TAP-I2C Bus Precharging for Speed and Power Trade-off
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Solution Overview
Problem
Existing I2C bus compatible devices face challenges in increasing speed while reducing average power consumption, as faster bus speeds require lower resistance pull-up resistors, which increase power demand.
Innovation Solution
The implementation of a transient active pull-up I2C (TAP-I2C) module with high-side driver transistors on the SDA and SCL lines, which precharges bus capacitance during logic level transitions, allowing for faster data transfer and reducing the need for external pull-up resistors, thereby increasing resistance values and lowering power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If lower resistance pull-up resistors are used to increase bus speed, then data transfer speed is improved, but power consumption increases
Solution Approach 1:
The patent applies preliminary action by precharging the bus lines to a predetermined voltage level before actual data transmission begins. This precharge phase prepares the bus capacitance in advance, allowing the main pull-up resistors to be designed with higher resistance values for lower power consumption, while still achieving fast bus transitions when needed during data transfer operations.
2Use of energy by moving object
If higher resistance pull-up resistors are used to reduce power consumption, then power consumption is reduced, but bus transfer speed decreases
Solution Approach 1:
The precharge circuit performs preliminary charging of the bus lines before data transmission, enabling the use of higher resistance pull-up resistors that consume less power during normal operation, while still achieving fast bus transitions when needed during data transfer operations.
Solution Approach 2:
The patent employs periodic action through the precharge pulse that is periodically applied to the bus lines at appropriate intervals. This periodic precharging maintains the bus in a ready state, allowing high-speed data transfer without requiring continuously low-resistance pull-up resistors that would consume excessive power.
3Speed
If active pull-up devices are used to precharge bus lines, then bus charging speed is improved, but device complexity increases
Solution Approach 1:
The patent merges the precharge function with the existing I2C bus interface circuitry by integrating the precharge circuit into the host device's I2C controller. This combination approach enables fast bus charging without adding separate independent precharge circuits, thereby reducing overall system complexity while still achieving high-speed bus transitions.
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 solution accelerates I2C bus transfer operations, achieving speeds of up to 5-10 MHz while reducing power consumption by using higher resistance pull-up resistors only to maintain logic levels, rather than charge bus capacitance during transitions.
Implementation Method 1
precharge the capacitance of the SDA or SCL bus line to a predetermined voltage level... rapidly charging the capacitance much faster
Implementation Method 2
control the on time of the P-channel FET... substantially shorts out the pull-up resistor and effectively charges the capacitance
Data Source
Figure 1
Figure 2~3
Figure 4A
AI summary
An I2C-bus compatible device when functioning as a clock master comprises a transient active pull-up I2C ("TAP-I2C") logic module having high side driver transistors, e.g., P-channel field effect transistors (FETs), coupled between a positive supply voltage and respective serial data ("SDA") and serial clock ("SCL") lines on the I2C bus. The high side output driver transistors for the SDA and SCL lines are sequentially pulsed on by the TAP I2C logic module for brief periods to first precharge the capacitance of the SDA line and then prechargc the capacitance of the SCL line during low to high logic level transitions thereof. Precharging the capacitances of the I2C bus lines will also accelerate bus transfer operations for all I2C compatible devices since the capacitances of the I2C bus lines will be charged much faster through the low impedance active pull-up driver transistors then through the passive pull-up resistors.