LTC4331 datasheet(16/26 Pages) AD

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LTC4331

Rev 0

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APPLICATIONS INFORMATION

BydefaultthelocaladdressableslavedeviceintheLTC4331

recognizes the Alert Response Address (ARA) and par-

ticipates in the Alert Response protocol. If an EVENT is

triggered and its corresponding ALERT_EN bit is set high,

ALERT is driven low. If the master transmits the Alert Re-

sponse protocol and the LTC4331’s internal slave address

is the lowest numerically, then the LTC4331 releases its

local alert output. Note that local ALERT could continue

to be low due to a low value from a remote ALERT pin.

The remote ALERT function in the LTC4331 is not directly

affected by an Alert Response transaction. The signal on

the remote ALERT pin is always propagated to the local

side if connected. If using SMBus slave devices on both

sides of the link that respond to the ARA, the remote

slaves must have higher priority device addresses than

the devices on the local side, see section Considerations.

The LTC4331’s internal slave device can be programmed

to ignore the ARA and switch the function of pin ALERT

from SMBALERT to interrupt mode. To switch to interrupt

mode set INTR_MODE in the CONFIG register to 1. To

clear the interrupt set the triggered event or the corre-

sponding event enable bit to 0. This method is also valid

in SMBALERT mode in lieu of the ARA protocol.

Control

Through the CTRL pin, the LTC4331 provides an addi-

tional signal to control a remote device’s input pin. When

in remote mode, the CTRL pin is an output and reflects

the value either on the local side CTRL pin or the value

programmed into the bit field SW_CTRL. A separate bit

field CTRL_SEL selects pin or register control. By default

the value on local CTRL pin is used. Local CTRL values

transfer to the remote side CTRL only when the commu-

nication link is established and pin LINK is low.

At startup the CTRL output driver is disabled and a weak

internal pull-up prevents the pin from floating. The CTRL

pin’soutputdriverenablesonlywhenlinkcommunicationis

established.Thereafter,theremoteCTRLpin’soutputdriver

is always enabled except after a remote reset event where

it is disabled until link communication is reestablished.

I2C Address Translation

The address translation feature allows the use of multiple

I2C slave devices with fixed or limited device address

rangesonthesamenetwork.TheLTC4331I2Cslavedevice

automatically translates the incoming address using an

XOR function against the internal register ADDR_TRANS.

Address translation is enabled by setting this register to

a non-zero value. ADDR_TRANS must be programmed

before any accesses to the remote slave if that slave

requires address translation or there will be a collision.

See Figure12.

Timeouts

The LTC4331 respects SMBus SMBCLK low timeouts on

the SCL pin. When in local mode and SCL is held low for a

minimum of tTIMEOUT:SLAVE:MAX, the I2C Interface is reset

and SCL and SDA are released if held low. On the remote

ADDR = 0x10

µP

SCL

SDA

LTC4331

ADDR = 0x16

DEVICE

ADDR_TRANS

LTC4331

ADDR = 0x16

DEVICE

SCL

SDA

ACK

SCL

SDA

NACK

INCOMING

ADDR

OUTGOING

ADDR

REMOTE

REMOTE SLAVE

LOCAL SLAVE

4331 F12

Figure12. Address 0x10 Is Translated to 0x16 for the Remote Device

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