Accelerometer having a root-mean-square (RMS) output

A method of making an accelerometer, the method comprising:

• fabricating a semiconductor package to include a microelectromechanical systems (MEMS) device and an application-specific integrated circuit (ASIC), the fabricating comprising:
• providing the MEMS device including a capacitive structure having a capacitance that is configured to change in response to acceleration of an object;
• and
• configuring the ASIC to determine acceleration of the object based at least in part on changes in the capacitance of the capacitive structure, the configuring comprising:
• incorporating analog circuitry into the ASIC, the analog circuitry configured to measure the changes in the capacitance of the capacitive structure and further configured to generate analog signals that represent the changes in the capacitance;
• incorporating an analog-to-digital converter (ADC) into the ASIC, the ADC configured to convert the analog signals to digital signals;
• incorporating RMS firmware into the ASIC, the RMS firmware configured to perform a root-mean-square (RMS) calculation on a representation that is based on the digital signals to provide an RMS value that represents an amount of the acceleration of the object;
• and
• incorporating an interrupt controller into the ASIC, the interrupt controller configured to provide an interrupt signal, based at least in part on the RMS value being greater than or equal to a threshold value for at least a specified period of time.

A method of making an accelerometer, the method comprising:

• providing a semiconductor substrate;
• forming a microelectromechanical systems (MEMS) device, which includes a capacitive structure having a capacitance that is configured to change in response to acceleration of an object, on the semiconductor substrate;
• and
• forming an application-specific integrated circuit (ASIC), which includes analog circuitry, an analog-to-digital converter (ADC), RMS firmware, and an interrupt controller, on the semiconductor substrate to determine acceleration of the object based at least in part on changes in the capacitance of the capacitive structure, wherein forming the ASIC on the semiconductor substrate comprises:
• configuring the analog circuitry to measure the changes in the capacitance of the capacitive structure and to generate analog signals that represent the changes in the capacitance;
• configuring the ADC to convert the analog signals to digital signals;
• configuring the RMS firmware to perform a root-mean-square (RMS) calculation on a representation that is based on the digital signals to provide an RMS value that represents an amount of the acceleration of the object;
• and
• configuring the interrupt controller to provide an interrupt signal, based at least in part on the RMS value being greater than or equal to a threshold value for at least a specified period of time.

An accelerometer comprising:

• a microelectromechanical systems (MEMS) device that includes a capacitive structure having a capacitance that is configured to change in response to acceleration of an object;
• and
• an application-specific integrated circuit (ASIC) configured to determine acceleration of the object based at least in part on changes in the capacitance of the capacitive structure, the ASIC configured to:
• calculate a representative value that represents the changes in the capacitance in a designated frequency range, wherein the representative value is a root-mean-square (RMS) of an input value;
• and
• based at least in part on the representative value being greater than or equal to a threshold value for at least a specified period of time, provide an interrupt signal.