Selectable Mode Transmitter Driver Circuit for High Output Swing
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Solution Overview
Problem
Existing transmitter driver circuits face limitations in achieving high output swing due to increased power demands and chip area requirements, with risks of electrical overstress and unwanted reflections, especially when using high-efficiency voltage mode drivers with current mode logic or low-impedance parallel circuits.
Innovation Solution
A transmitter driver circuit that operates in selectable modes, combining a main voltage-mode driver with a parallel pseudo-CML and low-Z circuit, allowing for controlled current boost and impedance adjustment without significant additional power consumption or chip area, using a secondary voltage-mode driver circuit with a current source and switch to enable or disable parallel operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high efficiency voltage mode driver is combined with a CML current boost circuit to increase output swing, then the signal amplitude improves, but the chip area and power consumption increase
Solution Approach 1:
The patent merges the CML current boost circuit with the voltage mode driver by sharing common components. The secondary voltage mode driver circuit shares its input with the main driver, and the current source is integrated into the same circuit structure. This consolidation reduces the overall chip area while maintaining the output swing enhancement capability.
Solution Approach 2:
The secondary voltage mode driver circuit serves multiple functions: it provides current boost when the current source is enabled, acts as a parallel driver when the switch is enabled, and can be disabled entirely when neither is needed. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby reducing chip area.
2Strength
If a low-Z driver circuit is added in parallel to provide high-swing boost, then the output swing improves, but the impedance changes causing unwanted reflections
Solution Approach 1:
The patent introduces a switch that can dynamically enable or disable the secondary voltage mode driver circuit. This allows the impedance to be changed from a higher value (reducing reflections) to a lower value (boosting swing) based on operational needs. The switch provides dynamic control over the parallel connection, allowing the circuit to adapt its impedance characteristics.
3Strength
If additional parallel circuits are added to increase output swing, then the signal amplitude improves, but the power consumption increases
Solution Approach 1:
The patent uses a switch to periodically enable or disable the secondary voltage mode driver circuit based on the transmission requirements. When high output swing is not needed, the secondary circuit is disabled, reducing power consumption. When high swing is needed, the switch enables the secondary circuit to provide the boost. This periodic activation reduces average power consumption compared to continuous operation.
Solution Approach 2:
The patent changes the operational parameters of the secondary voltage mode driver circuit through the switch and current source control. By controlling whether the current source is active and whether the secondary driver is connected in parallel, the circuit can adjust its power consumption level to match the transmission requirements, reducing unnecessary power usage.
Data Source
AI summary
A circuit for a transmitter driver is disclosed. The transmitter driver circuit includes a main voltage-mode driver circuit configured to receive an input signal at the input port and to drive an output signal at the output port. The transmitter driver circuit also includes a secondary circuit connected to the input port and the output port in parallel with the main voltage-mode driver circuit. The secondary circuit includes: a secondary voltage-mode driver circuit; a current source connected to the secondary voltage-mode driver circuit and controllable to enable or disable a current boost to the output signal; and a switch connected to the secondary voltage-mode driver circuit and controllable to enable or disable the secondary voltage-mode driver circuit to drive the output signal in parallel with the main voltage-driver circuit.