Hello All,

I am studying on MM9Z1J638 and trying to understand its basics for a while. I have one question regarding to ADC values I obtained from current and temperature channels. I see 24 bit current measurement result and 16 bit raw value related to temperature. However, I do not understand what these values mean. I know that the value I read from temperature channel is dependent on the NTC I used, but is this value a voltage value, or is it something other? How I can convert, for instance the value I see from current channel to something I can understand in terms of Amps?

The demo code makes some conversions however I did not quite get how it gets temperature result form Raw ADC value. It also converts current to miliamps but I am not sure if the result I get is miliamps because what I watched on CodeWarrior is a number in Billion levels or so on. I am not sure if 12billion miliamp is something logical or not.

I am looking forward to see your response about this issue.

Thanks in advance

Hi Kadir,

I suppose that the current reading value represents the voltage which should be converted by following equation:

Voltage = ADC_reading * (REFERENCE_VOLTAGE) / ADC_resolution

And then, that voltage divided by shunt resistor value (100uOhm) to get actual current value in Amps.

The sigma-delta ADC resolution is 16-bit. Not sure if the reference voltage is 5V

I suppose we should consider the PGA gain too in this equation.

The big number as current reading you get is maybe because you are measuring negative current.

Regards,

iggi