Biasing circuitry for MEMS transducers

摘要

Circuitry for biasing a MEMS transducer and associated signal processing circuitry. A reference voltage generator is configured to generate a reference voltage at a reference voltage node. Control circuitry generates a drive signal to control a first current source which is operable to supply a current to the reference voltage generator in response to the drive signal. A switched DC-DC converter, such as a charge pump has a voltage input connected to the reference voltage node and a voltage output for providing a bias voltage for the MEMS transducer. The DC-DC converter cyclically switches in a sequence of states including at least a first state where a first converter capacitance is disconnected from the voltage input followed by a second state where the first converter capacitance is connected to the voltage input. A second current source Is operable to supply a bias current in response to a voltage at a bias control node. Switch control circuitry is configured to cyclically open and close a switch connected between the drive node and the bias control node, such that the switch is open during a time window that includes the time at which the switched DC-DC converter switches from the first state to the second state.