Bandgap Reference Startup Verification Circuit
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Solution Overview
Problem
Bandgap reference (BGR) circuits may fail to properly start in applications with low power and slow supply voltage ramp rates, leading to undesirable operation in the off-state.
Innovation Solution
The implementation of a startup verification circuit comprising multiple sub-circuits, including current and voltage comparators, which provide independent verification outputs to a digital logic state machine to determine the startup status of the BGR circuit, ensuring it transitions correctly from the off-state to the on-state across various power supply ramp rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the BGR circuit is designed to operate with slow power supply ramp rates, then the circuit may fail to properly start and remain in the off-state, but adding startup verification sub-circuits increases device complexity and power consumption
Solution Approach 1:
The verification system is divided into multiple independent sub-circuits, each responsible for verifying a specific startup condition (voltage threshold, current flow, temperature stability). This segmentation allows each sub-circuit to be simple and focused, while collectively providing comprehensive verification without excessive overall complexity
Solution Approach 2:
A digital state machine acts as an intermediary that coordinates the multiple verification sub-circuits, processes their outputs, and controls the overall startup verification process. This intermediary manages the complexity by providing a centralized control logic that orchestrates the distributed verification functions
2Reliability
If multiple startup verification sub-circuits are enabled continuously, then comprehensive verification is achieved, but power consumption increases
Solution Approach 1:
The verification sub-circuits are enabled periodically or conditionally based on startup phase rather than continuously. The digital state machine controls the enabling/disabling of sub-circuits based on verification progress and power supply conditions, activating verification functions only when needed during the startup sequence
Solution Approach 2:
The verification system automatically disables itself after successful verification without requiring external control. Once all sub-circuits confirm proper startup, the digital state machine automatically disables the verification sub-circuits to conserve power, making the system self-managing
3Reliability
If the BGR circuit uses a startup circuit to force transition to on-state, then startup is assisted, but the startup circuit must be electrically disconnected after startup which adds control complexity
Solution Approach 1:
The digital state machine receives feedback from multiple verification sub-circuits about the BGR circuit status and uses this feedback to control the startup circuit connection/disconnection. The feedback mechanism ensures the startup circuit is disconnected only when verification confirms successful startup, providing intelligent control based on actual circuit state
Data Source
AI summary
A bandgap reference (BGR) startup verification circuit includes a current minor for receiving an output current from a bandgap reference (BGR) circuit and generating output currents therefrom. A first verification sub-circuit is coupled to receive a first output current to generate a detection voltage (Vdet) and includes a voltage comparator receiving Vdet and a voltage output of the BGR circuit (VBG) to provide a first verification output. A second verification sub-circuit including a voltage comparator is coupled to receive a second output current and a second reference current and provide a second verification output. A third verification sub-circuit includes a current comparator coupled to receive a third output current and a third reference current and provide a third verification output. A digital state machine has inputs receiving the first, second and third verification output, and circuitry for processing these outputs to determine whether the BGR circuit has properly started.