This application note provides the user with a low cost oscillator solution with discrete components and based on a resonator or quartz that can be used for STR71x MCU.
This application note addresses the need for a low-cost oscillator solution for the STR71x 32-bit MCU family, offering an alternative to purchasing expensive oscillator chips. It details a design based on discrete components and a quartz crystal operating in parallel resonance mode to balance start-up time and frequency accuracy.
The document provides a theoretical overview of oscillator principles and quartz crystal characteristics, including series and parallel resonance. It then guides the user through the design of a Pierce oscillator using an STMicroelectronics 74V1GU04 inverter, detailing the selection of feedback resistors and load capacitors to ensure stable operation.
The document recommends using a quartz crystal that operates in parallel resonance mode.
The design uses an STMicroelectronics unbuffered inverter 74V1GU04 and a 2MΩ feedback resistor.
Stray capacitance typically falls between 2pF and 7pF.