LTC4307 datasheet(7/16 Pages) LINER

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LTC4317

4317fa

For more information www.linear.com/LTC4317

operaTion

Figure 1. Basic Functions of the LTC4317

4317 F01

VCC1

MASTER

SCLOUT

SDAOUT

SCLIN

SDAIN

VCC2

SLAVE

LTC4317

SLAVE

7-BIT ADDRESS

TRANSLATION

BYTE SHIFT REGISTER

0000010

ENABLE

ADDRESS

TRANSLATION

1.8V

CMP2

–

XOR

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 LTC4317

turns off N2 to disconnect SDAIN from SDAOUT. As the

master sends the address byte, the LTC4317 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 LTC4317 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

masterandslave.Theaddresstranslationprocessrestarts

when the master issues a new START bit.

TheLTC4317isanI2C/SMBusaddresstranslator.Itbridges

two segments of an I2C bus, reading incoming addresses

on the master side and retransmitting them to the slave

side with the 7-bit I2C addresses translated in real time.

This allows multiple I2C 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 LTC4317 allows hot swapping isolated bus segments

together.

Figure 1 shows an I2C master connected to the input bus

of the LTC4317 (SCLIN and SDAIN). The slave devices

requiring address translation are connected to the output

bus of the LTC4317 (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

LTC4317. Two switches (N1 and N2) inside the LTC4317

connect the input bus to the output bus. N1 connects

SCLIN to SCLOUT while N2 connects SDAIN to SDAOUT.

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