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# DC2425A-B - Issue in calculating the ADC input voltage from ADC Code

Category: Datasheet/Specs
Product Number: DC2425A-B

Hi team,

We are using the EVK kit DC2425A-B. We are feeding the voltage in to the analog inputs & can read the ADC code in the SPI bus. While back calculating the ADC input voltage from the read ADC code, it is showing the improper result. The formula used is (ADC CODE x (VREF/(2^15))). Surprisingly we can get the proper voltage if we are using the formula (ADC CODE x (VREF/(2^13))) assuming that it is 14 bit ADC. We suspected that ADC mounted in the EVK could be 14 bit ADC instead of 16bit. But while verifying the top marking, it is 16bit ADC. Please refer the below scenario for more details

ADC input voltage (Ain+ -  Ain-) = 1V

Reference voltage = 5V

Read ADC code = 0X066e

Calculated voltage = 0.25115966796875 (using 16 bit ADC formula, (ADC CODE x (VREF/(2^15))) )

We can able to get the actual ADC input voltage 1.004638671875 ( if we use 14 bit ADC formula (ADC CODE x (VREF/(2^13))) ).

The above scenario tested for 2V, 3V, 4V & 5V. The respective codes are 0X0CD0, 0x1341, 0x19A6 & 0x1FFF.

Kindly help us on this issue.

Regards,

Ahamed Faize

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