STM32F091XB datasheet(63/127 Pages) STMICROELECTRONICS

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STM32F091xB STM32F091xC

Electrical characteristics

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, 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 internal peripheral current consumption measured previously (see

Table 35: 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:

ISW

VDDIOx fSW C

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.

STM32F091XB Datasheet(PDF) 63 Page - STMicroelectronics