Rainbow Electronics MAX6681 - Manual (Page 6)

MAX6680/MAX6681
Detailed Description
The MAX6680/MAX6681 are temperature sensors designed
to work in conjunction with a microprocessor or other
intelligence in thermostatic, process-control, or monitoring
applications. Communication with the MAX6680/MAX6681
occurs through the SMBus serial interface and dedicated
alert pin. The overtemperature alarm OVERT is asserted if
the software or hardware programmed temperature thresh-
olds are exceeded. OVERT can be connected to a fan,
system shutdown, or other thermal management circuitry.
The MAX6680/MAX6681 convert temperatures at a pro-
grammed rate or a single conversion. Legacy mode
conversions have a 1°C resolution. Legacy resolution
represents temperature as 7 bits + sign bit and allows
for faster autonomous conversion rates at 8Hz. The
remote diode temperature can also be represented in
extended-resolution mode. Extended resolution repre-
sents temperature as 10 bits + sign bit and is available
for autonomous conversions that are 4Hz or slower and
single-shot conversions.
The MAX6680/MAX66681 default low-temperature mea-
surement limit is 0 °C. The device temperature measure-
ment can be placed in extended temperature range by
setting bit 3 of the Configuration register to 1. In extend-
ed temperature range, the remote and local temperature
measurement range is extended down to -64°C.
ADC and Multiplexer
The averaging ADC integrates over a 60ms period
(each channel, typically, in the 7-bit + sign “legacy”
mode). Using an averaging ADC attains excellent noise
rejection.
The multiplexer automatically steers bias currents
through the remote and local diodes. The ADC and
associated circuitry measure each diode’s forward volt-
±1°C Fail-Safe Remote/Local Temperature
Sensors with SMBus Interface
6 _______________________________________________________________________________________
RESET
CIRCUITRY
MUX
REMOTE
LOCAL
ADC
2
CONTROL
LOGIC
SMBus
READ
WRITE
8
8
ADDRESS
DECODER
7
S
R
Q
DIODE
FAULT
DXP
DXN
ADD0
SMBCLK
SMBDATA
ADD1
REGISTER BANK
COMMAND BYTE
REMOTE TEMPERATURE
LOCAL TEMPERATURE
ALERT THRESHOLD
ALERT RESPONSE ADDRESS
OVERT THRESHOLD (EXT)
OVERT THRESHOLD (INT)
CRIT0
CRIT1
INT_SEL
STBY
RESET V CC
S
R
Q
OVERT
ALERT
SENS_SEL
MAX6680
MAX6681
Figure 1. MAX6680/MAX6681 Functional Diagram