MAX1617 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX1617

Remote/Local Temperature Sensor with SMBus Serial Interface

Maxim Integrated 

MAX1617

Remote/Local Temperature Sensor

with SMBus Serial Interface

the MAX1617 can be forced to perform A/D conversions

via the one-shot command, despite the RUN/STOP bit

being high.

Activate hardware standby mode by forcing the STBY pin

low. In a notebook computer, this line may be connected

to the system SUSTAT# suspend-state signal.

The STBY pin low state overrides any software conversion

command. If a hardware or software standby command is

received while a conversion is in progress, the conversion

cycle is truncated, and the data from that conversion is not

latched into either temperature reading register. The previ-

ous data is not changed and remains available.

Supply-current drain during the 125ms conversion period

is always about 450μA. Slowing down the conversion

rate reduces the average supply current (see Typical

Operating Characteristics). In between conversions, the

instantaneous supply current is about 25μA due to the

current consumed by the conversion rate timer. In stand-

by mode, supply current drops to about 3μA. At very low

supply voltages (under the power-on-reset threshold), the

supply current is higher due to the address pin bias cur-

rents. It can be as high as 100μA, depending on ADD0

and ADD1 settings.

SMBus Digital Interface

From a software perspective, the MAX1617 appears as a

set of byte-wide registers that contain temperature data,

alarm threshold values, or control bits. A standard SMBus

2-wire serial interface is used to read temperature data

and write control bits and alarm threshold data. Each A/D

channel within the device responds to the same SMBus

slave address for normal reads and writes.

The MAX1617 employs four standard SMBus protocols:

Write Byte, Read Byte, Send Byte, and Receive Byte

(Figure 3). The shorter Receive Byte protocol allows

quicker transfers, provided that the correct data regis-

ter was previously selected by a Read Byte instruction.

Use caution with the shorter protocols in multi-master

systems, since a second master could overwrite the com-

mand byte without informing the first master.

The temperature data format is 7 bits plus sign in twos-com-

plement form for each channel, with each data bit represent-

ing 1°C (Table 2), transmitted MSB first. Measurements are

offset by +1/2°C to minimize internal rounding errors; for

example, +99.6°C is reported as +100°C.

Write Byte Format

S

ADDRESS

WR

ACK

COMMAND

ACK

DATA

ACK

P

7 bits

8 bits

8 bits

1

Slave Address: equiva-

lent to chip-select line of

a 3-wire interface

Read Byte Format

Command Byte: selects which

register you are writing to

Data Byte: data goes into the register

set by the command byte (to set

thresholds, configuration masks, and

sampling rate)

S ADDRESS WR ACK COMMAND ACK S ADDRESS RD ACK DATA ///

P

7 bits

8 bits

7 bits

8 bits

Slave Address: equiva-

lent to chip-select line

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

Receive Byte Format

S ADDRESS WR ACK COMMAND ACK P

7 bits

8 bits

Command Byte: sends com-

mand with no data, usually

used for one-shot command

S = Start condition

P = Stop condition

Shaded = Slave transmission

/// = Not acknowledged

S ADDRESS RD ACK DATA ///

P

7 bits

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 3. SMBus Protocols

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