Digital-domain thermal sensor using voltage-to-frequency readout
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Solution Overview
Problem
Integrating analog thermal sensors into high-power-consuming integrated circuits (ICs) and systems on a chip (SoCs) is challenging due to noise sensitivity, interference, and space constraints in digitally-synthesized areas, making it difficult to monitor temperature effectively.
Innovation Solution
A digital-domain-based thermal sensor is developed, which operates using full digital signals, is powered by a low-voltage digital power supply, and employs a bandgap reference circuit and voltage-to-frequency readout circuit with switched capacitors to convert temperature into a digital value, seamlessly integrating within the digital domain and mitigating noise issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog thermal sensors are integrated into digitally-synthesized areas, then temperature monitoring capability is improved, but noise sensitivity and interference increase
Solution Approach 1:
The patent replaces the analog thermal sensor system with a digital-domain thermal sensor that uses digital signals throughout. The analog-to-digital conversion is eliminated, and temperature measurement is achieved through digital counting of clock cycles, thereby eliminating noise sensitivity and interference problems associated with analog signals in digitally-synthesized areas.
Solution Approach 2:
The patent changes the signal domain parameter from analog to digital. By using digital signals for both input and output, and operating the thermal sensor with a digital power supply, the system achieves immunity to noise and interference that plagues analog implementations in digital environments.
2Measurement precision
If analog thermal sensors are integrated into digitally-synthesized areas, then temperature monitoring capability is improved, but device complexity and integration difficulty increase
Solution Approach 1:
The digital-domain thermal sensor uses the same digital infrastructure (clock signals, power supply, logic circuits) that already exists in digitally-synthesized areas. This universal use of digital components eliminates the need for separate analog infrastructure, reducing device complexity and making integration straightforward.
Solution Approach 2:
The patent merges the thermal sensor functionality with the existing digital circuitry by using shared clock signals and power supplies. The thermal sensor is combined with digital logic elements (counters, multiplexers) rather than being a separate analog subsystem, thereby simplifying integration.
3Measurement precision
If analog thermal sensors are integrated into digitally-synthesized areas, then temperature monitoring capability is improved, but available space decreases
Solution Approach 1:
By changing from analog to digital implementation, the patent enables the thermal sensor to use standard digital CMOS transistors and logic gates, which occupy significantly less area than analog components such as operational amplifiers, precision resistors, and capacitors required by traditional analog thermal sensors.
Solution Approach 2:
The replacement of analog components with digital logic elements (counters, multiplexers, digital-to-analog converters) results in a compact implementation that fits within the densely packed digitally-synthesized areas without requiring additional space for analog infrastructure.
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 solution allows for seamless integration of thermal sensors within ICs and SoCs, enabling effective temperature monitoring without exacerbating hot spots and reducing design and integration challenges, as the digital-domain-based thermal sensor uses existing digital infrastructure and filters out noise, providing accurate temperature readings.
Implementation Method 1
a bandgap reference circuit configured to generate, from a digital chip supply voltage, a reference voltage and a proportional-to-absolute temperature voltage
Implementation Method 2
a voltage-to-frequency readout circuit, implemented as a closed loop, to receive the reference voltage and the proportional-to-absolute temperature voltage as inputs
Implementation Method 3
a voltage-controlled oscillator driven by a difference between a feedback voltage and the reference voltage
Data Source
AI summary
An integrated circuit includes a bandgap reference circuit configured to generate, from a digital chip supply voltage, a reference voltage and a proportional-to-absolute temperature (PTAT) voltage. A voltage-to-frequency (VTF) readout circuit to receive the reference voltage and the PTAT voltage as inputs. The VTF readout circuit includes sets of switched capacitors that operate as a voltage divider. The capacitors of the sets of switched capacitors are selectively charged by the PTAT voltage and generate a feedback voltage. A voltage-controlled oscillator (VCO) is driven by a difference between the feedback voltage and the reference voltage and generates a VCO clock. A clock generator generates a feedback clock based on the VCO clock. First switches of the sets of switched capacitors are controlled by the feedback clock.