US 11,689,848 B2Granted

Capacitive sensor assembly and electrical circuit therefor

AssigneeKnowles Electronics, LLC

InventorsMichael Pedersen, Peter V. Loeppert

Life of this patent

Estimating the term…

Loading patent…

Abstract

A capacitive sensor assembly includes a capacitive transduction element and an electrical circuit disposed in the housing and electrically coupled to contacts on an external-device interface of the housing. The electrical circuit includes a sampling circuit having an operational sampling phase during which a voltage produced by the capacitive sensor is sampled by a sampling capacitor coupled to a comparator and an operational charging phase during which a second capacitor is charged by a charge and discharge circuit until the output of the comparator changes state, wherein the output of the sampling circuit is a pulse width modulated signal representative of the voltage on the input of the sampling circuit during each sample period. The output of the sampling circuit can be coupled to a delta-sigma analog-to-digital (A/D) converter.

Claims20

Dependent claims

An electrical circuit for a capacitive sensor assembly, the circuit comprising:

a sampling circuit having an input connectable to a node of a capacitive sensor, the sampling circuit comprising:
a comparator having an input coupled to the input of the sampling circuit, the comparator having an output coupled to the output of the sampling circuit;
a sampling capacitor having a first node coupled to the input of the comparator;
a second capacitor having a first node coupled to a second node of the sampling capacitor;
a charge and discharge circuit coupled to the first node of the second capacitor;
the sampling circuit having an operational sampling phase during which a voltage on the input of the sampling circuit is sampled by the sampling capacitor when the second capacitor is discharged, and the sampling circuit having an operational charging phase during which the second capacitor is charged while coupled in series to the sampling capacitor,
wherein the output of the sampling circuit is a pulse width modulated signal representative of a voltage on the input of the sampling circuit during each sample period.

4 more elements

An electrical circuit for a capacitive sensor assembly, the circuit comprising:

a sampling circuit having an input connectable to a node of a capacitive sensor, the sampling circuit comprising:
a comparator having an input coupled to the input of the sampling circuit, the comparator having an output coupled to the output of the sampling circuit;
a sampling capacitor having a first node coupled to the input of the comparator;
a second capacitor;
a charge and discharge circuit coupled to the first node of the sampling capacitor and to a first node of the second capacitor,
the sampling circuit having an operational sampling phase during which a voltage on the input of the sampling circuit is sampled by the sampling capacitor, the sampling circuit having an operational charging phase during which the sampling capacitor and the second capacitor are charged by the charge and discharge circuit, and the sampling circuit having an operational reset phase during which the sampling capacitor and the second capacitor are at least partially discharged,
wherein the output of the sampling circuit is a pulse width modulated signal representative of a voltage on the input of the sampling circuit during each sample period.

4 more elements

Dependencies are inferred from the claim text.