Low Power Analog Switch with Over-Voltage Protection
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Solution Overview
Problem
Existing analog switch circuits with over-voltage protection are inefficient in power usage and do not effectively protect downstream devices from input voltages significantly higher than the positive power supply voltage rail or lower than the negative power supply voltage rail, nor do they provide upstream protection or protection during power-off conditions, such as electrostatic discharge events.
Innovation Solution
The design incorporates a p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) switching element and a tri-state inverter to compare incoming voltage signals to both high and low reference voltages, allowing the switch to open and prevent damage, while maintaining a very low quiescent supply current, and includes additional circuitry to provide symmetric over- and under-voltage protection and power-off protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If band-gap reference circuit and comparator are used for over-voltage protection, then over-voltage protection is provided, but quiescent supply current increases to 10s of microAmps
Solution Approach 1:
The patent extracts and removes the power-hungry band-gap reference circuit and comparator from the protection mechanism. Instead, it uses a simple voltage divider network with resistors and a transistor-based switching mechanism that provides over-voltage protection with minimal quiescent current consumption, eliminating the need for continuous power-intensive monitoring circuits.
Solution Approach 2:
The patent employs a simple, low-cost resistor-based voltage division network instead of expensive, power-intensive integrated reference circuits. The protection mechanism uses passive components and a single transistor that can be easily replaced or reset, providing economical protection with minimal power consumption.
2Reliability
If traditional over-voltage protection circuits are used, then protection is provided for limited voltage ranges, but protection is not effective for voltages significantly higher than Vdd or lower than Vss
Solution Approach 1:
The patent creates a universal protection circuit that handles multiple voltage anomaly conditions (over-voltage above Vdd, under-voltage below Vss, and ESD events) using a single integrated mechanism. The circuit uses a voltage divider network that can detect and respond to any voltage deviation from the normal operating range, providing comprehensive protection across an extended voltage spectrum.
Solution Approach 2:
The protection circuit dynamically adapts to different voltage conditions by using a transistor switching mechanism that automatically activates protection when voltage thresholds are exceeded. The circuit transitions between normal operation and protection modes based on real-time voltage monitoring, enabling it to handle both moderate and extreme voltage anomalies effectively.
3Reliability
If standard analog switch protection is implemented, then downstream protection is provided, but upstream protection and power-off protection are not provided
Solution Approach 1:
The patent segments the protection function into distinct operational modes: normal operation, over-voltage protection, under-voltage protection, and power-off protection. Each mode is handled by the same physical circuit mechanism but activated under different conditions, allowing the circuit to provide comprehensive protection coverage including upstream protection and ESD protection during power-off states.
Solution Approach 2:
The protection circuit performs preliminary action by continuously monitoring voltage conditions and being pre-configured to activate protection mechanisms before damage occurs. The voltage divider network and transistor switching mechanism are always ready to respond to voltage anomalies, including ESD events, even when the main device is powered off, providing proactive protection.
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 effectively protects downstream devices from a wide range of voltage events, draws significantly less current than traditional solutions, and provides protection during both normal operation and power-off conditions, making it suitable for mobile applications.
Implementation Method 1
an external P-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) switching element, which can also be referred to as a PMOS switching element
Implementation Method 2
a tri-state inverter to compare incoming voltage signals to both high and low reference voltages
Data Source
AI summary
Analog switch circuits, methods for use with analog switch circuits, and devices and systems including analog switch circuits are disclosed herein. Such analog switch circuits include an analog switch input terminal (In), an analog switch output terminal (Out), and an analog switch control terminal (Ctl). During a normal-voltage condition, the input terminal (In) of the analog switch circuit is selectively connected and disconnected to/from the output terminal (Out) in dependence on a control signal received at the control terminal (Ctl). During an over-voltage condition, the input terminal (In) is disconnected from the output terminal (Out) regardless of the control signal received at the control terminal (Ctl). Additionally, during an under-voltage condition, the input terminal (In) is disconnected from the output terminal (Out) regardless of the control signal received at the analog switch control terminal (Ctl). In specific embodiments, symmetric protection and/or power-off protection is/are also provided.