5

LTC1710

BLOCK DIAGRA

OUT1

7

1

2

SW0D

OUT0

4

GND

1710 BD

UNDERVOLTAGE

LOCKOUT

POWER-ON

RESET

2V

ACK

A

B

OUTPUT

LATCHES

SHIFT

REGISTER

ADDRESS

DECODER

COUNTER

INPUT

BUFFERS

THERMAL

SHUTDOWN

REGULATED

CHARGE

PUMPS

ADDRESS

COMPARATOR

LOGIC

START

AND

STOP

DETECTORS

3

AD1

5

CLK

6

8

DATA

TI I G DIAGRA

CLK

DATA

START

STOP

1710 TD

OPERATIO

SMBus Operation

SMBus is a serial bus interface that uses only two bus lines,

DATA and CLK, to control low power peripheral devices in

portable equipment. It consists of masters, also known as

hosts, and slave devices. The master of the SMBus is

always the one to initiate communications to the slave

devices by varying the status of the DATA and CLK lines.

The SMBus specification establishes a set of protocols that

devices on the bus must follow for communications.

The protocol that the LTC1710 uses is the Send Byte Pro-

tocol. In this protocol, the master first sends out a Start

signal by switching the DATA line from high to low while

CLK is high. (Because there may be more than one master

on the same bus, an arbitration process takes place if two

masters attempt to take control of the DATA line simulta-

neously; the first master that outputs a one while the other

master is zero loses the arbitration and becomes a slave

itself.) Upon detecting this Start signal, all slave devices on

the bus wake up and prepare to shift in the next byte of data.