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US 8,786,477 B1Granted
Digital-to-analog conversion with improved dynamic range
AssigneeTexas Instruments Incorporated
InventorXavier Albinet
Life of this patent
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Abstract
An audio downlink path is provided including a Dynamic Range Boost (DRB), a modified Digital-to-Analog Converter (DAC), and a modified audio driver gain control to produce a very high Dynamic Range (DR) while maintaining a limited scale and complexity of the components within the audio downlink path.
Claims20
A method comprising:
- at a Dynamic Range Boost (DRB) circuit:
- receiving a digital signal;
- calculating an approximation of an output level of a Digital to Analog Converter (DAC);
- comparing the approximation of the output level of the DAC to an approximation of a saturation level of the DAC;
- determining a gain adjustment factor by which to adjust a previous gain based on the comparing, the previous gain having been applied to a previous digital signal by the DRB circuit;
- adjusting the previous gain by the gain adjustment factor to create a new gain;
- digitally amplifying the digital signal by the new gain to create an amplified digital signal;
- at the DAC, wherein the DAC is coupled to the DRB circuit:
- calculating an intermediate sample signal responsive to the amplified digital signal;
- adjusting a feedback signal of the DAC by a feedback adjustment factor corresponding to a value of the gain adjustment factor to create an adjusted feedback signal;
- adding the adjusted feedback signal to the intermediate sample signal to create an analog output signal;
- at a gain stage coupled to the DRB circuit:
- amplifying a signal corresponding to the analog output signal by an inverse of the new gain to create an amplified analog signal.
10 more elements
An apparatus comprising:
- a Dynamic Range Boost (DRB) circuit comprising:
- at least one input configured to receive a digital signal;
- a calculator circuit configured to calculate an approximation of an output level of a Digital to Analog Converter (DAC);
- a comparing circuit configured to compare the approximation of the output level of the DAC to an approximation of a saturation level of the DAC;
- a logic circuit configured to:
- determine a gain adjustment factor by which to adjust a previous gain based on the comparing by the comparing circuit, the previous gain having been applied to a previous digital signal;
- and
- adjust the previous gain by the gain adjustment factor to create a new gain;
- and
- a digital amplification circuit to digitally amplify the digital signal according to the new gain to create an amplified digital signal;
- the DAC operatively coupled to the DRB circuit and comprising:
- a switching circuit configured to generate an intermediate sample signal responsive to the amplified digital signal;
- and
- an amplification circuit configured to:
- adjust a feedback signal of the DAC by a feedback adjustment factor corresponding to a value of the gain adjustment factor to create an adjusted feedback signal;
- and
- add the adjusted feedback signal to the intermediate sample signal to create an analog output signal;
- wherein a gain stage coupled to an output of the DAC is configured to amplify a signal corresponding to the analog output voltage according an inverse of the new gain.
15 more elements
An apparatus comprising:
- a Dynamic Range Boost (DRB) circuit comprising:
- at least one input configured to receive a digital signal responsive to a digital filter and originating from a Pulse Density Modulated digital signal;
- a calculator circuit configured to:
- calculate a calculated amplified digital signal by digitally amplifying the digital signal by a previous gain, the previous gain having been applied to a previous digital signal;
- and
- calculate an approximation of an output level of a Digital Analog Converter (DAC) by modeling the effect of the DAC on the calculated amplified digital signal and a previous calculated approximation of the output level using at least one modeled characteristic of the DAC;
- a logic circuit configured to:
- determine a highest gain adjustment factor that, when applied to the approximation of the output level of the DAC, does not exceed a saturation level of the DAC, wherein the gain adjustment factor is a multiplier selected from the group consisting of 2, 1, and 0.5;
- and
- adjust the previous gain by the gain adjustment factor to create a new gain;
- a digital amplification circuit configured to digitally amplify the digital signal according to the new gain to create an amplified digital signal;
- the DAC operatively coupled to the DRB circuit, wherein the DAC comprises a switched capacitor DAC using a charge-transfer technique, the DAC configured to:
- a switching circuit configured to calculate an intermediate sample signal responsive to the amplified digital signal;
- an amplification circuit comprising at least a first feedback capacitive component and a second feedback capacitive component, the amplification circuit configured to:
- multiply a feedback signal of the DAC by a value of the gain adjustment factor to create an adjusted feedback signal;
- and
- add the adjusted feedback signal to the intermediate sample signal to create an analog output signal;
- wherein a gain stage coupled to an output of the DAC is configured to amplify a signal corresponding to the analog output voltage according an inverse of the new gain.
15 more elements
Dependencies are inferred from the claim text.