STM32U535NET6QTR datasheet(173/278 Pages) STMICROELECTRONICS

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DS14217 Rev 1

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STM32U535xx

Electrical characteristics

253

I/O system current consumption

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

I/O static current consumption

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

pin is externally held to the opposite level. The value of this current consumption can be

simply computed by using the pull-up/pull-down resistors values given in Section 5.3.14: I/O

port characteristics.

For the output pins, any internal or external pull-up or 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 the ADC input pins, that must 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, they 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 on-chip peripheral current consumption (see Table 71 for peripheral

current consumption in Run mode), 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

and external) connected to the pin:

where:

•

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

•

VDDIOx 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 = CINT+ CEXT + CS.

•

CS is the PCB board capacitance including the pad pin.

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

frequency.

ISW

VDDIOx fSW C

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