Application Note
17 of 38
001-86233 Rev. *I
2021-11-04
PSoC™ 4 MCU low
-power modes and power reduction techniques
Other low-power mode considerations
The time required for some tasks does not change even if the system clock frequency increases. Sensor reading
and data transmitting fall into this category. Other tasks, however, require less time if the CPU operates at a
faster frequency.
At some point, the benefit of a shorter active time is overcome by the energy required to drive the clocks at a
higher rate. Assume that the optimal speed is 12 MHz, as
shows. With a 12-MHz clock, the time spent in
active mode is about half as long as with a 3-MHz clock.
shows that the peak current consumption is
greater when the clocks are faster, but the overall average is lower.
A B
C D E
A
–
Wake from sleep
B
–
Read sensor data
C
–
Manipulate data
D
–
Transmit result
E
–
Go back to sleep
Cur
re
nt
Time
Figure 6
Analysis of tasks in active mode at 12 MHz
Average
current
Cur
re
nt
Time
Active
Sleep
Figure 7
Example current profile with a 12-MHz clock
You may also be able to reduce the peak active current by applying other suggestions in this application note.
is an example project that wakes once a second, takes a temperature reading with
the ADC, transmits the data via a UART, and then goes back to deep sleep.