Differential Output Circuit for Multi-Standard Interface Level Conversion
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Solution Overview
Problem
Existing semiconductor integrated circuits face challenges in transmitting signals between different interface levels, such as PECL and LVDS, due to conflicting characteristics like power supply voltage dependence and manufacturing variations in resistance values, leading to inconsistent output levels that fail to meet standard compatibility.
Innovation Solution
An output circuit with a differential section, current source, load resistance, and control unit that adjusts current and resistance values based on a signal to convert and balance-transmit differential signals, ensuring compatibility with various interface standards like PECL, LVDS, and PCI-express by using internal and external resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed resistance value is used in the output circuit, then the circuit structure is simple, but the output level cannot satisfy different interface standards (PECL, LVDS) due to manufacturing variations and power supply voltage dependencies
Solution Approach 1:
The patent applies dynamics by making the resistance value changeable based on the selected interface standard. The output circuit includes a resistance setting unit that dynamically adjusts the resistance value of the load resistance section according to control signals indicating whether PECL or LVDS standard is selected. This resolves the contradiction by transitioning from a fixed resistance structure to a dynamic adjustment mechanism that maintains output level precision across different standards while keeping the overall circuit structure relatively simple.
Solution Approach 2:
The patent implements parameter changes by varying the resistance value of the load resistance section based on the selected interface standard. When PECL is selected, one resistance value is applied; when LVDS is selected, a different resistance value is applied. This parameter adjustment compensates for manufacturing variations and power supply voltage dependencies, ensuring that output levels meet the precise requirements of each interface standard without requiring completely different circuit designs.
2Manufacturing precision
If separate output circuits are designed for each interface standard (PECL, LVDS), then the output level precision for each standard is high, but the device complexity increases significantly
Solution Approach 1:
The patent applies universality by designing a single output circuit that can function for multiple interface standards (PECL and LVDS). The output circuit includes a differential section, a current source section, a load resistance section, and a resistance setting unit. By dynamically adjusting the resistance value based on the selected standard, this single circuit structure replaces what would traditionally require separate dedicated circuits for each interface, thereby reducing device complexity while maintaining high output level precision for both standards.
Solution Approach 2:
The patent uses dynamics to enable one circuit structure to adapt to multiple interface standards. The resistance setting unit dynamically changes the load resistance value based on control signals indicating the selected standard. This dynamic adjustment allows the same physical circuit to satisfy the different output level requirements of PECL and LVDS standards without requiring multiple static circuit configurations, thus reducing overall device complexity.
3Reliability
If the resistance value is changed according to power supply voltage variation, then the output level can track the power supply voltage, but the circuit complexity increases due to additional control mechanisms
Solution Approach 1:
The patent implements feedback by monitoring the power supply voltage and automatically adjusting the resistance value of the load resistance section in response to voltage variations. The resistance setting unit receives information about power supply voltage changes and modifies the resistance accordingly to maintain stable output levels. This feedback mechanism ensures reliability by compensating for power supply variations without requiring complex external regulation circuits.
Solution Approach 2:
The output circuit applies self-service by automatically adjusting its own resistance value in response to power supply voltage variations. The resistance setting unit is integrated within the output circuit itself, allowing it to autonomously compensate for voltage changes without requiring external control systems. This self-adjusting capability maintains output level stability while minimizing additional circuit complexity.
Data Source
AI summary
An output circuit includes a differential section configured to amplify an inputted differential signal; a current source section configured to supply a current to the differential section; a load resistance section connected with the differential section; and a control unit configured to set a value of the current from the current source section and a resistance value of the load resistance section based on a signal supplied to the control unit. The output circuit converts the differential signal into an output signal of a different interface level from that of the differential signal and balance-transmits the output signal.