Features

• 1Mbps Isolated SPI Data Communications
• Simple Galvanic Isolation Using Standard Transformers
• Bidirectional Interface Over a Single Twisted Pair
• Supports Cable Lengths Up to 100 Meters
• Very Low EMI Susceptibility and Emissions
• Configurable for High Noise Immunity or Low Power
• Engineered for ISO26262 Compliant Systems
• Requires No Software Changes in Most SPI Systems
• Ultralow, 2μA Idle Current
• Automatic Wake-Up Detection
• Operating Temperature Range: –40°C to 125°C
• 2.7V to 5.5V Power Supply
• Interfaces to All Logic from 1.7V to 5.5V
• Available in 16-Lead QFN and MSOP Packages

Typical Application

Description

The LTC®6820 provides bidirectional SPI communications between two isolated devices through a single twisted pair 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 LTC6820 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.