SAADC. 
 RESULT = (V(P) – V(N)) * (GAIN/REFERENCE) * 2(RESOLUTION - m) 
 where 
 
 V(P) 
 is the voltage at input P 
 V(N) 
 is the voltage at input N 
 GAIN 
 is the selected gain 
 REFERENCE 
 is the selected reference voltage 
 RESOLUTION 
 is output resolution in bits, as configured in register RESOLUTION 
 m 
 is 0 for single-ended channels 
 is 1 for differential channels 
 
 Results are sign extended to 16 bits and stored as little-endian byte order in RAM. 
 What I get is the result for input as either 3.6V or 3V. How do I measure adc for 3.3V? 
 Input range = (0.6 V)/(1/6) = 3.6 V
or 
Input range = (0.6 V)/(1/5) = 3.0 V 
 The voltage range tells you what the largest number you can measure i.e. if you want to measure 3.3, then you need to have an input range of 3.6V. Kind regards, Oeyvind

Calculate ADC value for 3.3V as max input

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