MAX6658 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX6658

±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms

Maxim Integrated 

±1°C, SMBus-Compatible Remote/Local Temperature

Sensors with Overtemperature Alarms

ture registers are not updated. The previous data is not

changed and remains available.

SMBus Digital Interface

From a software perspective, each of the MAX6657/

MAX6658/MAX6659 appears as a series of 8-bit regis-

ters that contain temperature data, alarm threshold

values, and control bits. A standard SMBus-compatible

2-wire serial interface is used to read Temperature Data

and Write Control bits and alarm threshold data. The

device responds to the same SMBus slave address for

access to all functions.

The MAX6657/MAX6658/MAX6659 employ four stan-

dard SMBus protocols: Write Byte, Read Byte, Send

Byte, and Receive Byte (Figures 2, 3, and 4). The short-

er Receive Byte protocol allows quicker transfers, pro-

vided that the correct data register was previously

selected by a Read Byte instruction. Use caution with

the shorter protocols in multimaster systems, since a

second master could overwrite the command byte with-

out informing the first master.

When the conversion rate is greater than 4Hz, temperature

data can be read from the Read Internal Temperature

(00h) and Read External Temperature (01h) registers.

The temperature data format is 7 bits + sign in two's-

complement form for each channel, with the LSB repre-

senting 1°C (Table 2). The MSB is transmitted first.

When the conversion rate is 4Hz or less, the first 8 bits

of temperature data can be read from the Read Internal

Temperature (00h) and Read External Temperature

(01h) registers, the same as for faster conversion rates.

An additional 3 bits can be read from the Read External

Extended Temperature (10h) and Read Internal

Extended Temperature (11h) registers, which extends

the data to 10 bits + sign and the resolution to

+0.125°C per LSB (Table 3).

When a conversion is complete, the Main register and

the Extended register are updated almost simultane-

ously. Ensure that no conversions are completed

between reading the Main and Extended registers so

that when data that is read, both registers contain the

result of the same conversion.

To ensure valid extended data, read extended resolu-

tion temperature data using one of the following

approaches:

1) Put the MAX6657/MAX6658/MAX6659 into standby

mode by setting bit 6 of the Configuration register to

Write Byte Format

S

ADDRESS

WR

7 bits

Slave Address: equiva-

lent to chip-select line of

a 3-wire interface

Read Byte Format

ADDRESS WR

ACK

ACK

COMMAND

ACK

8 bits

Command Byte: selects which

register you are writing to

COMMAND ACK S ADDRESS

DATA

ACK

P

8 bits

1

Data Byte: data goes into the register

set by the command byte (to set

thresholds, configuration masks, and

sampling rate)

RD ACK DATA

///

P

7 bits

Slave Address: equiva-

lent to chip-select line

8 bits

Command Byte: selects

which register you are

reading from

7 bits

Slave Address: repeated

due to change in data-

flow direction

8 bits

Data Byte: reads from

the register set by the

command byte

Send Byte Format

ADDRESS WR

7 bits

ACK COMMAND ACK P

8 bits

Command Byte: sends com-

mand with no data, usually

used for one-shot command

S = Start condition Shaded = Slave transmission

P = Stop condition /// = Not acknowledged

Receive Byte Format

S ADDRESS RD

7 bits

ACK DATA ///

P

8 bits

Data Byte: reads data from

the register commanded

by the last Read Byte or

Write Byte transmission;

also used for SMBus Alert

Response return address

Figure 2. SMBus Protocols

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