The LTC6820HUD provides bidirectional SPI communications between two isolated devices through a single twistedpair connection. Each LTC6820 encodes logic states into signals that are transmitted across an isolation barrier to another LTC6820. The receiving LTC6820 decodes the transmission and drives the slave bus to the appropriate logic states. The isolation barrier can be bridged by a simple pulse transformer to achieve hundreds of volts of isolation.
The LTC6820HUD drives differential signals using matched source and sink currents, eliminating the requirement for a transformer center tap and reducing EMI. Precision window comparators in the receiver detect the differential signals. The drive currents and the comparator thresholds are set by a simple external resistor divider, allowing the system to be optimized for required cable lengths and desired signal-to-noise performance.