AN2857 datasheet(19/31 Pages) STMICROELECTRONICS

19 / 31 page

AN2857

Power consumption and wakeup time measurements and results

Doc ID 15241 Rev 3

19/31

Figure 4.

Power supply setup

Figure 4 does not show the decoupling capacitors for all power supplies. Ceramic

decoupling capacitors, with very low parasitc serial resistance, are used for the power

measurements. Current leakage through such decoupling capacitors is not visible.

When the power measurements are performed with an external crystal, there is no internal

clock division. The crystal is physically changed for each frequency. Figure 5 shows the

crystal oscillator setup.

Figure 5.

Crystal oscillator setup

When the power measurements are taken with an external clock, the following configuration

is used: The function generator provides a ‘SIN’ waveform at a given frequency. The wave

oscillates from 0 V to 5 V or 3.3 V depending on the supply voltage. As the OSCOUT pin is

not used, it is configured like other GPIOs (output push-pull outputting low level).

STM8

VDDIO

VDDA

VSSIO

VSSA

VSS

VDD

3.3 V or 5 V

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STM8

OSCIN

OSCOUT

CL1 = 22 pF

CL2 = 22 pF

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AN2857 Datasheet(PDF) 19 Page - STMicroelectronics