Measure current and voltage with K26

[javierhernande1]

Hello!

I need to measure current and voltage with MK26FN2M0VMI18

I have a DC input from 5V up to 28V

Is it possible to measure it with a shunt resistor resistor of 0m50 and the ADC?

If so, I need to use VREF or VREF_OUT ?

This circuit can serve ?, it is similar to my requirements. If so, I have to place the R1 closed to GND and R2 closed to K26F ADC pin?

Best regards.

[jingpan]

Hi Javier,

I guess this is a very low frequency ADC test circuit. The load and the battery will not change in a high frequency. So I think it is nessesary to put a small cap near the AD pad. Because in ADC there is a Cadin. It's value is around 5~10pf. You can see it in datasheet. Since there is a big resistor R2 before ADC, Cadin will cause AD value distort. I think the value of the CAP should over 50pf. Details please find in AN4373. You can search this document on NXP website.
As to VREF select, please refer to section 39.3.3(Voltage Reference Select) in reference manual. You can also use the examples in SDK.

Regards,

Jing