LPC540xx
NXP Semiconductors
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 Rpu and Rpd given in Table 20 for a given input
voltage VI. For pins set to output, the current drive strength is given by parameters IOH and
IOL in Table 20, 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 VDD 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 Isw can be calculated as follows for any
given switching frequency fsw if the external capacitive load (Cext) is known (see Table 20
for the internal I/O capacitance):
Isw = VDD x fsw x (Cio + Cext)
LPC540xx
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Product data sheet
Rev. 1.8 — 22 June 2018
148 of 168
NXP [ NXP ]
