LVDS Fail-Safe Circuit for Small-Amplitude Signal Detection
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Solution Overview
Problem
Existing LVDS data receivers face challenges in detecting nonstandard small amplitude differential input signals, requiring a fail-safe circuit that is sensitive, power-efficient, and occupies minimal area, especially in frequency bands below several tens of MHz, and is not easily adaptable to varying frequency ranges.
Innovation Solution
A data receiver with a fail-safe circuit comprising a high-pass filter, comparator, and pulse width extending circuit that removes DC components, compares voltage levels, and extends pulse width to detect nonstandard small amplitudes, allowing for low voltage operation and minimal area usage while maintaining high sensitivity to normal amplitudes and low sensitivity to fail-safe operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional squelch detection circuit with pulse width extending circuit is used, then high-speed data communication is achieved, but circuit area is substantially increased due to requiring 1000 or more inverters
Solution Approach 1:
The invention extracts and removes redundant components from the conventional squelch detection circuit. Specifically, it eliminates the need for numerous inverters (1000 or more) by using a different pulse width extension approach based on a single inverter and capacitor, thereby substantially reducing circuit area while maintaining high-speed data communication capability
Solution Approach 2:
The invention changes the operational parameters of the pulse width extending circuit by using a capacitor to extend the pulse width of the detection signal by at least one period of the differential signals, replacing the inverter-based approach with a capacitor-based timing mechanism that achieves the same function with minimal area
2Measurement precision
If diodes are used in the detection circuit, then voltage level detection is achieved, but upper limit of output voltage is imposed in low voltage specification
Solution Approach 1:
The invention replaces diodes with transistors that can operate in low voltage specifications without imposing upper voltage limits. The transistor-based detection circuit uses the transistor's switching characteristics to detect voltage levels, providing adaptability to low voltage specifications while maintaining detection accuracy
Solution Approach 2:
The invention changes the detection mechanism from diode-based voltage clamping to transistor-based switching detection, allowing the circuit to adapt to low voltage specifications by utilizing the transistor's ability to switch at lower voltage levels without being constrained by diode forward voltage drops
3Measurement precision
If hysteresis amplifier is used as comparator, then normal amplitude detection is achieved, but power consumption increases and area is not minimized
Solution Approach 1:
The invention extracts and removes the hysteresis amplifier from the circuit, replacing it with a simpler transistor-based detection mechanism that achieves normal amplitude detection without the continuous power consumption associated with operational amplifiers, thereby minimizing power consumption while maintaining detection accuracy
Solution Approach 2:
The invention uses the intrinsic switching characteristics of transistors to perform amplitude detection without requiring external hysteresis amplification, allowing the circuit to detect amplitude levels using the transistor's natural switching behavior driven by the input signal itself
4Measurement precision
If hysteresis amplifier is used as comparator, then amplitude comparison is achieved, but circuit is easily influenced by process variation widening gray zone
Solution Approach 1:
The invention replaces the hysteresis amplifier with transistors that provide more stable and predictable switching characteristics less sensitive to process variations, eliminating the gray zone problem by using the transistor's sharp threshold switching behavior which is more consistent across process variations
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 handles differential input signals across 20 MHz to 160 MHz frequency bands with high sensitivity to normal amplitudes and low sensitivity to nonstandard small amplitudes, consuming low power and occupying minimal area, and can be adjusted for different frequency bands and sensitivity settings.
Implementation Method 1
a high-pass filter that removes DC components from the differential input signals and outputs a high voltage input signal and a low voltage input signal
Implementation Method 2
a comparator that compares a voltage level of the high voltage input signal with a voltage level of the low voltage input signal, and outputs a comparison result signal indicating a comparison result thereof
Implementation Method 3
a pulse width extending circuit that extends a pulse width of a voltage level of the comparison result signal indicating that the voltage level of the high voltage input signal is lower than the voltage level of the low voltage input signal, by a predetermined period of time
Data Source
AI summary
A data receiver has a reception circuit and a fail-safe circuit. The reception circuit has an input amplifier, a logic signal processing circuit, and a reception stop control circuit. The fail-safe circuit has a high-pass filter, a comparator, and a pulse width extending circuit. The reception circuit receives a serial data of differential input signals based on a predetermined standard, converts the serial data into a serial data of a single-ended output signal, and outputs a converted serial data. The fail-safe circuit detects whether the differential input signals have a nonstandard small amplitude and outputs a fail-safe detection signal indicating a detection result.