autonomous mode (RUN/STOP = 0). This variable rate

control can be used to reduce the supply current in

portable-equipment applications. The conversion rate

byte’s POR state is 02h (0.25Hz). The MAX6680/

MAX6681 use only the 3LSBs of this register. The

5MSBs are “don’t care” and should be set to zero when

possible. The conversion rate tolerance is ±25% at any

rate setting.

Valid A/D conversion results for both channels are avail-

able one total conversion time (125ms nominal, 156ms

maximum) after initiating a conversion, whether conver-

sion is initiated through the RUN/STOP bit, hardware

STBY pin, One-Shot command, or initial power-up.

Slave Addresses

The MAX6680/MAX6681 device address can be initially

set to nine different values by pin strapping ADD0 and

ADD1 so that more than one MAX6680/MAX6681 can

±1°C Fail-Safe Remote/Local Temperature

Sensors with SMBus Interface

14

______________________________________________________________________________________

BIT

NAME

POR STATE

FUNCTION

7 (MSB)

ALERT MASK

0

Mask

ALERT active state when 1. When 1, ALERT does not respond to

any fault related to the four limit registers.

6

RUN/STOP

0

Standby mode control bit; if 1, immediately stops converting and enters

standby mode. If zero, it converts in either one-shot or timer mode.

5

SPNP

1

When 1, the remote sensor is a common-collector substrate PNP. When

zero, the remote sensor is a diode-connected transistor.

4

Extended Resolution

0

When zero, remote- and local-sensors’ temperature data are 7 bits +

sign with 1°C resolution. When 1, the remote-sensor temperature data is

10 bits + sign with 0.125°C resolution.

3

Extended Range

0

Extended temperature range. 0 = normal, 1 = extended to -64°C.

2

SMBus Timeout

0

When set to 1, it disables the SMBus timeout, as well as the alert

response.

1

Software Reset

0

Software reset from SMBus from customer.

0

RFU

0

Reserved

Table 6. Configuration-Byte Bit Assignment

BIT

NAME

POR

STATE

FUNCTION

7 (MSB)

BUSY

0

When 1, the A/D is busy converting.

6

LHIGH

0

When 1, internal high-temperature alarm has tripped; cleared by POR or readout

of the Status register, if the fault condition no longer exists.

5

LLOW

0

When 1, internal low-temperature alarm has tripped; cleared by POR or readout of

the Status register, if the fault condition no longer exists.

4

RHIGH

0

When 1, external high-temperature alarm has tripped; cleared by POR or readout

of the Status register, if the fault condition no longer exists.

3

RLOW

0

When 1, external low-temperature alarm has tripped; cleared by POR or readout of

the Status register if the fault condition no longer exists.

2

OPEN

0

When 1 indicates an external diode open; cleared by POR or readout of the Status

register, if the fault condition no longer exists.

1

OVI

0

When 1, internal temperature exceeds the RWOI limit.

0

OVE

0

When 1, external temperature exceeds the RWOE limit.

Table 7. Status Register Bit Assignments