Programmable Voltage Reference Circuit With Curvature Compensation
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Solution Overview
Problem
Existing voltage reference circuits in integrated circuits face challenges in generating flexible temperature coefficient voltages while compensating for second-order curvature introduced by bipolar junction transistors (BJTs), which degrades as CMOS technology scales.
Innovation Solution
A programmable temperature coefficient analog second-order curvature compensated voltage reference circuit is developed, utilizing a voltage reference circuit with p-channel field effect transistors, operational amplifiers, resistor ladders, and BJTs to generate zero, negative, and positive temperature coefficient voltages, along with a method to trim these voltages using control signals to maintain a constant temperature coefficient over a range of temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bipolar junction transistors (BJTs) are used in voltage reference circuits, then the circuits can generate voltage references, but second-order curvature errors are introduced that degrade performance as CMOS technology scales
Solution Approach 1:
The patent converts the harmful second-order curvature effect into a beneficial compensation mechanism by deliberately introducing matching curvature through programmable current sources. The harmful curvature from BJTs is transformed into useful curvature compensation that cancels the error, turning a degradation source into a performance enhancement tool.
Solution Approach 2:
The patent changes the temperature coefficient parameters of current sources to achieve curvature compensation. By programmatically adjusting the temperature coefficient of current sources and mixing different temperature coefficient currents (positive and negative), the circuit dynamically compensates for second-order curvature effects while maintaining voltage reference stability.
2Reliability
If fixed temperature coefficient voltage references are used, then specific circuits can be compensated, but flexibility to provide different temperature coefficients for different circuits is limited
Solution Approach 1:
The patent transforms fixed temperature coefficient voltage references into dynamic, programmable references. By using programmable current sources with adjustable temperature coefficients and digital control mechanisms, the circuit can dynamically adapt to provide different temperature coefficients (zero, positive, or negative) based on the specific requirements of different circuits within the IC.
Solution Approach 2:
The patent creates a universal voltage reference system that can serve multiple functions and different circuits simultaneously. The programmable architecture allows a single voltage reference circuit to provide customized temperature coefficients for various loads (ADCs, power management, switches), making the system multi-functional and highly adaptable to diverse application requirements.
3Adaptability or versatility
If multiple current sources with different temperature coefficients are mixed, then flexible temperature coefficient voltages can be generated, but circuit complexity increases
Solution Approach 1:
The patent merges multiple current sources with different temperature coefficients into a unified programmable current generation system. By combining positive temperature coefficient currents, negative temperature coefficient currents, and curvature compensation currents through programmable mixing, the circuit achieves flexible temperature coefficient control while consolidating functionality to manage complexity.
Solution Approach 2:
The patent uses parameter changes in current source temperature coefficients to achieve flexibility without proportionally increasing complexity. By programmatically adjusting current magnitude and temperature coefficient parameters rather than adding separate dedicated circuits for each function, the system achieves adaptability with controlled complexity growth.
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 solution effectively compensates for temperature-induced curvature errors, providing stable voltage references with adjustable temperature coefficients, enhancing the precision and flexibility of voltage references in integrated circuits.
Implementation Method 1
A first current source in the voltage reference circuit is configured to generate a proportional-to-temperature current in response to a first control voltage and a second current source is configured to generate a complementary-to-temperature current in response to a second control voltage
Implementation Method 2
The voltage reference circuit includes p-channel field effect transistors, operational amplifiers, resistor ladders, and BJTs to generate zero, negative, and positive temperature coefficient voltages
Data Source
Figure 1~2
Figure 3~4
Figure 5A
AI summary
An example voltage reference circuit includes: a reference circuit (202) comprising a first circuit (308) configured to generate a proportional-to-temperature current and corresponding first control voltage and a second circuit (316) configured to generate a complementary-to-temperature current and corresponding second control voltage; a first current source (5141) coupled to a first load circuit (512), the first current source generating a sum current of the proportional-to-temperature current and the complementary-to-temperature current in response to the first and second control voltages, the first load circuit generating a zero temperature coefficient (Tempco) voltage from the sum current; and a second current source (7151) coupled to a second load circuit (718, 720), the second current source generating the sum current of the proportional-to-temperature current and the complementary-to-temperature current in response to the first and second control voltages, the second load circuit generating a negative Tempco voltage from the sum current and the complementary-to-temperature current.