Configurable Serial Interface Voltage Detection
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Solution Overview
Problem
Existing configurable serial interfaces face challenges with incompatible logic levels and voltage differences between integrated circuits and bus masters, leading to functional hazards, increased power consumption, and impaired communication, particularly when dealing with different supply voltages.
Innovation Solution
A configurable serial interface that uses a configuration pin to detect bus supply voltage and adjust mode select logic, allowing for dual use as a power source and mode selector, reducing pin count and optimizing noise immunity by scaling input buffer circuits and output drivers to match supply voltages, supporting both SPI and I2C protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a configuration pin is used to switch between SPI and I2C modes in prior art devices, then mode selection is achieved, but the chip select line remains undefined during power-up causing functional hazards
Solution Approach 1:
The patent applies preliminary action by detecting the bus supply voltage on the configuration pin before mode selection is finalized. The voltage detection circuitry determines whether VDDLOGIC is present during power-up, and only after this detection does the system configure the serial interface mode. This ensures the chip select line is properly defined before any functional operation, eliminating the power-up hazard while maintaining ease of mode selection.
2Adaptability or versatility
If open collector output drivers are used to mitigate independent supply voltage issues, then voltage compatibility is improved, but external pull-up resistors are required increasing power consumption and loading output drivers
Solution Approach 1:
The patent applies dynamics by making the output driver configuration adaptive rather than static. The system dynamically selects between push-pull and open-collector output driver configurations based on the detected bus supply voltage. When VDDLOGIC is detected, push-pull drivers are enabled for full voltage swing without external pull-up resistors. When incompatible voltages are detected, the system switches to open-collector mode. This dynamic adaptation eliminates continuous power consumption from external pull-up resistors while maintaining voltage compatibility when needed.
3Adaptability or versatility
If a configurable serial interface supports both SPI and I2C protocols, then versatility is improved, but pin count increases and I2C address selection is limited
Solution Approach 1:
The patent applies universality by making the configuration pin serve multiple functions: it detects the bus supply voltage, selects the operational mode (SPI or I2C), and provides address selection in I2C mode. This multi-functional use of the configuration pin eliminates the need for separate pins for mode selection and address configuration, reducing the overall pin count while maintaining full SPI and I2C protocol support with multiple address options.
4Adaptability or versatility
If address select pins are tied to serial communication pins to increase I2C addresses, then address selection capability is improved, but functional hazards occur during power-up
Solution Approach 1:
The patent applies preliminary action by detecting the bus supply voltage on the configuration pin before any I2C address selection is activated. The system determines the operational mode and configures address pins only after confirming VDDLOGIC is present. This sequential approach ensures that address select pins tied to serial communication pins are properly configured before use, eliminating functional hazards during power-up while maintaining expanded I2C address selection capability.
Data Source
AI summary
Method and system for configuring a serial interface. The system includes one or more input nodes each coupled to a corresponding serial bus. One or more output nodes are coupled to a respective serial bus, each output node having a respective driver. A voltage detection circuit determines the voltage at a configuration node. Mode of serial bus operation is based on the voltage level detected at the configuration node. In at least one mode of serial bus operation, the configuration node is used as a mode select input and power source for at least one output driver.