Unified USB Transmit Driver for Multi-Mode Signal Integrity
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Solution Overview
Problem
Existing USB data signal transmitters require separate drivers for different modes (LS, FS, HS, HSIC), leading to increased costs, power consumption, and IC area usage due to the need for multiple configurations.
Innovation Solution
A unified transmit driver that adjusts rail voltage, output impedance, slew rate, and equalization based on a mode signal to accommodate multiple USB data modes, including LS, FS, HS, and HSIC, using a predriver, rail voltage generator, bias voltage generator, level shifter, equalizer control circuit, and emphasis equalizer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate transmit drivers are used for different USB modes (LS, FS, HS, HSIC), then each mode can meet its specific voltage domain requirements, but the device complexity, cost, and power consumption increase due to multiple drivers
Solution Approach 1:
The patent implements a unified transmit driver that can operate across multiple USB modes (LS, FS, HS, HSIC) by dynamically adjusting its parameters. The driver uses a mode indicator signal to select appropriate rail voltages, output impedances, and slew rates, allowing a single device to perform multiple functions that previously required separate drivers for each mode.
Solution Approach 2:
The transmit driver employs dynamic parameter adjustment based on the operating mode. The rail voltage generator dynamically switches between different voltage levels (3.0V for LS/FS, 0.8V for HS, 1.2V for HSIC), and the output impedance and slew rate are dynamically configured according to the selected mode, enabling the driver to adapt its characteristics in real-time.
2Reliability
If multiple transmit drivers are implemented to support different USB modes, then each mode's specific requirements can be met, but the IC area usage increases
Solution Approach 1:
The unified transmit driver consolidates multiple mode-specific drivers into a single IC structure. By sharing common components such as the differential output stage, termination circuitry, and control logic, the design achieves multi-mode support while occupying significantly less silicon area than would be required for separate dedicated drivers for each USB mode.
Solution Approach 2:
The patent merges the functionality of multiple mode-specific transmit drivers into a single integrated unit. The rail voltage generator, bias voltage generator, and equalizer control circuits are combined into a unified architecture that serves all USB modes, eliminating the need for separate driver circuits and reducing overall IC area consumption.
3Device complexity
If a unified transmit driver is used for multiple USB modes, then device complexity and cost are reduced, but the challenge arises of meeting different voltage domain, impedance, and slew rate requirements with a single configuration
Solution Approach 1:
The unified transmit driver incorporates dynamic parameter adjustment mechanisms that respond to the operating mode. The rail voltage generator dynamically switches between 3.0V, 0.8V, and 1.2V levels based on the mode indicator, while the output impedance is dynamically adjusted to match the specific requirements of each USB mode, and slew rate control is adapted to meet the gradual requirements of LS/FS modes versus the sharp edge requirements of HS/HSIC modes.
Solution Approach 2:
The patent employs parameter changes to adapt the transmit driver's characteristics for different USB modes. The rail voltage, output impedance, and slew rate are varied as control parameters based on the selected mode, allowing the single driver to optimize its performance for each specific mode's requirements through programmable parameter adjustment.
4Reliability
If different rail voltages are used for different USB modes, then voltage domain requirements are met, but the power consumption varies significantly across modes
Solution Approach 1:
The rail voltage generator dynamically adjusts the supply voltage to the transmit driver based on the operating mode. For power-sensitive LS and FS modes, the driver can operate at lower voltages when appropriate, while HS and HSIC modes utilize higher voltages to achieve the required signal quality. This dynamic voltage scaling optimizes power consumption while maintaining compliance with each mode's voltage domain requirements.
Data Source
AI summary
A transmit driver or transmitter is provided to generate an output data signal based on different input modes, such as low speed (LS), full speed (FS), high speed (HS), and high speed interconnect (HSIC) modes of a Universal Serial Bus (USB) standard. The transmit driver includes a rail voltage generator for generating a rail voltage for a set of transmit driver slices based on the selected mode. The transmit driver includes a bias voltage generator for generating a bias voltage based on the selected mode for protecting transistors in the transmit driver slices from over-voltage stress. The transmit driver includes a predriver and level shifter for generating input signals for the transmit driver slices to set the output impedance of the transmit driver and the slew rate of the output data signal. The transmit driver includes an emphasis equalizer for providing controllable emphasis equalization to the output data signal.