Datasheet

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SBOS371A − AUGUST 2006 − REVISED OCTOBER 2007
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6
APPLICATIONS INFORMATION
The TMP401 is a dual-channel digital temperature sensor
that combines a local die temperature measurement
channel and a remote junction temperature measurement
channel in a single MSOP-8 package. The TMP401 is
Two-Wire- and SMBus interface-compatible and is
specified over a temperature range of −40°C to +125°C.
The TMP401 contains multiple registers for holding
configuration information, temperature measurement
results, temperature comparator limits, and status
information.
User-programmed high and low temperature limits stored
in the TMP401 can be used to monitor local and remote
temperatures to trigger an over/under temperature alarm
(ALERT
). Additional thermal limits can be programmed
into the TMP401 and used to trigger another flag (THERM
)
that can be used to initiate a system response to rising
temperatures.
The TMP401 requires only a transistor connected
between D+ and D− for proper remote temperature
sensing operation. The SCL and SDA interface pins
require pull-up resistors as part of the communication bus,
while ALERT
and THERM are open-drain outputs that also
need pull-up resistors. ALERT
and THERM may be shared
with other devices if desired for a wired-OR
implementation. A 0.1µF power-supply bypass capacitor
is recommended for good local bypassing. Figure 11
shows a typical configuration for the TMP401.
0.1
µ
F
10k
Ω
(typ)
10k
Ω
(typ)
10k
Ω
(typ)
10k
Ω
(typ)
TMP401
D+
D
−
V+
1
8
7
6
4
5
3
2
R
S
(2)
R
S
(2)
C
DIFF
(3)
C
DIFF
(3)
R
S
(2)
R
S
(2)
GND
SCL
SDA
ALERT/THERM2
THERM
+5V
SMBus
Controller
Fan Controller
Diode−connected configuration
(1)
:
Series Resistance
Transistor−connected configuration
(1)
:
(1) Diode−connected configuration provides better settling time.
Transistor−connected configuration provides better series resistance
cancellation. 2N3906 PNP.
(2) R
S
should be < 1.5k
Ω
in most applications.
(3) C
DIFF
should be < 1000pF in most applications.
NOTES:
Figure 11. Basic Connections