Microphone assembly having a direct current bias circuit
AssigneeKnowles Electronics, LLC
InventorsRaminder Jit Singh, Jose Prado
Life of this patent
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Abstract
The disclosure describes devices and methods for starting up a microphone assembly. The device may be implemented on an integrated circuit that includes a direct current (DC) bias circuit. The DC bias circuit may be coupled to a transducer and configured to supply a DC bias signal to the transducer. The DC bias circuit includes a multi-stage charge pump and a low pass filter (LPF) circuit. The LPF circuit includes an adjustable resistance and a capacitor. A resistance of the adjustable resistance may be reduced to reduce the settling time of the LPF while starting (e.g., turning on) the microphone assembly.
Claims21
A microphone assembly configured for integration with a host device, the assembly comprising:
- a housing having a host device interface;
- a microelectromechanical systems (MEMS) transducer disposed in the housing and configured to generate an electrical signal responsive to acoustic activity;
- and
- an integrated circuit disposed in the housing and electrically coupled to contacts of the host device interface, the integrated circuit including a direct current (DC) bias circuit comprising:
- a multi-stage charge pump circuit configured to generate a DC voltage at an output;
- a booster circuit coupled to the output of the multi-stage charge pump circuit, the booster circuit configured to generate an output voltage based on the DC voltage;
- and
- a low pass filter circuit having a capacitance and an adjustable resistance controlled by the output voltage of the booster circuit, the low pass filter circuit having an input coupled to the output of the multi-stage charge pump circuit, and the low pass filter circuit having an output coupled to the MEMS transducer.
An integrated circuit connectable to a capacitive microelectromechanical systems (MEMS) transducer in a microphone assembly, the circuit comprising:
- a direct current (DC) bias circuit including:
- a multi-stage charge pump circuit configured to generate a DC voltage at an output;
- a booster circuit coupled to the output of the multi-stage charge pump circuit, the booster circuit configured to generate an output voltage based on the DC voltage;
- and
- a low pass filter circuit having an adjustable resistance controlled by the output voltage of the booster circuit and a capacitance, the low pass filter circuit having an input coupled to the output of the multi-stage charge pump circuit, and the low pass filter circuit having an output connectable to the MEMS transducer,
- wherein a settling time of the low pass filter circuit is reduced by reducing the adjustable resistance during a startup time of the multi-stage charge pump circuit.
A method of operating an audio circuit in a microphone assembly, the method comprising:
- generating a direct current (DC) bias voltage with a multi-stage charge pump circuit;
- generating an output voltage with a booster circuit based on the output of the multi-stage charge pump circuit filtering the DC bias voltage with a low pass filter circuit including an adjustable resistance element and a capacitor;
- adjusting a resistance of the adjustable resistance element with the output voltage of the booster circuit applying the filtered DC bias voltage to a capacitive transducer of the microphone assembly;
- and
- reducing a settling time of the low pass filter circuit by reducing the resistance of the adjustable resistance element during a startup time of the multi-stage charge pump circuit.
Dependencies are inferred from the claim text.