A Compact, Power-Efficient, and On-the-Fly I2C-to-SPI Converter for Distributed E-Textile Systems

This paper presents a 0.36-mm² I2C-to-SPI converter chip designed for electronic textile (E-textile) applications, featuring an on-the-fly conversion scheme that eliminates the need for on-chip data buffers and internal clock generation. By leveraging the synchronous nature of both I2C and SPI protocols, the proposed design forwards each incoming I2C data bit, SDA (Serial Data Line) directly to the SPI output using the I2C serial clock line (SCL), thereby reducing both area and power consumption. Two versions of the chip are proposed: a ‘full’ die and a ‘compact’ die. The converter enables seamless integration into distributed in-textile architectures by minimizing silicon overhead. The ‘full’ die implementation achieves a $7.33\times $ area reduction compared to commercially available I2C-to-SPI converters, while the ‘compact’ version further reduces the footprint by $14.73\times $ through the use of a small corner seal-ring and a linear pad ring layout. Measurement results confirm robust operation at ultra-fast I2C frequency (5 MHz), consuming only 0.379 mW for the ‘full’ die and 0.333 mW for the ‘compact’ variant. At standard I2C speeds (400 kHz), the converter demonstrates a $48\times $ improvement (‘full’ die) in power efficiency over commercial off-the-shelf (COTS) solutions, making it an effective and unobtrusive solution for next-generation E-textile systems.