STM8T141 datasheet(25/50 Pages) STMICROELECTRONICS

25 / 50 page

STM8T141

Device operation

Doc ID 15699 Rev 7

25/50

7.4.4

Extreme Low Power mode

With the STM8T141 in Extreme Low Power mode, burst cycles only occur every 17th

tSAMPLING period (or 5.88% of the Normal Power mode), thus adding 16 extra delays of

tSAMPLING between charge cycles to conserve power.

This reduces the amount of burst cycles in Extreme Low Power mode even more than Low

Power mode which in turn saves even more power but comes at the expense of a higher

system response time (Figure 19).

Figure 19.

Charge cycle timing diagram in Extreme Low Power mode

7.5

Charge transfer frequency

The STM8T141 offers two charge transfer frequencies. The charge transfer frequency must

be adjusted depending on the CS capacitor. The charge transfer frequency may need to be

raised to 250 kHz in order to reduce tBURST when the CS capacitance is large.

●

125 kHz

●

250 kHz

Bit 1 of option byte OPT1 is used to select the correct charge transfer frequency.

7.6

Sampling period

The default sampling period (tSAMPLING) is configurable in order to allow different

compromises between power consumption and conversion rates:

●

20-ms sampling rate to reduce average power consumption

●

10-ms sampling rate to increase detection response time

When using a faster sampling rate (tSAMPLING = 10 ms), all the timing values of the Power

modes will occur at twice the speed.

BIt 2 of option byte OPT1 is used to select the correct conversion period.

345678

Burst cycle every 17th tSAMPLING period

tLP

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