FIELD OF DISCLOSURE

The field of representative embodiments of this disclosure relates to methods, apparatus and/or implementations concerning or relating to ADC (analogue-to-digital converter) circuitry.

BACKGROUND

There are a number of applications where analogue to digital conversion is implemented, for example for converting analogue audio signals generated by an input transducer, such as a microphone, to digital signals for processing, transmission and/or storage. Typically, an ADC circuit with an analogue-front-end (AFE) is used to receive the analogue input signals and convert to digital. Preferably, the ADC circuit should be able to convert received input signals at the maximum expected signal amplitude in normal operation without distortion or clipping, which may require the ADC circuit to have a relatively high dynamic range. In at least some applications it may also be desirable for the ADC circuit to also be able to convert relatively low amplitude input signals with a relatively good SNR (signal-to-noise ratio), which requires the ADC circuit to be able to operate with relatively low noise.

One way to implement an ADC circuit that provides good performance with a high dynamic range is to provide the ADC circuit with multiple conversion paths, where each conversion path is coupled to the ADC input and is optimised for a particular input signal range. For example a dual-path ADC circuit may comprise one conversion path which is optimised for lower amplitude input signals to provide good SNR for low signal levels, and another conversion path which is optimised for converting higher amplitude signals without significant distortion, so that the ADC circuit can provide a relatively high dynamic range. Depending on the level of the input signal, the appropriate path can be used to provide the digital output.

SUMMARY

Embodiments of the present disclosure relate to ADC circuitry that is capable of multi-path operation.

According to an aspect of the disclosure there is provided analogue to digital conversion circuitry comprising a first input node for receiving a first analogue input signal, a second input node for receiving a second analogue input signal, a first conversion path for converting analogue signals to digital, and a second conversion path for converting analogue signals to digital. The analogue to digital conversion circuitry is selectively operable in a first mode or a second mode. In the first mode, the first conversion path is connected to the first input node to convert the first analogue input signal to a first digital signal and the second conversion path is connected to the second input node to convert the second analogue input signal to a second digital signal. In the first mode each of the first and second conversion paths are configured for processing a full scale of the respective first and second analogue input signals and the first and second digital signals are output as first and second output signals respectively. In the second mode, the first conversion path and the second conversion path are both connected to the first input node to convert the first analogue input signal to respective first and second digital signals. In the second mode, the first and second conversion paths are configured for processing different signal levels of the first analogue input signal and a selector is configured to select the first digital signal or the second digital to be output as an output signal based on an indication of amplitude of the first analogue input signal.

In some examples, the second mode, the first conversion path may be configured for processing a full scale of the first analogue input signal and the second conversion path may be configured for processing lower amplitude signal levels of the first analogue input signal.

The first and second conversion paths may each comprise respective analogue-front-ends. In the second mode of operation, the respective analogue-front-end of the second conversion path may be configured to apply a larger gain to the first analogue input signal that the analogue-front-end of the first conversion path. In some implementations, the analogue-front-end of the second conversion path may comprise a programmable gain amplifier. A mode controller may control the gain of the programmable gain amplifier of the analogue-front-end of the second conversion path to be different in the first and second modes. The analogue-front-end of the first conversion path may additionally or alternatively comprise a programmable gain amplifier.

At least one of the first and second conversion paths may comprise a digital gain element for applying a gain to the relevant first digital signal or second digital signal in the second mode to provide gain matching of the first and second conversion paths.

In some embodiments, the analogue to digital circuitry may be operable to dynamically switch between the first and second modes in use.

The circuitry may comprise at least one switch for selectively connecting the second conversion path to the first input node or the second input node. The second conversion path may be configured to be switchably connected to the first input node via a first input resistor and switchably connected to the second input node via a second, different input resistor.

In some examples, the selector may comprise a fader configured to transition between outputting one of the first and second digital signals as the selector output signal to outputting the other of the first and second digital signals by cross-fading between the first and second digital signals.

In some example a controller may be configured to, when operating in the second mode, suspend or disable at least some components of the first conversion path in response to a low-signal condition. The low-signal condition may comprise the amplitude of the second digital signal remaining below a defined threshold for a defined period of time.

In some examples there may be at least one additional conversion path operable, in one mode, to be connected to an associated additional input node to convert an additional analogue input signal received at that additional input node to a digital signal. The at least one additional conversion path may be further operable, in another mode, to be connected to one of the first input node, the second input node or a further additional input node, to convert the analogue input signal received at the relevant input node to a digital signal.

In some examples a clipping controller may be configured to, when operating in the second mode, to control the second conversion path to reduce or prevent a non-linear current being drawn from the first input node due to clipping of the second conversion path. The clipping controller may be configured to control a gain of the second conversion path to prevent clipping of the second conversion path and/or the clipping controller may be configured to reconfigure the second conversion path to provide regulation of a virtual earth node of the second conversion path.

In some examples the circuit may be configured to output an indication of instantaneous noise and/or dynamic range. The analogue to digital conversion circuitry may comprise a module for determining the indication of instantaneous noise and/or dynamic range based on a setting of the selector that determines contribution to the output signal from the first digital signal and the second digital signal.

The analogue to digital conversion may be implemented as an integrated circuit. In some cases, a first microphone may be coupled to the first input node of the integrated circuit and a second microphone may be coupled to the second input node of the integrated circuit.

Aspects also relate to an electronic device comprising analogue to digital conversion circuitry according to any of the embodiments discussed herein.

In another aspect there is provided an analogue to digital conversion circuit comprising: a first analogue-to-digital conversion path, and a second analogue-to-digital conversion path. The analogue to digital conversion circuit is operable in: a first mode in which the first and second analogue-to-digital conversion path are connected to different input nodes to one another to process separate input signals from separate sources; and a second mode in which the first and second analogue-to-digital conversion path are connected to the same input node as one another to process different signal levels of the same input signal.

In another aspect there is provided an ADC circuit comprising: a first ADC path, and a second ADC path, wherein the ADC circuit is operable is operable to connect the first and second ADC paths to different inputs to process separate analogue input signals from separate sources and is also operable to connect the first and second ADC paths to the same input to process the same input signal with different analogue gains applied.

Unless expressly indicated to the contrary, any of the various features of the various implementations discussed herein may be implemented together with any one or more of the other described features in any and all suitable combinations.

