lm73cimkx-1 National Semiconductor Corporation, lm73cimkx-1 Datasheet - Page 9

• Manufacturer Part Number: lm73cimkx-1
• Description: 2.7v, Sot-23, 11-to-14 Bit Digital Temperature Sensor With 2-wire Interface
• Manufacturer: National Semiconductor Corporation

1.0 Functional Description
1.4 SMBus INTERFACE
The LM73 operates as a slave on the SMBus. The SMBDAT
line is bidirectional. The SMBCLK line is is an input only. The
LM73 never drives the SMBCLK line and it does not support
clock stretching.
The LM73 uses a 7-bit slave address. It is available in two
versions. Each version can be configured for one of three
unique slave addresses, for a total of six unique address.
Temperature
Temperature
+0.03125˚C
−0.03125˚C
+0.0625˚C
−0.0625˚C
+150˚C
+150˚C
+25˚C
−25˚C
−40˚C
+25˚C
−25˚C
−40˚C
+1˚C
−1˚C
+1˚C
−1˚C
Part Number
0˚C
0˚C
LM73-0
LM73-1
13-bit (12-bit plus sign)
14-bit (13-bit plus sign)
0000 0000 1000 0000
0000 0000 0000 1000
0000 0000 0000 0000
0000 0000 1000 0000
0000 0000 0000 0100
0000 0000 0000 0000
0100 1011 0000 0000
0000 1100 1000 0000
0100 1011 0000 0000
0000 1100 1000 0000
1110 1100 0000 0000
1110 1100 0000 0000
1111 0011 1000 0000
1111 0011 1000 0000
1111 1111 1000 0000
1111 1111 1000 0000
1111 1111 1111 1000
1111 1111 1111 1100
Address Pin
Ground
Ground
Float
Float
V
V
Binary
Binary
DD
DD
Digital Output
Digital Output
1001 000
1001 001
1001 010
1001 100
1001 101
1001 110
Address
Device
(Continued)
EC00h
FFFCh
EC00h
0C80h
FFF8h
0C80h
4B00h
0080h
0008h
0000h
FF80h
F380h
4B00h
0080h
0004h
0000h
FF80h
F380h
Hex
Hex
9
The SMBDAT output is an open-drain output and does not
have internal pull-ups. A “high” level will not be observed on
this pin until pull-up current is provided by some external
source, typically a pull-up resistor. Choice of resistor value
depends on many system factors but, in general, the pull-up
resistor should be as large as possible without effecting the
SMBus desired data rate. This will minimize any internal
temperature reading errors due to internal heating of the
LM73.
The LM73 features an integrated low-pass filter on both the
SMBCLK and the SMBDAT line. These filters increase com-
munications reliability in noisy environments.
If either the SMBCLK or SMBDAT line is held low for a time
greater than t
for the value of t
to the SMBus idle state, releasing the data line. Once the
SMBDAT is released high, the master may initiate an SMBus
start.
1.5 ALERT FUNCTION
The ALERT output is an over-temperature indicator. At the
end of every temperature conversion, the measured tem-
perature is compared to the value in the T
the measured temperature exceeds the value stored in
T
This over-temperature condition will also cause the ALRT-
_STAT bit in the Control/Status Register to change value
(this bit mirrors the logic level of the ALERT pin).
The ALERT pin and the ALRT_STAT bit are cleared when
any of the following occur:
1. The measured temperature falls below the value stored
2. A "1" is written to the ALERT Reset bit in the Configura-
3. The master resets it through an SMBus Alert Response
If ALERT has been cleared by the master writing a "1" to the
ALERT Reset bit, while the measured temperature still ex-
ceeds the T
the completion of the next temperature conversion.
Each temperature reading is associated with a Temperature
High (THI) and a Temperature Low (TLOW) flag in the
Control/Status Register. A digital comparison determines
whether that reading is above the T
the T
digital comparisons to the T
on an 11-bit temperature comparison. Regardless of the
resolution setting of the LM73, the lower three temperature
LSBs will not affect the state of the ALERT output, THI flag,
and TLOW flag.
HIGH
in the T
tion Register
Address (ARA) procedure
LOW
, the ALERT output goes active (see Figure Figure 1).
setpoint. If so, the corresponding flag is set. All
LOW
HIGH
TIMEOUT
TIMEOUT
Register
setpoint, ALERT will go active again after
(see Logic Electrical Characteristics
), the LM73 state machine will reset
HIGH
, and T
HIGH
LOW
setpoint or below
values are based
HIGH
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Register. If