CIRCUIT060096

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 half-wave rectifier circuit design files. The precision half-wave rectifier inverts and transfers only the negative-half input of a time varying input signal (preferably sinusoidal) to its output. This circuit uses the MSP430FR2311 SAC_L1 op-amp in an inverting amplifier configuration with the appropriate diodes in place. There is room for further integration by using the integrated DAC in the MSP430FR2355 SAC_L3 block to provide the bias voltage on the noninverting op-amp terminal. By appropriately selecting the feedback resistor values, different gains can be achieved. Precision half-wave rectifiers are commonly used with other op amp circuits such as a peakdetector or bandwidth limited non-inverting amplifier to produce a DC output voltage. The output of the SAC_L3 op-amp can be cascaded with the other three SAC_L3 blocks in the MSP430FR2355 to expand upon the analog signal chain functionality or sampled directly by the onboard ADC or monitored by the onboard comparator for further processing inside the MCU. This configuration has been designed to work for sinusoidal input signals between 0.2 Vpp and 2 Vpp at frequencies up to 50 kHz.