Driver Circuit With Bias-Control For High Voltage Swing
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Solution Overview
Problem
Existing driver circuits in serial communication links face challenges in varying impedance and achieving high voltage swings without damaging transistors, while also minimizing power consumption and area occupancy.
Innovation Solution
A driver circuit comprising a first inverter, a bias-control circuit, and a second inverter, where the bias-control circuit reduces the voltage level difference between the supply voltages, enabling a high voltage swing without overstressing the transistors, and includes transistors and a capacitor to generate a level-shifted data signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driver circuit operates at a low voltage level to prevent transistor damage and reduce power consumption, then transistor reliability and power efficiency are improved, but the voltage swing of the output data signal becomes too low for the receiver to distinguish logic states
Solution Approach 1:
The driver circuit is divided into multiple inverters connected in series, where each inverter contributes to the cumulative voltage swing. The first inverter operates at a first supply voltage (lower, for reliability), while subsequent inverters build upon this to achieve the required total voltage swing for reliable data transmission without overstressing individual transistors.
Solution Approach 2:
The patent introduces a second supply voltage dimension alongside the first supply voltage. By using multiple supply voltage levels (first supply voltage for initial inversion, second supply voltage for subsequent inverters), the circuit achieves both low-power operation and sufficient voltage swing simultaneously.
2Measurement precision
If a resistor is included to match the impedance of the transmitter with the transmission line, then signal transmission accuracy is improved, but the fabrication process irregularities cause the resistance to be unequal to the desired resistance
Solution Approach 1:
Instead of relying on a fixed resistor value that is sensitive to fabrication variations, the patent uses the inherent output impedance of the inverter circuit itself as the matching element. By adjusting the inverter's operating conditions and structure, the output impedance is made equal to the transmission line impedance, eliminating the need for separate resistors and their associated manufacturing tolerances.
3Adaptability or versatility
If multiple driver circuits are connected in parallel to vary the impedance of the transmitter, then impedance matching capability is improved, but the power consumption and device complexity increase
Solution Approach 1:
The patent makes the driver circuit dynamic by using enable signals to control the activation of individual inverters in the series chain. By selectively enabling or disabling inverters based on the required impedance matching conditions, the circuit can adapt its output impedance without requiring multiple parallel driver circuits, thus maintaining simplicity while achieving versatility.
Data Source
AI summary
A driver circuit includes a first inverter, a bias-control circuit, and a second inverter. The first inverter, which is connected between a first supply voltage and ground, receives an input data signal and generates an inverted version of the input data signal. The bias-control circuit, which is connected between a second supply voltage and the first inverter, receives the inverted version of the input data signal and a bias signal, and generates a level-shifted data signal based on the inverted version of the input data signal, the bias signal, and the second supply voltage. The bias-control circuit reduces a difference between voltage levels of the second supply voltage and the inverted version of the input data signal. The second inverter is connected between the second supply voltage and ground, and further connected to the bias-control circuit and first inverter and generates an output data signal.