Rx Termination Resistor Calibration for Arbitrary Voltage Matching
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Solution Overview
Problem
Conventional semiconductor integrated circuit apparatuses lack the ability to adjust termination resistors at the receive (Rx) side, particularly when an arbitrary termination voltage different from the power source voltage is applied, which complicates resistance value adjustment in transceiver circuits.
Innovation Solution
A resistance adjusting circuit and method that includes a high-speed serial interface with a CMOS analog circuit, capable of adjusting termination resistor values at both the transmit (Tx) and receive (Rx) sides using reference resistors and current sources, ensuring optimal impedance matching regardless of termination voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable resistor element is grounded at the second terminal, then the resistance value can be adjusted using conventional methods, but it becomes difficult to adjust the resistance value when an arbitrary termination voltage different from the power source voltage is supplied at the receive side
Solution Approach 1:
Instead of grounding the second terminal of the variable resistor element as in conventional designs, the patent inverts the connection by supplying the arbitrary termination voltage to the second terminal. This allows the resistance adjustment mechanism to work correctly under arbitrary termination voltages at the receive side, resolving the contradiction between adaptability and ease of operation.
Solution Approach 2:
The patent changes the voltage parameter configuration by allowing the second terminal to accept arbitrary termination voltages rather than being fixed at ground potential. This parameter change enables the resistance adjusting circuit to adapt to different termination voltage conditions while maintaining adjustability through the control signal mechanism.
2Device complexity
If conventional parameter correcting circuits are used, then the circuit structure is simple, but the termination resistor cannot be adjusted at the receive side
Solution Approach 1:
The patent extends the functionality of the parameter correcting circuit to include both transmit side and receive side termination resistor adjustment. By making the circuit universal, it can handle arbitrary termination voltages at the receive side while maintaining the simple structured approach of conventional circuits, thus resolving the contradiction between device complexity and adaptability.
Solution Approach 2:
The patent introduces a control signal mechanism that acts as an intermediary to coordinate the adjustment of termination resistors at both transmit and receive sides. This intermediary control system enables the receive side adjustment capability without significantly increasing overall circuit complexity, as the control signals can be generated and distributed through existing circuit infrastructure.
3Reliability
If the variable resistor element is connected to a mirror circuit with grounded second terminal, then the circuit operation is straightforward, but impedance matching cannot be achieved with arbitrary termination voltages
Solution Approach 1:
The patent inverts the conventional connection approach by supplying the arbitrary termination voltage to the second terminal of the variable resistor element rather than grounding it. This inversion enables proper impedance matching under arbitrary termination voltage conditions at the receive side, ensuring signal transmission quality while adapting to different voltage levels.
Solution Approach 2:
The patent changes the voltage parameter at the second terminal from fixed ground potential to arbitrary termination voltage. This parameter change allows the mirror circuit and variable resistor element to work together effectively for impedance matching regardless of the termination voltage level, thereby maintaining reliability while improving adaptability.
Data Source
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Figure 3A~3B
AI summary
To provide a resistance adjusting circuit and a resistance adjusting method that can adjust resistance value in accordance with an arbitrary termination voltage at a receive (Rx) side.. A resistance adjusting circuit including, a reference resistor (70), a first power source (150) connected to a first terminal of the reference resistor (70) and configured to output a first voltage, a first current source (121) connected to a second terminal of the reference resistor (70) and configured to output a first current based on a reference current which is set by using the reference resistor (70), a first variable resistor (160) configured to include a first terminal, the first terminal being connected to an output terminal of the first power source (150), a second current source (123) connected to a second terminal of the first variable resistor (160) and configured to output a second current obtained by multiplying the first current by a reciprocal ratio, the reciprocal ratio being obtained as a reciprocal number of a ratio of a target resistance value of the first variable resistor (160) to a resistance value of the reference resistor (70), and a controller (100D) configured to set the resistance value of the first variable resistor (160) so that a voltage value at the second terminal of the reference resistor (70) and a voltage value at a connecting part of the first variable resistor (160) and the second current source (123) become equal to each other.