Voltage Reference Circuit Using PTAT-CTAT Temperature Compensation
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Solution Overview
Problem
The miniaturization of integrated circuits has led to stricter design and manufacturing specifications, as well as reliability challenges due to increased temperature-dependency of voltage references in power supply circuits.
Innovation Solution
A voltage reference circuit utilizing temperature-sensitive devices with opposite temperature coefficients, such as PTAT (Proportional to Absolute Temperature) and CTAT (Complementary to Absolute Temperature) devices, is implemented to generate a reference voltage that reduces temperature-dependency by combining their voltage outputs, which is then applied to a low-dropout regulator to control a power regulating transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If miniaturization of integrated circuits is pursued, then device size and power consumption are reduced, but temperature-dependency of voltage references increases
Solution Approach 1:
The patent combines a PTAT voltage generator and a CTAT voltage generator into a single voltage reference circuit. The PTAT circuit generates a voltage that increases with temperature, while the CTAT circuit generates a voltage that decreases with temperature. By summing these two voltages with properly selected weighting factors, the temperature-dependent terms cancel out, producing a reference voltage with reduced temperature-dependency. This merging of opposite temperature coefficient circuits resolves the contradiction between miniaturization and temperature stability.
Solution Approach 2:
The patent changes the temperature coefficient parameter of the voltage reference by combining two voltage sources with opposite temperature coefficients. By adjusting the weighting factors applied to the PTAT and CTAT voltages, the overall temperature coefficient of the reference voltage can be tuned. This parameter transformation allows the circuit to maintain stability despite the increased temperature-dependency caused by miniaturization effects.
2Reliability
If temperature-sensitive devices with opposite temperature coefficients are combined, then temperature-dependency of reference voltage is reduced, but device complexity increases
Solution Approach 1:
The patent implements a multi-functional voltage reference circuit that simultaneously generates a stable reference voltage, compensates for temperature variations, and provides bias currents for other circuit blocks. The same PTAT and CTAT voltage generation blocks serve multiple purposes: they create the temperature-compensated reference voltage while also providing bias currents for differential pairs and other temperature-sensitive circuit elements. This multi-functionality reduces the overall complexity despite the added temperature compensation mechanism.
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
This approach effectively reduces the temperature-dependency of the generated supply voltage, allowing for stable operation within a desired voltage range despite lower reference voltages, enhancing the reliability and efficiency of power supply circuits.
Implementation Method 1
a first temperature-sensitive device to generate a first voltage that monotonically increases with an absolute temperature
Implementation Method 2
a second temperature-sensitive device to generate a second voltage that monotonically decreases with the absolute temperature
Data Source
AI summary
An integrated circuit includes a first temperature-sensitive device configured to generate a first voltage, a second temperature-sensitive device configured to generate a second voltage, and an output terminal configured to generate a reference voltage which is a summation of the first voltage and the second voltage. The first voltage monotonically increases with an absolute temperature. The second voltage monotonically decreases with the absolute temperature. In the integrated circuit, a low-dropout regulator has a first input connected to the output terminal and an output connected to the gate of a power regulating transistor. The channel of the power regulating transistor is connected between a first terminal configured to receive a first supply voltage and a second terminal configured to generate a second supply voltage.