Bandgap Reference Trimming with Parallel Bipolar Diodes
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Solution Overview
Problem
Existing analog circuit designs face challenges in achieving precise voltages and resistor values due to variations in process, temperature, and power supply, leading to inaccurate bandgap reference voltages and resistor drift, which can result in substantial errors in integrated circuit operation.
Innovation Solution
An integrated circuit with a bandgap generation circuit that includes a current source, resistors, and bipolar diode devices, where the number of bipolar diode devices in parallel can be controlled to trim the bandgap reference voltage, using MOSFETs and a control unit with non-volatile memory to adjust the resistor values and maintain stability across temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser trimming is used to achieve precise resistor values, then manufacturing precision is improved, but reliability deteriorates due to drift after trimming and accelerated by thermocycling
Solution Approach 1:
The trimming function is segmented into multiple discrete bipolar diode elements that can be individually activated or deactivated. Instead of continuously trimming a single resistor, the circuit uses multiple parallel diode paths (e.g., 8 diodes providing 3 bits of trimming resolution), where each diode represents a discrete trimming step. This segmentation allows precise control of the trimming current while avoiding the drift issues of laser-trimmed resistors.
2Manufacturing precision
If multiple fusible link elements are used for trimming element values, then manufacturing precision is improved, but device complexity increases and area consumption rises
Solution Approach 1:
The trimming functionality is merged with the existing bandgap reference circuit structure. The bipolar diode elements are integrated into the differential amplifier and current mirror circuits that already exist in the bandgap reference, rather than being separate trimming components. This merging allows the trimming function to be achieved using the inherent circuit topology, reducing overall device complexity and area consumption.
Solution Approach 2:
The bipolar diode elements serve multiple functions: they provide the trimming function, maintain the bandgap reference voltage, and can be controlled through existing circuit nodes. The same diode structures that form part of the bandgap reference circuit are also used for trimming purposes, making the circuit elements multi-functional and reducing the need for additional dedicated trimming components.
3Stability of the object's composition
If traditional bandgap reference circuits are used, then stability is improved, but manufacturing precision deteriorates due to process and temperature variations
Solution Approach 1:
The circuit employs feedback mechanisms where the bandgap reference voltage is used to control current sources that in turn regulate the operation of the differential amplifier and bipolar diode elements. This feedback loop compensates for process and temperature variations by automatically adjusting the operating points of the circuit components, thereby maintaining both stability and precision simultaneously.
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 allows for precise trimming of bandgap reference voltages, reducing errors and maintaining stability over temperature variations, while minimizing area consumption and external pin requirements, and providing a large trim range with low curvature variations and low power consumption.
Implementation Method 1
a first bipolar diode device, at least two further bipolar diode devices, each bipolar diode device coupled in parallel with the first bipolar diode device
Data Source
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AI summary
An integrated circuit has an untrimmed bandgap generation circuit; and a bandgap generation circuit coupled to the untrimmed bandgap generation circuit. The bandgap generation circuit has a current source controlled by the untrimmed bandgap generation circuit and coupled in series with a resistor and a first bipolar diode device, one or more of bipolar diode devices, each bipolar diode device coupled in parallel with the first bipolar diode device, wherein a trimmed bandgap reference voltage output of the integrated circuit is a function of the number of bipolar diode devices.