ΔΣ AD Converter Offset Adjustment Without Multiplier Circuits
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Solution Overview
Problem
Conventional temperature sensor devices face challenges with increased circuit size and cost due to the need for larger multiplier circuits to achieve higher accuracy, especially when increasing the number of digits in multiplication coefficients.
Innovation Solution
A ΔΣ AD converter is designed with an accumulator, counter, adjustment value storage, and a control circuit that adjusts count and offset values based on temperature ranges, eliminating the need for a multiplier circuit and reducing circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multiplier circuit is used to adjust raw digital data with gain/offset for higher accuracy, then conversion accuracy is improved, but circuit size increases
Solution Approach 1:
The patent segments the gain adjustment function into multiple temperature range-specific adjustment values stored in a lookup table. Instead of using a single multiplier circuit to handle all gain adjustments, the system divides the temperature range into multiple segments and applies pre-calculated adjustment values for each segment, thereby eliminating the need for a large-scale multiplier circuit while maintaining accuracy.
Solution Approach 2:
The patent pre-calculates and stores gain adjustment values for different temperature ranges in an adjustment value storage unit before operation. By performing the multiplication operation in advance and storing the results, the system avoids the need for real-time multiplication during conversion, thus eliminating the requirement for a large multiplier circuit while preserving conversion accuracy.
2Measurement precision
If the number of digits of the multiplication coefficient is increased for higher accuracy, then conversion accuracy is improved, but the scale of the multiplier circuit increases
Solution Approach 1:
The patent segments the high-precision gain adjustment into multiple smaller adjustment values corresponding to different temperature ranges. Each adjustment value requires fewer digits than a single high-precision coefficient would, thereby reducing the complexity of any multiplication operation needed while maintaining overall conversion accuracy through the combination of multiple segmented adjustments.
Solution Approach 2:
The patent pre-calculates adjustment values with the required precision and stores them in the adjustment value storage unit. This preliminary action transfers the computational complexity from the operational multiplier circuit to the offline calculation phase, allowing the actual conversion process to use simpler, smaller-scale multiplication or even direct lookup operations.
Data Source
AI summary
The present invention provides a ΔΣ AD converter and a sensor device having a small circuit scale and high conversion accuracy. A ΔΣ AD converter includes a ΔΣ AD modulator, an accumulator, a counter, an adjustment value storage part, a first adder, a cumulative value latch part, and a control circuit. The control circuit outputs to the adjustment value storage part a signal designating a temperature range according to the adjustment cumulative value received from the first adder in a case where the count value received from the counter reaches a predetermined value. The adjustment value storage part outputs the adjustment value of the offset value and the adjustment value of the count value according to the signal to the first adder and the counter. The control circuit outputs the latch signal to the cumulative value latch part in response to completion of counting by the counter.