CIRCUIT060091

Some MSP430™ microcontrollers (MCUs) contain configurable integrated signal chain elements such as op-amps, DACs and programmable gain stages. These elements make up a peripheral called the smart analog combo (SAC). For information on the different types of SACs and how to leverage their configurable analog signal chain capabilities, visit MSP430 MCUs Smart Analog Combo Training. To get started with your design, download the Temperature Sensing PTC Circuit Design Files. This temperature sensing circuit uses a resistor in series with a positive-temperature-coefficient (PTC) thermistor to form a voltage divider, which produces an output voltage that is linear over temperature. The circuit uses the MSP430FR2311 SAC_L1 op-amp in a noninverting amplifier configuration with inverting reference to offset and amplify the signal, which helps to use the full ADC resolution and increase measurement accuracy. (Note: The MSP430FR2355 features four SAC_L3 peripherals which each contain a built-in DAC and PGA, providing a single-chip solution for generating Vref and measuring the thermistor circuit.) The output of the integrated SAC op-amp can be sampled directly by the on board ADC or monitored by the on-board comparator for further processing inside the MCU.