Introduction

This application note will explain how and when to use the analog signal condition(OPAMP) peripheral available on the Microchip AVR® DB Family of microcontrollers as an adjustable power supply. The internal op amps have internal resistor ladders capable of outputting eight derivatives of V_DD completely without external components.

In a multitude of applications, it is necessary to use two or more voltage domains to fulfill the design specifications, either for power saving reasons or due to specific components needing a specific I/O level. This has traditionally led to the necessity of extra power supplies.

This power supply feature will be showcased by acting as the second power supply for the Multi-Voltage I/O (MVIO). The MVIO peripheral allows for a subset of ports in the AVR® to operate on a separate voltage domain V_DDIO2. The voltage range of V_DDIO2 is the same as for V_DD, although the Brown-out Detector (BOD) for V_DDIO2 is fixed and has a typical value of 1.6V.

Utilizing the internal ADC, it is possible to verify the voltage level on the output of the op amp. This can be useful for functional safety applications where it is necessary to have a stable and/or accurate voltage level before/under use to ensure proper operation.

The example code for replicating the results described in this application note is available on GitHub.

Additional details on OPAMP performance and general configuration are available in the device data sheet.