Datasheet

Product data sheet Rev. 1.8 — 22 June 2018 148 of 168

NXP Semiconductors

LPC540xx

32-bit ARM Cortex-M4 microcontroller

13.4 I/O power consumption

I/O pins are contributing to the overall dynamic and static power consumption of the part.

If pins are configured as digital inputs, a static current can flow depending on the voltage

level at the pin and the setting of the internal pull-up and pull-down resistors. This current

can be calculated using the parameters R

and R

given in Ta b le 2 0 for a given input

voltage V

. For pins set to output, the current drive strength is given by parameters I

and

in Ta ble 2 0 , but for calculating the total static current, you also need to consider any

external loads connected to the pin.

I/O pins also contribute to the dynamic power consumption when the pins are switching

because the V

supply provides the current to charge and discharge all internal and

external capacitive loads connected to the pin in addition to powering the I/O circuitry.

The contribution from the I/O switching current I

can be calculated as follows for any

given switching frequency f

if the external capacitive load (C

ext

) is known (see Tab le 20

for the internal I/O capacitance):

= V

x f

x (C

+ C

ext

)