MAX1618 Просмотр технического описания (PDF) - Maxim Integrated

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MAX1618

Remote Temperature Sensor with SMBus Serial Interface

Maxim Integrated 

Remote Temperature Sensor

with SMBus Serial Interface

Write Byte Format

S

ADDRESS

WR

7 bits

Slave Address: equiva-

lent to chip-select line of

a 3-wire interface

ACK

COMMAND

ACK

8 bits

Command Byte: selects which

register you are writing to

DATA

ACK

P

8 bits

Data Byte: data goes into the register

set by the command byte (to set

thresholds, configuration masks, and

sampling rate)

Read Byte Format

S ADDRESS WR ACK COMMAND ACK

S ADDRESS RD ACK DATA

A

P

7 bits

8 bits

7 bits

8 bits

Slave Address: equiva-

lent to chip-select line of

a 3-wire interface

Command Byte: selects

which register you are

reading from

Slave Address: repeated

due to change in data-

flow direction

Data Byte: reads from

the register set by the

command byte

Send Byte Format

S ADDRESS WR ACK

DATA

ACK P

7 bits

8 bits

S = Start condition

P = Stop condition

Data Byte: writes data to the

register commanded by the

last Read Byte or Write Byte

transmission

Shaded = Slave transmission

A = Not acknowledged

Figure 2. SMBus Protocols

Receive Byte Format

S ADDRESS WR

7 bits

ACK DATA A

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

+3V TO +5.5V

SMBUS

SERIAL

INTERFACE

(TO HOST)

2N3904

+12V

STBY VCC

MAX1618

SMBCLK

SMBDATA

DXP

DXN

ADD0

ALERT

ADD1

GND

Figure 3. Fan Control Application

and does not go inactive until the temperature drops

below TLOW.

Enable thermostat mode through the configuration reg-

ister (Table 4), with one bit to enable the feature and

another bit to set the output polarity (active high or

active low). The ALERT thermostat comparison is made

after each conversion, or at the end of any SMBus

transaction. For example, if the limit is changed while

the device is in standby mode, the ALERT output

responds correctly according to the last valid A/D

result. Upon entering thermostat mode, the ALERT out-

put is reset so that if the temperature is in the hysteresis

band ALERT initially goes inactive. The power-on reset

(POR) state disables thermostat mode.

Diode Fault Alarm

A continuity fault detector at DXP detects whether the

remote diode has an open-circuit condition, short-cir-

cuit to GND, or short-circuit DXP-to-DXN condition. At

the beginning of each conversion, the diode fault is

checked, and the status byte is updated. This fault

detector is a simple voltage detector; if DXP rises

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