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Amplifiers/Converters??

Bus buffers provide high noise margins, stuck bus recovery

Posted: 26 Oct 2011 ?? ?Print Version ?Bookmark and Share

Keywords:bus buffers? I<sup>2</sup>C? noise margin?

Linear Technology Corp. has rolled its newest hot swap I2C bus buffers, the LTC4313 and LTC4315. These high noise margin buffers can provide extension capabilities and capacitance buffering to I2C/SMBus/PMBus systems. Due to the many possible devices on an I2C bus, rise times are significantly affected by additive capacitances. Linear Technology's LTC4313 and LTC4315 help solve this problem by offering the additional advantage of its high-logic, low-noise margin and by segmenting the bus, a feature with a guaranteed minimum VIL of 0.3VCC.

This allows the LTC4313 and LTC4315 to operate with noncompliant I2C devices that drive a high logic low output voltage. This also permits a number of LTC4313s or LTC4315s to be connected in series, and improves the reliability of I2C communications in large noisy systems.

The devices are well suited for a variety of computing, networking and data storage systems that use multiple I/O cards with different supply and bus voltage levels. They provide automatic level translation from low voltage systems down to 1.4V to higher voltage systems up to 5.5V. The LTC4315 has a second supply pin, allowing use of separate input and output bus pull-up supplies. Rise time accelerators provide pull-up currents during bus rising edges that reduce rise times, ultimately resulting in reduced power consumption, improved logic low noise margins and the ability to design with higher bus capacitances beyond I2C limitations. The LTC4313 provides strong, slew-limited switch (LTC4313-1) or 2mA current source (LTC4313-2) rise time accelerator current, while the LTC4315 provides pin-selectable (strong slew-limited switch, 2mA or off) rise time accelerator current. Safety measures include a stuck bus disconnect and recovery feature to disengage the input from all enabled output channels and to issue clocks to try to get the stuck slave to release the data line, a fault output to signal the host a bus is stuck low (LTC4315 only), and 4kV HBM ESD protection for increased ruggedness.

The LTC4313 and LTC4315 are available today in commercial and industrial temperature grades. The LTC4313 is available in an 8-pin 3 3mm DFN or 8-lead MSOP package, and the LTC4315 is available in a 12-pin 4 3mm DFN or 12-lead MSOP package. All packages are RoHS compliant. The devices are priced starting at $2.40 each in 1,000-piece quantities and are available today in production quantities.





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