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nRF51822 - IO Impedance

Jose Xavier

Hi,

I'm using the following TI IC www.ti.com/.../tps62736 to get 3V from a LiPo battery. It has a VIN_OK pin that I can configure to alert of battery low level. The problem is that this pin is pulled up to Vbattery so when the battery is charged this pin will be at 4.2V. I need to use a voltage divider but I don't know what is the input impedance of the GPIO on the MCU so I don't know if I can go into the MegaOhms resistor value or not.

If I use per example a 430K and 1M resistor it will add 3uA consunption what is ok on my application but will it be able to drive the IO?

  • 0

    This is the closest question I can find to yours.

    devzone.nordicsemi.com/.../

    That says input impedance is 'close to infinity' and leakage current 'of the order of nA' which would suggest your chosen resistors would work fine, in fact you could probably use even larger values without problems. You could just try it and measure the voltage you get, the worst that happens is you get a lower voltage than you need and you put the resistor values down.

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