PTAT Temperature Sensor Curvature Compensation Circuit
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Solution Overview
Problem
Conventional temperature sensors using PTAT generators face non-linearity issues due to the non-linear temperature dependency of diode junction voltages, leading to inaccuracies in digital temperature output.
Innovation Solution
A temperature sensor system that includes a PTAT current generator with first and second curvature compensation circuits, where the first compensating current corrects internal node non-linearity and the second compensating current cancels out residual non-linearity, ensuring a linear temperature-dependent output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a PTAT generator is used to produce temperature-dependent output, then temperature measurement capability is achieved, but non-linearity in the output signal occurs due to diode junction voltage characteristics
Solution Approach 1:
The patent changes the electrical parameters (currents and voltages) within the PTAT generator circuit to compensate for non-linearities. Specifically, it adjusts the relationship between reference current, PTAT current, and compensation currents to counteract the non-linear temperature dependency of diode junction voltages, thereby improving measurement accuracy while maintaining signal linearity
Solution Approach 2:
The patent implements a feedback mechanism where a portion of the output signal is fed back to the input through compensation circuits. The compensation current, derived from a fraction of the reference current and combined with the PTAT current, creates a feedback loop that actively corrects non-linearities in real-time, ensuring both accurate temperature measurement and stable linear output
2Measurement precision
If diode junction voltage is used for temperature sensing, then temperature dependency is obtained, but non-linear temperature dependency introduces errors in digital output
Solution Approach 1:
The patent modifies the electrical parameters of the diode junction by controlling the current density ratios between different diodes. By carefully selecting and adjusting the current values (IPDAT, IREF, ICOP) flowing through the diodes, the system exploits the non-linear exponential relationship between diode voltage and current to generate a compensated output that is linear with temperature, thus preventing information loss
Solution Approach 2:
The patent introduces an intermediary compensation current (ICOP) that acts as a mediator between the non-linear diode junction voltages and the final temperature output. This compensation current, generated through specific current mirrors and summing circuits, intermediate-corrects the non-linearities before the final measurement is taken, preserving measurement linearity and preventing digital output errors
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
The system provides accurate, linear temperature measurements by effectively compensating for non-linearities, enhancing measurement accuracy and reducing errors in digital output.
Implementation Method 1
a voltage difference between two diodes having two current densities may also be used to measure temperature. A circuit that uses such a voltage difference is commonly referred to as a proportional to absolute temperature (PTAT) generator
Implementation Method 2
the first compensating current has a first non-linearity with respect to temperature, a portion of the first non-linearity is present in the first temperature dependent current, the second compensating current includes a second non-linearity with respect to temperature, such that the second non-linearity in the second compensating current substantially cancels out the first non-linearity
Data Source
AI summary
In accordance with an embodiment, a temperature sensor includes a proportional to absolute temperature (PTAT) current generator having a first current output configured to provide a first temperature dependent current, a first curvature compensation circuit configured to provide a first compensating current to an internal node of the PTAT current generator, and a second curvature compensation circuit configured to add a second compensating current to the first current output. The first compensating current has a first non-linearity with respect to temperature, a portion of the first non-linearity is present in the first temperature dependent current, the second compensating current includes a second non-linearity with respect to temperature, such that the second non-linearity in the second compensating current substantially cancels out the first non-linearity in the first temperature dependent current.