LVDS Receiver Loopback Circuit for Common-Mode Voltage Testing
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Solution Overview
Problem
Existing LVDS receiver testing methods do not provide complete coverage of the entire allowable common mode voltage range, leading to potential defects going undetected.
Innovation Solution
Incorporating a loopback circuit with a tunable common mode voltage generator, allowing for comprehensive testing of LVDS receivers over a wide common mode voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LVDS receiver is designed for wide common mode voltage range, then adaptability is improved, but testing completeness deteriorates
Solution Approach 1:
The patent implements a loopback circuit that nests a dummy transmitter within the receiver structure, allowing the transmitter to feed test signals directly into the receiver inputs. This nested configuration enables comprehensive testing of the wide common mode voltage range without requiring external test equipment for each voltage level, thereby resolving the contradiction between wide adaptability and testing completeness.
Solution Approach 2:
The receiver circuit performs self-testing through the integrated loopback path, where the dummy transmitter generates test signals that circulate through the receiver. This self-service mechanism allows the device to test its own performance across the entire common mode voltage range, eliminating the need for external testing resources and achieving complete coverage despite the wide operating range.
2Device complexity
If probe testing is performed at single common mode voltage, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent introduces a tunable common mode voltage generator that dynamically adjusts the common mode voltage level during testing. This dynamic capability allows the testing system to sweep through multiple voltage levels automatically, achieving precise measurement across the entire common mode range without requiring multiple fixed-voltage test setups, thus resolving the contradiction between simple testing setup and comprehensive voltage coverage.
Solution Approach 2:
The loopback circuit incorporates a tunable common mode voltage generator that changes the operating voltage parameter during testing. By systematically varying the common mode voltage across the full operating range, the system achieves precise measurement of receiver performance at different voltage levels while maintaining a single, relatively simple test configuration, thereby resolving the contradiction between device complexity and measurement precision.
Data Source
AI summary
A low voltage differential signaling (LVDS) receiver includes a receiver circuit including first and second inputs coupled to first and second conductive pads, respectively, and an output coupled to an input of a digital controller, and a dummy transmitter circuit including a first input coupled to receive a common mode voltage (VCM) tune signal, a second input coupled to a loopback input signal, a third input coupled to a loopback enable signal, a first output coupled to the first input of the receiver circuit, and a second output coupled to the second input of the receiver circuit. When a test mode of operation is enabled, the digital controller asserts the loopback enable signal, and the dummy transmitter circuit generates a pair of test differential signals based on the VCM tune signal, wherein the VCM tune signal varies to test the LVDS receiver over a range of common mode voltages.