Buried Zener Voltage Reference with Digital Drift Correction
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Solution Overview
Problem
Existing battery monitoring systems face accuracy limitations due to reference temperature drift and susceptibility to package stress, particularly when using traditional BJT bandgap voltage references.
Innovation Solution
A battery monitoring system employing a buried Zener diode as a reference voltage source, combined with analog and digital circuitry, including a second or third order digital correction process to enhance temperature stability and resist package stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional BJT bandgap voltage reference is used, then the reference voltage can be generated, but temperature drift and package stress susceptibility occur reducing measurement accuracy
Solution Approach 1:
The patent changes the fundamental parameters of the voltage reference by transitioning from BJT bandgap architecture to buried Zener diode with PTAT current generation. This involves changing the operating principles, temperature coefficients, and electrical characteristics to achieve superior temperature stability and reduced package stress sensitivity while maintaining reference voltage generation capability
Solution Approach 2:
The patent creates a composite voltage reference system by combining the buried Zener diode (providing stable breakdown voltage) with PTAT current circuitry (providing positive temperature coefficient). This composite approach merges two different physical mechanisms to achieve temperature-independent reference voltage output
2Reliability
If traditional BJT bandgap voltage reference is used, then the reference voltage can be generated, but package stress susceptibility reduces reliability
Solution Approach 1:
The patent extracts the voltage reference function from the traditional BJT bandgap circuit architecture and implements it using a buried Zener diode-based structure. This extraction removes the problematic BJT components that are susceptible to package stress while preserving the essential voltage reference generation capability through the Zener breakdown mechanism combined with PTAT current
3Measurement precision
If digital correction is applied to compensate for temperature drift, then measurement accuracy improves, but system complexity increases
Solution Approach 1:
The patent performs preliminary temperature compensation by generating PTAT (proportional to absolute temperature) current that preemptively counteracts the negative temperature coefficient of the buried Zener diode. This preliminary action occurs within the analog circuitry itself, reducing the need for complex post-processing digital correction and achieving temperature stability before measurement
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 system achieves improved accuracy with reduced temperature drift and package stress sensitivity, maintaining ±0.8 millivolt accuracy on a 4V scale, equivalent to ±0.02% accuracy.
Implementation Method 1
A buried Zener diode may be used as a reference voltage source in a battery monitoring system because the reference voltage may not be as susceptible to package stress
Implementation Method 2
an analog-to-digital converter (ADC) configured to receive the battery voltage and compare the battery voltage to the reference voltage to produce a digitized result
Data Source
AI summary
In an example, a system includes a buried Zener diode having a first terminal coupled to a voltage terminal. The system also includes a first resistor having a first terminal coupled to a second terminal of the buried Zener diode. The system includes a second resistor having a first terminal coupled to a second terminal of the first resistor. The system also includes a first transistor having a control terminal coupled to the first terminal of the second resistor. The system includes a second transistor having a control terminal coupled to a second terminal of the second resistor and an emitter coupled to an emitter of the first transistor. The system also includes a resistor network coupled to the second terminal of the first resistor, where the resistor network is configured to produce a reference voltage.