+145°C Precision SMBus-Compatible Remote/

Local Sensors with Overtemperature Alarms

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11

Slave Addresses

The MAX6646/MAX6647/MAX6649 have fixed slave

addresses (see Table 9). All devices also respond to the

SMBus alert response slave address (see the Alert

Response Address section).

POR and UVLO

To prevent ambiguous power-supply conditions from

corrupting the data in memory and causing erratic

the logic blocks begin operating, although reads and

prevents the ADC from converting until there is sufficient

Power-Up Defaults

Power-up defaults include:

• Interrupt latch is cleared.

• ADC begins autoconverting at a 4Hz rate.

• Command byte is set to 00h to facilitate quick local

temperature receive byte queries.

(MAX6649)/+95°C (MAX6646/MAX6647)

• OVERT (internal) limit is set to +85°C

• OVERT (external) limit is set to +85°C (MAX6649)/

+125°C (MAX6646/MAX6647)

DATA

CONVERSION

RATE (Hz)

00h

0.0625

01h

0.125

02h

0.25

03h

0.5

04h

1

05h

2

06h

4

07h

4

08h-FFh

Reserved

Table 8. Conversion-Rate Control Byte

(04h)

BIT

NAME

POR

STATE

FUNCTION

7 (MSB)

BUSY

0

A/D is busy converting when 1.

6

LHIGH

0

Local (internal) high-temperature alarm has tripped when 1; cleared by POR or readout of the

status byte if the fault condition no longer exists.

5

LLOW

0

Local (internal) low-temperature alarm has tripped when 1; cleared by POR or readout of the

status byte if the fault condition no longer exists.

4

RHIGH

0

Remote (external) high-temperature alarm has tripped when 1; cleared by POR or readout of the

status byte if the fault condition no longer exists.

3

RLOW

0

Remote (external) low-temperature alarm has tripped when 1; cleared by POR or readout of the

status byte if the fault condition no longer exists.

2

FAULT

0

A 1 indicates DXN and DXP are either shorted or open; cleared by POR or readout of the status

byte if the fault condition no longer exists.

1

EOT

0

A 1 indicates the remote (external) junction temperature exceeds the external

OVERT threshold.

0

IOT

0

A 1 indicates the local (internal) junction temperature exceeds the internal

OVERT threshold.

Table 7. Status Register Bit Assignments (02h)

PART

SLAVE ADDRESS

MAX6646

1001 101

MAX6647

1001 110

MAX6649

1001 100

Table 9. Slave Addresses