Texas Instruments MSP430x1xx manual ComparatorA Operation, Input Analog Switches

Comparator_A Operation

16.2 Comparator_A Operation

The comparator_A module is configured with user software. The setup and operation of comparator_A is discussed in the following sections.

16.2.1 Comparator

The comparator compares the analog voltages at the + and – input terminals. If the + terminal is more positive than the – terminal, the comparator output CAOUT is high. The comparator can be switched on or off using control bit CAON. The comparator should be switched off when not in use to reduce current consumption. When the comparator is switched off, the CAOUT is always low.

16.2.2 Input Analog Switches

The analog input switches connect or disconnect the two comparator input terminals to associated port pins using the P2CAx bits. Both comparator terminal inputs can be controlled individually. The P2CAx bits allow:

-Application of an external signal to the + and – terminals of the comparator

-Routing of an internal reference voltage to an associated output port pin

Internally, the input switch is constructed as a T-switch to suppress distortion in the signal path.

Note: Comparator Input Connection

When the comparator is on, the input terminals should be connected to a signal, power, or ground. Otherwise, floating levels may cause unexpected interrupts and increased current consumption.

The CAEX bit controls the input multiplexer, exchanging which input signals are connected to the comparator’s + and – terminals. Additionally, when the comparator terminals are exchanged, the output signal from the comparator is inverted. This allows the user to determine or compensate for the comparator input offset voltage.

16-4Comparator_A