Power IO Inputs¶

The Power IO shield offers 6 high-voltage-capable digital inputs, which can be accessed via a spring terminal block.

../../../../../_images/inputs.png

The input channels are implemented using a ULN2002 Darlington transistor array to provide a reasonable threshold voltage of ~10V. In addition, a 100V depletion-mode N-channel MOSFET is used as a high-voltage current source to limit each channel’s input current to less than 2 mA, well below the ULN2002’s maximum continuous base current of 25mA.

../../../../../_images/mosfet.png

The 6 input channels are connected to the \(I^2C\) port expander as indicated in the table below. A high voltage at an input channel pulls the respective port expander-pin low, resulting in an open-collector behaviour.

Port Expander Mapping¶

IO	Port expander port
IN 0	GPB 0
IN 1	GPB 1
IN 2	GPB 2
IN 3	GPB 3
IN 4	GPB 4
IN 5	GPB 5