LTC4309 Level Shifting Low Offset Hot Swappable 2-Wire Bus Buffer with Stuck Bus Recovery FEATURESDESCRIPTION n Bidirectional Buffer Increases Fanout The LTC®4309 hot swappable 2-wire bus buffer allows n 60mV Buffer Offset Independent of Load I/O card insertion into a live backplane without corrup- n Optional Disconnect when Bus is Stuck Low tion of the data and clock busses. The LTC4309 provides n Prevents SDA and SCL Corruption During Live bidirectional buffering, keeping the backplane and card Board Insertion and Removal from Backplane capacitances isolated. Low offset and high VOL tolerance n Level Shift 2.5V, 3.3V and 5V Busses allows cascading of multiple devices on the clock and data n Compatible with Non-Compliant VOL I2C Devices busses. If SDAOUT or SCLOUT are low for 30ms, FAULT n ±6kV Human Body Model ESD Ruggedness will pull low indicating a stuck bus low condition. If DISCEN n Isolates Input SDA and SCL Lines from Output is tied high, the LTC4309 will automatically break the bus n Compatible with I2C™, I2C Fast-Mode and SMBus connection and generate up to 16 clock pulses and a stop n READY Open Drain Output bit in an attempt to free the bus. A connection will resume n FAULT Open Drain Output if the stuck bus is cleared. If DISCEN is connected to GND, n 1V Precharge on All SDA and SCL Lines the busses will remain connected with no clock or stop n Optional Rise Time Accelerators bit generation. ACC input enables rise-time accelerators n High Impedance SDA, SCL Pins for VCC = 0 for high capacitively loaded busses. n Available in Small 12-Pin DFN (4mm x 3mm) and During insertion, the SDA and SCL lines are precharged to 16-Lead SSOP Packages 1V to minimize bus disturbances. When driven high, the ENABLE input allows the LTC4309 to connect after a stop APPLICATIONS bit or bus idle. Driving ENABLE low breaks the connection between SDAIN and SDAOUT, SCLIN and SCLOUT. READY n Live Board Insertion is an open drain output which indicates that the backplane n Servers and card sides are connected. n Capacitance Buffer/Bus Extender n L RAID Systems , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including n ATCA 6356140, 6650174, 7032051. TYPICAL APPLICATION 3.3V Rising Edge from Asserted Low 5V 0.01μF 1000 10k 10k V 0.01 CC μF V V V CC2 CC2 CC 800 EN ENABLE ACC ACC 2.7k 2.7k ENABLE LTC4309 100k LTC4309 10k 10k 600 /DIV LOW OFFSET SDAOUT SCL1 SCLIN SCLOUT SCLIN SCLOUT SCL2 200mV 400 SDA1 SDAIN SDAOUT SDAIN SDAOUT SDA2 3.3V 5V SDAIN 3.3V 5V 200 DISCEN 10k DISCEN 10k 0 10k READY 10k READY 0 100 200 300 400 500 600 100ns/DIV FAULT FAULT FAULT FAULT GND GND 4309 G01 BACKPLANE CARD 4309 TA01 CONNECTOR CONNECTOR 4309fa 1
