ADC Digital Gain Compensation for External Input Filtering
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Solution Overview
Problem
External filtering in analog-to-digital converter (ADC) systems can corrupt the gain of the amplifier, leading to a reduced usable range, and existing solutions like using a buffer or measuring gain error are impractical in many applications.
Innovation Solution
A combined ADC circuit with programmable input and feedback resistors allows for digital gain compensation by applying a digital gain to the ADC output, accounting for external filter characteristics entered by the user, ensuring accurate signal scaling without external buffer requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external filtering is applied to the input signal, then signal protection and noise reduction are improved, but amplifier gain accuracy deteriorates
Solution Approach 1:
The system implements digital feedback by measuring the actual gain through calibration and applying compensation to the digital output. The ADC measures the amplified signal, the microcontroller calculates the compensation factor based on expected vs. actual gain, and applies this factor to correct the digital output, thereby compensating for the gain error introduced by external filtering.
Solution Approach 2:
The system changes the digital gain parameter dynamically based on the measured actual gain. By calculating a compensation factor from the ratio of expected gain to actual gain, the system adjusts the digital output parameter to compensate for the analog gain error, effectively maintaining accurate signal representation despite external filter effects.
2Measurement precision
If a buffer is used before the amplifier to prevent gain corruption, then amplifier gain accuracy is improved, but device complexity and power requirements increase
Solution Approach 1:
The system replaces the mechanical/analog solution (buffer circuit) with a digital solution. Instead of adding analog components to prevent gain corruption, the system allows the corruption to occur and then compensates for it digitally through calibration and software-based gain correction, thereby reducing analog circuit complexity while achieving the same goal.
Solution Approach 2:
The invention extracts the gain compensation function from the analog domain and moves it to the digital domain. By separating the amplification function (analog) from the gain accuracy function (digital), the system eliminates the need for complex analog buffer circuits while maintaining gain accuracy through digital processing.
3Measurement precision
If a buffer is used before the amplifier, then amplifier gain accuracy is improved, but power consumption increases
Solution Approach 1:
The system replaces the power-consuming analog buffer with a low-power digital compensation approach. The microcontroller performs calculations and applies digital gain adjustment, consuming significantly less power than an analog buffer would require, while achieving the same gain accuracy improvement.
4Reliability
If external filtering is applied to the input signal, then signal quality is improved, but ADC usable range is reduced
Solution Approach 1:
The system dynamically adjusts the digital gain parameter to compensate for the reduced usable range caused by external filtering. By calculating and applying a compensation factor to the digital output, the system restores the effective input range of the ADC, allowing it to accommodate the full range of input signals despite the presence of external filters.
Data Source
AI summary
Techniques are provided for compensating gain of a combined amplifier and analog-to-digital converter (ADC) circuit, for example, due to additional filtering added to an input of the circuit. In an example, an integrated circuit including an amplifier and ADC can include an amplifier circuit configured to receive an input signal and to amplify the input signal based on an input resistance and a feedback resistance, and to provide an amplified representation of the input signal, and an ADC circuit configured to receive an output of the amplifier, to determine a digital coefficient associated with an additional input resistance coupled to the amplifier, and to provide a compensated digital representation of the amplified representation of the input signal using the digital compensation coefficient.