Electronic – ADC Supply Current in Microcontroller and how much current will a GPIO take

adcmicrocontrollernxpvoltage-reference

I am having this Microcontroller

In this Microcontroller, I am using the ADC peripheral and normal GPIO port.

My questions:

  1. On Page 58, table 42, There is a parameter called as Supply Current per ADC which is mentioned as 1mA. What does it mean? It also mentions that it depends on the conversion rate.
    Does it mean, if I connect a voltage (within the mentioned limits of the pin) with a series resistor to that ADC pin, that pin will consume 1mA?
    So, if I connect two ADC inputs to the ADC peripheral, it will consume 2mA?

  2. Suppose, I configure a port as Input port. How much maximum current will the Microcontroller pin draw?
    Injection current will come only when I impress a voltage above that the supply voltage of the GPIO. And Leakage current, will come into picture only when the device is operating in low power state or shutdown.
    So, If I donot use the microcontroller in the above two conditions, (applying voltage to the pin within limits and in normal working mode), how much will the microcontroller pin take for a normal GPI input?

  3. This Microcontroll has two supplies. ADC Reference supply high and ADC Reference supply low? Usually, I have seen only ADC reference supply as a single reference supply pin. But here, there is reference high and reference low? Any idea on why is this implemented and any use case of it?

Best Answer

1) It means the current consumption of the ADC circuit within the IC, not from the input pin. Each ADC that you enable consumes 1 mA from the IC power supply.

2) That is the leakage current. 0.5 µA max., in or out. But if you use the ADC to sample a voltage, it gulps current in to charge its sample-hold capacitor.

3) It is implemented to enable the user to select both Vref- and Vref+ for the ADC. Users might want full-scale readings between 0.5 V and 2.8 V instead of between 0 V and 3.3 V.

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