PTAT Voltage Circuit Without Dynamic Element Matching
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Solution Overview
Problem
Existing temperature measurement methods using proportional to absolute temperature (PTAT) voltage in integrated circuits (ICs) face accuracy limitations due to mismatch errors in current sources and transistors, particularly when using metal oxide semiconductor (MOS) current sources, and are prone to switch IR drop mismatch.
Innovation Solution
An integrated circuit design that measures base-emitter voltage (VBE) at different current densities without dynamic element matching, using a single current source and coupling resistors to the emitters of bipolar junction transistors, to obtain a more accurate ΔVBE for temperature calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dynamic element matching methods are used to achieve accurate PTAT voltage determination, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the complex dynamic element matching circuitry from the temperature sensing system. By using a static circuit configuration with simple switches that connect current sources to transistor emitters without requiring dynamic matching, the invention achieves accurate PTAT voltage determination while removing the source of circuit complexity
Solution Approach 2:
The patent segments the temperature sensing function into distinct operational phases (first temperature determination, second temperature determination) that can be performed sequentially using simple switch connections rather than requiring complex simultaneous dynamic matching circuits
2Measurement precision
If dynamic element matching methods are used to reduce current source mismatch errors, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs preliminary temperature determination using a first current source and stores this information. This preliminary action allows the system to have an initial accurate temperature reading without requiring time-consuming dynamic matching operations, and this stored information can be used to inform subsequent measurements
3Measurement precision
If multiple current sources are used with dynamic element matching to reduce mismatch errors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the functionality of multiple current sources into a single current source that is sequentially connected to different transistor emitters through switches. This combining approach eliminates the need for multiple parallel current sources and their associated dynamic matching circuitry, reducing component quantity while maintaining measurement precision through sequential measurement of different transistor pairs
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Achieves accurate PTAT voltage determination quickly and with a smaller footprint by reducing current source mismatch and switch IR drop errors, providing similar accuracy to dynamic element matching methods but with fewer components and steps.
Implementation Method 1
separately measuring a base-emitter voltage (VBE) of the first one of the plurality of transistors when all of the plurality of switches are closed and a VBE of the first one of the plurality of transistors when only the switch associated with the first one of the plurality of transistors is closed
Implementation Method 2
The measurement circuitry is further configured to determine a ΔVBE by calculating a difference between the VBE when only the switch associated with the first one of the plurality of transistors is closed and the VBE when all of the plurality of switches are closed
Data Source
AI summary
An integrated circuit comprises a current source, a plurality of transistors arranged in parallel, a plurality of resistors, a plurality of switches, switch control circuitry, and measurement circuitry. Each resistor is coupled with the emitter of a respective transistor. Each switch selectively couples the current source to a respective resistor such that a bias current flows from the current source to the emitter of a respective transistor when a respective switch is closed. The measurement circuitry is coupled to the first transistor between its emitter and a respective resistor. The measurement circuitry is configured to separately measure a base-emitter voltage (VBE1) of the first transistor when all of the switches are closed and a base-emitter voltage (VBE2) of the first transistor when only the switch associated with the first transistor is closed and to determine a ΔVBE by calculating a difference between VBE2 and VBE 1.