Bandgap Reference Start-Up Circuit for Zero Steady-State Current
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Solution Overview
Problem
Conventional start-up circuits for NAND flash devices fail to simultaneously achieve zero steady-state current, wide supply range operation, and dynamic behavior, which are crucial for efficient and reliable performance, especially in smartphones.
Innovation Solution
A capacitor action-based start-up circuit is introduced, featuring a start-up capacitor connected to a bandgap voltage node that determines the operational state of the BGR sub-block and an output transistor that charges the slowest node to maintain normal operation, ensuring dynamic behavior and zero steady-state current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional start-up circuits are used in NAND flash devices, then basic operation is achieved, but zero steady-state current, wide supply range operation, and dynamic behavior cannot be simultaneously achieved
Solution Approach 1:
The patent implements dynamic behavior through a start-up circuit that automatically activates only when the bandgap reference voltage is below a threshold level. The circuit uses a start-up transistor that turns on when VBG is low and turns off when VBG reaches the normal operating range, providing dynamic adaptation to supply voltage conditions and enabling wide supply range operation while maintaining reliability.
Solution Approach 2:
The patent changes the operating parameters of the start-up circuit based on the bandgap reference voltage level. The start-up transistor's conduction state changes dynamically with VBG voltage, allowing the circuit to adapt to different supply voltage conditions and achieve both wide supply range operation and reliable dynamic behavior simultaneously.
2Reliability
If start-up circuits continuously operate to maintain dynamic behavior, then reliability is improved, but steady-state current consumption increases
Solution Approach 1:
The start-up circuit operates periodically rather than continuously. The start-up transistor is activated only during the start-up phase when VBG is below the threshold and automatically turns off when VBG reaches the normal operating range. This periodic operation maintains the necessary dynamic behavior for reliability while eliminating continuous steady-state current consumption.
Solution Approach 2:
The patent extracts the start-up function from the main operational circuit by using a separate start-up transistor that is only active during initialization. This separation allows the main BGR circuit to operate with zero steady-state current while the start-up circuit provides dynamic behavior only when needed, resolving the contradiction between reliability and energy consumption.
3Adaptability or versatility
If voltage regulators are added to achieve wide supply range operation, then adaptability is improved, but device complexity increases
Solution Approach 1:
The start-up circuit is designed to be self-regulating and self-activating based on the VBG voltage level. The start-up transistor automatically turns on when VBG is below the threshold and turns off when VBG reaches the normal range, eliminating the need for external voltage regulators or complex control logic. This self-service mechanism achieves wide supply range operation while keeping the circuit simple.
Solution Approach 2:
The patent merges the start-up function with the existing bandgap reference circuit by using the VBG node itself as the control signal for the start-up transistor. This integration eliminates the need for separate voltage regulation circuits and reduces overall device complexity while still achieving wide supply range operation through the inherent voltage-dependent behavior of the combined circuit.
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 enables zero steady-state current, dynamic behavior, and wide supply range operation, effectively addressing the limitations of conventional start-up circuits by ensuring reliable performance and power efficiency in NAND flash devices.
Implementation Method 1
a start-up capacitor connected to a bandgap voltage (VBG) node of a BGR sub-circuit, the start-up capacitor configured to determine whether an operating state of the BGR sub-circuit is in a normal state or a failure state
Implementation Method 2
an output transistor connected to a desired node (e.g. a first node) of the BGR sub-circuit, the output transistor is configured to charge the slowest node to change the operating state of the BGR sub-circuit to the normal state
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
Various example embodiments relate to a capacitor action-based start-up circuit for bandgap reference (BGR) generation. The start-up circuit comprises a start-up capacitor (C_ST) connected to a VBG node of a BGR sub-circuit. The start-up capacitor (C_ST) determines if a state of operation of the BGR sub-block is one of normal, and failure. The start-up circuit comprises an output transistor (M0) connected to an NB node of the BGR. The output transistor (M0) charges the NB node to maintain normal operation of the BGR sub-block, if the state of operation of the BGR sub-block is failure, thereby facilitating dynamic behavior.