Thermally Stabilized Voltage Reference Circuit for 0.65V Operation
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Solution Overview
Problem
Traditional voltage reference circuits face challenges in achieving high precision and performance due to sensitivity to power supply noise, device noise, leakage currents, and circuit element mismatch, especially at supply voltages below 1.0V, and are difficult to implement with bipolar junction transistors in modern integrated circuits.
Innovation Solution
A voltage reference circuit utilizing a feedback loop with a heater device and thermally coupled circuit components to stabilize local temperature, generating voltages with different temperature coefficients, and using an adjustment circuit to achieve equilibrium at a target temperature, allowing operation at very low supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional bandgap reference circuits are used, then reference voltage can be generated, but they cannot operate at supply voltages below 0.9V due to insufficient voltage to bias bipolar junction transistors
Solution Approach 1:
The patent replaces the mechanical/electrical biasing requirement of traditional BJT bandgap circuits with a different physical approach - using a feedback-controlled heater device to thermally bias the circuit components. This substitution allows operation at supply voltages as low as 0.65V by eliminating the need for high-voltage biasing networks and enabling the use of MOSFETs instead of BJTs.
Solution Approach 2:
The patent fundamentally changes the biasing parameter from electrical voltage biasing to thermal biasing. By controlling the temperature of circuit components through a feedback-heated heater device, the reference voltage is generated through temperature-dependent characteristics rather than voltage-dependent biasing, enabling ultra-low voltage operation.
2Device complexity
If open-loop voltage reference circuits are used, then circuit complexity is reduced, but precision and performance deteriorate due to high sensitivity to power supply noise, device noise, leakage currents, and circuit element mismatch
Solution Approach 1:
The patent implements a feedback mechanism where the generated reference voltage is fed back to control a heater device, which in turn controls the temperature of the circuit components. This closed-loop feedback system automatically compensates for variations in power supply noise, device noise, leakage currents, and circuit element mismatch, achieving high precision reference voltage output while maintaining relatively simple circuit architecture.
3Reliability
If bipolar junction transistors are used in voltage reference circuits, then reference voltage generation is enabled, but manufacturing precision deteriorates due to increased manufacturing spread of device properties
Solution Approach 1:
The patent substitutes bipolar junction transistors with MOSFETs (metal-oxide-semiconductor field-effect transistors) in the voltage reference circuit. MOSFETs exhibit better manufacturing precision and reduced property spread compared to BJTs, while still enabling reference voltage generation through their temperature-dependent characteristics when properly biased through the thermal feedback mechanism.
4Use of energy by moving object
If supply voltage is reduced below 1.0V, then power consumption is reduced, but the ability to operate voltage reference circuits deteriorates
Solution Approach 1:
The patent changes the fundamental operating parameter from electrical voltage biasing to thermal biasing. By using a feedback-controlled heater to maintain optimal temperature conditions, the circuit can operate reliably at supply voltages as low as 0.65V, achieving ultra-low power consumption while maintaining reference voltage generation capability that would be impossible with traditional electrical biasing methods.
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 circuit provides a precise reference voltage with no curvature versus temperature, operating at supply voltages as low as 0.65V, while stabilizing local temperature to a certain value, thus enhancing precision and performance.
Implementation Method 1
a heater device, wherein the heater device is configured to generate heat in response to being controlled by the control signal
Implementation Method 2
the heater device is thermally coupled to the one or more circuit components
Implementation Method 3
the first voltage has a first temperature coefficient, and the second voltage has a second temperature coefficient that is different from the first temperature coefficient
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A voltage reference circuit (10) comprises one or more circuit components (D1, D2, Q1, Q2) configured to generate a first voltage (V1) and a second voltage (V2), wherein the first voltage has a first temperature coefficient, and the second voltage has a second temperature coefficient that is different from the first temperature coefficient. An adjustment circuit (12) is configured to generate an adjusted voltage (Vx) as product of the first voltage and an adjustment factor (x), wherein the adjusted voltage is designed to equal the second voltage in equilibrium at a target temperature (T0). A control device (14) is configured to provide a control signal (CV) based on a difference between the adjusted voltage and the second voltage. A heater device (16) is configured to generate heat (H) in response to being controlled by the control signal, wherein the heater device is thermally coupled to the one or more circuit components, thus forming a feedback loop for establishing the equilibrium at the target temperature. An output terminal (18) is configured to provide a reference voltage (Vref) as function of the first voltage or the second voltage.