TI LM83 Triple-diode input and local digital temperature sensor with two-wire interface Datasheet

LM83
LM83 Triple-Diode Input and Local Digital Temperature Sensor with Two-Wire
Interface
Literature Number: SNIS111A
LM83
Triple-Diode Input and Local Digital Temperature Sensor
with Two-Wire Interface
General Description
The LM83 is a digital temperature sensor with a 2 wire serial
interface that senses the voltage and thus the temperature of
three remote diodes using a Delta-Sigma analog-to-digital
converter with a digital over-temperature detector. The LM83
accurately senses its own temperature as well as the temperature of three external devices, such as Pentium II ® Processors or diode connected 2N3904s. The temperature of
any ASIC can be detected using the LM83 as long as a dedicated diode (semiconductor junction) is available on the die.
Using the SMBus interface a host can access the LM83’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 four T_HIGH registers. Three state
logic inputs allow two pins (ADD0, ADD1) to select up to 9
SMBus address locations for the LM83. The sensor powers
up with default thresholds of 127˚C for T_CRIT and all
T_HIGHs. The LM83 is pin for pin and register compatible
with the LM84 as well as the Maxim MAX1617 and the Analog Devices ADM1021.
Features
n Accurately senses die temperature of 3 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 LM83s 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)
± 3˚C (max)
± 4˚C (max)
+25˚C to +100˚C
0˚C to +125˚C
Applications
n
n
n
n
n
System Thermal Management
Computers
Electronic Test Equipment
Office Electronics
HVAC
Simplified Block Diagram
DS101058-1
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
DS101058
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LM83 Triple-Diode Input and Local Digital Temperature Sensor with Two-Wire Interface
November 1999
LM83
Connection Diagram
Ordering Information
QSOP-16
Order
Number
NS
Package
Number
Transport
Media
LM83CIMQA
MQA16A
(QSOP-16)
95 Units in
Rail
LM83CIMQAX
MQA16A
(QSOP-16)
2500 Units on
Tape and
Reel
DS101058-2
TOP VIEW
Typical Application
DS101058-3
Pin Description
Label
Pin #
D1+, D2+, D3+
1, 3, 5
VCC
2
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Function
Typical Connection
Diode Current Source
To Diode Anode. Connected to remote discrete
diode junction or to the diode junction on a remote
IC whose die temperature is being sensed. When
not used they should be left floating.
Positive Supply Voltage
Input
DC Voltage from 3.0 V to 3.6 V
2
Label
LM83
Pin Description
(Continued)
Pin #
Function
Typical Connection
D−
4
Diode Return Current
Sink
To all Diode Junction Cathodes using a star
connection to pin. Must float when not used.
ADD0–ADD1
10, 6
User-Set SMBus (I2C)
Address Inputs
Ground (Low, “0”), VCC (High, “1”) or open
(“TRI-LEVEL”)
GND
7, 8
Power Supply Ground
Ground
Manufacturing test pins.
Left floating. PC board traces may be routed
through the pads for these pins, although the
components that drive these traces should share
the same supply as the LM83 so that the Absolute
Maximum Rating, Voltage at Any Pin, is not
violated.
NC
9, 13, 15
INT
11
Interrupt Output,
open-drain
Pull Up Resistor, Controller Interrupt or Alert Line
12
SMBus (I2C) Serial
Bi-Directional Data Line,
open-drain output
From and to Controller, Pull-Up Resistor
SMBData
SMBCLK
14
SMBus (I2C) Clock Input
From Controller, Pull-Up Resistor
T_CRIT_A
16
Critical Temperature
Alarm, open-drain output
Pull Up Resistor, Controller Interrupt Line or
System Shutdown
3
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LM83
Absolute Maximum Ratings (Note 1)
Supply Voltage
Voltage at Any Pin
QSOP Package (Note 3)
Vapor Phase (60 seconds)
Infrared (15 seconds)
ESD Susceptibility (Note 4)
Human Body Model
Machine Model
−0.3 V to 6.0 V
−0.3 V to
(VCC + 0.3 V)
± 1 mA
D− Input Current
Input Current at All Other Pins (Note
2)
5 mA
Package Input Current (Note 2)
20 mA
SMBData, T_CRIT_A, INT Output
Sink Current
10 mA
SMBCLK, SMBData, T_CRIT_A, INT
Output Voltage
6.0 V
Storage Temperature
−65˚C to +150˚C
Soldering Information, Lead Temperature
215˚C
220˚C
2000 V
200 V
Operating Ratings
(Notes 1, 5)
Specified Temperature Range
LM83
Supply Voltage Range (VCC)
TMIN to TMAX
−40˚C to +125˚C
+3.0V to +3.6V
Temperature-to-Digital Converter Characteristics
Unless otherwise noted, these specifications apply for VCC =+3.0Vdc to 3.6Vdc. Boldface limits apply for TA = TJ = TMIN to
TMAX; all other limits TA = TJ =+25˚C, unless otherwise noted.
Parameter
Temperature Error using Local
Diode ((Note 8))
Temperature Error using Remote
Diode ((Note 8))
Conditions
Typical
Limits
(Note 6)
(Note 7)
(Limit)
±1
±3
˚C (max)
TA = −40 ˚C to +125˚C,
VCC =+3.3V
±4
˚C (max)
TA = +60 ˚C to +100˚C,
VCC =+3.3V
±3
TA = 25 ˚C to +100˚C,
VCC =+3.3V
±3
˚C (max)
TA = 0 ˚C to +125˚C,
VCC =+3.3V
±4
˚C (max)
TA = 0 ˚C to +85˚C,
VCC =+3.3V
Units
˚C (max)
Diode Channel to Channel Matching
0
˚C
Resolution
8
Bits
1
Conversion Time of All
Temperatures
(Note 10)
Quiescent Current (Note 9)
SMBus (I2C) Inactive
˚C
460
600
ms (max)
0.500
0.80
mA (max)
(D+ − D−)=+ 0.65V; high
level
125
µA (max)
60
µA (min)
Low level
15
µA (max)
5
µA (min)
T_CRIT_A and INT Output
Saturation Voltage
IOUT = 3.0 mA
0.4
Power-On Reset Threshold
On VCC input, falling
edge
2.3
1.8
Local and Remote T_CRIT and
HIGH Default Temperature settings
(Note 11)
D− Source Voltage
Diode Source Current
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0.7
+127
4
V
V (max)
V (max)
V (min)
˚C
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)
Logical “1” Input Voltage
2.1
V (min)
VIN(0)
Logical “0”Input Voltage
0.8
V (max)
VIN(HYST)
SMBData and SMBCLK Digital
Input Hysteresis
300
mV
IIN(1)
Logical “1” Input Current
VIN = VCC
0.005
1.5
µA (max)
IIN(0)
Logical “0” Input Current
VIN = 0 V
−0.005
1.5
µA (max)
ADD0, ADD1
VIN(1)
Logical “1” Input Voltage
VCC
1.5
V (min)
VIN(0)
Logical “0”Input Voltage
GND
0.6
V (max)
IIN(1)
Logical “1” Input Current
VIN = VCC
2
µA (max)
IIN(0)
Logical “0” Input Current
VIN = 0 V
-2
µA (max)
ALL DIGITAL INPUTS
CIN
Input Capacitance
20
pF
ALL DIGITAL OUTPUTS
IOH
High Level Output Current
VOH = VCC
100
µA (max)
VOL
SMBus Low Level Output
Voltage
IOL = 3 mA
IOL = 6 mA
0.4
0.6
V (max)
5
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LM83
Logic Electrical Characteristics
LM83
Logic Electrical Characteristics
(Continued)
SMBus DIGITAL SWITCHING CHARACTERISTICS
Unless otherwise noted, these specifications apply for VCC =+3.0 Vdc to +3.6 Vdc, CL (load capacitance) on output lines = 80
pF. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25˚C, unless otherwise noted.
The switching characteristics of the LM83 fully meet or exceed the published specifications of the SMBus or I2C bus. The following parameters are the timing relationships between SMBCLK and SMBData signals related to the LM83. They are not the
I2C or SMBus bus specifications.
Symbol
Parameter
fSMB
SMBus Clock Frequency
tLOW
SMBus Clock Low Time
Conditions
Typical
Limits
Units
(Note 6)
(Note 7)
(Limit)
100
10
kHz (max)
kHz (min)
10 % to 10 %
1.3
25
µs (min)
ms (max)
10
ms (max)
0.6
tLOWMEXT Cumulative Clock Low Extend Time
tHIGH
SMBus Clock High Time
90 % to 90%
tR,SMB
SMBus Rise Time
10% to 90%
1
tF,SMB
SMBus Fall Time
90% to 10%
0.3
tOF
Output Fall Time
CL = 400 pF,
IO = 3 mA
tTIMEOUT
SMBData and SMBCLK Time Low for
Reset of Serial Interface (Note 12)
µs (min)
µs (max)
ns (max)
250
ns (max)
25
40
ms (min)
ms (max)
t1
SMBCLK (Clock) Period
10
µs (min)
t 2,
tSU;DAT
Data In Setup Time to SMBCLK High
100
ns (min)
t 3,
tHD;DAT
Data Out Stable after SMBCLK Low
300
TBD
ns (min)
ns (max)
t 4,
tHD;STA
SMBData Low Setup Time to SMBCLK
Low
100
ns (min)
t 5,
tSU;STO
SMBData High Delay Time after
SMBCLK High (Stop Condition Setup)
100
ns (min)
t 6,
tSU;STA
SMBus Start-Condition Setup Time
0.6
µs (min)
tBUF
SMBus Free Time
1.3
µs (min)
SMBus Communication
DS101058-4
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6
LM83
Logic Electrical Characteristics
(Continued)
SMBus TIMEOUT
DS101058-7
See drawing DS10105807
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating
the device beyond its rated operating conditions.
Note 2: When the input voltage (VI) at any pin exceeds the power supplies (VI < GND or VI > VCC), the current at that pin should be limited to 5 mA. The 20 mA
maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5 mA to four.
Parasitic components and or ESD protection circuitry are shown in the figure below for the LM83’s pins. The nominal breakdown voltage of the zener D3 is 6.5 V.
Care should be taken not to forward bias the parasitic diode, D1, present on pins: D+, D−, ADD1 and ADD0. Doing so by more than 50 mV may corrupt a temperature
or voltage measurement.
Pin Name
D1
D2
D3
D4
Pin Name
D1
T_CRIT_A & INT
VCC
x
SMBData
D+
x
x
x
NC (pins 9 & 15)
D−
x
x
x
ADD0, ADD1
x
x
x
x
D2
D3
D4
x
x
x
x
x
SMBCLK
x
x
NC (pin 13)
x
x
x
Note: An x indicates that the diode exists.
DS101058-13
FIGURE 1. ESD Protection Input Structure
Note 3: See AN-450 “Surface Mounting Methods and Their Effect on Product Reliability” or the section titled “Surface Mount” found in a current National Semiconductor Linear Data Book for other methods of soldering surface mount devices.
Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Machine model, 200 pF discharged directly into each pin.
Note 5: Thermal resistance of the QSOP-16 package is xyz˚C/W, junction-to-ambient when attached to a printed circuit board with 2 oz. foil as shown in Figure 3
.
7
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LM83
Logic Electrical Characteristics
(Continued)
Note 6: Typicals are at TA = 25˚C and represent most likely parametric norm.
Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 8: The Temperature Error will vary less than ± 1.0 ˚C for a variation in VCC of 3 V to 3.6 V from the nominal of 3.3 V.
Note 9: Quiescent current will not increase substantially with an active SMBus.
Note 10: This specification is provided only to indicate how often temperature data is updated. The LM83 can be read at any time without regard to conversion state
(and will yield last conversion result).
Note 11: Default values set at power up.
Note 12: Holding the SMBData and/or SMBCLK lines Low for a time interval greater than tTIMEOUT will cause the LM83 to reset SMBData and SMBCLK to the IDLE
state of an SMBus communication (SMBCLK and SMBData set High).
DS101058-5
FIGURE 2. Temperature-to-Digital Transfer Function (Non-linear scale for clarity)
DS101058-24
FIGURE 3. Printed Circuit Board Used for Thermal Resistance Specifications
1.0 Functional Description
1. Remote Diode 2 (D2RT)
2. Remote Diode 1 (D1RT)
3. Remote Diode 3 (D3RT)
This round robin sequence takes approximately 480 ms to
complete as each temperature is digitized in approximately
120 ms.
The LM83 temperature sensor incorporates a band-gap type
temperature sensor using a Local or three Remote diodes
and an 8-bit ADC (Delta-Sigma Analog-to-Digital Converter).
The LM83 is compatible with the serial SMBus and I2C two
wire interfaces. Digital comparators compare Local (LT) and
Remote (D1RT, D2RT and D3RT) temperature readings to
user-programmable setpoints (LHS, D1RHS, D2RHS,
D3RHS and TCS). Activation of the INT output indicates that
a comparison is greater than the limit preset in a HIGH register. The T_CRIT setpoint (TCS) interacts with all the temperature readings. Activation of the T_CRIT_A output indicates that any or all of the temperature readings have
exceed the T_CRIT setpoint.
1.2 INT OUTPUT and T_HIGH LIMITS
Each temperature reading (LT, D1RT, D2RT, and D3RT) is
associated with a T_HIGH setpoint register (LHS, D1RHS,
D2RHS, D3RHS). At the end of a temperature reading a digital comparison determines whether that reading has exceed
its HIGH setpoint. If the temperature reading is greater than
the HIGH setpoint, a bit is set in one of the Status Registers,
to indicate which temperature reading, and the INT output is
activated.
Local and remote temperature diodes are sampled in sequence by the A/D converter. The INT output and the Status
1.1 CONVERSION SEQUENCE
The LM83 converts its own temperature as well as 3 remote
diode temperatures in the following sequence:
1. Local Temperature (LT)
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8
Local and remote temperature diodes are sampled in sequence by the A/D converter. The T_CRIT_A output and the
Status Register flags are updated at the completion of a conversion. T_CRIT_A and the Status Register flags are reset
only after the Status Register is read and if a temperature
conversion is below the T_CRIT setpoint, as shown in Figure
6. Figure 7 shows a simplified logic diagram of the
T_CRIT_A and related circuitry.
(Continued)
Register flags are updated at the completion of a conversion,
which occurs approximately 60 ms after a temperature diode
is sampled. INT is deactivated when the Status Register,
containing the set bit, is read and a temperature reading is
less than or equal to it’s corresponding HIGH setpoint, as
shown in Figure 4. Figure 5shows a simplified logic diagram
for the INT output and related circuitry.
DS101058-6
* Note: Status Register Bits are reset by a read of Status Register where
bit is located.
FIGURE 6. T_CRIT_A Temperature Response Diagram
with remote diode 1 and local temperature masked.
DS101058-14
* Note: Status Register Bits are reset by a read of Status Register where
bit is located.
FIGURE 4. INT Temperature Response Diagram with
D2RHS and D3RHS set to 127˚C.
DS101058-21
DS101058-20
FIGURE 5. INT output related circuitry logic diagram
FIGURE 7. T_CRIT_A output related circuitry logic
diagram
The INT output can be disabled by setting the INT mask bit,
D7, of the configuration register. INT can be programmed to
be active high or low by the state of the INT inversion bit, D1,
in the configuration register. A “0” would program INT to be
active low. INT is an open-drain output.
Located in the Configuration Register are the mask bits for
each temperature reading, seeSection 2.5. When a mask bit
is set, its corresponding status flag will not propagate to the
T_CRIT_A output, but will still be set in the Status Registers.
Setting all four mask bits or programming the T_CRIT setpoint to 127˚C will disable the T_CRIT_A output.
1.3 T_CRIT_A OUTPUT and T_CRIT LIMIT
T_CRIT_A is activated when any temperature reading is
greater than the limit preset in the critical temperature setpoint register (T_CRIT), as shown in Figure 6. The Status
Registers can be read to determine which event caused the
alarm. A bit in the Status Registers is set high to indicate
which temperature reading exceeded the T_CRIT setpoint
temperature and caused the alarm, see Section 2.3.
1.4 POWER ON RESET DEFAULT STATES
LM83 always powers up to these known default states:
1. Command Register set to 00h
2. Local Temperature set to 0˚C
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LM83
1.0 Functional Description
LM83
1.0 Functional Description
3.
Diode 1, Diode 2, and Diode 3 Remote Temperature set
to 0˚C until the LM83 senses a diode present between
the D+ and D− input pins.
4.
Status Registers 1 and 2 set to 00h.
5.
Configuration Register set to 00h; INT enabled and all
T_CRIT setpoints enabled to activate T_CRIT_A.
6.
1.6 TEMPERATURE DATA FORMAT
(Continued)
Temperature data can be read from the Local and Remote
Temperature, T_CRIT, and HIGH setpoint registers; and written to the T_CRIT and HIGH setpoint registers. Temperature
data is represented by an 8-bit, two’s complement byte with
an LSB (Least Significant Bit) equal to 1˚C:
Temperature
Hex
+125˚C
0111 1101
7Dh
+25˚C
0001 1001
19h
+1˚C
0000 0001
01h
0˚C
0000 0000
00h
Local and all Remote T_CRIT set to 127˚C
1.5 SMBus INTERFACE
The LM83 operates as a slave on the SMBus, so the
SMBCLK line is an input (no clock is generated by the LM83)
and the SMBData line is bi-directional. According to SMBus
specifications, the LM83 has a 7-bit slave address. Bit 4 (A3)
of the slave address is hard wired inside the LM83 to a 1.
The remainder of the address bits are controlled by the state
of the address select pins ADD1 and ADD0, and are set by
connecting these pins to ground for a low, (0) , to VCC for a
high, (1), or left floating (TRI-LEVEL).
Therefore, the complete slave address is:
A6
A5
A4
1
A2
A1
MSB
A0
LSB
LM83 SMBus
Slave Address
ADD0
ADD1
0
0
001 1000
0
TRI-LEVEL
001 1001
0
1
001 1010
A6:A0 binary
TRI-LEVEL
0
010 1001
TRI-LEVEL
TRI-LEVEL
010 1010
TRI-LEVEL
1
010 1011
1
0
100 1100
1
TRI-LEVEL
100 1101
1
1
100 1110
1111 1111
FFh
1110 0111
E7h
−55˚C
1100 1001
C9h
1.8 DIODE FAULT DETECTION
Before each external conversion the LM83 goes through an
external diode fault detection sequence. If a D+ input is
shorted to VCC or floating then the temperature reading will
be +127 ˚C, and its OPEN bit in the Status Register will be
set. If the T_CRIT setpoint is set to less than +127 ˚C then
the D+ inputs RTCRIT bit in the Status Register will be set
which will activate the T_CRIT_A output, if enabled. If a D+
is shorted to GND or D−, its temperature reading will be 0 ˚C
and its OPEN bit in the Status Register will not be set.
The LM83 latches the state of the address select pins during
the first read or write on the SMBus. Changing the state of
the address select pins after the first read or write to any device on the SMBus will not change the slave address of the
LM83.
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−1˚C
−25˚C
1.7 OPEN-DRAIN OUTPUTS
The SMBData, INT and T_CRIT_A outputs are open-drain
outputs and do not have internal pull-ups. A “high” level will
not be observed on these pins until pull-up current is provided from 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. This will minimize any internal temperature reading
errors due to internal heating of the LM83. The maximum resistance of the pull up, based on LM83 specification for High
Level Output Current, to provide a 2.1V high level, is 30kΩ.
and is selected as follows:
Address Select Pin State
Digital Output
Binary
10
LM83
1.0 Functional Description
(Continued)
1.9 COMMUNICATING with the LM83
DS101058-9
There are 19 data registers in the LM83, selected by the
Command Register. At power-up the Command Register is
set to “00”, the location for the Read Local Temperature Register. 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 predefined as read only or write only. Read and write registers
with the same function contain mirrored data.
A Write to the LM83 will always include the address byte and
the command byte. A write to any register requires one data
byte.
Reading the LM83 can take place either of two ways:
1. If the location latched in the Command Register is correct (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 LM83), 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 address byte, command byte, repeat start, and another address byte will accomplish a read.
The data byte has the most significant bit first. At the end of
a read, the LM83 can accept either Acknowledge or No Acknowledge from the Master (No Acknowledge is typically
used as a signal for the slave that the Master has read its
last byte).
1.10 SERIAL INTERFACE ERROR RECOVERY
The LM83 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 LM83 may or may not reset the state of
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LM83
1.0 Functional Description
(Continued)
the serial interface logic if either of the SMBData or SMBCLK
lines are held low between 25 ms and 40 ms. TIMEOUT allows a clean recovery in cases where the master may be reset while the LM83 is transmitting a low bit thus preventing
possible bus lock up.
Whenever the LM83 sees the start condition its serial interface will reset to the beginning of the communication, thus
the LM83 will expect to see an address byte next. This simplifies recovery when the master is reset while the LM83 is
transmitting a high.
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LM83
1.0 Functional Description
(Continued)
2.0 LM83 REGISTERS
2.1 COMMAND REGISTER
Selects which registers will be read from or written to. Data for this register should be transmitted during the Command Byte of
the SMBus write communication.
P7
P6
P5
P4
0
P3
P2
P1
P0
Command Select
P0-P7: Command Select
Command Select Address
< P7:P0 > hex
Power On Default State
< D7:D0 > binary
Register Name
Register Function
< D7:D0 > decimal
00h
0000 0000
0
RLT
01h
0000 0000
0
RD2RT
02h
0000 0000
0
RSR1
03h
0000 0000
0
RC
04h
0000 0000
0
05h
0111 1111
127
0111 1111
127
RD2RHS
WC
Read Local HIGH Setpoint
Read D2 Remote HIGH
Setpoint
Write Configuration
Reserved
0111 1111
127
WD2LHS
0Ch
0Dh
Read Configuration
Reserved
0000 0000
0Ah
0Bh
Read Status Register 1
Reserved
08h
09h
Read D2 Remote
Temperature
Reserved
RLHS
06h
07h
Read Local Temperature
Write Local HIGH Setpoint
Reserved
0111 1111
127
WD2RHS
30h
0000 0000
0
RD1RT
Read D1 Remote
Temperature
31h
0000 0000
0
RD3RT
Read D3 Remote
Temperature
0000 0000
0
RSR2
0Eh-2Fh
Reserved for Future Use
32h-34h
35h
Reserved for Future Use
36h-37h
38h
0111 1111
127
RD1RHS
0111 1111
127
RD3RHS
0111 1111
127
RTCS
0111 1111
127
WD1RHS
0111 1111
127
WD3RHS
Write D1 Remote HIGH
Setpoint
Reserved for Future Use
53h-59h
5Ah
Read T_CRIT Setpoint
Reserved for Future Use
51h
52h
Read D3 Remote HIGH
Setpoint
Reserved for Future Use
43h-4Fh
50h
Read D1 Remote HIGH
Setpoint
Reserved for Future Use
3Bh-41h
42h
Read Status Register 2
Reserved for Future Use
39h
3Ah
Write D2 Remote HIGH
Setpoint
Write D3 Remote HIGH
Setpoint
Reserved for Future Use
0111 1111
127
WTCS
13
Write T_CRIT Setpoint
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LM83
1.0 Functional Description
Command Select Address
(Continued)
Power On Default State
< P7:P0 > hex
< D7:D0 > binary
Register Name
Register Function
< D7:D0 > decimal
5Ch-6Fh and
F0h-FDh
Reserved for Future Use
FEh
0000 0001
1
FFh
RMID
Read Manufacturers ID
RSR
Read Stepping or Die
Revision Code
2.2 LOCAL and D1, D2 and D3 REMOTE TEMPERATURE REGISTERS (LT, D1RT, D2RT, and D3RT)
(Read Only Address 00h, 01h, 30h and 31h):
D7
D6
D5
D4
D3
D2
D1
D0
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
D7–D0: Temperature Data. One LSB = 1˚C. Two’s complement format.
2.3 STATUS REGISTERS 1 and 2
2.3.1 Status Register 1 (SR1) (Read Only Address 02h):
D7
D6
D5
D4
D3
D2
D1
D0
0
LHIGH
0
D2RHIGH
0
D2OPEN
D2CRIT
LCRIT
Power up default is with all bits “0” (zero).
D0: LCRIT: When set to a 1 indicates an Local Critical Temperature alarm.
D1: D2CRIT: When set to a 1 indicates a Remote Diode 2 Critical Temperature alarm.
D2: D2OPEN: When set to 1 indicates a Remote Diode 2 disconnect.
D4: D2RHIGH: When set to 1 indicates a Remote Diode 2 HIGH Temperature alarm.
D6: LHIGH: When set to 1 indicates a Local HIGH Temperature alarm.
D7, D5, and D3: These bits are always set to 0 and reserved for future use.
Status Register 2
2.3.2 Status Register 2 (SR2) (Read Only Address 35h):
D7
D6
D5
D4
D3
D2
D1
D0
D1RHIGH
0
D1OPEN
D3RHIGH
0
D3OPEN
D3CRIT
D1CRIT
Power up default is with all bits “0” (zero).
D0: D1CRIT, when set to 1 indicates a Remote Diode 1 Critical Temperature alarm.
D1: D3CRIT, when set to 1 indicates a Remote Diode 3 Critical Temperature alarm.
D2: D3OPEN, when set to 1 indicates a Remote Diode 3 disconnect.
D4: D3RHIGH, when set to 1 indicates a Remote Diode 3 HIGH Temperature alarm.
D5: D1OPEN, when set to 1 indicates a Remote Diode 1 disconnect.
D7: D1RHIGH, when set to 1 indicates a Remote Diode 1
HIGH Temperature alarm.
D6, and D3: These bits are always set to 0 and reserved for future use.
2.4 MANUFACTURERS ID REGISTER
(Read Address FEh) Default value 01h.
2.5 CONFIGURATION REGISTER
(Read Address 03h/Write Address 09h):
D7
D6
D5
D4
D3
D2
D1
D0
INT mask
0
D1
T_CRIT_A
mask
D2
T_CRIT_A
mask
D3
T_CRIT_A
mask
Local
T_CRIT_A
mask
INT Inversion
0
Power up default is with all bits “0” (zero).
D7: INT mask: When set to 1 INT interrupts are masked.
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14
LM83
1.0 Functional Description
(Continued)
D5: T_CRIT mask for Diode 1, when set to 1 a Diode 1 temperature reading that exceeds T_CRIT setpoint will not activate the
T_CRIT_A pin.
D4: T_CRIT mask for Diode 2, when set to 1 a Diode 2 temperature reading that exceeds T_CRIT setpoint will not activate the
T_CRIT_A pin.
D3: T_CRIT mask for Diode 3, when set to 1 a Diode 3 temperature reading that exceeds T_CRIT setpoint will not activate the
T_CRIT_A pin.
D2: T_CRIT mask for Local reading, when set to 1 a Local temperature reading that exceeds T_CRIT setpoint will not activate
the T_CRIT_A pin.
D1: INT active state inversion. When INT Inversion is set to a 1 the active state of the INT output will be a logical high. A low would
then select an active state of a logical low.
D6 and D0: These bits are always set to 0 and reserved for future use. A write of 1 will return a 0 when read.
2.6 LOCAL, DIODE 1, DIODE 2 and DIODE 3 HIGH SETPOINT REGISTERS (LHS, D1RHS, D2RHS and D3RHS)
(Read Address 05h, 07h, 38h, 3Ah /Write Address 0Bh, 0Dh,
50h, 52h):
D7
D6
D5
D4
D3
D2
D1
D0
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
D7–D0: HIGH setpoint temperature data. Power up default is LHIGH = RD1HIGH=RD2HIGH=RD3HIGH = 127˚C.
2.7 T_CRIT REGISTER (TCS)
(Read Address 42h/Write Address 5Ah):
D7
D6
D5
D4
D3
D2
D1
D0
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
D7–D0: T_CRIT setpoint temperature data. Power up default is T_CRIT = 127˚C.
15
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LM83
3.0 SMBus Timing Diagrams
DS101058-10
(a) Serial Bus Write to the internal Command Register followed by a the Data Byte
DS101058-11
(b) Serial Bus Write to the internal Command Register
DS101058-12
(c) Serial Bus Read from a Register with the internal Command Register preset to desired value.
FIGURE 8. Serial Bus Timing Diagrams
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16
LM83
4.0 Application Hints
The LM83 can be applied easily in the same way as other
integrated-circuit temperature sensors, and its remote diode
sensing capability allows it to be used in new ways as well.
It can be soldered to a printed circuit board, and because the
path of best thermal conductivity is between the die and the
pins, its temperature will effectively be that of the printed circuit board lands and traces soldered to the LM83’s pins. This
presumes that the ambient air temperature is almost the
same as the surface temperature of the printed circuit board;
if the air temperature is much higher or lower than the surface temperature, the actual temperature of the of the LM83
die will be at an intermediate temperature between the surface and air temperatures. Again, the primary thermal conduction path is through the leads, so the circuit board temperature will contribute to the die temperature much more
strongly than will the air temperature.
To measure temperature external to the LM83’s die, use a
remote diode. This diode can be located on the die of a target IC, allowing measurement of the IC’s temperature, independent of the LM83’s temperature. The LM83 has been optimized to measure the remote diode of a Pentium II
processor as shown in Figure 9. A discrete diode can also be
used to sense the temperature of external objects or ambient
air. Remember that a discrete diode’s temperature will be affected, and often dominated, by the temperature of its leads.
where:
•
η is the non-ideality factor of the process the diode is
manufactured on,
• q is the electron charge,
• k is the Boltzmann’s constant,
• N is the current ratio,
• T is the absolute temperature in ˚K.
The temperature sensor then measures ∆VBE and converts
to digital data. In this equation, k and q are well defined universal constants, and N is a parameter controlled by the temperature sensor. The only other parameter is η, which depends on the diode that is used for measurement. Since
∆VBE is proportional to both η and T, the variations in η cannot be distinguished from variations in temperature. Since
the non-ideality factor is not controlled by the temperature
sensor, it will directly add to the inaccuracy of the sensor. For
the Pentium II Intel specifies a ± 1% variation in η from part
to part. As an example, assume a temperature sensor has
an accuracy specification of ± 3 ˚C at room temperature of 25
˚C and the process used to manufacture the diode has a
non-ideality variation of ± 1%. The resulting accuracy of the
temperature sensor at room temperature will be:
TACC = ± 3˚C + ( ± 1% of 298 ˚K) = ± 6 ˚C.
The additional inaccuracy in the temperature measurement
caused by η, can be eliminated if each temperature sensor is
calibrated with the remote diode that it will be paired with.
3.2 PCB LAYOUT for MINIMIZING NOISE
In a noisy environment, such as a processor mother board,
layout considerations are very critical. Noise induced on
traces running between the remote temperature diode sensor and the LM83 can cause temperature conversion errors.
The following guidelines should be followed:
1. Place a 0.1 µF power supply bypass capacitor as close
as possible to the VCCpin and the recommended 2.2 nF
capacitor as close as possible to the D+ and D− pins.
Make sure the traces to the 2.2nF capacitor are
matched.
2. The recommended 2.2nF diode bypass capacitor actually has a range of 200pF to 3.3nF. The average temperature accuracy will not degrade. Increasing the capacitance will lower the corner frequency where
differential noise error affects the temperature reading
thus producing a reading that is more stable. Conversely, lowering the capacitance will increase the corner frequency where differential noise error affects the
temperature reading thus producing a reading that is
less stable.
3. Ideally, the LM83 should be placed within 10cm of the
Processor diode pins with the traces being as straight,
short and identical as possible. Trace resistance of 1Ω
can cause as much as 1˚C of error.
4. Diode traces should be surrounded by a GND guard ring
to either side, above and below if possible. This GND
guard should not be between the D+ and D− lines. In the
event that noise does couple to the diode lines it would
be ideal if it is coupled common mode. That is equally to
the D+ and D− lines.(See Figure 10)
5. Avoid routing diode traces in close proximity to power
supply switching or filtering inductors.
DS101058-15
Pentium or 3904 Temperature vs LM83 Temperature
Reading
Most silicon diodes do not lend themselves well to this application. It is recommended that a 2N3904 transistor base
emitter junction be used with the collector tied to the base.
A diode connected 2N3904 approximates the junction available on a Pentium microprocessor for temperature measurement. Therefore, the LM83 can sense the temperature of this
diode effectively.
3.1 ACCURACY EFFECTS OF DIODE NON-IDEALITY
FACTOR
The technique used in today’s remote temperature sensors
is to measure the change in VBE at two different operating
points of a diode. For a bias current ratio of N:1, this difference is given as:
17
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LM83
4.0 Application Hints
6.
(Continued)
Avoid running diode traces close to or parallel to high
speed digital and bus lines. Diode traces should be kept
at least 2cm. apart from the high speed digital traces.
7.
If it is necessary to cross high speed digital traces, the
diode traces and the high speed digital traces should
cross at a 90 degree angle.
8. The ideal place to connect the LM83’s GND pin is as
close as possible to the Processors GND associated
with the sense diode. For the Pentium II this would be
pin A14.
9. Leakage current between D+ and GND should be kept
to a minimum. One nano-ampere of leakage can cause
as much as 1˚C of error in the diode temperature reading. Keeping the printed circuit board as clean as possible will minimize leakage current.
DS101058-17
FIGURE 10. Ideal Diode Trace Layout
Noise coupling into the digital lines greater than 300mVp-p
(typical hysteresis), overshoot greater than 500mV above
VCC, and undershoot less than 500mV below GND, may prevent successful SMBus communication with the LM83. SMBus no acknowledge is the most common symptom, causing
unnecessary traffic on the bus. Although, the SMBus maximum frequency of communication is rather low (100kHz
max) care still needs to be taken to ensure proper termination within a system with multiple parts on the bus and long
printed circuit board traces. An R/C lowpass filter with a 3db
corner frequency of about 40MHz has been included on the
LM83’s SMBCLK input. Additional resistance can be added
in series with the SMBData and SMBCLK lines to further
help filter noise and ringing. Minimize noise coupling by
keeping digital traces out of switching power supply areas as
well as ensuring that digital lines containing high speed data
communications cross at right angles to the SMBData and
SMBCLK lines.
4.0 Typical Applications
DS101058-22
FIGURE 11. LM83 Demo Board Diode Layout
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18
LM83
4.0 Typical Applications
(Continued)
DS101058-23
Any two or three D+ inputs can be connected in parallel to increase the number of High temperature setpoints for a particular temperature reading. If all three
D+ inputs are tied as shown here, D1+, D2+ and D3+ temperature readings will be identical, unless affected by PCB D+ trace resistance differences.
FIGURE 12. Connecting all Three LM83 Diode Inputs in Parallel will Increase the Number of HIGH Setpoints for a
Single Temperature Reading to Three.
19
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LM83 Triple-Diode Input and Local Digital Temperature Sensor with Two-Wire Interface
Physical Dimensions
inches (millimeters) unless otherwise noted
16-Lead QSOP Package
Order Number LM83CIMQA or LM83CIMQAX
NS Package Number MQA16
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