Fast Common-Mode Charging for Serial Signal Lines After Sleep
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Solution Overview
Problem
High-speed serial communications systems face delays and inefficiencies in charging signal lines to a common mode voltage during transitions from sleep mode, which can consume significant current and prolong system availability.
Innovation Solution
A transmitter circuit adjusts signal line voltages by transmitting pulses exceeding the common mode voltage, using a control circuit to measure and equalize voltages, and employing discharge circuits to manage overshoot, thereby reducing charging time and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the signal lines are charged to the common mode voltage using conventional methods, then the charging operation can be completed, but the charging time is prolonged and current consumption increases
Solution Approach 1:
The patent applies preliminary action by equalizing the voltages on the true and complement signal lines before initiating the charging operation. This is achieved by shorting the signal lines together prior to charging, ensuring they start from the same voltage potential. This preliminary step prevents voltage imbalances that would otherwise require additional charging time and current, thereby reducing both the charging duration and energy consumption while ensuring efficient common mode voltage recharging upon sleep mode exit.
2Speed
If the voltage of transmitted pulses exceeds the common mode voltage to reduce charging time, then the charging speed increases, but voltage overshoot may occur
Solution Approach 1:
The patent implements feedback by continuously monitoring the voltage levels on the signal lines during the charging operation. The transmitter circuit adjusts the pulse transmission based on the measured voltage levels, transmitting pulses only when needed to reach the target common mode voltage. This feedback mechanism prevents voltage overshoot by stopping the charging process at the precise moment the target voltage is achieved, thereby maintaining both high charging speed and voltage accuracy.
Solution Approach 2:
The patent applies partial action by transmitting pulses with voltages that exceed the common mode voltage only when necessary to overcome the RC time constant limitations and achieve faster charging. The pulse voltage and duration are carefully controlled to provide just enough excess voltage to accelerate charging without causing significant overshoot, balancing speed requirements with voltage precision.
3Reliability
If the transmitter circuit transmits pulses to charge the signal lines, then the common mode voltage is restored, but operational delays occur during the charging process
Solution Approach 1:
The patent applies periodic action by using pulsed voltage transmission instead of continuous charging. The transmitter circuit transmits a series of controlled pulses at optimized intervals, allowing the signal lines to charge during pulse transmission and settle between pulses. This periodic approach restores the common mode voltage efficiently while minimizing the total operational delay, as the pulses are transmitted only when voltage adjustment is needed rather than maintaining continuous high-current charging.
Data Source
AI summary
An apparatus for performing a fast common mode recharge is disclosed. The apparatus includes a transmitter circuit configured to transmit a differential signal on a communication bus that includes a true signal line and a complement signal line and a measurement circuit configured to measure respective voltage levels of the true signal line and the complement signal line. The apparatus further includes a control circuit configured to, in response to exiting a sleep mode, select one of a plurality of operation modes using the respective voltage levels of the true signal line and the complement signal line. The transmitter circuit is further configured to adjust the respective voltage levels of the true signal line and the complement signal line based on a selected operation mode of the plurality of operation modes.