VML Driver Impedance Switching for Stable Jitter Across Modes
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Solution Overview
Problem
In semiconductor devices using VML signals, the variation in current consumption between emphasis and de-emphasis modes leads to variations in supply voltage, affecting the jitter characteristic of the output signal due to differences in impedance and resistance values between modes.
Innovation Solution
A semiconductor device with first and second output terminals coupled with a load resistor, featuring a variable resistor and drivers with adjustable output impedances, controlled by a controller to maintain constant current flow and impedance ratios between emphasis and de-emphasis modes, ensuring consistent resistance values and reduced voltage variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the driver circuit uses different impedance values between emphasis mode and de-emphasis mode to control signal amplitude, then the amplitude of the differential signal can be adjusted, but the current consumption varies between modes causing supply voltage variation and deteriorating jitter characteristic
Solution Approach 1:
The patent changes the resistance value of the internal resistor based on the operating mode. In emphasis mode, the internal resistor is connected in parallel with the load resistor to provide signal amplitude enhancement. In de-emphasis mode, the internal resistor is disconnected to maintain normal operation. This parameter change allows the circuit to achieve different signal amplitudes while maintaining stable current consumption and supply voltage, thereby improving jitter characteristic.
2Adaptability or versatility
If the internal resistance is enabled in emphasis mode and disabled in de-emphasis mode to vary signal amplitude, then the differential signal amplitude can be controlled, but the current consumption becomes variable causing supply voltage fluctuation
Solution Approach 1:
The patent implements a dynamic switching mechanism controlled by a mode selection signal. The control circuit dynamically connects or disconnects the internal resistor between the first and second output terminals based on the operating mode. This dynamic configuration allows the circuit to adapt between emphasis and de-emphasis modes while the control circuit ensures that current consumption remains stable across modes, preventing supply voltage fluctuation and maintaining system stability.
3Adaptability or versatility
If the driver circuit configuration changes between modes to achieve emphasis and de-emphasis, then signal amplitude can be varied, but the impedance mismatch causes current consumption variation and supply voltage change
Solution Approach 1:
The patent introduces a control circuit as an intermediary between the power supply and the H-bridge circuit. This control circuit monitors the operating mode and adjusts the connection state of the internal resistor accordingly. By acting as an intermediary, the control circuit ensures that the impedance changes in the H-bridge circuit do not directly translate to current consumption variations, thereby maintaining stable power delivery while still enabling emphasis and de-emphasis functionality.
Data Source
AI summary
A semiconductor device includes a variable resistor that sets a resistance value as a first resistance value in an emphasis mode, and as a second resistance value smaller than the first resistance value in a de-emphasis mode, a first driver that sets an output impedance as a third resistance value in the emphasis mode, and as a fourth resistance value larger than the third resistance value in the de-emphasis mode, a second driver that sets the output impedance as a fifth resistance value in the emphasis mode, and as a sixth resistance value larger than the fifth resistance value in the de-emphasis mode, and a controller that controls conductive states of the first and second drivers according to an input signal, and switches the output impedances of the first and second drivers and the resistance value of the variable resistor between the emphasis mode and the de-emphasis mode.