conversion results until they have been read. If the

most significant bits have not been read within an

SMBus timeout period (nominally 37ms), normal updat-

ing continues. Table 1 shows the main temperature

register (high byte) data format, and Table 2 shows the

extended resolution register (low byte) data format.

Diode Fault Detection

If a channel’s input DXP_ and DXN_ are left open or short-

ed together, the MAX6602 detects a diode fault. A diode

fault, whether a short or an open circuit, does not cause

either ALERT or OVERT to assert. A bit in the status regis-

ter for the corresponding channel is set to 1 and the tem-

perature data for the channel is stored as all 1s. It takes

approximately 4ms for the MAX6602 to detect a diode

fault. Once a diode fault is detected, the MAX6602 jumps

onto the next channel in the conversion sequence.

Five-Channel Precision Temperature Monitor

8

_______________________________________________________________________________________

Write Byte Format

Read Byte Format

Send Byte Format

Receive Byte Format

Slave Address: equiva-

lent to chip-select line of

a 3-wire interface

Command Byte: selects to

which register you are writing

Data Byte: data goes into the register

set by the command byte (to set

thresholds, configuration masks, and

sampling rate)

Slave Address: equiva-

lent to chip-select line

Command Byte: selects

from which register you

are reading

Slave Address: repeated

due to change in data-

flow direction

Data Byte: reads from

the register set by the

command byte

Command Byte: sends com-

mand with no data, usually

used for one-shot command

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

S = Start condition

Shaded = Slave transmission

P = Stop condition

/// = Not acknowledged

S

ADDRESS

RD

ACK

DATA

///

P

7 bits

8 bits

WR

S

ACK

COMMAND

ACK

P

8 bits

ADDRESS

7 bits

P

1

ACK

DATA

8 bits

ACK

COMMAND

8 bits

ACK

WR

ADDRESS

7 bits

S

S

ADDRESS

WR

ACK

COMMAND

ACK

S

ADDRESS

7 bits

8 bits

7 bits

RD

ACK

DATA

8 bits

///

P

Figure 2. SMBus Protocols

TEMP (°C)

DIGITAL OUTPUT

> +127

0111 1111

+127

0111 1111

+126

0111 1110

+25

0001 1001

0

0000 0000

< 0

0000 0000

Diode fault (short or open)

1111 1111

Table 1. Main Temperature Register

(High Byte) Data Format

TEMP (°C)

DIGITAL OUTPUT

0

000X XXXX

+0.125

001X XXXX

+0.250

010X XXXX

+0.375

011X XXXX

+0.500

100X XXXX

+0.625

101X XXXX

+0.725

110X XXXX

+0.875

111X XXXX

Table 2. Extended Resolution Temperature

Register (Low Byte) Data Format