Reference Voltage Generator Temperature Compensation
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Solution Overview
Problem
Existing reference voltage generators struggle to suppress fluctuations in reference voltage across a wide operating temperature range due to nonlinear characteristics of circuit elements, particularly at high temperatures, which affects IC performance.
Innovation Solution
A reference voltage generator is designed with a first and second constant current circuit, and a voltage generation circuit that adjusts temperature coefficients to minimize fluctuations by switching between these circuits based on temperature ranges, using depletion and enhancement type NMOS transistors and current adjusting diodes to maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dummy diffusion layer is provided to suppress PN-junction leak current influence, then the reference voltage stability at high temperature is improved, but the nonlinear characteristic of circuit elements cannot be reduced, resulting in reference voltage fluctuation
Solution Approach 1:
The patent divides the temperature compensation function into two separate circuits: a first constant current circuit for temperatures below LCET and a second constant current circuit for temperatures at or above LCET. This segmentation allows each circuit to be optimized for its specific temperature range, addressing both the leak current suppression and nonlinear characteristic reduction without requiring a single complex circuit to handle all conditions.
Solution Approach 2:
The patent changes the dominant current source parameter based on temperature. Below LCET, the first constant current circuit dominates to suppress nonlinear characteristics. At or above LCET, the second constant current circuit dominates to suppress PN-junction leak current. This dynamic parameter change resolves the contradiction by adapting the circuit behavior to temperature conditions.
2Adaptability or versatility
If the operating temperature range is expanded, then the IC applicability is improved, but the reference voltage fluctuation increases due to PN-junction leak current and nonlinear characteristics
Solution Approach 1:
The patent implements dynamic switching between two constant current circuits based on temperature conditions. The first constant current circuit operates below LCET to minimize nonlinear effects, while the second constant current circuit operates at or above LCET to counteract PN-junction leak current. This dynamic adaptation enables the reference voltage generator to maintain stability across an expanded temperature range from -40°C to 180°C.
3Device complexity
If a single constant current circuit is used, then the device complexity is reduced, but the reference voltage cannot be stabilized across the entire temperature range
Solution Approach 1:
The patent segments the temperature range into two distinct regions separated by LCET, with each region served by a dedicated constant current circuit. This segmentation strategy justifies the increased device complexity by achieving comprehensive temperature range coverage with optimized performance in each segment, rather than using a single circuit that would compromise stability.
Solution Approach 2:
The patent employs parameter changes by switching between two different constant current circuits with different characteristics. The first circuit is optimized for low-temperature operation (below LCET) to minimize nonlinear effects, while the second circuit is optimized for high-temperature operation (at or above LCET) to suppress leak current. This parameter switching enables stable reference voltage generation across the entire temperature range.
Data Source
AI summary
A reference voltage generator is constructed to be equipped with a first constant current circuit which outputs a first constant current with respect to an input voltage, a second constant current circuit which outputs a second constant current, and a voltage generation circuit which generates a voltage based on an input current, and to take a current based on the first constant current and the second constant current as an input current of the voltage generation circuit and output a reference voltage from the voltage generation circuit.