Transmit Buffer Charge Sharing for Low-Swing Die-to-Die Signaling
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Solution Overview
Problem
Conventional die-to-die interfaces in computing systems consume significant power, which is a concern for mobile devices, as they typically use a full voltage swing for data transmission, leading to high power consumption and reduced battery life.
Innovation Solution
The implementation of a capacitive charge sharing mechanism in transmit buffer circuits, where a capacitor is charged for binary zeros and discharged for binary ones, reducing the voltage swing on the transmission line to a level (VOH) less than the power supply voltage (VDD), thereby conserving power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a full voltage swing (VDD) is used for data transmission, then signal integrity is improved, but power consumption increases
Solution Approach 1:
The patent changes the voltage parameter from full VDD swing to a reduced swing where the high state is VOH < VDD. This parameter change reduces power consumption while maintaining sufficient signal integrity for reliable data transmission across the die-to-die interface.
Solution Approach 2:
The capacitor is pre-charged to VOH before data transmission. This preliminary charging action allows the transmit buffer to switch between VOH and ground for binary ones, reducing the voltage swing and power consumption while maintaining signal integrity through the prepared charge state.
2Use of energy by moving object
If power supply voltage (VDD) is reduced to save power, then power consumption decreases, but signal integrity deteriorates
Solution Approach 1:
The capacitor acts as an intermediary energy storage element that is pre-charged to VOH. This intermediary allows the circuit to maintain a higher effective voltage swing for signal integrity while the actual power supply can operate at lower voltages, reducing overall power consumption.
Solution Approach 2:
The patent introduces dynamic voltage switching where the output voltage transitions between VOH (pre-charged capacitor state) and ground. This dynamic operation allows the system to achieve sufficient signal swing for reliability while consuming less power compared to static full VDD operation.
3Use of energy by moving object
If capacitive charge sharing is implemented, then power consumption decreases, but circuit complexity increases
Solution Approach 1:
The transmit buffer circuit is segmented into distinct functional blocks: a capacitor for charge storage, a pre-charge circuit for setting the initial voltage state, and a switching network for data transmission. This segmentation makes the complex charge-sharing mechanism more manageable and implementable.
Solution Approach 2:
The capacitor serves multiple functions: storing charge for voltage swing, enabling power reduction through charge sharing, and facilitating data transmission. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in circuit complexity.
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 usage at die-to-die interfaces by lowering the voltage swing, extending battery life in mobile devices while maintaining high signal integrity through the use of capacitive charge sharing.
Implementation Method 1
The transmit data buffer discharges the capacitor onto the transmission line. The transmission line has an associated capacitance that receives some of the charge from the capacitor.
Data Source
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AI summary
A circuit (100) includes a data input (data) in communication with a first transistor stack (M0); a first capacitor (C1) having a first capacitance and in communication with a power supply (Vdd) via a first transistor (M0) of the first transistor stack, wherein the first transistor is configured to charge the first capacitor in response to the data input receiving a signal corresponding to a first binary value (data= 0); a data output node (Dout) coupled between the first transistor stack and a transmission line having a second capacitance (C2); and wherein the first capacitor is coupled between the data output node and a second transistor of the first transistor stack, further wherein the second transistor (M1) is configured to discharge the first capacitor to the data output node in response to the data input receiving a signal corresponding to a second binary value (data= 1).