Cyclic Diode Switching for RTN Reduction in Bandgap Circuits
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Solution Overview
Problem
Random telegraph noise (RTN) in bandgap circuits causes sudden and unpredictable voltage shifts, leading to inaccurate readings in sensor devices like pressure sensors, which are sensitive to RTN-induced base current increases in bipolar transistors.
Innovation Solution
A cyclic switching design is implemented in the bandgap circuit, where diodes are switched in response to a train of pulses, distributing the current across multiple diodes to reduce the impact of RTN, with switches connecting diodes to either rail of a voltage divider or resistor, thereby reducing the effect of RTN on the reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional bandgap circuit is used to generate reference voltage, then the circuit provides a stable reference voltage, but the circuit is sensitive to RTN causing sudden voltage shifts and measurement errors
Solution Approach 1:
The circuit segments the current path by introducing multiple parallel diodes (D1, D2, D3) instead of a single diode. Each diode can be independently switched on or off, allowing the circuit to distribute current across multiple segments. This segmentation reduces the impact of RTN in any single diode on the overall reference voltage stability and sensor measurement accuracy.
Solution Approach 2:
The circuit introduces dynamic switching control through control signals (SIG1, SIG2, SIG3) that dynamically activate or deactivate specific diodes based on operational requirements. This dynamic configuration allows the system to adaptively manage RTN effects by switching between different diode combinations, thereby maintaining both reference voltage stability and measurement precision under varying conditions.
2Reliability
If multiple diodes are introduced in parallel to reduce RTN impact, then the RTN effect is reduced, but the circuit complexity increases
Solution Approach 1:
The circuit merges multiple diodes into a single parallel configuration where all diodes share common connection points. This merging approach allows the circuit to achieve RTN reduction through diversity while maintaining a relatively compact structure. The control signals are also merged into a unified switching mechanism that manages all diodes through a coordinated system, preventing excessive complexity escalation.
3Reliability
If diodes are dynamically switched to reduce RTN impact, then voltage stability is improved, but the switching control complexity increases
Solution Approach 1:
The circuit employs periodic switching action where diodes are systematically activated and deactivated in a repeating sequence. This periodic approach to dynamic switching simplifies the control logic compared to fully adaptive switching, as the control signals follow a predictable pattern. The periodic nature of the switching allows for easier timing synchronization and reduces the complexity of the control mechanism while still achieving effective RTN mitigation through temporal diversity.
Data Source
AI summary
Aspects of the subject technology relate to a circuit for reducing random-telegraph noise in bandgap circuits. The circuit includes a number of diodes coupled in parallel at their respective first nodes to a ground potential. A number of switches are coupled to respective second nodes of the diodes. The circuit further includes a first resistor and a resistor voltage divider. The first node of the first resistor is coupled to a first node of a current source, and the first node of the resistor voltage divider is coupled to the first node of the current source. The switches are used to implement cyclic switching of the diodes in response to a train of pulses. An output voltage of the circuit is derived between a mid-node of the resistor voltage divider and a second node of the first resistor.