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PDF LM82 Data sheet ( Hoja de datos )
| Número de pieza | LM82 | |
| Descripción | Remote Diode and Local Digital Temperature Sensor with Two-Wire Interface | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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January 2000
LM82
Remote Diode and Local Digital Temperature Sensor
with Two-Wire Interface
General Description
The LM82 is a digital temperature sensor with a 2 wire serial
interface that senses the voltage and thus the temperature of
a remote diode using a Delta-Sigma analog-to-digital con-
verter with a digital over-temperature detector. The LM82 ac-
curately senses its own temperature as well as the tempera-
ture of external devices, such as Pentium II® Processors or
diode connected 2N3904s. The temperature of any ASIC
can be detected using the LM82 as long as a dedicated di-
ode (semiconductor junction) is available on the die. Using
the SMBus interface a host can access the LM82’s registers
at any time. Activation of a T_CRIT_A output occurs when
any temperature is greater than a programmable comparator
limit, T_CRIT. Activation of an INT output occurs when any
temperature is greater than its corresponding programmable
comparator HIGH limit.
The host can program as well as read back the state of the
T_CRIT register and the 2 T_HIGH registers. Three state
logic inputs allow two pins (ADD0, ADD1) to select up to 9
SMBus address locations for the LM82. The sensor powers
up with default thresholds of 127˚C for T_CRIT and all
T_HIGHs. The LM82 is pin for pin and register compatible
with the LM84, Maxim MAX1617 and Analog Devices
ADM1021.
Features
n Accurately senses die temperature of remote ICs, or
diode junctions
n On-board local temperature sensing
n SMBus and I2C compatible interface, supports
SMBus 1.1 TIMEOUT
n Two interrupt outputs: INT and T_CRIT_A
n Register readback capability
n 7 bit plus sign temperature data format, 1 ˚C resolution
n 2 address select pins allow connection of 9 LM82s on a
single bus
Key Specifications
j Supply Voltage
3.0V to 3.6V
j Supply Current
0.8mA (max)
j Local Temp Accuracy (includes quantization error)
0˚C to +85˚C ±3.0˚C (max)
j Remote Diode Temp Accuracy (includes quantization
error)
+25˚C to +100˚C
±3˚C (max)
0˚C to +125˚C
±4˚C (max)
Applications
n System Thermal Management
n Computers
n Electronic Test Equipment
n Office Electronics
n HVAC
Simplified Block Diagram
SMBus™ is a trademark of the Intel Corporation.
Pentium II® is a registered trademark of the Intel Corporation.
I2C® is a registered trademark of the Philips Corporation.
© 2000 National Semiconductor Corporation DS101297
DS101297-1
www.national.com
1 page  
Logic Electrical Characteristics
DIGITAL DC CHARACTERISTICS
Unless otherwise noted, these specifications apply for VCC=+3.0 to 3.6 Vdc. Boldface limits apply for TA = TJ = TMIN to
TMAX; all other limits TA= TJ=+25˚C, unless otherwise noted.
Symbol
Parameter
Conditions
Typical
Limits
Units
(Note 6)
(Note 7)
(Limit)
SMBData, SMBCLK
VIN(1)
VIN(0)
VIN(HYST)
Logical “1” Input Voltage
Logical “0”Input Voltage
SMBData and SMBCLK Digital
Input Hysteresis
2.1 V (min)
0.8 V (max)
300 mV
IIN(1)
IIN(0)
ADD0, ADD1
Logical “1” Input Current
Logical “0” Input Current
VIN = VCC
VIN = 0 V
0.005
−0.005
1.5 µA (max)
1.5 µA (max)
VIN(1)
Logical “1” Input Voltage
VIN(0)
Logical “0”Input Voltage
IIN(1)
Logical “1” Input Current
IIN(0)
Logical “0” Input Current
ALL DIGITAL INPUTS
VIN = VCC
VIN = 0 V
VCC
GND
1.5 V (min)
0.6 V (max)
2 µA (max)
-2 µA (max)
CIN Input Capacitance
ALL DIGITAL OUTPUTS
20 pF
IOH
High Level Output Current
VOH = VCC
VOL
SMBus Low Level Output
IOL = 3 mA
Voltage
IOL = 6 mA
100 µA (max)
0.4 V (max)
0.6
5 www.national.com
5 Page 
1.0 Functional Description (Continued)
1.9 COMMUNICATING with the LM82
There are 13 data registers in the LM82, selected by the
Command Register. At power-up the Command Register is
set to “00”, the location for the Read Local Temperature Reg-
ister. The Command Register latches the last location it was
set to. Reading the Status Register resets T_CRIT_A and
INT, so long as a temperature comparison does not signal a
fault (see Sections 1.2 and 1.3). All other registers are pre-
defined as read only or write only. Read and write registers
with the same function contain mirrored data.
A Write to the LM82 will always include the address byte and
the command byte. A write to any register requires one data
byte.
Reading the LM82 can take place either of two ways:
1. If the location latched in the Command Register is cor-
rect (most of the time it is expected that the Command
Register will point to one of the Read Temperature Reg-
isters because that will be the data most frequently read
from the LM82), then the read can simply consist of an
address byte, followed by retrieving the data byte.
2. If the Command Register needs to be set, then an ad-
dress byte, command byte, repeat start, and another ad-
dress byte will accomplish a read.
The data byte has the most significant bit first. At the end of
a read, the LM82 can accept either Acknowledge or No Ac-
knowledge from the Master (No Acknowledge is typically
used as a signal for the slave that the Master has read its
last byte).
DS101297-9
1.10 SERIAL INTERFACE ERROR RECOVERY
The LM82 SMBus lines will be reset to the SMBus idle state
if the SMBData or SMBCLK lines are held low for 40 ms or
more (tTIMEOUT). The LM82 may or may not reset the state of
the serial interface logic if either of the SMBData or SMBCLK
lines are held low between 25 ms and 40 ms. TIMEOUT al-
lows a clean recovery in cases where the master may be re-
set while the LM82 is transmitting a low bit thus preventing
possible bus lock up.
Whenever the LM82 sees the start condition its serial inter-
face will reset to the beginning of the communication, thus
the LM82 will expect to see an address byte next. This sim-
plifies recovery when the master is reset while the LM82 is
transmitting a high.
11 www.national.com
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet LM82.PDF ] | |
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