Datasheet LTC4317 (Analog Devices) - 7

LTC4317
operaTion
The LTC4317 is an I2C/SMBus address translator. It bridges In most conditions, N1 and N2 stay on so that the input two segments of an I2C bus, reading incoming addresses and output buses are connected. on the master side and retransmitting them to the slave Translation starts when the master issues a START bit side with the 7-bit I2C addresses translated in real time. (SDAIN goes low while SCLIN is high). The LTC4317 This allows multiple I2C devices with the same address turns off N2 to disconnect SDAIN from SDAOUT. As the to be connected to the same bus without interference. master sends the address byte, the LTC4317 translates The translated addresses are configured with external the incoming address at the SDAIN pin to a new address resistors, and no extra software is required. An ENABLE at the SDAOUT pin by XORing each incoming bit with pin allows bus segments to be enabled and disabled, and a user-configurable translation byte, one bit at a time. the LTC4317 allows hot swapping isolated bus segments N3 turns on and off to send out the new address to the together. SDAOUT pin. Once all 7 bits of the address are processed, Figure 1 shows an I2C master connected to the input bus the LTC4317 turns on N2 again to reconnect SDAIN to of the LTC4317 (SCLIN and SDAIN). The slave devices SDAOUT. The master then transmits the R/W bit directly requiring address translation are connected to the output to the slave. If the new, translated address on SDAOUT bus of the LTC4317 (SCLOUT and SDAOUT). Any other matches the slave’s address, the slave pulls SDAOUT low slave devices that do not require address translation are to acknowledge (ACK bit). N2 remains on and the rest of placed together with the master on the input bus of the the data bytes are transmitted unmodified between the LTC4317. Two switches (N1 and N2) inside the LTC4317 master and slave. The address translation process restarts connect the input bus to the output bus. N1 connects when the master issues a new START bit. SCLIN to SCLOUT while N2 connects SDAIN to SDAOUT. VCC1 VCC2 LTC4317 SCLIN N1 SCLOUT SLAVE MASTER #1 SDAIN N2 SDAOUT CMP2 + SLAVE N3 #2 XOR 1.8V – 0 0 0 0 0 1 0 ENABLE 7-BIT ADDRESS ADDRESS TRANSLATION TRANSLATION BYTE SHIFT REGISTER 4317 F01
Figure 1. Basic Functions of the LTC4317
4317fa For more information www.linear.com/LTC4317 7 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Timing Diagram Typical Performance Characteristics Pin Functions Block Diagram Operation Typical Applications Package Description Revision History Typical Application Related Parts