Adjustable Power-On-Reset Circuit for Precise Trigger Voltage
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Solution Overview
Problem
Conventional Power-on-Reset (POR) circuits have a wide variance in trigger voltage levels due to temperature and process variations, making them less precise and inflexible, and unable to set the trigger voltage to arbitrary values during operation.
Innovation Solution
A POR circuit using a Vbe-cell or Vgs-cell with bipolar transistors, where a control voltage derived from the supply voltage level controls the currents in two current paths, allowing for a precise and adjustable trigger voltage level through a voltage divider configuration, and incorporating hysteresis for stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional POR circuit with simple transistor and resistor configuration is used, then the circuit complexity is low, but the trigger voltage level has wide variance due to temperature and process variations
Solution Approach 1:
The patent introduces a voltage divider configuration with adjustable resistors that allows the trigger voltage level to be precisely controlled and adjusted. By changing the resistance values in the voltage divider, the trigger voltage can be set to specific values, compensating for variations caused by temperature and process differences, thus improving measurement precision without excessive complexity increase
Solution Approach 2:
The patent employs an intermediate voltage comparison stage that compares the divided supply voltage with a reference voltage. This intermediary comparison mechanism provides a more stable and precise trigger point by isolating the critical decision point from direct variations in the supply voltage, thereby improving trigger voltage precision
2Adaptability or versatility
If a conventional POR circuit with fixed trigger voltage is used, then the circuit structure is simple, but the trigger voltage level cannot be adjusted during operation
Solution Approach 1:
The patent transforms the static, fixed trigger voltage of conventional circuits into a dynamic, adjustable parameter. By incorporating a voltage divider with adjustable resistors, the trigger voltage can be modified during operation to adapt to different application requirements, enhancing versatility while maintaining reasonable circuit complexity
Solution Approach 2:
The voltage divider configuration serves multiple functions: it sets the trigger voltage level, provides adjustability for different applications, and stabilizes the trigger point against variations. This multi-functional element increases adaptability without proportionally increasing overall circuit complexity
3Speed
If the trigger voltage level is set to be sensitive to voltage changes, then the reset response is fast, but the circuit becomes more sensitive to noise and voltage fluctuations
Solution Approach 1:
The patent implements a feedback mechanism where the voltage divider continuously monitors the supply voltage and provides a stabilized reference for comparison. This feedback loop filters out high-frequency noise and minor voltage fluctuations while still responding to significant voltage drops, achieving both fast response and high reliability
Solution Approach 2:
The voltage divider configuration provides a cushioning effect by distributing the voltage monitoring function across multiple resistive elements. This structure inherently filters out small perturbations and noise before they can trigger a false reset, while still maintaining sensitivity to genuine voltage failures
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 provides a stable and precise POR output signal with a narrow trigger voltage range, adaptable during operation, and improved flexibility for various applications, reducing the impact of temperature and process variations.
Implementation Method 1
the negative temperature coefficients of a bipolar transistor with respect to time or gate-source voltage (Vgs) of MOSFETS is compensated by a component (e.g., a resistor) having a positive temperature coefficient
Implementation Method 2
a control voltage level is derived from the current or instantaneous supply voltage level of the circuitry
Data Source
AI summary
An electronic device comprising circuitry for providing a Power-on-Reset (POR) signal as a function of a supply voltage level of the circuitry. The circuitry comprises a Vbe-cell or a Vgs-cell comprising a first current path including a first transistor and a second current path including a second transistor. Each transistor has a control terminal for controlling a first current in the first current path and a second current in the second current path, wherein a control voltage level is commonly applied to the control terminals of the first and the second transistor. The control voltage level is derived from the current supply voltage level of the circuitry, and the circuitry further comprises a POR output node for providing a POR output signal, which changes from a first state to a second state in response to the ratio of the magnitudes of the first current and the second current.