Demonstration circuit 2799A uses the LTC4332 to extend a SPI interface with 3 slave devices to up to 1200m (150m with a 500kHz SCK as factory configured). The DC2799A is designed to be compatible with the popular Pmod interface to allow for easy evaluation with the many master and slave devices in this ecosystem.
The LTC4332 is a 2MHz SPI bus extender designed for operation in high noise industrial environments. The SPI bus is extended over two twisted pairs by ±60V fault protected differential transceivers. The LTC4332’s extended 25V common mode voltage range allows it to bridge across different ground potentials.
The DC2799A’s local side interfaces with the host SPI master as 4 different SPI slave devices. These slave devices support SPI modes (0,0) or (1,1) where (CPOL, CPHA). Three of the slave devices are associated with the remote side devices (SS1, SS2, SS3) and the fourth device (SSC) is used to configure the DC2799A’s LTC4332 SPI extenders. The DC2799A’s remote side interface implements a SPI master with 3 different slave selects. The remote side master supports all four SPI modes and a unique mode may be associated to each slave select.
By default, the remote SPI modes are all mode (0,0). The remote side SPI modes are configured by writing to the local side LTC4332 using the SSC slave device.
The LTC4332 data sheet gives a complete description of the part, its operation and application information. The data sheet should be referred to when reading this demo manual. The LTC4332 is available in a 20-lead QFN package and three temperature grades (commercial 0°C to 70°C, industrial –40°C to 85°C, and high temperature –40°C to 125°C).