LTC4261IGN datasheet(25/32 Pages) LINER

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LTC4261/LTC4261-2

42612fb

the R/W bit set to one. Any LTC4261/LTC4261-2 that is

pulling its ALERT pin low will acknowledge and begin

sending back its individual slave address.

An arbitration scheme ensures that the LTC4261/

LTC4261-2 with the lowest address will have priority;

all others will abort their response. The successful re-

sponder will then release its ALERT pin while any others

will continue to hold their ALERT pins low. Polling may

also be used to search for any LTC4261/LTC4261-2 that

have detected faults. Any LTC4261/LTC4261-2 pulling its

ALERT pin low will also release it if it is individually ad-

dressed during a read or write transaction.

The ALERT signal will not be pulled low again until the

FAULT register indicates a different fault has occurred or

the original fault is cleared and it occurs again. Note that

this means repeated or continuing faults will not gener-

ate alerts until the associated FAULT register bit has been

cleared.

Single-Wire Broadcast Mode

The LTC4261/LTC4261-2 provides a single-wire broadcast

mode in which selected register data are sent out to the

SDAO pin without clocking the SCL line (Figure 15). The

single-wire broadcast mode is enabled by setting the

ADR1 pin high and the ADR0 pin low (the I2C interface is

disabled). At the end of each conversion of the three ADC

channels, a stream of eighteen bits are broadcasted to

SDAO with a serial data rate of 15.3kHz ±20% in a format

as illustrated in Figure 16. The data bits are encoded with

an internal clock in a way similar to Manchester encoding

that can be easily decoded by a microcontroller or FPGA.

Each data bit consists of a noninverting phase and an

inverting phase. During the conversion of each ADC chan-

nel, SDAO is idle at high. At the end of the conversion, the

SDAO pulls low. The START bit indicates the beginning of

data broadcasting and is used along with the dummy bit

ALERT

RESPONSE

ADDRESS

0 0 0 1 1 0 0

DEVICE

ADDRESS

0 0 1 a3:a0 0 1

42612 F14

A P

Figure 14. LTC4261 Serial Bus SDA Alert Response Protocol

SDAI

SCL

SDAO

ADR1

ADR0

LTC4261

VIN

INTVCC

VEE

× 0.51k IN SERIES

1/4W EACH

–48V RTN

–48V INPUT

0.1

µF

7.5k

42612 F15

VDD

DIN

VCC

GND

ANODE

CATHODE

HCPL-0300

VOUT

MICRO-

CONTROLLER

Figure 14. LTC4261 Serial Bus SDA Alert Response Protocol

Figure 15. Single-Wire Broadcast Mode

INTERNAL

CLK

DATA

SDAO

START

DMY

CH1

CH0

PRTY

4261 F16

ADC9

.. .. .. ADC0

Figure 16. Single-Wire Broadcast Data Format

APPLICATIONS INFORMATION

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