LTC4308CDD#PBF

Signal Buffers, Repeaters, Splitters Overview

The LTC4308CDD#PBF is a low voltage, level shifting hot swappable 2-wire bus buffer with stuck bus recovery. It supports I2C and SMBus protocols with a maximum operating frequency of 600 kHz. The device operates on a supply voltage (VCC) ranging from 2.3 V to 5.5 V, drawing a typical supply current of 7 mA. It features bidirectional buffering with a propagation delay of 70 ns for high-to-low transitions. The input capacitance is 10 pF. The component is housed in an 8-lead DFN package measuring 3mm x 3mm x 0.75mm and is rated for an operating temperature range of 0°C to +70°C.

Signal Buffers, Repeaters, Splitters Feature Summary

• Provides bidirectional buffering while isolating backplane and card capacitances during live board insertion.
• Automatically detects stuck bus conditions lasting longer than 30ms and attempts recovery by generating clock pulses and stop bits.
• Features rise time accelerators on output lines to improve signal integrity on heavily loaded buses.
• Includes precharge circuitry that forces SDAOUT and SCLOUT to 1V during insertion to minimize bus disturbances.

Signal Buffers, Repeaters, Splitters Applications

• Servers
• RAID Systems
• ATCA
• Capacitance Buffer/Bus Extender

Signal Buffers, Repeaters, Splitters Procurement Notes

Verify the specific ordering suffix #PBF indicates lead-free finish and RoHS compliance when sourcing this component. Confirm the package type matches the required PCB footprint, as other variants like MSOP exist. Ensure the temperature grade corresponds to the application environment, as the C suffix denotes commercial range. Cross-reference the manufacturer part number directly with official documentation to avoid counterfeit components.

Signal Buffers, Repeaters, Splitters Selection Notes

Select the LTC4308CDD#PBF for applications requiring hot swapping capabilities on low voltage I2C or SMBus networks. This part is suitable where bus capacitance isolation is critical to maintain signal rise times. Consider the negative offset voltage feature if interfacing between devices with different logic low voltage tolerances. Ensure the system pull-up resistors are calculated to meet the slew rate requirements for the rise time accelerators to function correctly.

Signal Buffers, Repeaters, Splitters Part Context

This component belongs to the LTC4308 family of hot swappable bus buffers manufactured by Analog Devices. It is designed to protect sensitive bus lines during the insertion and removal of I/O cards into live backplanes. The device addresses challenges related to bus corruption and capacitance loading in mixed voltage environments.

Signal Buffers, Repeaters, Splitters Replacement Considerations

The LTC4301L is a functional predecessor but lacks automatic stuck bus recovery and rise time accelerators. When replacing an LTC4301L with the LTC4308, the control signal polarity must be inverted as the ENABLE pin is active high compared to the CS pin on the older model. Verify voltage compatibility as the LTC4308 supports lower minimum supply voltages.

Signal Buffers, Repeaters, Splitters FAQ

How does the LTC4308 handle a stuck bus condition?

If SDAOUT or SCLOUT remains low for 30ms, the device automatically breaks the connection and generates up to 16 clock pulses followed by a stop bit to attempt to free the bus.

What is the purpose of the precharge voltage on SDAOUT and SCLOUT?

During insertion, the pins are precharged to 1V to minimize the voltage differential with the backplane, thereby reducing electrical disturbances and potential data corruption.

Can the LTC4308 perform level shifting between different voltage domains?

Yes, it allows communication between output bus devices with high VOL and low voltage input side devices, supporting bus supplies as low as 0.9V on the input side.