Erratum XOSC8 for some MSP430™ microcontrollers (MCUs) places an extra consideration upon the crystal oscillator design beyond that found in the crystal oscillator design guide, MSP430 32-kHz Crystal Oscillators. Specifically, the erratum requires that the crystal oscillator circuit provides a minimum level of impedance to force the oscillator circuit of the MSP430 MCU to work harder. This can be done with increased load capacitance, increased ESR, or by placing a resistor from the crystal input to ground.

Each of these workarounds has potential side effects for the crystal-oscillator circuit. A positive side effect is increased noise immunity. The negative side effects include increased power consumption and a decrease in the safety factor. With the decrease in safety factor, the maintenance of an acceptable safety factor becomes more challenging.

Due to the numerous factors that influence the crystal-oscillator circuit, it is not possible to recommend a solution that works in all situations. This application report describes the different components of the crystal oscillator circuit that can be used to mitigate XOSC8, as well as workarounds and the implications of each. The workarounds include choosing a larger ESR crystal and using a shunt resistance on the oscillator input.