LTC4318
7
4318fa
For more information www.linear.com/LTC4318
The LTC4318 is an I
2
C/SMBus address translator. It bridges
two segments of an I
2
C bus, reading incoming addresses
on the master side and retransmitting them to the slave
side with the 7-bit I
2
C addresses translated in real time.
This allows multiple I
2
C devices with the same address
to be connected to the same bus without interference.
The translated addresses are configured with external
resistors, and no extra software is required. An ENABLE
pin allows bus segments to be enabled and disabled, and
the LTC4318 allows hot swapping isolated bus segments
together.
Figure 1 shows an I
2
C master connected to the input bus
of the LTC4318 (SCLIN and SDAIN). The slave devices
requiring address translation are connected to the output
bus of the LTC4318 (SCLOUT and SDAOUT). Any other
slave devices that do not require address translation are
placed together with the master on the input bus of the
LTC4318. Two switches (N1 and N2) inside the LTC4318
connect the input bus to the output bus. N1 connects
operaTion
SCLIN to SCLOUT while N2 connects SDAIN to SDAOUT.
In most conditions, N1 and N2 stay on so that the input
and output buses are connected.
Translation starts when the master issues a START bit
(SDAIN goes low while SCLIN is high). The LTC4318
turns off N2 to disconnect SDAIN from SDAOUT. As the
master sends the address byte, the LTC4318 translates
the incoming address at the SDAIN pin to a new address
at the SDAOUT pin by XORing each incoming bit with
a user-configurable translation byte, one bit at a time.
N3 turns on and off to send out the new address to the
SDAOUT pin. Once all 7 bits of the address are processed,
the LTC4318 turns on N2 again to reconnect SDAIN to
SDAOUT. The master then transmits the R/W bit directly
to the slave. If the new, translated address on SDAOUT
matches the slave’s address, the slave pulls SDAOUT low
to acknowledge (ACK bit). N2 remains on and the rest of
the data bytes are transmitted unmodified between the
master and slave. The address translation process restarts
when the master issues a new START bit.
Figure 1. Basic Functions of the LTC4318
4318 F01
MASTER
SCLOUT
SDAOUT
SCLIN
SDAIN
SLAVE
#1
LTC4318
SLAVE
#2
7-BIT ADDRESS
TRANSLATION
BYTE SHIFT REGISTER
0000010
ENABLE
ADDRESS
TRANSLATION
N3
1.8V
CMP2
–
+
XOR
N1
N2
