I2C Buffer translates backplane and card logic levels.
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Press Release Summary:
Housed in 8-pin MSOP and DFN, 3 x 3 mm packages, LTC4301 supply independent, hot-swappable, 2-wire bus buffer allows I/O card insertion into live backplane without corruption of bus data and clock lines. IC provides capacitive isolation between backplane and I2C busses, and SDA and SCL pins withstand 8 kV ESD. When I2C is distributed over a backplane, backplane bus sees only capacitance of buffer ICs, 10 pF each, increasing number of nodes that can be supported.
Original Press Release:
Hot-Swappable I2C Buffer Translates Backplane & Card Logic Levels & Eliminates the Need for Second Bias Supply
MILPITAS, CA - May 6, 2004 - Linear Technology Corporation introduces the LTC4301, a supply independent, hot-swappable 2-wire bus buffer that allows I/O card insertion into a live backplane without corruption of the bus data (SDA) and clock (SCL) lines. The IC provides capacitive isolation between the backplane and the card's I2C busses, even if their respective supplies are at different levels. Without compromising the I2C threshold levels, the supply independent feature eliminates the need to dedicate a connector pin for the backplane supply voltage.
In addition to facilitating live card insertion or removal, the LTC4301's SDA and SCL pins withstand 8kV ESD, thus protecting the card from damage due to handling. The part greatly simplifies the task of using a 2-wire bus to manage a large number of cards with different supply and bus voltage levels in a network server, desktop PC or telecom environment.
When I2C is distributed over a backplane, each individual card contributes to the whole system bus capacitance, making rise and fall time requirements difficult to meet. The LTC4300 family addresses this problem by providing capacitive buffering for I2C busses connected across the backplane. As a result, the backplane bus sees only the capacitance of the buffer ICs, about 10pF each, instead of the entire cards' bus capacitance. This dramatically increases the number of nodes that can be supported in a given system and eliminates most signal integrity problems.
During insertion, the LTC4301 pre-charges the SDA and SCL lines to 1V to minimize bus disturbance. Control circuitry prevents the backplane from being connected to the card until a stop bit or a bus idle is present. The READY output pin indicates that the backplane and card sides are connected together.
The LTC4301 is offered in commercial and industrial temperature ranges. Pricing begins at $1.95 each for 1,000-piece quantities.
Summary of Features: LTC4301
Allows Bus Pull-Up Voltages Above or Below Vcc
Bi-directional Buffer for SDA and SCL Lines Increases Fanout
Prevents SDA & SCL Corruption during Live Board Insertion & Removal from Backplane
Isolates SDA & SCL Line from Output
Compatible with I2C, I2C Fast Mode & SMBus Standards (Up to 400kHz Operation)
1V Precharge on All SDA & SCL Lines
8kV Human Body Model ESD Protection
Small 8-Pin MSOP & DFN (3mm x 3mm) Packages
Company Background
Linear Technology Corporation was founded in 1981 as a manufacturer of high performance linear integrated circuits. Linear Technology products include operational, instrumentation and audio amplifiers; voltage regulators,power management devices, DC-DC converters and voltage references; comparators; monolithic filters; communications interface circuits; one-chip data acquisition sub-systems; pulse-width modulators and sample-and-hold devices; and high frequencydevices. Applications for Linear Technology's high performance circuits include wireless and broadband telecommunications infrastructure, cellular telephones, networking products and satellite systems, notebook and desk top computers, computer peripherals, video/multimedia, industrial and medical instrumentation, automotive electronics, factory automation, process control, military and space systems, and high-end consumer products including digital cameras, MP3 players and other electronic products.
Note: LT, AND LTC are registered trademarks of Linear Technology Corp.
