USB-C CC Pull-Down Circuit for Low-Power Baseband Signaling
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Solution Overview
Problem
USB port controllers face challenges in maintaining robust baseband communications while minimizing power consumption, particularly due to inadequate pull down current leading to excessive charging of the CC line during long duration transitions in USB-C systems.
Innovation Solution
The implementation of a selective pull down circuit that sinks current from the supply node when the transmit data signal is in a first state and refrains from sinking current when in a second state, using adjustable and fixed pull down current sources to prevent CC line charge up, enhancing communication reliability with efficient class A LDO supply circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pull down current is provided to prevent CC line charge up during baseband transmission, then communication reliability is improved, but power consumption increases
Solution Approach 1:
The pull down current is made dynamic by enabling it only during baseband transmission periods and disabling it during idle periods. The circuit transitions between active and inactive states based on transmission requirements, allowing the system to maintain communication reliability when needed while minimizing power consumption during non-transmission periods.
Solution Approach 2:
The pull down current is applied periodically during baseband transmission bursts rather than continuously. The circuit activates the pull down current synchronously with transmission activity and deactivates it during idle intervals, creating a periodic on-off pattern that balances communication reliability with power efficiency.
2Adaptability or versatility
If pull up resistor and pull down resistor are used to set CC line voltage, then power configuration negotiation is enabled, but baseband transmitter supply node charges up during long duration transitions
Solution Approach 1:
The pull down circuit is activated in advance during baseband transmission to counteract the charging effect of the pull up resistor. By enabling the pull down current before and during transmission periods, the circuit preemptively prevents excessive voltage buildup on the CC line, maintaining signal levels within acceptable ranges throughout the transmission.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces power consumption and ensures reliable baseband communications across various USB power configurations, preventing significant CC line charge up and maintaining communication within acceptable voltage levels, without the need for costly class AB regulators.
Implementation Method 1
a pull down circuit selectively sinks a first current from a supply node of the transmitter in a first mode when the transmit data signal is in a first state
Data Source
AI summary
USB controllers, systems and methods are presented to conserve power in a USB controller, in which a transmitter transmits data to a line of a connected USB cable according to a transmit data signal, and a pull down circuit selectively sinks current from a supply node of the transmitter when the transmit data signal is in a first state, refrains from sinking the first current from the supply node when the transmit data signal is in a different second state.