Milpitas, Calif. " Count on an analog supplier to come up with those special-purpose interface functions that everyone needs, buty few know how to articulate " let alone productize. The LTC4302-1/LTC4302-2, from Linear Technology Corp., are addressable I2C and SMBus compatible bus buffers. They provide capacitive buffering, rise time acceleration - and facilitate input-to-output connection control using 2-wire bus commands.
The LTC4302 maintains electrical isolation between the backplane and peripheral board until the Vcc supplies are valid and the IC receives the 2-wire bus signal that tells it to initiate a connection. One of 32 possible I2C addresses can be selected using a single external resistive divider connected to the ADDRESS pin. The ICs work with supply voltages ranging from 2.7V to 5.5V. While it fits in laptop computers, the LTC4302 is ideal for big card cages - network servers, embedded control or telecom equipment " because its simplified 2-wire bus can be used to manage a large number of cards without proliferating control lines.
When I2C is distributed over a backplane, each individual card contributes to the whole system bus capacitance, making rise and fall time requirements sometimes difficult to meet. The LTC4302 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 LTC4302s, about 10pF each, instead of seeing 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.
The LTC4302-1 features two general-purpose input/output (GPIO) pins that can be configured as inputs, open-drain outputs, or push-pull outputs. The LTC4302-2 option replaces one GPIO pin with a second supply voltage pin, providing level shifting between different supply voltages.
The LTC4302-1 and LTC4302-2 are available in a 10-pin MSOP and specified over the commercial and industrial temperature ranges. Pricing starts at $2.50 each for 1,000 piece quantities.
Summary of Features: LTC4302
- Compatible with I2 C Standard Mode, I2 C Fast Mode and SMBus Standards
- Bi-Directional Buffer for SDA and SCL Lines Increases Fanout
- Prevents SDA and SCL Corruption During Live Card Insertion and Removal from Backplane
- Connect SDA and SCL Lines with 2-Wire Bus Commands
- Rise Time Accelerators on SDA and SCL Lines
- 1V Pre-Charge on all SDA and SCL Lines
- 32 Unique Addresses from a Single ADDRESS Pin
- Two General Purpose I/Os (LTC4302-1)
- Translates Between 5V and 3.3V Systems (LTC4302-2)
- Small 10-Pin MSOP Package
Call toll-free 1-800-4-LINEAR (for literature only), or go to the company's web site: www.linear.com
For the LTC4302 datasheet, click here.