Bandgap Reference Voltage Circuit for Package Pressure Shift Cancellation
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Solution Overview
Problem
Conventional bandgap reference voltage circuits are sensitive to package pressure during fabrication, leading to shifts in the fixed voltage produced, which can increase production costs and require costly packaging solutions or post-fabrication testing.
Innovation Solution
A reference voltage circuit that uses two bipolar junction transistors and a network of resistors and switches to generate a reference voltage by summing the voltage across one base-emitter pair with a difference voltage multiplied by a factor K, continuously toggling to cancel out voltage shifts induced by package pressure and operational amplifier offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bandgap reference voltage circuits are used, then the circuit produces a fixed voltage, but the fixed voltage shifts due to package pressure during fabrication
Solution Approach 1:
The circuit uses periodic switching between two base-emitter pairs (Q1/Q2 and Q3/Q4) through control signals that alternate between different configurations. This periodic action allows the circuit to average out the effects of package pressure over time, canceling voltage shifts while maintaining a stable reference output.
Solution Approach 2:
The invention changes the operational parameters of the reference circuit by introducing time-varying control signals that switch between different transistor pairs and resistor configurations. This allows the circuit to dynamically adjust its operating state to compensate for fabrication-induced voltage shifts.
2Reliability
If ceramic packages or die coats are used to avoid pressure-induced voltage shifts, then voltage stability is improved, but production cost increases
Solution Approach 1:
The reference voltage circuit performs self-correction by using its own internal components (multiple transistor pairs and resistors) to detect and compensate for voltage shifts caused by package pressure. The circuit automatically adjusts its operation to cancel out the effects of pressure without requiring external intervention or special packaging materials.
Solution Approach 2:
The invention extracts the pressure-sensitive component (the voltage reference) from the packaging environment by making the circuit itself insensitive to pressure through its operational configuration. Instead of relying on the package to protect the die, the circuit architecture inherently rejects pressure-induced variations.
3Manufacturing precision
If post-fabrication testing is performed to ensure voltage accuracy, then manufacturing precision is improved, but production time and cost increase
Solution Approach 1:
The circuit performs self-testing and self-correction through its periodic switching operation. By comparing voltages from different transistor pairs during alternating time periods, the circuit automatically identifies and compensates for offset errors without requiring external test equipment or manual calibration procedures.
Solution Approach 2:
The circuit incorporates feedback mechanisms where the output voltage is continuously monitored and compared against reference values during switching cycles. This feedback allows the circuit to automatically adjust its operation to maintain accurate voltage output, eliminating the need for separate post-fabrication testing steps.
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 corrects for bandgap voltage shifts during fabrication, reduces production costs, and in some cases eliminates the need for post-fabrication testing, resulting in a more cost-effective and reliable reference voltage circuit.
Implementation Method 1
Conventional bandgap reference voltage circuits use a combination of a bipolar (or diode) base-emitter junction voltage (Vbe) and a proportional to absolute temperature (PTAT) voltage
Implementation Method 2
Conventional bandgap reference voltage circuits use a combination of a bipolar (or diode) base-emitter junction voltage (Vbe) and a proportional to absolute temperature (PTAT) voltage
Data Source
AI summary
A reference voltage circuit corrects for bandgap voltage shifts induced during fabrication. The reference voltage circuit generates a reference voltage using first and second base-emitter pairs. The reference voltage circuit sums the voltage across the first base-emitter pair with a difference voltage. During a first time period, the difference voltage is the voltage across the first base-emitter pair minus the voltage across the second base-emitter pair, and during a second time period, the difference voltage is the voltage across the second base-emitter pair minus the voltage across the first base-emitter pair.