STM32F334X4 datasheet(59/115 Pages) STMICROELECTRONICS

59 / 115 page

DocID025409 Rev 5

59/115

STM32F334x4 STM32F334x6 STM32F334x8

Electrical characteristics

100

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, 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 (seeTable 33: 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 MCU 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 MCU supply voltage

fSW is the I/O switching frequency

C is the total capacitance seen by the I/O pin: C = CINT+ CEXT+CS

ISW

VDD fSW C

STM32F334X4 датащи(PDF) 59 Page - STMicroelectronics