Bandgap Reference Voltage Trimming via Power Level Adjustment
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Solution Overview
Problem
Conventional bandgap circuit trimming techniques are time-consuming and costly, limiting the temperature range of constant output voltage and requiring prolonged heating processes, which restricts the manufacturing efficiency of integrated circuits.
Innovation Solution
The bandgap circuit is trimmed using a power trimming method that involves heating the circuit and adjusting operational parameters, specifically by increasing input power and adjusting the PTAT and CTAT source contributions to maintain a constant output voltage, utilizing an adjustable gain linear impedance device to achieve a wider temperature-invariant range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If temperature trimming is used to provide precise reference voltage, then manufacturing precision is improved, but productivity deteriorates due to prolonged heating and trimming time
Solution Approach 1:
The patent changes the trimming parameter from temperature to input power level. Instead of heating the bandgap circuit to different temperatures for trimming, the method applies different input power levels to the proportional-to-absolute-temperature (PTAT) and complementary-to-absolute-temperature (CTAT) current sources. This allows trimming to be performed at a single temperature, dramatically reducing trimming time while maintaining precision through power-level adjustments to the current sources.
2Manufacturing precision
If temperature trimming is performed at multiple temperatures, then manufacturing precision is improved, but the temperature range of constant output voltage deteriorates
Solution Approach 1:
The patent employs dynamic adjustment of the input power levels to the PTAT and CTAT current sources based on the desired output reference voltage. By dynamically changing the power distribution to these temperature-dependent current sources, the system can maintain a constant output voltage across a wider temperature range. The adjustable gain linear impedance device further enables dynamic compensation to extend the temperature-invariance range beyond what fixed temperature trimming achieves.
3Manufacturing precision
If conventional trimming is performed during IC manufacture, then manufacturing precision is improved, but loss of time increases due to sequential processing
Solution Approach 1:
The patent performs preliminary characterization of the PTAT and CTAT current sources during manufacturing, storing their individual temperature coefficients and gain parameters in memory. This preliminary action allows the trimmed bandgap circuit to be later adjusted through simple power level changes rather than requiring time-consuming heating and iterative trimming during final assembly or testing. The preliminary characterization enables faster final trimming operations.
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 approach significantly reduces trimming time and enhances the temperature-invariance range of the bandgap reference voltage, allowing for more efficient manufacturing and predictable performance across a broader temperature range without the need for further trimming.
Implementation Method 1
a proportional-to-absolute-temperature (PTAT) current source... a complementary-to-absolute-temperature (CTAT) current source
Implementation Method 2
a proportional-to-absolute-temperature (PTAT) current source... a complementary-to-absolute-temperature (CTAT) current source
Implementation Method 3
heating the circuit, supplying increasing input power to the circuit... When the bandgap output voltage may remain constant, a constant input power may be applied
Data Source
AI summary
Techniques to perform bandgap circuit trimming that maximize the operating range and minimize the trimming time at which the bandgap will be accurate. A bandgap circuit output voltage may be trimmed by heating the circuit, supplying increasing input power to the bandgap circuit, and adjusting operational parameters of the bandgap circuit to generate a constant bandgap circuit output voltage. When the bandgap circuit output voltage may remain constant, a constant input power may be applied to the bandgap circuit and its output voltage may be adjusted to a predetermined voltage level.