AN2857 datasheet(25/31 Pages) STMICROELECTRONICS

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AN2857

Power consumption and wakeup time measurements and results

Doc ID 15241 Rev 3

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Figure 7.

Wakeup time measurement diagram

5.2.2

Wakeup time results

In most of cases, power supply voltage has no effect on wakeup time. The minus sign (-) in

Table 11 to Table 14 below indicates that the wakeup time is the same for both power supply

voltages.

5.2.3

Wakeup time results in wait mode

The wakeup time from wait mode is not always the same because the wakeup event is

synchronized with the CPU clock. The variation range is about one period of the CPU clock.

Data given in Table 11 are maximum values.

External event

Output pin

fCPU

tWKU

Execution of

ld A, #$02

ai15050

Table 11.

Wakeup time results in wait mode

Symbol

Parameter

Condition

VDD = 3.3 V

(1)

The minus sign (-) indicates that the wakeup time is the same as for VDD = 5 V.

VDD = 5 V

Unit

tWU(WFI)

Wakeup time

from wait

mode

HSE crystal

fCPU = FMASTER = 24 MHz

-1.0

µs

HSE crystal

fCPU = FMASTER = 16 MHz

-0.75

HSE crystal

fCPU = FMASTER = 8 MHz

-1.4

HSE crystal

fCPU = FMASTER = 4 MHz

-2.7

HSI

fCPU = FMASTER = 16 MHz

-0.75

HSI

fCPU = FMASTER/128 = 125 kHz

-80

LSI

fCPU = FMASTER = 128 kHz

-94

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