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Everything ARM and LPC
By muhammad saad malik
#186574
i am working on arm cortex m tm4c123h6pm microcontroller. i am measuring voltage using an ADC. i need to design a voltage divider to measure voltage and for that i need to consider the ADC's internal resistance as well. i checked out its value in the datasheet but i don't know whether it is in parallel or series with the pin? plz help
By dschlic1
#186756
Most ADCs have a dynamic input impedance: They charge a capacitor in a sample and hold function. Better place an op-amp buffer between the divider and the ADC input.
By jremington
#186757
The data sheet should tell you the maximum recommended source impedance, which you can use as a guideline.
The impedance of a voltage divider is the parallel combination of the two resistors.
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