2.2 Ambient Temperature Application with APM

Unlike the previous application example, this application will use the APM for the sensor data readings and processing schedules.

The APM module is configured with LFINTOSC as clock source with a one second period. The Start 1 event comes up in one ms and during this event the ADCA, OPA1 and DAC1 modules are enabled. The Start 2 event will be delayed with one ms after the previous event. The sensor needs up to 800 μs to turn on and enables the ADCD part of the ADC. The End 1 event is set to 1.2 ms after the Start 1 event and disables the ADCA part and DAC1, while the End 2 event is set to 1.3 ms after the same Start 1 event and will disable the ADCD part and OPA1 module. The figure below shows the APM timing.

Enable the analog part of the ADC peripheral before a conversion can occur, so generally, the ADCA Start Event must occur before the ADCD Start Event to ensure that the controller has been enabled and initialized before a conversion is triggered. Refer to the APM section of the Q71 data sheet for more information about the APM operation with ADC.

In this scenario, the first current usage reduction is shown. The average is around 406 µA. Considering the APM feature to periodically switch ON and OFF the used analog peripherals, observe a standby current decrease of up to three times. Eight ADC readings describes the shown signal. The image below presents the first one, where the UART module is used to print data on the PC terminal.