MDAC Amplifier Correction Circuit for ADC Settling Error
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Solution Overview
Problem
Conventional MDAC amplifiers in pipelined ADCs suffer from settling errors that increase exponentially with the decrease in ADC clock period, leading to inaccuracies in output voltage.
Innovation Solution
Incorporating a correction amplifier with a negative settling gain and a correction capacitor with reduced capacitance, coupled between the MDAC amplifier's output and input, to attenuate the output signal and apply a settling gain, thereby compensating for the settling error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ADC clock period TS is decreased to increase ADC speed, then productivity increases, but the settling error increases exponentially
Solution Approach 1:
The patent implements a feedback mechanism where the output of the MDAC amplifier is fed back through a correction capacitor to the inverting input terminal. This feedback loop continuously monitors the output voltage and adjusts it to compensate for settling errors, thereby maintaining measurement precision even at high conversion speeds.
Solution Approach 2:
The patent modifies the circuit parameters by introducing a correction capacitor with specifically designed capacitance value and configuring the MDAC amplifier with particular gain settings. These parameter changes optimize the settling behavior of the amplifier, reducing the exponential error growth that occurs with decreased clock period while maintaining high ADC speed.
2Measurement precision
If a correction amplifier with settling gain is added to reduce settling error, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent designs the correction amplifier to serve multiple functions: it provides settling error correction, maintains signal integrity, and works in conjunction with the existing MDAC amplifier architecture. By making the correction amplifier multi-functional, the patent reduces measurement precision errors without proportionally increasing device complexity.
Solution Approach 2:
The correction capacitor acts as an intermediary element between the MDAC amplifier output and the inverting input terminal. It mediates the feedback signal to apply the appropriate settling gain, thereby improving measurement precision while avoiding the need for complex additional circuitry.
Data Source
AI summary
Multiplying digital-to-analog converters (MDACs), which are generally employed in pipelined analog-to-digital converters (ADCs), can have a settling error associated with the MDAC amplifier. Here, a circuit is provided that includes additional amplifiers and a capacitor network that compensates for this settling error. Thus, a more accurate pipelined ADC can now be produced.