Wolfson Microelectronics Limited

Cirrus Logic Inc.

Cirrus Logic International Semiconductor Limited

Douglas James Wallace MacFarlane

Andrew James Howlett

Graeme Gordon Mackay

Holger Haiplik

Mark McCloy-Stevens

Andrew Notman

Colin Steele

A host device for use with a removable peripheral apparatus having a microphone, and to the biasing circuitry for said microphone. The host device may have a device connector for forming a mating connection with a respective peripheral connector. A source of bias is arranged to supply an electrical bias to a device microphone contact of the device connector via a biasing path. A capacitor is connected between a reference voltage node and a capacitor node of the biasing path. A first switch is located between the capacitor node and the device microphone contact. Detection circuitry detects disconnection of the peripheral connector and device connector; and control circuitry controls the switch to disable the biasing path.

Microphone biasing circuitry and method thereof

Methods and apparatus for control of DC-DC converters, especially in valley current mode. The DC-DC converter is operable so that a low side supply switch may be turned off, before the high side supply switch is turned on. During the period when both switches are off the current loop control remains active and the change in inductor (L) current is emulated. One embodiment uses a current sensor for lossless current sensing and emulates the change in inductor current by holding the value of the output of the current sensor (ISNS) at the time that the low side switch turns off and adding an emulated ramp signal (VISLP) until the inductor current reaches zero. Embodiment employing a pulse-skip mode of operation based on a minimum conduction time are also disclosed. The invention enables a seamless transition from Continuous Conduction Mode the Discontinuous Conduction Mode and Pulse Skipping and provide converters that are efficient at low current loads.

DC-DC converters operable in a discontinuous switching mode

An apparatus comprising a capacitive transducer, for example a MEMS microphone. A first voltage generator is connected to receive a first voltage (VDD*) and generate a second voltage (V) for biasing the capacitive transducer. A control circuit is adapted to, in use, control the first voltage (VDD*) based on a calibration value, wherein a different calibration value would lead to a different first voltage level and the calibration value is set such that an input signal of known amplitude produces an output signal of predetermined amplitude.

Apparatus and method for biasing a transducer

A method of generating a voltage supply (Vout+, Vout&#x2212;) from a single input supply (+V), comprising connecting at least one flying capacitor (Cf) to at least one reservoir capacitor (CR, CR) and to the input supply in repeated cycles so as to generate a voltage on said reservoir capacitor, the cycles differing between at least two modes so that each mode generates a different voltage on said reservoir capacitor the method including changing from an existing one of said modes to enter a new one of said modes during operation, and operating in at least one transitional mode for a period prior to entering fully said new mode.

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Edinburgh, United Kingdom

Douglas James Wallace MacFarlane