POR Trip Voltage Circuit Without Local Resistor Divider
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Solution Overview
Problem
Conventional power-on reset (POR) circuits are large, consume high quiescent current, and are costly due to the reliance on bandgap reference (BGR) circuitry and resistor dividers, which increase the area and complexity of integrated circuits.
Innovation Solution
The proposed POR circuitry generates a trip voltage based on a combination of intrinsic threshold voltages and reference voltages, eliminating the need for a local resistor divider and simplifying the BG_OK circuitry, thereby reducing size and cost while maintaining accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bandgap reference (BGR) circuitry and resistor dividers are used in conventional POR circuits, then the trip voltage can be generated, but the area and complexity of integrated circuits increase
Solution Approach 1:
The patent extracts and eliminates the local resistor divider from the POR circuit, using only intrinsic transistor threshold voltages and reference voltages to generate the trip voltage. This removes the complex resistor divider network while maintaining trip voltage generation capability through alternative means (combining threshold voltages of transistors Q1 and Q2 with selected reference voltages).
Solution Approach 2:
The patent utilizes the intrinsic threshold voltages of the transistors themselves as part of the voltage generation mechanism. The threshold voltages of transistors Q1 and Q2 are inherently available and are directly employed in generating the trip voltage, eliminating the need for external resistor dividers to create reference voltages.
2Measurement precision
If bandgap reference (BGR) circuitry and resistor dividers are used in conventional POR circuits, then the trip voltage can be generated, but the size of the POR circuit increases
Solution Approach 1:
The local resistor divider network is completely removed from the POR circuit design. The trip voltage is generated using only the intrinsic threshold voltages of transistors and externally provided reference voltages, eliminating the area occupied by resistor dividers while maintaining the ability to generate accurate trip voltages.
Solution Approach 2:
The reference voltage circuit is designed to provide multiple reference voltages that can be used both for trip voltage generation and for other circuit functions. This multi-functional approach eliminates the need for dedicated local resistor dividers, reducing overall circuit area while maintaining trip voltage accuracy.
3Measurement precision
If conventional POR circuits are designed with BGR circuitry and resistor dividers, then the trip voltage can be controlled, but the quiescent current consumption increases
Solution Approach 1:
The resistor divider network is removed from the circuit, eliminating the continuous current path it creates. The trip voltage control is achieved through the intrinsic threshold voltages of transistors and selectively activated reference voltages, which consume minimal quiescent current compared to resistor-based voltage division.
Solution Approach 2:
The reference voltages are provided selectively and periodically rather than continuously through resistor dividers. The circuit uses the intrinsic threshold voltages of transistors which are always available, combined with reference voltages that can be activated only when needed, reducing continuous quiescent current consumption.
Data Source
AI summary
An example apparatus includes: first circuitry configured to verify a set of reference voltages is stable; and second circuitry including a first transistor, a second transistor, a first number of parallel transistors, and a second number of parallel transistors, the second circuitry configured to, in response to the verification: produce a trip voltage based on: a comparison of a threshold voltage of the first transistor and a threshold voltage of the second transistor; and a reference voltage selected from the set and provided to a control terminal of the first transistor; and adjust the value of the trip voltage based on a comparison between a first current mirror having a first number of parallel transistors and a second current mirror connected to a second number of parallel transistors.