Analog watchdog during Stop mode

AN3248

8/17

Doc ID 17758 Rev 3

In an analog watchdog application, COMP1 is configured through external interrupt line 21

(EXTI line 21) to exit the MCU from Stop mode when the analog input voltage exceeds

analog voltage goes below the lower threshold. Throughout the time the analog voltage is

within the defined thresholds, the MCU is in Stop mode and power consumption is reduced.

When the analog voltage exceeds the defined thresholds, average power consumption can

be reduced by switching to Run mode.

Figure 6 gives an overview of an analog watchdog application with threshold1 higher than

threshold2.

Figure 6.

Analog watchdog during Stop mode

1.

While the MCU is in Stop mode, the input voltage exceeds threshold1 and the MCU exits Stop mode.

2.

While the MCU is in Run mode, the input voltage goes below threshold1 and the MCU enters Stop mode.

3.

While the MCU is in Stop mode, the input voltage goes below threshold2 and the MCU exits Stop mode.

Note:

1

to the specific device datasheet for power consumption values.

2

No hysteresis is implemented on either comparator inputs.

MCU state

Time

MCU exits

Stop mode

Sensor output

voltage

0 V

Time

Threshold1:

VREFINT

MCU exits

Stop mode

MCU enters

Stop mode

ai17495

Threshold2