Analog-to-Digital Converter (ADC)

12.2.7Internal Temperature Sensor

Thetemperaturesensorservestwoprimarypurposes:1)tonotifythesystemthatinternaltemperature is too high or low for reliable operation, and 2) to provide temperature measurements for calibration of the Hibernate module RTC trim value.

The temperature sensor does not have a separate enable, since it also contains the bandgap reference and must always be enabled. The reference is supplied to other analog modules; not just the ADC.

The internal temperature sensor provides an analog temperature reading as well as a reference voltage. The voltage at the output terminal SENSO is given by the following equation:

SENSO = 2.7 - ((T + 55) / 75)

This relation is shown in Figure 12-5 on page 284.

Figure 12-5. Internal Temperature Sensor Characteristic

12.3Initialization and Configuration

In order for the ADC module to be used, the PLL must be enabled and using a supported crystal frequency (see the RCC register). Using unsupported frequencies can cause faulty operation in the ADC module.

12.3.1Module Initialization

Initialization of the ADC module is a simple process with very few steps. The main steps include enabling the clock to the ADC and reconfiguring the sample sequencer priorities (if needed).

The initialization sequence for the ADC is as follows:

1.EnabletheADCclockbywritingavalueof0x0001.0000tothe RCGC0 register(seepage106).

2.If required by the application, reconfigure the sample sequencer priorities in the ADCSSPRI register. ThedefaultconfigurationhasSampleSequencer0withthehighestpriority,andSample Sequencer 3 as the lowest priority.

Preliminary