Power consumption factors

AN3404

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Doc ID 018847 Rev 3

1

Power consumption factors

The STM8TL5xxx microcontrollers are digital logic devices using the complementary metal

oxide semiconductor (CMOS) technology. In these type of devices, power consumption is a

sum of:

●

Static power (mainly caused by transistor polarization and leakage)

●

Dynamic power which depends on the supply voltage and the clock frequency

Dynamic power is calculated using Equation 1.

Equation 1

where:

●

C is the CMOS load capacitance

●

V is the supply voltage

●

f is the clock frequency

Static consumption is negligible compared to dynamic consumption when the clock is

running. In some low power modes, when no clock is running, static consumption is the

main consumption source.

Total consumption is a sum of static and dynamic consumption as given by Equation 2.

Equation 2

where:

●

●

●

Dynamic power

C

V

2

f





=

I

DD

fI

DynamicRun



µA

MHz





 I



+

=