Self-Starting Bandgap Circuit for Fast, Trim-Free Reference Voltage
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Solution Overview
Problem
Existing bandgap circuits in integrated circuits (ICs) often start slowly and require post-startup trimming, making them unsuitable for applications like FPGA devices where quick and accurate reference voltage generation is necessary.
Innovation Solution
A self-starting bandgap circuit with features such as chopping techniques, dynamic element matching, and an adaptive voltage regulator to reduce device mismatch and ensure fast activation upon power-up, providing a low pre-trim variation reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional bandgap circuits are used, then the circuit structure is simple, but the startup speed is slow and trimming is required
Solution Approach 1:
The patent applies preliminary action by implementing a startup circuit that pre-charges the bandgap core circuit before normal operation. The startup circuit includes a startup transistor that is activated during power-up to provide initial current to the bandgap core, enabling faster startup without requiring post-startup trimming. This preliminary charging action resolves the contradiction by preparing the circuit in advance for rapid operation.
Solution Approach 2:
The patent applies dynamics by making the circuit configuration changeable during startup. The startup transistor is dynamically controlled to be active only during the startup phase, providing high current for fast charging, and then automatically turning off once the bandgap reference voltage is established. This dynamic behavior allows the circuit to achieve fast startup speeds while maintaining simplicity during normal operation.
2Speed
If fast startup is achieved, then the reference voltage is available quickly, but device mismatch increases
Solution Approach 1:
The patent applies self-service by implementing an adaptive voltage regulator that automatically adjusts the startup current based on the actual circuit conditions. The regulator monitors the bandgap reference voltage and self-adjusts the charging current to optimize both startup speed and matching accuracy. This self-regulating mechanism resolves the contradiction by eliminating the need for external trimming while achieving fast startup.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the startup current magnitude based on process, voltage, and temperature conditions. The adaptive voltage regulator modifies the current parameter in real-time during startup to compensate for device mismatch variations, enabling fast startup across different manufacturing conditions without requiring post-fabrication trimming.
3Measurement precision
If trimming is performed to improve accuracy, then reference voltage precision increases, but additional time and complexity are required
Solution Approach 1:
The patent applies self-service through the adaptive voltage regulator that automatically compensates for device mismatch and process variations during startup. The regulator self-adjusts circuit parameters to achieve accurate reference voltage without requiring external trimming operations, eliminating the time loss and additional complexity associated with manual or automated trimming processes.
Solution Approach 2:
The patent applies preliminary action by pre-compensating for device mismatch during the startup phase through the adaptive voltage regulator. The regulator performs preliminary adjustments to the startup current and voltage levels before the bandgap reference is fully operational, ensuring high accuracy is achieved from the start without requiring subsequent trimming operations.
Data Source
AI summary
In some examples, a self-starting bandgap circuit is provided. It may include one or more chopping circuits to reduce pre-trim inaccuracies. It may also, or alternatively, include an adaptive bandgap supply regulator and/or a start-up comparator to speed up the bandgap circuit's ability to come up with an adequate bandgap reference voltage.