STM32WLE4JC datasheet(91/145 Pages) STMICROELECTRONICS

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DS13105 Rev 8

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STM32WLE5/E4xx

Electrical characteristics

133

I/O system current consumption

The current consumption of the I/O system has two components: a static and a dynamic.

I/O static current consumption

All the I/Os used as inputs with pull-up generate current consumption when the pin is

externally held low. The value of this current consumption can be simply computed by using

the pull-up/pull-down resistors values given in Table 72: I/O static characteristics.

For the output pins, any external pull-down or external load must also be considered to

estimate the current consumption.

Additional I/O current consumption is due to I/Os configured as inputs if an intermediate

voltage level is externally applied. This current consumption is caused by the input Schmitt

trigger circuits used to discriminate the input value. Unless this specific configuration is

required by the application, this supply current consumption can be avoided by configuring

these I/Os in analog mode. This is notably the case of ADC input pins which should be

configured as analog inputs.

Caution:

Any floating input pin can also settle to an intermediate voltage level or switch inadvertently,

as a result of external electromagnetic noise. To avoid current consumption related to

floating pins, these pins must either be configured in analog mode, or forced internally to a

definite digital value. This can be done either by using pull-up/down resistors or by

configuring the pins in output mode.

I/O dynamic current consumption

In addition to the internal peripheral current consumption measured previously (see

Table 53: Peripheral current consumption, the I/Os used by an application also contribute to

the current consumption. When an I/O pin switches, it uses the current from the I/O supply

voltage to supply the I/O pin circuitry and to charge/discharge the capacitive load (internal or

external) connected to the pin:

where

•

ISW is the current sunk by a switching I/O to charge/discharge the capacitive load.

•

VDD is the I/O supply voltage.

•

fSW is the I/O switching frequency.

•

C is the total capacitance seen by the I/O pin: C = CIo+ CEXT .

•

CEXT is the PCB board capacitance plus any connected external device pin

capacitance.

The test pin is configured in push-pull output mode and is toggled by software at a fixed

frequency.

ISW

VDD fSW C

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