Application Note
14 of 38
001-86233 Rev. *I
2021-11-04
PSoC™ 4 MCU low
-power modes and power reduction techniques
Power reduction techniques
5.5
Use PSoC™ 4 MCU device to gate current paths
Your PCB may contain other components that draw power; the
PSoC™
4 MCU device can be used to control the
current consumed by them. Note that the maximum pin source and sink capabilities listed in the datasheet
must not be exceeded. The following example is shown using a
PSoC™
Creator component, the same theory
applies to ModusToolbox
™ software
.
A good example of this scenario is a thermistor application, as
shows. In this case, the
PSoC™
4 MCU
device measures the temperature using the voltage on an analog pin, which changes as the thermistor
resistance changes.
Figure 2
Typical thermistor application
The ADC can be turned OFF when not in use, but external components still consume power because the current
path through the resistor and thermistor remains. A simple solution with
PSoC™
4 MCU is to use a second pin as
a switch to ground, as
Figure 3
Using a GPIO as a ground switch
In this configuration, the
current flow can be stopped by writing a ‘1’ to Pin_3
, allowing the pin to float. This
removes the current consumption by reducing the voltage differential across the two resistors to 0 V. Writing a
‘0’ resumes
the current flow. The resource use of this power-saving feature is only one pin and a few lines of
code.
Alternatively, when the measurement is not required, Pin_3 drive mode can be changed to High-Z analog so
that there is no path for the current to flow. For the measurement, Pin_3 drive mode should be set to strong
and logic 0 should be written at the pin.
