LTC4280CUFD datasheet(20/28 Pages) LINER

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LTC4280

4280f

APPLICATIONS INFORMATION

SCL

SDA

START

CONDITION

STOP

CONDITION

ADDRESS

R/W

ACK

DATA

ACK

DATA

ACK

1 - 7

4280 F06

a6 - a0

b7 - b0

1 - 7

Figure 6. Data Transfer Over I2C or SMBus

Digital Interface

The LTC4280 communicates with a bus master using a

2-wire interface compatible with I2C Bus and SMBus, an

I2C extension for low power devices.

The LTC4280 is a read-write slave device and supports

SMBus bus Read Byte, Write Byte, Read Word and Write

Word commands. The second word in a Read Word

command is identical to the ﬁrst word. The second word

in a Write Word command is ignored. Data formats for

these commands are shown in Figures 6 to 11.

START and STOP Conditions

When the bus is idle, both SCL and SDA are high. A bus

master signals the beginning of a transmission with a start

condition by transitioning SDA from high to low while SCL

is high, as shown in Figure 6. When the master has ﬁnished

communicating with the slave, it issues a STOP condition

by transitioning SDA from low to high while SCL is high.

The bus is then free for another transmission.

I2C Device Addressing

Twenty-seven distinct bus addresses are available using

three 3-state address pins, ADR0-ADR2. Table 1 shows

the correspondence between pin states and addresses.

Note that address bits B7 and B6 are internally conﬁgured

to 10. In addition, the LTC4280 responds to two special

addresses. Address (1011 111) is a mass write address

that writes to all LTC4280s, regardless of their individual

address settings. Mass write can be disabled by setting

Response Address. If the LTC4280 is pulling low on the

ALERT pin, it acknowledges this address by broadcasting

its address and releasing the ALERT pin.

Acknowledge

The acknowledge signal is used in handshaking between

transmitter and receiver to indicate that the last byte of

data was received. The transmitter always releases the

SDA line during the acknowledge clock pulse. When the

slave is the receiver, it pulls down the SDA line so that it

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