Resistor-String DAC Shunting for Dual-Supply Accuracy
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Solution Overview
Problem
Resistive divider type digital-to-analog converters occupy significant space in integrated circuits, and their operation is affected by changes in high side operating voltages, leading to issues with resolution and accuracy.
Innovation Solution
A digital-to-analog converter design that uses a resistor string divided into two series-connected portions with selective tapping and shunting mechanisms to adapt to different voltage ranges, allowing operation with two different high side supply voltages while minimizing the number of resistors and transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a resistive divider circuit is used for digital-to-analog conversion, then the converter can be implemented with a simple circuit configuration, but the resistors and transistors occupy a significant amount of area
Solution Approach 1:
The resistor string is divided into two separate sets of series-connected resistors (first set and second set). Each set can be independently controlled through selective shunting, allowing the converter to achieve multiple voltage ranges without requiring a single large resistor string. This segmentation reduces the total area occupied while maintaining the resistive divider functionality.
Solution Approach 2:
The patent introduces selectively actuated shunts that can dynamically reconfigure the resistor network based on the digital signal input. By selectively connecting or disconnecting portions of the resistor string through shunts, the circuit can adapt its effective resistance values to match different voltage ranges, reducing the need for a fixed large-area resistor string designed for the maximum voltage range.
2Device complexity
If a single digital-to-analog converter is designed for a fixed voltage range, then the circuit can be simplified, but it cannot operate correctly when the high side operating voltage changes
Solution Approach 1:
The converter circuit is designed to handle multiple voltage ranges by incorporating two sets of resistors with different resistance values and selectively actuated shunts. The same basic circuit architecture can operate correctly whether the high side supply voltage is at a first level or a second level, making the converter universal across different voltage conditions without requiring separate converters for each voltage range.
Solution Approach 2:
The patent changes the effective resistance parameters of the divider circuit by selectively shunting portions of the resistor string. When the high side operating voltage changes, the control logic activates appropriate shunts to adjust the effective resistance values, thereby maintaining the correct voltage division ratio and conversion accuracy across different voltage ranges.
3Adaptability or versatility
If the high side operating voltage changes in a resistive divider based converter, then the converter can adapt to different operational modes, but the resolution and accuracy are adversely affected
Solution Approach 1:
When the high side operating voltage changes, the control circuit activates specific shunts to modify the effective resistance values in the divider network. This parameter change compensates for the voltage variation, maintaining the precise voltage division ratios needed for accurate digital-to-analog conversion. The selective shunting ensures that the resolution and accuracy are preserved across different voltage conditions.
Data Source
AI summary
A digital-to-analog converter, in response to a digital signal, selectively taps a resistor string to generate an analog output and selectively shunts around resistors in the string to voltage shift the analog output. If two supply voltage sets are present, two strings are provided. A mutually exclusively selection of outputs is made to select a source of the analog output. An integrated circuit temperature sensor uses the converter and includes a sensing circuit that determines exposure to one of a relatively low or high temperature. A measured voltage across the base-emitter of a bipolar transistor is selected in low temperature exposure and compared against a first reference for a too cold temperature condition. Alternatively, a measured delta voltage across the base-emitter is selected in high temperature exposure and compared against a second reference voltage for a too hot temperature condition. Through the comparisons, a temperature exposure detection is made.