LM95221
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SNIS134B – MAY 2004 – REVISED MARCH 2013
LM95221 Dual Remote Diode Digital Temperature Sensor with SMBus Interface
Check for Samples: LM95221
FEATURES
APPLICATIONS
•
•
1
2
•
•
•
•
•
•
•
•
•
Accurately Senses Die Temperature of Remote
ICs or Diode Junctions
Remote Diode Fault Detection
On-board Local Temperature Sensing
Remote Temperature Readings
– 0.125°C LSb
– 10-bits Plus Sign or 11-bits Programmable
Resolution
– 11-bits Resolves Temperatures Above
127°C
Local Temperature Readings
– 0.25°C
– 9-bits Plus Sign
Status Register Support
Programmable Conversion Rate Allows User
Optimization of Power Consumption
Shutdown Mode One-shot Conversion Control
SMBus 2.0 Compatible Interface, Supports
TIMEOUT
8-pin VSSOP Package
KEY SPECIFICATIONS
•
•
•
•
Local Temperature Accuracy
– TA = 0°C to 85°C ± 3.0°C (max)
Remote Diode Temperature Accuracy
– TA = 30°C to 50°C, TD = 45°C to 85°C
±1.0 °C (Max)
– TA = 0°C to 85°C, TD = 25°C to 140°C
±3.0°C (Max)
Supply Voltage 3.0 V to 3.6 V
Supply Current 2 mA (Typ)
•
•
Processor/Computer System Thermal
Management (e.g. Laptop, Desktop,
Workstations, Server)
Electronic Test Equipment
Office Electronics
DESCRIPTION
The LM95221 is a dual remote diode temperature
sensor in an 8-lead VSSOP package. The 2-wire
serial interface of the LM95221 is compatible with
SMBus 2.0. The LM95221 can sense three
temperature zones, it can measure the temperature
of its own die as well as two diode connected
transistors. The diode connected transistors can be a
thermal diode as found in Pentium and AMD
processors or can simply be a diode connected
MMBT3904 transistor. The LM95221 resolution
format for remote temperature readings can be
programmed to be 10-bits plus sign or 11-bits
unsigned. In the unsigned mode the LM95221 remote
diode readings can resolve temperatures above
127°C. Local temperature readings have a resolution
of 9-bits plus sign.
The temperature of any ASIC can be accurately
determined using the LM95221 as long as a
dedicated diode (semiconductor junction) is available
on the target die. The LM95221 remote sensor
accuracy of ±1°C is factory trimmed for a series
resistance of 2.7 ohms and 1.008 non-ideality factor.
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2004–2013, Texas Instruments Incorporated
LM95221
SNIS134B – MAY 2004 – REVISED MARCH 2013
www.ti.com
Simplified Block Diagram
3.0V-3.6V
LM95221
Local
Diode Selector
D+
D-
Remote
Diode1 Selector
D+
D-
Remote
Diode2 Selector
Control Logic
'-6 Converter
11-Bit or 10-Bit Plus Sign Remote
9-bit Plus Sign Local
Temperature
Sensor
Circuitry
Local
Remote 1
Temperature Temperature
Registers
Registers
Remote 2
Temperature
Registers
Configuration
Register
Status
Registrer
Revision &
Manufacturer
ID Registers
SMBDAT
SMBCLK
Two-Wire Serial
Interface
Connection Diagram
D1+
1
D1-
2
8
SMBCLK
7
D2+
3
6
SMBDAT
VDD
D2-
4
5
GND
LM95221
Figure 1. VSSOP-8
TOP VIEW
PIN DESCRIPTIONS
2
Label
Pin #
Function
D1+
1
Diode Current Source
To Diode Anode. Connected to remote discrete diodeconnected transistor junction or to the diode-connected
transistor junction on a remote IC whose die temperature is
being sensed. A 2.2 nF diode bypass capacitor is
recommended to filter high frequency noise. Place the 2.2 nF
capacitor between and as close as possible to the LM95221's
D+ and D− pins. Make sure the traces to the 2.2 nF capacitor
are matched. Ground this pin if this thermal diode is not used.
Typical Connection
D1−
2
Diode Return Current Sink
To Diode Cathode. A 2.2 nF capacitor is recommended
between D1+ and D1-. Ground this pin if this thermal diode is
not used.
D2+
3
Diode Current Source
To Diode Anode. Connected to remote discrete diodeconnected transistor junction or to the diode-connected
transistor junction on a remote IC whose die temperature is
being sensed. A 2.2 nF diode bypass capacitor is
recommended to filter high frequency noise. Place the 2.2 nF
capacitor between and as close as possible to the LM95221's
D+ and D− pins. Make sure the traces to the 2.2 nF capacitor
are matched. Ground this pin if this thermal diode is not used.
D2−
4
Diode Return Current Sink
To Diode Cathode. A 2.2 nF capacitor is recommended
between D2+ and D2-. Ground this pin if this thermal diode is
not used.
GND
5
Power Supply Ground
Ground
VDD
6
Positive Supply Voltage Input
DC Voltage from 3.0 V to 3.6 V. VDD should be bypassed with
a 0.1 µF capacitor in parallel with 100 pF. The 100 pF
capacitor should be placed as close as possible to the power
supply pin. Noise should be kept below 200 mVp-p, a 10 µF
capacitor may be required to achieve this.
SMBDAT
7
SMBus Bi-Directional Data Line, From and to Controller; may require an external pull-up resistor
Open-Drain Output
SMBCLK
8
SMBus Clock Input
From Controller; may require an external pull-up resistor
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Typical Application
+3.3V
Standby
C3*
2.2 nF
Pentium® 4
PROCESSOR
1
2
3
C4*
2.2 nF
4
D1+
SMBCLK
D1-
SMBDAT
R1
1.3k
8
R2
1.3k
SMBCLK
7
SMBDAT
6
D2+
VDD
5
GND
D2-
LM95221
C1*
100 pF
C2
0.1 PF
SMBus
Master
Q1
MMBT3904
* Note, place close to LM95221 pins.
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings (1)
−0.3 V to 6.0 V
Supply Voltage
−0.5V to 6.0V
Voltage at SMBDAT, SMBCLK
−0.3 V to (VDD +
0.3 V)
Voltage at Other Pins
D− Input Current
±1 mA
Input Current at All Other Pins (2)
±5 mA
Package Input Current (2)
30 mA
SMBDAT Output Sink Current
10 mA
−65°C to +150°C
Storage Temperature
Soldering Information, Lead Temperature
VSSOP-8 Package (3)
ESD Susceptibility (4)
Human Body Model
Vapor Phase (60 seconds)
215°C
Infrared (15 seconds)
220°C
2000 V
Machine Model
(1)
(2)
(3)
(4)
200 V
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.
When the input voltage (VI) at any pin exceeds the power supplies (VI < GND or VI > VDD), the current at that pin should be limited to 5
mA. Parasitic components and or ESD protection circuitry are shown in Figure 3 below for the LM95221's pins. The nominal breakdown
voltage of D4 is 6.5 V. Care should be taken not to forward bias the parasitic diode, D1, present on pins: D1+, D2+, D1−, D2−. Doing so
by more than 50 mV may corrupt the temperature measurements.
See the URL ”http://www.ti.com/packaging/“ for other recommendations and methods of soldering surface mount devices.
Human body model, 100pF discharged through a 1.5kΩ resistor. Machine model, 200pF discharged directly into each pin.
Operating Ratings (1) (2)
Operating Temperature Range
0°C to +115°C
Electrical Characteristics Temperature Range
TMIN≤TA≤TMAX
LM95221CIMM
0°C≤TA≤+85°C
Supply Voltage Range (VDD)
+3.0V to +3.6V
(1)
(2)
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.
Thermal resistance junction-to-ambient when attached to a printed circuit board with 2 oz. foil:
— VSSOP-8 = 210°C/W
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LM95221
SNIS134B – MAY 2004 – REVISED MARCH 2013
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Temperature-to-Digital Converter Characteristic
Unless otherwise noted, these specifications apply for VDD=+3.0Vdc to 3.6Vdc. Boldface limits apply for TA = TJ =
TMIN≤TA≤TMAX; all other limits TA= TJ=+25°C, unless otherwise noted. TJ is the junction temperature of the LM95221. TD is the
junction temperature of the remote thermal diode.
Parameter
Conditions
TA = 0°C to +85°C (3)
Accuracy Using Local Diode
Accuracy Using Remote Diode, see
Diode Processor Type.
(4)
for Thermal
Typical (1)
Limits (2)
Units
(Limit)
±1
±3
°C (max)
TA = +30°C to
+50°C
TD = +45°C to
+85°C
±1
°C (max)
TA = +0°C to +85°C
TD = +25°C to
+140°C
±3
°C (max)
Remote Diode Measurement Resolution
11
Local Diode Measurement Resolution
Bits
0.125
°C
10
Bits
0.25
°C
Conversion Time of All Temperatures at the Fastest
Setting
See (5)
66
73
ms (max)
Quiescent Current (6)
SMBus Inactive, 15Hz conversion
rate
2.0
2.6
mA (max)
Shutdown
335
µA
0.7
V
D− Source Voltage
Diode Source Current
(D+ − D−)=+ 0.65V; high-level
Low-level
188
11.75
Low-Level Diode Source Current Variation over
Temperature
TA = +30°C to +50°C
+0.5
TA = +30°C to +85°C
+1.5
Power-On Reset Threshold
Measure on VDD input, falling edge
(1)
(2)
(3)
(4)
(5)
(6)
4
315
µA (max)
110
µA (min)
20
µA (max)
7
µA (min)
µA
µA
2.4
1.8
V (max)
V (min)
Typicals are at TA = 25°C and represent most likely parametric normal.
Limits are specified to Texas Instruments' AOQL (Average Outgoing Quality Level).
Local temperature accuracy does not include the effects of self-heating. The rise in temperature due to self-heating is the product of the
internal power dissipation of the LM95221 and the thermal resistance. See Note 2 of the Operating Ratings table for the thermal
resistance to be used in the self-heating calculation.
The accuracy of the LM95221CIMM is ensured when using the thermal diode with a non-ideality of 1.008 and series R= 2.7Ω. When
using an MMBT3904 type transistor as the thermal diode the error band will be offset by -3.25°C
This specification is provided only to indicate how often temperature data is updated. The LM95221 can be read at any time without
regard to conversion state (and will yield last conversion result).
Quiescent current will not increase substantially with an SMBus.
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SNIS134B – MAY 2004 – REVISED MARCH 2013
Logic Electrical Characteristics
DIGITAL DC CHARACTERISTICS
Unless otherwise noted, these specifications apply for VDD=+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 (1)
Limits (2)
Units
(Limit)
SMBDAT, SMBCLK INPUTS
VIN(1)
Logical “1” Input Voltage
2.1
V (min)
VIN(0)
Logical “0”Input Voltage
0.8
V (max)
VIN(HYST)
SMBDAT and SMBCLK Digital Input
Hysteresis
IIN(1)
Logical “1” Input Current
VIN = VDD
0.005
±10
µA (max)
IIN(0)
Logical “0” Input Current
VIN = 0 V
−0.005
±10
µA (max)
CIN
Input Capacitance
400
mV
5
pF
SMBDAT OUTPUT
IOH
High Level Output Current
VOH = VDD
10
µA (max)
VOL
SMBus Low Level Output Voltage
IOL = 4mA
IOL = 6mA
0.4
0.6
V (max)
(1)
(2)
Typicals are at TA = 25°C and represent most likely parametric normal.
Limits are specified to Texas Instruments' AOQL (Average Outgoing Quality Level).
SMBus DIGITAL SWITCHING CHARACTERISTICS
Unless otherwise noted, these specifications apply for VDD=+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 LM95221 fully meet or exceed the published specifications of the SMBus version 2.0. The
following parameters are the timing relationships between SMBCLK and SMBDAT signals related to the LM95221. They
adhere to but are not necessarily the SMBus bus specifications.
Symbol
Conditions
Typical (1)
Limits (2)
Units
(Limit)
100
10
kHz (max)
kHz (min)
fSMB
SMBus Clock Frequency
tLOW
SMBus Clock Low Time
from VIN(0)max to VIN(0)max
4.7
25
µs (min)
ms (max)
tHIGH
SMBus Clock High Time
from VIN(1)min to VIN(1)min
4.0
µs (min)
(3)
tR,SMB
SMBus Rise Time
See
tF,SMB
SMBus Fall Time
See (4)
tOF
Output Fall Time
CL = 400pF,
IO = 3mA (4)
1
µs (max)
0.3
µs (max)
250
ns (max)
SMBDAT and SMBCLK Time Low for Reset of
Serial Interface (5)
25
35
ms (min)
ms (max)
tSU;DAT
Data In Setup Time to SMBCLK High
250
ns (min)
tHD;DAT
Data Out Stable after SMBCLK Low
300
900
ns (min)
ns (max)
tHD;STA
Start Condition SMBDAT Low to SMBCLK Low
(Start condition hold before the first clock falling
edge)
100
ns (min)
tSU;STO
Stop Condition SMBCLK High to SMBDAT Low
(Stop Condition Setup)
100
ns (min)
tSU;STA
SMBus Repeated Start-Condition Setup Time,
SMBCLK High to SMBDAT Low
0.6
µs (min)
tTIMEOUT
(1)
(2)
(3)
(4)
(5)
Parameter
Typicals are at TA = 25°C and represent most likely parametric normal.
Limits are specified to Texas Instruments' AOQL (Average Outgoing Quality Level).
The output rise time is measured from (VIN(0)max + 0.15V) to (VIN(1)min − 0.15V).
The output fall time is measured from (VIN(1)min - 0.15V) to (VIN(1)min + 0.15V).
Holding the SMBDAT and/or SMBCLK lines Low for a time interval greater than tTIMEOUT will reset the LM95221's SMBus state machine,
therefore setting SMBDAT and SMBCLK pins to a high impedance state.
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LM95221
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SMBus DIGITAL SWITCHING CHARACTERISTICS
Unless otherwise noted, these specifications apply for VDD=+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 LM95221 fully meet or exceed the published specifications of the SMBus version 2.0. The
following parameters are the timing relationships between SMBCLK and SMBDAT signals related to the LM95221. They
adhere to but are not necessarily the SMBus bus specifications.
Symbol
tBUF
Parameter
Typical (1)
Conditions
Limits (2)
Units
(Limit)
1.3
µs (min)
SMBus Free Time Between Stop and Start
Conditions
tLOW
tR
tF
VIH
SMBCLK
VIL
tHD;STA
tBUF
tHIGH
tSU;STA
tSU;DAT
tHD;DAT
tSU;STO
VIH
SMBDAT VIL
P
S
P
Figure 2. SMBus Communication
Pin
Name
PIN #
VDD
D1
D2
D3
D4
1
D6
D7
R1
SNP
x
x
(1)
D1+
2
x
x
D1−
3
x
x
x
D2+
4
x
x
x
D2-
6
x
x
x
SMBDAT
7
x
x
SMBCLK
8
x
x
(1)
D5
ESD
CLAMP
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Note: An “x” indicates that the component exists for the designated pin. SNP refers to a snap-back device.
V+
D1
D3
D4
D6
I/O
D2
SNP
ESD
Clamp
R1
D5
D7
GND
Figure 3. ESD Protection Input Structure
6
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Typical Performance Characteristics
Thermal Diode Capacitor or PCB Leakage Current Effect
Remote Diode Temperature Reading
Remote Temperature Reading Sensitivity to Thermal
Diode Filter Capacitance
Figure 4.
Figure 5.
Conversion Rate Effect on Average Power Supply Current
Figure 6.
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LM95221
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FUNCTIONAL DESCRIPTION
The LM95221 is a digital sensor that can sense the temperature of 3 thermal zones using a sigma-delta analogto-digital converter. It can measure its local die temperature and the temperature of two diode connected
MMBT3904 transistors using a ΔVbe temperature sensing method. The 2-wire serial interface, of the LM95221, is
compatible with SMBus 2.0 and I2C. Please see the SMBus 2.0 specification for a detailed description of the
differences between the I2C bus and SMBus.
The temperature conversion rate is programmable to allow the user to optimize the current consumption of the
LM95221 to the system requirements. The LM95221 can be placed in shutdown to minimize power consumption
when temperature data is not required. While in shutdown, a 1-shot conversion mode allows system control of
the conversion rate for ultimate flexibility.
The remote diode temperature resolution is eleven bits and is programmable to 11-bits unsigned or 10-bits plus
sign. The least-significant-bit (LSb) weight for both resolutions is 0.125°C. The unsigned resolution allows the
remote diodes to sense temperatures above 127°C. Local temperature resolution is not programmable and is
always 9-bits plus sign and has a 0.25°C LSb.
The LM95221 remote diode temperature accuracy will be trimmed for the thermal diode of a Prescott processor
and the accuracy will be ensured only when using this diode.
Diode fault detection circuitry in the LM95221 can detect the presence of a remote diode: whether D+ is shorted
to VDD, D- or ground, or whether D+ is floating.
The LM95221 register set has an 8-bit data structure and includes:
1. Most-Significant-Byte (MSB) Local Temperature Register
2. Least-Significant-Byte (LSB) Local Temperature Register
3. MSB Remote Temperature 1 Register
4. LSB Remote Temperature 1 Register
5. MSB Remote Temperature 2 Register
6. LSB Remote Temperature 2 Register
7. Status Register: busy, diode fault
8. Configuration Register: resolution control, conversion rate control, standby control
9. 1-shot Register
10. Manufacturer ID
11. Revision ID
CONVERSION SEQUENCE
The LM95221 takes approximately 66 ms to convert the Local Temperature, Remote Temperature 1 and 2, and
to update all of its registers. Only during the conversion process the busy bit (D7) in the Status register (02h) is
high. These conversions are addressed in a round robin sequence. The conversion rate may be modified by the
Conversion Rate bits found in the Configuration Register (03h). When the conversion rate is modified a delay is
inserted between conversions, the actual conversion time remains at 66ms (26 ms for each remote and 14 ms
for local). Different conversion rates will cause the LM95221 to draw different amounts of supply current as
shown in Figure 7.
8
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Figure 7. Conversion Rate Effect on Power Supply Current
POWER-ON-DEFAULT STATES
LM95221 always powers up to these known default states. The LM95221 remains in these states until after the
first conversion.
1. Command Register set to 00h
2. Local Temperature set to 0°C
3. Remote Diode Temperature set to 0°C until the end of the first conversion
4. Status Register depends on state of thermal diode inputs
5. Configuration register set to 00h; continuous conversion, time = 66ms
SMBus INTERFACE
The LM95221 operates as a slave on the SMBus, so the SMBCLK line is an input and the SMBDAT line is
bidirectional. The LM95221 never drives the SMBCLK line and it does not support clock stretching. According to
SMBus specifications, the LM95221 has a 7-bit slave address. All bits A6 through A0 are internally programmed
and can not be changed by software or hardware. The LM95221 has the following SMBus slave address:
Version
A6
A5
A4
A3
A2
A1
A0
LM95221
0
1
0
1
0
1
1
TEMPERATURE DATA FORMAT
Temperature data can only be read from the Local and Remote Temperature registers .
Remote temperature data is represented by an 11-bit, two's complement word or unsigned binary word with an
LSb (Least Significant Bit) equal to 0.125°C. The data format is a left justified 16-bit word available in two 8-bit
registers. Unused bits will always report "0".
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Table 1. 11-bit, 2's complement (10-bit plus sign)
Temperature
Digital Output
Binary
Hex
+125°C
0111 1101 0000 0000
7D00h
+25°C
0001 1001 0000 0000
1900h
+1°C
0000 0001 0000 0000
0100h
+0.125°C
0000 0000 0010 0000
0020h
0°C
0000 0000 0000 0000
0000h
−0.125°C
1111 1111 1110 0000
FFE0h
−1°C
1111 1111 0000 0000
FF00h
−25°C
1110 0111 0000 0000
E700h
−55°C
1100 1001 0000 0000
C900h
Table 2. 11-bit, unsigned binary
Temperature
Digital Output
Binary
Hex
+255.875°C
1111 1111 1110 0000
FFE0h
+255°C
1111 1111 0000 0000
FF00h
+201°C
1100 1001 0000 0000
C900h
+125°C
0111 1101 0000 0000
7D00h
+25°C
0001 1001 0000 0000
1900h
+1°C
0000 0001 0000 0000
0100h
+0.125°C
0000 0000 0010 0000
0020h
0°C
0000 0000 0000 0000
0000h
Local Temperature data is represented by a 10-bit, two's complement word with an LSb (Least Significant Bit)
equal to 0.25°C. The data format is a left justified 16-bit word available in two 8-bit registers. Unused bits will
always report "0". Local temperature readings greater than +127.875°C are not clamped to +127.875°C, they will
roll-over to negative temperature readings.
Temperature
10
Digital Output
Binary
Hex
+125°C
0111 1101 0000 0000
7D00h
+25°C
0001 1001 0000 0000
1900h
+1°C
0000 0001 0000 0000
0100h
+0.125°C
0000 0000 0010 0000
0020h
0°C
0000 0000 0000 0000
0000h
−0.25°C
1111 1111 1100 0000
FFE0h
−1°C
1111 1111 0000 0000
FF00h
−25°C
1110 0111 0000 0000
E700h
−55°C
1100 1001 0000 0000
C900h
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SMBDAT OPEN-DRAIN OUTPUT
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 LM95221. The maximum resistance of the pull-up to provide a 2.1V high
level, based on LM95221 specification for High Level Output Current with the supply voltage at 3.0V, is
82kΩ(5%) or 88.7kΩ(1%).
DIODE FAULT DETECTION
The LM95221 is equipped with operational circuitry designed to detect fault conditions concerning the remote
diodes. In the event that the D+ pin is detected as shorted to GND, D−, VDD or D+ is floating, the Remote
Temperature reading is –128.000 °C if signed format is selected and +255.875 if unsigned format is selected. In
addition, the appropriate status register bits RD1M or RD2M (D1 or D0) are set.
COMMUNICATING with the LM95221
The data registers in the LM95221 are 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. Each data register in the LM95221 falls into one of four types of user accessibility:
1. Read only
2. Write only
3. Write/Read same address
4. Write/Read different address
A Write to the LM95221 will always include the address byte and the command byte. A write to any register
requires one data byte.
Reading the LM95221 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 Registers because that will be the data most frequently
read from the LM95221), 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 LM95221 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). It takes the LM95221 66 ms to measure the temperature of the remote diodes and internal
diode. When retrieving all 11 bits from a previous remote diode temperature measurement, the master must
insure that all 11 bits are from the same temperature conversion. This may be achieved by reading the MSB
register first. The LSB will be locked after the MSB is read. The LSB will be unlocked after being read. If the user
reads MSBs consecutively, each time the MSB is read, the LSB associated with that temperature will be locked
in and override the previous LSB value locked-in.
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SMBus Timing Diagrams
1
9
1
9
SMBCLK
SMBDAT
A6
A5
A4
A3
A2
D7
Ack
by
LM95221
A1
D6
A0 R/W
Start by
Master
D5
D4
Frame 1
Serial Bus Address Byte
D3
D2
SMBDAT
(Continued)
D0
Ack
by
LM95221
Frame 2
Command Byte
1
SMBCLK
(Continued)
D1
9
D7
D6
D5
D4
D3
D2
D1
D0
Ack by Stop
LM95221 by
Master
Frame 3
Data Byte
Figure 8. Serial Bus Write to the internal Command Register followed by a the Data Byte
1
9
1
9
SMBCLK
SMBDAT
A6
A5
A4
A3
A2
A1
D7
Ack
by
LM95221
D6
A0 R/W
Start by
Master
D5
D4
Frame 1
Serial Bus Address Byte
D3
D2
D1
D0
Ack by Stop
LM95221 by
Master
Frame 2
Command Byte
Figure 9. Serial Bus Write to the Internal Command Register
1
9
1
9
SMBCLK
SMBDAT
A6
A5
A4
A3
A2
A1
D7
Ack
by
LM95221
A0 R/W
Start by
Master
D6
D5
D4
D3
D2
D1
D0
NoAck Stop
by
by
Master Master
Frame 1
Serial Bus Address Byte
Frame 2
Data Byte from the LM95221
Figure 10. Serial Bus Read from a Register with the Internal Command Register preset to desired value.
1
9
1
9
SMBCLK
SMBDAT
A6
A5
A4
A3
A2
D7
Ack
by
LM95221
A1
D6
A0 R/W
Start by
Master
D5
Frame 1
Serial Bus Address Byte
SMBCLK
(Continued)
SMBDAT
(Continued)
9
A5
A4
A3
A2
A1
Frame 3
Serial Bus Address Byte
D3
D2
D1
D0
Ack
Repeat
by
Start by
LM95221 Master
Frame 2
Command Byte
1
A6
D4
1
D7
Ack
by
LM95221
A0 R/W
9
D6
D5
D4
D3
D2
D1
D0
No Ack Stop
by
by
Master Master
Frame 4
Data Byte from the LM95221
Figure 11. Serial Bus Write followed by a Repeat Start and Immediate Read
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SERIAL INTERFACE RESET
In the event that the SMBus Master is RESET while the LM95221 is transmitting on the SMBDAT line, the
LM95221 must be returned to a known state in the communication protocol. This may be done in one of two
ways:
1. When SMBDAT is LOW, the LM95221 SMBus state machine resets to the SMBus idle state if either
SMBDAT or SMBCLK are held low for more than 35ms (tTIMEOUT). Note that according to SMBus
specification 2.0 all devices are to timeout when either the SMBCLK or SMBDAT lines are held low for 2535ms. Therefore, to insure a timeout of all devices on the bus the SMBCLK or SMBDAT lines must be held
low for at least 35ms.
2. When SMBDAT is HIGH, have the master initiate an SMBus start. The LM95221 will respond properly to an
SMBus start condition at any point during the communication. After the start the LM95221 will expect an
SMBus Address address byte.
ONE-SHOT CONVERSION
The One-Shot register is used to initiate a single conversion and comparison cycle when the device is in standby
mode, after which the device returns to standby. This is not a data register and it is the write operation that
causes the one-shot conversion. The data written to this address is irrelevant and is not stored. A zero will
always be read from this register.
LM95221 Registers
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
P3
P2
P1
P0
Command
P0-P7: Command
Table 3. Register Summary
Name
Command
(Hex)
Power-On
Default Value
(Hex)
Read/Write
# of used bits
Comments
Status Register
02h
-
RO
3
2 status bits and 1 busy bit
Configuration Register
03h
00h
R/W
4
Includes conversion rate control
1-shot
0Fh
-
WO
-
Activates one conversion for all
3 channels if the chip is in
standby mode (i.e. RUN/STOP
bit = 1). Data transmitted by the
host is ignored by the LM95221.
Local Temperature MSB
10h
-
RO
8
Remote Temperature 1 MSB
11h
-
RO
8
Remote Temperature 2 MSB
12h
-
RO
8
Local Temperature LSB
20h
-
RO
2
All unused bits will report zero
Remote Temperature 1 LSB
21h
-
RO
3
All unused bits will report zero
Remote Temperature 2 LSB
22h
-
RO
3
All unused bits will report zero
Manufacturer ID
FEh
01h
RO
Revision ID
FFh
61h
RO
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STATUS REGISTER (Read Only Address 02h)
D7
D6
D5
0
0
Busy
D4
D3
D2
0
0
Reserved
0
D1
D0
RD2M
RD1M
Bits
Name
Description
7
Busy
When set to "1" the part is converting.
6-2
Reserved
Reports "0" when read.
1
Remote diode 2 missing (RD2M)
Remote Diode 2 is missing. (i.e. D2+ shorted to VDD, Ground or D2-, or D2+ is
floating). Temperature Reading is FFE0h which converts to 255.875 °C if
unsigned format is selected or 8000h which converts to –128.000 °C if signed
format is selected.
0
Remote diode 1 missing (RD1M)
Remote Diode 1 is missing. (i.e. D1+ shorted to VDD, Ground or D1-, or D1+ is
floating). Temperature Reading is FFE0h which converts to 255.875 °C if
unsigned format is selected or 8000h which converts to –128.000 °C if signed
format is selected.
CONFIGURATION REGISTER (Read Address 03h / Write Address 03h)
D7
D6
D5
D4
D3
D2
D1
D0
0
RUN/STOP
CR1
CR0
0
R2DF
R1DF
0
Bits
Name
Description
7
Reserved
Reports "0" when read.
6
RUN/STOP
Logic 1 disables the conversion and puts the part in standby mode.
Conversion can be activated by writing to one-shot register.
5-4
Conversion Rate (CR1:CR0)
00: continuous mode 66ms, 15 Hz (typ)
01: converts every 200ms, 5 Hz (typ)
10: converts every 1 second, 1 Hz (typ)
11: converts every 3 seconds, ⅓ Hz (typ)
Note: typically a remote diode conversion takes 26 ms and local conversion
takes 14 ms.
3
Reserved
Reports "0" when read.
2
Remote 2 Data Format (R2DF)
Logic 0: unsigned Temperature format (0 °C to +255.875 °C)
Logic 1: signed Temperature format (-128 °C to +127.875 °C)
1
Remote 1 Data Format (R1DF)
Logic 0: unsigned Temperature format (0 °C to +255.875 °C)
Logic 1: signed Temperature format (-128 °C to +127.875 °C)
0
Reserved
Reports "0" when read.
Power up default is with all bits “0” (zero)
LOCAL and REMOTE MSB and LSB TEMPERATURE REGISTERS
Table 4. Local Temperature MSB (Read Only Address 10h) 9-bit plus sign format (1):
(1)
BIT
D7
D6
D5
D4
D3
D2
D1
D0
Value
SIGN
64
32
16
8
4
2
1
Temperature Data: LSb = 1°C.
Table 5. Local Temperature LSB (Read Only Address 20h) 9-bit plus sign format (1):
(1)
14
BIT
D7
D6
D5
D4
D3
D2
D1
D0
Value
0.5
0.25
0
0
0
0
0
0
Temperature Data: LSb = 0.25°C
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Table 6. Remote Temperature MSB (Read Only Address 11h, 12h) 10 bit plus sign format (1):
(1)
BIT
D7
D6
D5
D4
D3
D2
D1
D0
Value
SIGN
64
32
16
8
4
2
1
Temperature Data: LSb = 1°C.
Table 7. Remote Temperature MSB (Read Only Address 11h, 12h) 11-bit unsigned format (1):
BIT
D7
D6
D5
D4
D3
D2
D1
D0
Value
128
64
32
16
8
4
2
1
(1)
Table 8. Remote Temperature LSB(Read Only Address 21, 22h) 10-bit plus sign or 11-bit unsigned binary
formats (1):
(1)
BIT
D7
D6
D5
D4
D3
D2
D1
D0
Value
0.5
0.25
0.125
0
0
0
0
0
Temperature Data: LSb = 0.125°C.
For data synchronization purposes, the MSB register should be read first if the user wants to read both MSB and
LSB registers. The LSB will be locked after the MSB is read. The LSB will be unlocked after being read. If the
user reads MSBs consecutively, each time the MSB is read, the LSB associated with that temperature will be
locked in and override the previous LSB value locked-in.
MANUFACTURERS ID REGISTER
(Read Address FEh) The default value is 01h.
DIE REVISION CODE REGISTER
(Read Address FFh) Value to be determined. This register will increment by 1 every time there is a revision to
the die by Texas Instruments.
Applications Hints
The LM95221 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 LM95221'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 LM95221 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 LM95221'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 LM95221's temperature.
The LM95221 has been optimized to measure the remote thermal diode with a non-ideality of 1.008 and a series
resistance of 2.7Ω. The thermal diode on the Pentium 4 processor on the 90 nm process has a typical nonideality of 1.011 and a typical series resistance of 3.33Ω. Therefore, when measuring this thermal diode with the
LM95221 a typical offset of +1.5°C will be observed. This offset can be compensated for easily by subracting
1.5°C from the LM95221's readings. 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.
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.
When measuring a diode-connected 2N3904, with an LM95221, an offset of -3.25°C will be observed. This offset
can simply be added to the LM95221's reading:
T2N3904 = TLM95221 + 3.25°C
(1)
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DIODE NON-IDEALITY
Diode Non-Ideality Factor Effect on Accuracy
When a transistor is connected as a diode, the following relationship holds for variables VBE, T and If:
Vbe
IF = IS e KVt - 1
where
•
•
•
•
•
•
•
•
Vt = kqT
q = 1.6×10−19 Coulombs (the electron charge),
T = Absolute Temperature in Kelvin
k = 1.38×10−23joules/K (Boltzmann's constant),
η is the non-ideality factor of the process the diode is manufactured on,
IS = Saturation Current and is process dependent,
If= Forward Current through the base emitter junction
VBE = Base Emitter Voltage drop
(2)
In the active region, the -1 term is negligible and may be eliminated, yielding the following equation:
Vbe
IF = IS eKVt
(3)
In the above equation, η and IS are dependant upon the process that was used in the fabrication of the particular
diode. By forcing two currents with a very controlled ratio (N) and measuring the resulting voltage difference, it is
possible to eliminate the IS term. Solving for the forward voltage difference yields the relationship:
Vbe = K kqT ln (N)
(4)
The voltage seen by the LM95221 also includes the IFRS voltage drop of the series resistance. The non-ideality
factor, η, is the only other parameter not accounted for and depends on the diode that is used for measurement.
Since ΔVBE 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 4 and Mobile Pentium Processor-M Intel specifies a ±0.1% variation in
η from part to part. As an example, assume a temperature sensor has an accuracy specification of ±1°C at room
temperature of 25 °C and the process used to manufacture the diode has a non-ideality variation of ±0.1%. The
resulting accuracy of the temperature sensor at room temperature will be:
TACC = ± 1°C + (±0.1% of 298 °K) = ±1.4 °C
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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.
η, non-ideality
Processor Family
Series R
min
typ
max
Pentium II
1
1.0065
1.0173
Pentium III CPUID 67h
1
1.0065
1.0125
Pentium III CPUID
68h/PGA370Socket/Celeron
1.0057
1.008
1.0125
Pentium 4, 423 pin
0.9933
1.0045
1.0368
Pentium 4, 478 pin
0.9933
1.0045
1.0368
Pentium 4 on 0.13 micron process,
2-3.06GHz
1.0011
1.0021
1.0030
Pentium 4 on 90 nm process
Pentium M Processor (Centrino)
AMD Athlon MP model 6
3.33 Ω
1.011
1.00151
MMBT3904
1.00220
3.64 Ω
1.00289
3.06 Ω
1.003
1.002
1.008
1.016
Compensating for Diode Non-Ideality
In order to compensate for the errors introduced by non-ideality, the temperature sensor is calibrated for a
particular processor. Texas Instruments temperature sensors are always calibrated to the typical non-ideality of a
given processor type. The LM95221 is calibrated for a non-ideality of 1.008 and a series resistance of 2.7Ω.
When a temperature sensor calibrated for a particular processor type is used with a different processor type or a
given processor type has a non-ideality that strays from the typical, errors are introduced.
Temperature errors associated with non-ideality may be reduced in a specific temperature range of concern
through use of an offset calibration accomplished through software.
Please send an email to hardware.monitor.team@nsc.com requesting further information on our recommended
offset value for different processor types.
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PCB LAYOUT FOR MINIMIZING NOISE
Figure 12. Ideal Diode Trace Layout
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 LM95221 can cause temperature
conversion errors. Keep in mind that the signal level the LM95221 is trying to measure is in microvolts. The
following guidelines should be followed:
1. VDD should be bypassed with a 0.1µF capacitor in parallel with 100pF. The 100pF capacitor should be placed
as close as possible to the power supply pin. A bulk capacitance of approximately 10µF needs to be in the
near vicinity of the LM95221.
2. A 2.2nF diode bypass capacitor is required to filter high frequency noise. Place the 2.2nF capacitor as close
as possible to the LM95221's D+ and D− pins. Make sure the traces to the 2.2nF capacitor are matched.
3. Ideally, the LM95221 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. This
error can be compensated by using simple software offset compensation.
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.
5. Avoid routing diode traces in close proximity to power supply switching or filtering inductors.
6. 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 LM95221's GND pin is as close as possible to the Processors GND
associated with the sense diode.
9. Leakage current between D+ and GND and between D+ and D− should be kept to a minimum. Thirteen
nano-amperes of leakage can cause as much as 0.2°C of error in the diode temperature reading. Keeping
the printed circuit board as clean as possible will minimize leakage current.
Noise coupling into the digital lines greater than 400mVp-p (typical hysteresis) and undershoot less than 500mV
below GND, may prevent successful SMBus communication with the LM95221. 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 RC lowpass filter with a 3db
corner frequency of about 40MHz is included on the LM95221's SMBCLK input. Additional resistance can be
added in series with the SMBDAT 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 SMBDAT and SMBCLK lines.
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SNIS134B – MAY 2004 – REVISED MARCH 2013
REVISION HISTORY
Changes from Revision A (March 2013) to Revision B
•
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 18
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LM95221CIMM/NOPB
ACTIVE
VSSOP
DGK
8
1000
RoHS & Green
SN
Level-1-260C-UNLIM
0 to 85
T21C
LM95221CIMMX/NOPB
ACTIVE
VSSOP
DGK
8
3500
RoHS & Green
SN
Level-1-260C-UNLIM
0 to 85
T21C
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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