Features and Benefits

  • Optimized for Low Voltage Systems Down to 0.9V
  • Bidirectional Buffer with Stuck Bus Recovery
  • -200mV Offset In-Out/+300mV Offset Out-In
  • 30ms Stuck Bus Timeout
  • Compatible with Non-Compliant VOL I2C Devices
  • Prevents SDA and SCL Corruption During Live Board Insertion and Removal from Backplane
  • ±6kV Human Body Model (HBM) ESD Protection
  • Isolates Input SDA and SCL Lines from Output
  • Compatible with I2C, I2C Fast Mode and SMBus
  • READY Open-Drain Output
  • 1V Precharge on SDAOUT and SCLOUT Lines
  • Small 8-Lead (3mm × 3mm × 0.75mm) DFN and 8-Lead MSOP Packages

Product Details

The LTC4308 hot swappable, 2-wire bus buffer allows I/O card insertion into a live backplane without corruption of the data and clock busses. The LTC4308 provides bidirectional buffering, keeping the backplane and card capacitances isolated. Negative offset from output to input allows communication between output bus devices with high VOL and devices on the low voltage input side, where bus supplies can be as low as 0.9V. If SDAOUT or SCLOUT are low for 30ms, the LTC4308 will automatically break the Input-Output connection. At this time the LTC4308 automatically generates up to 16 clock pulses on SCLOUT in an attempt to free the bus. A connection will resume if the stuck bus is cleared.

During insertion, the SDAOUT and SCLOUT lines are pre-charged to 1V to minimize bus disturbances. When driven high, the ENABLE input allows the LTC4308 to connect after a stop bit or bus idle condition. Driving ENABLE low breaks the connection between SDAIN and SDAOUT, SCLIN and SCLOUT. READY is an open-drain output which indicates that the backplane and card sides are connected.


  • Live Board Insertion
  • Servers
  • Capacitance Buffer/Bus Extender
  • RAID Systems
  • ATCA

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Product Recommendations

LTC4308 Companion Parts

Recommended µModule Isolator

Design Resources

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.

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The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.

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