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LM80 Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor
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1FEATURES KEY SPECIFICATIONS
2• Temperature Sensing • Voltage Monitoring Error ±1% (Max)
• 7 Positive Voltage Inputs • Temperature Error (−25°C to +125°C) ±3°C
(Max)
• 2 Programmable Fan Speed Monitoring Inputs • Supply Voltage Range 2.8 to 5.75 V
• 10 mV LSB and 2.56V Input Range Accepts
Outputs From Linear Temperature Sensors • Supply Current: Operating 0.2 mA typ
Such as the LM50 • Supply Current: Shutdown 15 µA typ
• Chassis Intrusion Detector Input • ADC Resolution 8 Bits
• WATCHDOG Comparison of all Monitored • Temperature Resolution 0.5ºC
Values
• Separate Input to Show Status in Interrupt DESCRIPTION
Status Register of Additional External The LM80 provides 7 positive voltage inputs,
Temperature Sensors such as the LM56 or temperature measurement, fan speed measurement,
and hardware monitoring on an I2C interface. The
LM75 LM80 performs WATCHDOG comparisons of all
• I2C Serial Bus Interface Compatibility measured values and an open-drain interrupt output
• Shutdown Mode to Minimize Power becomes active when any values exceed
Consumption programmed limits. A Chassis Intrusion input is
provided to monitor and reset an external circuit
• Programmable RST_OUT/OS pin: RST_OUT designed to latch a chassis intrusion event.
Provides a Reset Output; OS Provides an
Interrupt Output Activated by an The LM80 is especially suited to interface to both
Overtemperature Shutdown Event linear and digital temperature sensors. The 10 mV
LSB and 2.56 volt input range is ideal for accepting
APPLICATIONS inputs from a linear sensor such as the LM50. The
BTI is used as an input from either digital or
• System Thermal and Hardware Monitoring for thermostat sensors such as LM75 and LM56.
Servers and PCs The LM80's 2.8V to 5.75V supply voltage range, low
• Office Electronics supply current, and I2C interface make it ideal for a
• Electronic Test Equipment and wide range of applications. These include hardware
Instrumentation monitoring and protection applications in personal
computers, electronic test equipment, and office
electronics.
1Please 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.
2All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 1999–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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PIN DESCRIPTIONS
Pin Pin Number Type Description
Name(s) Number of Pins
INT_IN 1 1 Digital Input This is an active low input that propagates the INT_IN signal to the INT
output of the LM80 via Interrupt Mask Register 1 Bit 7 and INT enable Bit
1 of the Configuration Register.
SDA 2 1 Digital I/O Serial Bus bidirectional Data. Open-drain output.
SCL 3 1 Digital Input Serial Bus Clock.
FAN1-FAN2 4-5 2 Digital Inputs 0 to V+fan tachometer inputs.
BTI 6 1 Digital Input Board Temperature Interrupt driven by O.S. outputs of additional
temperature sensors such as LM75. Provides internal pull-up of 10 kΩ.
CI (Chassis 7 1 Digital I/O An active high input from an external circuit which latches a Chassis
Intrusion) Intrusion event. This line can go high without any clamping action
regardless of the powered state of the LM80. The LM80 provides an
internal open drain on this line, controlled by Bit 5 of the Configuration
Register, to provide a minimum 10 ms reset of this line.
GND 8 1 GROUND Internally connected to all of the digital circuitry.
V+(+2.8V to 9 1 POWER +3.3V or +5V V+power. Bypass with the parallel combination of 10 μF
+5.75V) (electrolytic or tantalum) and 0.1 μF (ceramic) bypass capacitors.
INT 10 1 Digital Output Non-Maskable Interrupt (open source)/Interrupt Request (open drain).
The mode is selected with Bit 5 of the Configuration Register and the
output is enabled when Bit 1 of the Configuration Register is set to 1.
The default state is disabled.
GPO (Power Switch 11 1 Digital Output An active low open drain output intended to drive an external P-channel
Bypass) power MOSFET for software power control.
NTEST_IN/ 12 1 Digital Input An active-low input that enables NAND Tree board-level connectivity
RESET_IN testing. Refer to NAND TREE TESTS on NAND Tree testing. Whenever
NAND Tree connectivity is enabled the LM80 is also reset to its power on
state.
RST_OUT/OS 13 1 Digital Output Master Reset, 5 mA driver (open drain), active low output with a 10 ms
minimum pulse width. Available when enabled via Bit 4 in Configuration
Register and Bit 7 of the Fan Divisor/RST_OUT/OS Register. Bit 6 of the
Fan Divisor/RST_OUT/OS Register enables this output as an active low
Overtemperature Shutdown (OS).
GNDA 14 1 GROUND Internally connected to all analog circuitry. The ground reference for all
analog inputs. This pin needs to be taken to a low noise analog ground
plane for optimum performance.
IN6-IN0 15-21 7 Analog Inputs 0V to 2.56V full scale range Analog Inputs.
A0/NTEST_OUT 22 1 Digital I/O The lowest order bit of the Serial Bus Address. This pin functions as an
output when doing a NAND Tree test.
A1-A2 23-24 2 Digital Inputs The two highest order bits of the Serial Bus Address.
TOTAL PINS 24
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.
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Absolute Maximum Ratings(1)(2)
Positive Supply Voltage (V+) 6.5V
Voltage on Any Input or Output Pin −0.3V to (V++0.3V)
Ground Difference (GND - GNDA) ±300 mV
Input Current at any Pin(3) ±5 mA
Package Input Current(3) ±20 mA
Maximum Junction Temperature (TJmax) 150°C
ESD Susceptibility(4) Human Body Model 2000V
Machine Model 125V
Soldering Information
PW Package Vapor Phase (60 seconds) 215°C
Infrared (15 seconds) 235°C
Storage Temperature −65°C to +150°C
For soldering specifications http://www.ti.com/lit/SNOA549
(1) All voltages are measured with respect to GND, unless otherwise specified
(2) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. For ensured specifications and test conditions, see
Electrical Characteristics. The ensured specifications apply only for the test conditions listed. Some performance characteristics may
degrade when the device is not operated under the listed test conditions.
(3) When the input voltage (VIN) at any pin exceeds the power supplies (VIN< (GND or GNDA) or VIN>V +), 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.
(4) The human body model is a 100 pF capacitor discharged through a 1.5 kΩresistor into each pin. The machine model is a 200 pF
capacitor discharged directly into each pin.
Operating Ratings(1)(2)
Operating Temperature Range TMIN ≤TA≤TMAX
LM80CIMT-3, LM80CIMT-5 −25°C ≤TA≤+125°C
Specified Temperature Range TMIN ≤TA≤TMAX
LM80CIMT-3, LM80CIMT-5 −25°C ≤TA≤+125°C
Junction to Ambient Thermal Resistance Package Number: PW 95°C/W
(θJA(3) )
Supply Voltage (V+) +2.8V to +5.75V
Ground Difference (|GND −GNDA|) ≤100 mV
VIN Voltage Range −0.05V to V++ 0.05V
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. For ensured specifications and test conditions, see
Electrical Characteristics. The ensured specifications apply only for the test conditions listed. Some performance characteristics may
degrade when the device is not operated under the listed test conditions.
(2) All voltages are measured with respect to GND, unless otherwise specified
(3) The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax, θJA and the ambient temperature,
TA. The maximum allowable power dissipation at any temperature is PD= (TJmax−TA)/θJA.
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DC Electrical Characteristics
The following specifications apply for +2.8 VDC ≤V+≤+3.8 VDC for LM80CIMT-3, +4.25 VDC ≤V+≤+5.75 VDC for LM80CIMT-5,
IN0-IN6 RS= 25Ω, unless otherwise specified. Boldface limits apply for TA= TJ= TMIN to TMAX;all other limits TA= TJ=
25°C.(1)
Units
Symbol Parameter Conditions Typical(2) Limits(3) (Limits)
POWER SUPPLY CHARACTERISTICS
I+Supply Current Interface Inactive and V+= 5.75V 0.2 2.0 mA (max)
Interface Inactive and V+= 3.8V 0.18 1.5 mA (max)
Shutdown Mode 15 μA
TEMPERATURE-to-DIGITAL CONVERTER CHARACTERISTICS
Temperature Error −25°C ≤TA≤+125°C ±3 °C (max)
Resolution 0.5 °C (min)
ANALOG-to-DIGITAL CONVERTER CHARACTERISTICS
Resolution (8 bits with full-scale at 2.56V) 10 mV
TUE Total Unadjusted Error See(4) ±1 % (max)
DNL Differential Non-Linearity ±1 LSB (max)
PSS Power Supply Sensitivity ±1 %/V
tCTotal Monitoring Cycle Time See(5)
9-bit Temp resolution 1.0 1.5 sec (max)
12-bit Temp resolution 2sec (max)
MULTIPLEXER/ADC INPUT CHARACTERISTICS
On Resistance 0.5 10 kΩ(max)
Input Current (On Channel Leakage Current) ±1 μA
Off Channel Leakage Current ±1 μA
FAN RPM-to-DIGITAL CONVERTER
Fan RPM Error +25°C ≤TA≤+75°C ±10 % (max)
−10°C ≤TA≤+100°C ±15 % (max)
−25°C ≤TA≤+125°C ±20 % (max)
Full-scale Count 255 (max)
FAN1 and FAN2 Nominal Input Divisor = 1, Fan Count = 153(6) 8800 RPM
RPM (See FAN INPUTS)Divisor = 2, Fan Count = 153(6) 4400 RPM
Divisor = 3, Fan Count = 153(6) 2200 RPM
Divisor = 4, Fan Count = 153(6) 1100 RPM
Internal Clock Frequency +25°C ≤TA≤+75°C 20.2 kHz (min)
22.5 24.8 kHz (max)
19.1 kHz (min)
−10°C ≤TA≤+100°C 22.5 25.9 kHz (max)
18 kHz (min)
−25°C ≤TA≤+125°C 22.5 27 kHz (max)
(1) Each input and output is protected by a nominal 6.5V breakdown voltage zener diode to GND; as shown below, input voltage magnitude
up to 0.3V above V+or 0.3V below GND will not damage the LM80. There are parasitic diodes that exist between the inputs and the
power supply rails. Errors in the ADC conversion can occur if these diodes are forward biased by more than 50 mV. As an example, if
V+is 4.50 VDC, input voltage must be ≤4.55 VDC, to ensure accurate conversions.
(2) Typicals are at TJ=TA=25°C and represent most likely parametric norm.
(3) Limits are specified to AOQL (Average Outgoing Quality Level).
(4) TUE (Total Unadjusted Error) includes Offset, Gain and Linearity errors of the ADC.
(5) Total Monitoring Cycle Time includes temperature conversion, 7 analog input voltage conversions and 2 tachometer readings. Each
input voltage conversion takes 100 ms typical and 112 ms maximum. 8-plus sign Temperature resolution takes 100 ms typical and 112
ms maximum, while 11-bit plus sign takes 800 ms typical and 900 ms maximum. Fan tachometer readings take 20 ms typical, at 4400
rpm, and 200 ms max.
(6) The total fan count is based on 2 pulses per revolution of the fan tachometer output.
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DC Electrical Characteristics (continued)
The following specifications apply for +2.8 VDC ≤V+≤+3.8 VDC for LM80CIMT-3, +4.25 VDC ≤V+≤+5.75 VDC for LM80CIMT-5,
IN0-IN6 RS= 25Ω, unless otherwise specified. Boldface limits apply for TA= TJ= TMIN to TMAX;all other limits TA= TJ=
25°C.(1)
Units
Symbol Parameter Conditions Typical(2) Limits(3) (Limits)
DIGITAL OUTPUTS: A0/NTEST_OUT, INT
VOUT(1) Logical “1” Output Voltage IOUT = +5.0 mA at V+= +4.25V, 2.4 V (min)
IOUT = +3.0 mA at V+= +2.8V
VOUT(0) Logical “0” Output Voltage IOUT =−5.0 mA at V+= +5.75V, 0.4 V (max)
IOUT =−3.0 mA at V+= +3.8V
OPEN DRAIN OUTPUTS: GPO, RST_OUT/OS, CI
VOUT(0) Logical “0” Output Voltage IOUT =−5.0 mA at V+= +5.75V, 0.4 V (min)
IOUT =−3.0 mA at V+= +3.8V
IOH High Level Output Current VOUT = V+0.1 100 μA (max)
RST_OUT/OS, 30 10 ms (min)
CI Pulse Width
OPEN DRAIN SERIAL BUS OUTPUT: SDA
VOUT(0) Logical “0” Output Voltage IOUT =−3.0 mA at V+= +5.75V, 0.4 V (min)
IOUT =−3.0 mA at V+= +3.8V
IOH High Level Output Current VOUT = V+0.1 100 μA (max)
DIGITAL INPUTS: A0/NTEST_Out, A1-A2, BTI, CI (Chassis Intrusion), INT_IN, and NTEST_IN/Reset_IN
VIN(1) Logical “1” Input Voltage 2.0 V (min)
VIN(0) Logical “0” Input Voltage 0.8 V (max)
SERIAL BUS INPUTS (SCL, SDA) and FAN TACH PULSE INPUTS (FAN1, FAN2)
VIN(1) Logical “1” Input Voltage 0.7 × V+V (min)
VIN(0) Logical “0” Input Voltage 0.3 × V+V (max)
ALL DIGITAL INPUTS Except for BTI
IIN(1) Logical “1” Input Current VIN = V+−0.005 −1μA (min)
IIN(0) Logical “0” Input Current VIN = 0 VDC 0.005 1μA (max)
CIN Digital Input Capacitance 20 pF
BTI Digital Input
IIN(1) Logical “1” Input Current VIN = V+−1−10 μA (min)
IIN(0) Logical “0” Input Current VIN = 0 VDC 500 2000 μA (max)
CIN Digital Input Capacitance 20 pF
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AC Electrical Characteristics
The following specifications apply for +2.8 VDC ≤V+≤+3.8 VDC for LM80CIMT-3, +4.25 VDC ≤V+≤+5.75 VDC for LM80CIMT-5,
unless otherwise specified. Boldface limits apply for TA= TJ= TMIN to TMAX;all other limits TA= TJ= 25°C.(1)
Symbol Typical(2) Limits(3) Units
Parameter Conditions (Limits)
SERIAL BUS TIMING CHARACTERISTICS
t1SCL (Clock) Period 2.5 μs (min)
t2Data In Setup Time to SCL High 100 ns (min)
t3Data Out Stable After SCL Low 0ns (min)
t4SDA Low Setup Time to SCL Low (start) 100 ns (min)
t5SDA High Hold Time After SCL High (stop) 100 ns (min)
(1) Timing specifications are tested at the Serial Bus Input logic levels, VIN(0) = 0.3 × V+for a falling edge and VIN(1) =0.7 × V+for a rising
edge, when the SCL and SDA edge rates are similar.
(2) Typicals are at TJ=TA=25°C and represent most likely parametric norm.
(3) Limits are specified to AOQL (Average Outgoing Quality Level).
Figure 1. Serial Bus Timing Diagram
Figure 2. ESD Protection Input Structure
Pin Name D1 D2 D3 Pin Name D1 D2 D3
INT_IN x(1) x x NTEST_IN/ x
Reset_IN
CI x x IN0-IN6 x x x
GPO x x BTI x x x
FAN1–FAN2 x INT x x x
SCL x A1-A2 x x x
SDA x x A0/NTEST_Out x x x
RST_OUT/OS x
(1) An x indicates that the diode exists.
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FUNCTIONAL DESCRIPTION
GENERAL DESCRIPTION
The LM80 provides 7 analog inputs, a temperature sensor, a Delta-Sigma ADC (Analog-to-Digital Converter), 2
fan speed counters, WATCHDOG registers, and a variety of inputs and outputs on a single chip. A two wire
Serial Bus interface is provided. The LM80 performs power supply, temperature, fan control and fan monitoring
for personal computers.
The LM80 continuously converts analog inputs to 8-bit digital words with a 10 mV LSB (Least Significant Bit)
weighting, yielding input ranges of 0 to 2.56V. The Analog inputs are intended to be connected to the several
power supplies present in a a typical computer. Temperature can be converted to a 9-bit or 12-bit two's
complement word with resolutions of 0.5°C LSB or 0.0625°C LSB, respectively.
Fan inputs can be programmed to accept either fan failure indicator or tachometer signals. Fan failure signals
can be programmed to be either active high or active low. Fan inputs measure the period of tachometer pulses
from the the fans, providing a higher count for lower fan speeds. The fan inputs are digital inputs with and
acceptable range of 0 to V+volts and a transition level of approximately V+/2 volts. Full scale fan counts are 255
(8-bit counter), which represent a stopped or very slow fan. Nominal speed based on a count of 153, are
programmable from 1100 to 8800 RPM. Signal conditioning circuitry is included to accommodate slow rise and
fall times.
The LM80 provides a number of internal registers, as detailed in Figure 4. These include:
•Configuration Register: Provides control and configuration.
•Interrupt Status Registers: Two registers to provide status of each WATCHDOG limit or Interrupt event.
•Interrupt Mask Registers: Allows masking of individual Interrupt sources, as well as separate masking for
each of both hardware Interrupt outputs.
•Fan Divisor/RST_OUT/OS Registers: Bits 0-5 of this register contain the divisor bits for FAN1 and FAN2
inputs. Bits 6-7 control the function of the RST_OUT/OS output.
•OS Configuration/Temperature Resolution Register: The configuration of the OS (Overtemperature
Shutdown) is controlled by the lower 3 bits of this register. Bit 3 enables 12-bit temperature conversions. Bits
4-7 reflect the lower four bits of the temperature reading for a 12-bit resolution.
•Value RAM: The monitoring results: temperature, voltages, fan counts, and Fan Divisor/RST_OUT/OS
Register limits are all contained in the Value RAM. The Value RAM consists of a total of 32 bytes. The first 10
bytes are all of the results, the next 20 bytes are the Fan Divisor/RST_OUT/OS Register limits, and are
located at 20h-3Fh, including two unused bytes in the upper locations.
When the LM80 is started, it cycles through each measurement in sequence, and it continuously loops through
the sequence approximately once every second. Each measured value is compared to values stored in
WATCHDOG, or Limit registers. When the measured value violates the programmed limit the LM80 will set a
corresponding Interrupt in the Interrupt Status Registers. Two hardware Interrupt lines, INT and RST_OUT/OS
are available. INT is fully programmable with masking of each Interrupt source, and masking of each output.
RST_OUT/OS is dedicated to the temperature reading WATCHDOG registers. In addition, the Fan Divisor
register has control bits to enable or disable the hardware Interrupts.
Additional digital inputs are provided for chaining of INT, outputs of multiple external LM75 temperature sensors
via the BTI (Board Temperature Interrupt) input, and a CI (Chassis Intrusion) input. The Chassis Intrusion input is
designed to accept an active high signal from an external circuit that latches when the case is removed from the
computer.
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Internal Registers of the LM80
Table 1. The internal registers and their corresponding internal LM80 address is as follows:
Register LM80 Internal Hex Power on Value Notes
Address (This is the data
to be written to the
Address Register)
Configuration Register 00h 0000 1000
Interrupt Status Register 1 01h 0000 0000
Interrupt Status Register 2 02h 0000 0000
Interrupt Mask Register 1 03h 0000 0000
Interrupt Mask Register 2 04h 0000 0000
Fan Divisor/RST_OUT/OS 05h 0001 0100 FAN1 and FAN2 divisor = 2 (count of 153 = 4400 RPM)
Register
OS/ Configuration and 06h 0000 0001
Temperature Resolution
Register
Value RAM 20h-3Fh
Serial Bus Interface
Serial Bus Timing
Figure 5. Serial Bus Write to the Internal Address Register followed by the Data Byte
Figure 6. Serial Bus Write to the Internal Address Register Only
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Figure 7. Serial Bus Read from a Register with the Internal Address Register Preset to Desired Location
The Serial Bus control lines consists of the SDA (serial data), SCL (serial clock) and A0-A1 (address) pins. The
LM80 can only operate as a slave. The SCL line only controls the serial interface, all other clock functions within
LM80 such as the ADC and fan counters are done with a separate asynchronous internal clock.
When using the Serial Bus Interface a write will always consist of the LM80 Serial Bus Interface Address byte,
followed by the Internal Address Register byte, then the data byte. There are two cases for a read:
1. If the Internal Address Register is known to be at the desired Address, simply read the LM80 with the Serial
Bus Interface Address byte, followed by the data byte read from the LM80.
2. If the Internal Address Register value is unknown, write to the LM80 with the Serial Bus Interface Address
byte, followed by the Internal Address Register byte. Then restart the Serial Communication with a Read
consisting of the Serial Bus Interface Address byte, followed by the data byte read from the LM80.
The default power on Serial Bus address for the LM80 is: 0101(A2)(A1)(A0) binary, where A0-A2 reflect the state
of the pins defined by the same names.
All of these communications are depicted in the Serial Bus Interface Timing Diagrams as shown in Serial Bus
Timing.
USING THE LM80
Power On
When power is first applied, the LM80 performs a “power on reset” on several of its registers. The power on
condition of registers is shown in Table 1. Registers whose power on values are not shown have power on
conditions that are indeterminate (this includes the value RAM and WATCHDOG limits). The ADC is inactive. In
most applications, usually the first action after power on would be to write WATCHDOG limits into the Value
RAM.
Resets
Configuration Register INITIALIZATION accomplishes the same function as power on reset. The Value RAM
conversion results, and Value RAM WATCHDOG limits are not Reset and will be indeterminate immediately after
power on. If the Value RAM contains valid conversion results and/or Value RAM WATCHDOG limits have been
previously set, they will not be affected by a Configuration Register INITIALIZATION. Power on reset, or
Configuration Register INITIALIZATION, clear or initialize the following registers (the initialized values are shown
in Table 1):
• Configuration Register
• Interrupt Status Register 1
• Interrupt Status Register 2
• Interrupt Mask Register 1
• Interrupt Mask Register 2
• Fan Divisor/RST_OUT/OS Register
• OS Configuration/Temperature Resolution Register
• Value Ram (Registers at Address 20h - 3Fh, which include: Temperature reading, IN0-IN6 readings, FAN1
and FAN2 readings, and WATCHDOG limits)
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Configuration Register INITIALIZATION is accomplished by setting Bit 7 of the Configuration Register high. This
Bit automatically clears after being set.
The LM80 can be reset to it's “power on state” by taking NTEST_IN/Reset_IN pin low for at least 50 ns.
Using the Configuration Register
The Configuration Register provides all control over the LM80. At power on, the ADC is stopped and INT_Clear
is asserted, clearing the INT and RST_OUT/OS hardwire outputs. The Configuration Register starts and stops
the LM80, enables and disables INT outputs, clears and sets CI and GPO I/O pins, initiates reset pulse on
RST_OUT/OS pin, and provides the Reset function described in Resets.
Bit 0 of the Configuration Register controls the monitoring loop of the LM80. Setting Bit 0 low stops the LM80
monitoring loop and puts the LM80 in shutdown mode, reducing power consumption. Serial Bus communication
is possible with any register in the LM80 although activity on these lines will increase shutdown current, up to as
much as maximum rated supply current, while the activity takes place. Taking Bit 0 high starts the monitoring
loop, described in more detail subsequently.
Bit 1 of the Configuration Register enables the INT Interrupt hardwire output when this bit is taken high.
Bit 2 of the Configuration Register defines whether the INT pin is open source or open drain.
Bit 3 clears the INT output when taken high. The LM80 monitoring function will stop until bit 3 is taken low. The
content of the Interrupt (INT) Status Registers will not be affected.
Bit4, when taken high, will initiate a 10 ms RESET signal on the RST_OUT/OS output (when this pin is in the
RST mode).
When bit 5 is taken high the CI (Chassis Intrusion) pin is reset.
Bit 6 of the configuration register sets or clears the GPO output. This pin can be used in software power control
by activating an external power control MOSFET.
Starting Conversions
3.4 STARTING CONVERSION The monitoring function (Analog inputs, temperature, and fan speeds) in the
LM80 is started by writing to the Configuration Register and setting INT_Clear (Bit 3), low, and Start (Bit 0), high.
The LM80 then performs a round-robin monitoring of all analog inputs, temperature, and fan speed inputs
approximately once a second. If the temperature resolution is set to 12 bits one complete monitoring function will
take approximately 2 seconds. The sequence of items being monitored corresponds to locations in the Value
RAM (except for the Temperature reading) and is:
1. Temperature
2. IN0
3. IN1
4. IN2
5. IN3
6. IN4
7. IN5
8. IN6
9. Fan 1
10. Fan 2
Reading Conversion Results
The conversion results are available in the Value RAM. Conversions can be read at any time and will provide the
result of the last conversion. Because the ADC stops, and starts a new conversion whenever the conversion is
read, reads of any single value should not be done more often than once every 120 ms. When reading all values
with the temperature resolution set to 9-bits, allow at least 1.5 seconds between reading groups of values.
Reading more frequently than once every 1.5 seconds can also prevent complete updates of Interrupt Status
Registers and Interrupt Outputs. If the temperature resolution is set to 12-bit, allow at least 2.0 seconds between
reading groups of values.
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A typical sequence of events upon power on of the LM80 would consist of:
1. Set WATCHDOG Limits
2. Set Interrupt Masks
3. Start the LM80 monitoring process
ANALOG INPUTS
The 8-bit ADC has a 10 mV LSB, yielding a 0V to 2.55V (2.56 - 1LSB) input range. This is true for all analog
inputs. In PC monitoring applications these inputs would most often be connected to power supplies. The 2.5,
3.3, ± 5 and ± 12 volt inputs should be attenuated with external resistors to any desired value within the input
range. Care should be taken not to exceed the power supply voltage (V+) at any time.
A typical application, such as is shown in Figure 8, might select the input voltage divider to provide 1.9V at the
analog inputs of the LM80. This is sufficiently high for good resolution of the voltage, yet leaves headroom for
upward excursions from the supply of about 25%. To simplify the process of resistor selection, set the value of
R2 first. Select a value for R2 or R4 between 10 kΩand 100 kΩThis is low enough to avoid errors due to input
leakage currents yet high enough to both protect the inputs under overdrive conditions as well as minimize
loading of the source. Then select R1 or R3 to provide a 1.9V input as show in Figure 8.
Resistor values shown in table provide approximately 1.9V at the analog inputs.
Figure 8. Input Examples
For positive input voltages the equation for calculating R1 is as follows:
R1 = [ (VS−VIN) / VIN] R2 (1)
For negative input voltages the equation for Calculating R3 is as follows:
R3 = [ (VS−VIN) / (VIN −5V)] R4 (2)
The analog inputs have internal diodes that clamp inputs exceeding the power supply and ground. Exceeding
any analog input has no detrimental effect on other channels. The input diodes will also clamp voltages
appearing at the inputs of an un-powered LM80. External resistors should be included to limit input currents to
the values given in the ABSOLUTE MAXIMUM RATINGS for Input Current At Any Pin. Inputs with the attenuator
networks will usually meet these requirements. If it is possible for inputs without attenuators to be turned on while
LM80 is powered off, additional resistors of about 10 kΩshould be added in series with the inputs to limit the
input current.
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Voltage Measurements R1 or R3 R2 or R4 Voltage at Analog Inputs
(VS) ( ADC code 190)
+2.5V 23.7 kΩ75 kΩ+1.9V
+3.3V 22.1 kΩ30 kΩ+1.9V
+5.0V 24 kΩ14.7 kΩ+1.9V
+12V 160 kΩ30.1 kΩ+1.9V
−12V 160 kΩ35.7 kΩ+1.9V
−5V 36 kΩ16.2 kΩ+1.9V
LAYOUT AND GROUNDING
Analog inputs will provide best accuracy when referred to the AGND pin or a supply with low noise. A separate,
low-impedance ground plane for analog ground, which provides a ground point for the voltage dividers and
analog components, will provide best performance but is not mandatory. Analog components such as voltage
dividers should be located physically as close as possible to the LM80.
The power supply bypass, the parallel combination of 10 μF (electrolytic or tantalum) and 0.1 μF (ceramic)
bypass capacitors connected between pin 9 and ground, should also be located as close as possible to the
LM80.
FAN INPUTS
Inputs are provided for signals from fans equipped with tachometer outputs. These are logic-level inputs with an
approximate threshold of V+/2. Signal conditioning in the LM80 accommodates the slow rise and fall times typical
of fan tachometer outputs. The maximum input signal range is 0 to V+. In the event these inputs are supplied
from fan outputs which exceed 0 to V+, either resistive division or diode clamping must be included to keep
inputs within an acceptable range, as shown in Alternatives for Fan Inputs. R2 is selected so that it does not
develop excessive error voltage due to input leakage. R1 is selected based on R2 to provide a minimum input of
2V and a maximum of V+. R1 should be as low as possible to provide the maximum possible input up to V+for
best noise immunity. Alternatively, use a shunt reference or zener diode to clamp the input level.
If fans can be powered while the power to the LM80 is off, the LM80 inputs will provide diode clamping. Limit
input current to the Input Current at Any Pin specification shown in the Absolute Maximum Ratings section. In
most cases, open collector outputs with pull-up resistors inherently limit this current. If this maximum current
could be exceeded, either a larger pull up resistor should be used or resistors connected in series with the fan
inputs.
The Fan Inputs gate an internal 22.5 kHz oscillator for one period of the Fan signal into an 8-bit counter
(maximum count = 255). The default divisor, located in the VID/Fan Divisor Register, is set to 2 (choices are 1, 2,
4, and 8) providing a nominal count of 153 for a 4400 rpm fan with two pulses per revolution. Typical practice is
to consider 70% of normal RPM a fan failure, at which point the count will be 219.
Determine the fan count according to:
(3)
Note that Fan 1 and Fan 2 Divisors are programmable via the Fan Divisor/RST_OUT/OS Register.
FAN1 and FAN2 inputs can also be programmed to be level sensitive digital inputs.
Fans that provide only one pulse per revolution would require a divisor set twice as high as fans that provide two
pulses, thus maintaining a nominal fan count of 153. Therefore the divisor should be set to 4 for a fan that
provides 1 pulse per revolution with a nominal RPM of 4400.
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Alternatives for Fan Inputs
Fan with Tach Pull-Up to +5V
Fan with Tach Pull-Up to +12V, or Totem-Pole Output and Resistor Attenuator
Fan with Tach Pull-Up to +12V and Diode Clamp
Fan with Strong Tach Pull-Up or Totem Pole Output and Diode Clamp
Counts are based on 2 pulses per revolution tachometer outputs.
RPM Time per Revolution Counts for “Divide by 2” Comments
(Default) in Decimal
4400 13.64 ms 153 counts Typical RPM
3080 19.48 ms 219 counts 70% RPM
2640 22.73 ms 255 counts 60% RPM
(maximum counts)
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Counts for the Given Speed Time per Revolution for
Mode Select Nominal RPM Time per Revolution 70% RPM
in Decimal 70% RPM
Divide by 1 8800 6.82 ms 153 6160 9.74 ms
Divide by 2 4400 13.64 ms 153 3080 19.48 ms
Divide by 4 2200 27.27 ms 153 1540 38.96 ms
Divide by 8 1100 54.54 ms 153 770 77.92 ms
(4)
Temperature Measurement System
The LM80 bandgap type temperature sensor and ADC perform 9-bit or a 12-bit two's-complement conversions of
the temperature. An 8-bit digital comparator is also incorporated that compares the readings to the user-
programmable Hot and Overtemperature setpoints, and Hysteresis values.
(Non-Linear Scale for Clarity)
Figure 9. 9-bit Temperature-to-Digital Transfer Function
(Non-Linear Scale for Clarity)
Figure 10. 12-bit Temperature-to-Digital Transfer Function
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Temperature Data Format
Temperature data can be read from the Temperature, Thot, Thot hyst, Tos, and Tos hyst setpoint registers; and written
to the Thot, Thot hyst, Tos, and Tos hyst setpoint registers. These registers are located in register addresses 38h -
3Bh, and each setpoint is represented by an 8-bit, two's complement word with an LSB (Least Significant Bit)
equal to 1°C:
Temperature Digital Output
Binary Hex
+125°C 0111 1101 7Dh
+25°C 0001 1001 19h
+1.0°C 0000 0001 01h
+0°C 0000 0000 00h
−1.0°C 1111 1111 FFh
−25°C 1110 0111 E7h
−55°C 1100 1001 C9h
By default Temperature Register data is represented by a 9-bit two's complement digital word with the LSB
having a resolution of 0.5°C:
Temperature Digital Output
Binary Hex
+125°C 0 1111 1010 0 FAh
+25°C 0 0011 0010 0 32h
+1.5°C 0 0000 0011 0 03h
+0°C 0 0000 0000 0 00h
−0.5°C 1 1111 1111 1 FFh
−25°C 1 1100 1110 1 CEh
−55°C 1 1001 0010 1 92h
Temperature Register data can also be represented by a 12-bit two's complement digital word with a LSB of
0.0625°C:
Temperature Digital Output
Binary Hex
+125°C 0111 1100 0000 7 D0h
+25°C 0001 1001 0000 1 90h
+1.0°C 0000 0001 0000 0 10h
+0.0625°C 0000 0000 0001 0 01h
0°C 0000 0000 0000 00h
−0.0625°C 1111 1111 1111 F FFh
−1.0°C 1111 1111 0000 F F0h
−25°C 1110 0111 0000 E 70h
−55°C 1100 1001 0000 C 90h
The 8 MSBs of the Temperature reading can be found at Value RAM address 27 h. The remainder of the
Temperature reading can be found in the OS Configuration/Temperature Resolution Register bits 7-4. In 9-bit
format bit 7 is the only valid bit.
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Temperature Interrupts
There are four Value RAM WATCHDOG limits for the Temperature reading that affect the INT and OS outputs of
the LM80. They are: Hot Temperature Limit, Hot Temperature Hysteresis Limit, OS Limit, OS Hysteresis Limit.
There are three interrupt modes of operation: “One-Time Interrupt” mode, “Default Interrupt” mode, and
“Comparator Mode”. The OS output of the LM80 can be programmed for “One-Time Interrupt” mode and
“Comparator” mode. INT can be programmed for “Default Interrupt” mode and “One-Time” Interrupt.
“Default Interrupt mode” operates in the following way: Exceeding Thot causes an Interrupt that will remain
active indefinitely until reset by reading Interrupt Status Register 1 or cleared by the INT_Clear bit in the
Configuration register. Once an Interrupt event has occurred by crossing Thot, then reset, an Interrupt will occur
again once the next temperature conversion has completed. The interrupts will continue to occur in this manner
until the temperature goes below Thot hyst, at which time the Interrupt output will automatically clear.
“One-Time Interrupt” mode operates in the following way: Exceeding Thot causes an Interrupt that will remain
active indefinitely until reset by reading Interrupt Status Register 1 or cleared by the INT_Clear bit in the
Configuration register. Once an Interrupt event has occurred by crossing Thot, then reset, an Interrupt will not
occur again until the temperature goes below Thot hyst.
“Comparator” mode operates in the following way: Exceeding Tos causes the OS output to go Low (default).
OS will remain Low until the temperature goes below Tos. Once the temperature goes below Tos, OS will go
High.
A. This diagram does not reflect all the possible variations in the operation of the OS and INT outputs nor the OS and
Hot Temp bits. The interrupt outputs are cleared by reading the appropriate Interrupt Status Register.
Figure 11. Temperature Interrupt Response Diagram
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THE LM80 INTERRUPT STRUCTURE
Figure 12. Interrupt Structure
Figure 12 depicts the Interrupt Structure of the LM80. The LM80 can generate Interrupts as a result of each of its
internal WATCHDOG registers on the analog, temperature, and fan inputs.
Interrupt Inputs
External Interrupts can come from the following sources. While the label suggests a specific type or source of
Interrupt, this label is not a restriction of its usage, and it could come from any desired source:
•BTI - This is an active low Interrupt intended to come from the O.S. output of LM75 temperature sensors.
The LM75 O.S. output goes active when its temperature exceeds a programmed threshold. Up to 8 LM75's
can be connected to a single Serial Bus bus with their O.S. output's wire or'd to the BTI input of the LM80. If
the temperature of any LM75 exceeds its programmed limit, it drives BTI low. This generates an Interrupt to
notify the host of a possible overtemperature condition. Provides an internal pull-up of 10 kΩ.
•CI (Chassis Intrusion) - This is an active high interrupt from any type of device that detects and captures
chassis intrusion violations. This could be accomplished mechanically, optically, or electrically, and circuitry
external to the LM80 is expected to latch the event. The design of the LM80 allows this input to go high even
with no power applied to the LM80, and no clamping or other interference with the line will occur. This line
can also be pulled low for at least 10 ms by the LM80 to reset a typical Chassis Intrusion circuit. Accomplish
this reset by setting Bit 5 of Configuration Register high. The bit in the Register is self-clearing.
•INT_IN - This active low Interrupt merely provides a way to chain the INT (Interrupt) from other devices
through the LM80 to the processor.
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Interrupt Outputs
All Interrupts are indicated in the two Interrupt Status Registers.
•INT output has two mask registers, and individual masks for each Interrupt. As described in Using the
Configuration Register, this hardware Interrupt line can also be enabled/disabled in the Configuration
Register. The Configuration Register is also used to set the mode of the INT Interrupt line.
•OS is dedicated to the Temperature reading WATCHDOG. In the “Fan Divisor/RST_OUT/OS Register” the
OS enable bit (Bit-6), must be set high and the RST enable bit (Bit -7) must be set low to enable the OS
function on the RST_OUT/OS pin. OS pin has two modes of operation: “One-Time Interrupt” and
“Comparator”. “One-Time Interrupt” mode is selected by taking bit-2 of the “OS Configuration/Temperature
Resolution Register” high. If bit-2 is taken low “Comparator” mode is selected. Unlike the OS pin, the OS bit in
“Interrupt Status Register 2” functions in “Default Interrupt” and “One-Time Interrupt” modes. The OS bit can
be masked to INT pin by taking bit-5 in the “Interrupt Mask Register 2” low. A description of “Comparator”,
“Default Interrupt” and “One-Time Interrupt” modes can be found in Temperature Data Format.
Interrupt Clearing
Reading an Interrupt Status Register will output the contents of the Register, and reset the Register. A
subsequent read done before the analog “round-robin” monitoring loop is complete will indicate a cleared
Register. Allow at least 1.5 seconds to allow all Registers to be updated between reads. In summary, the
Interrupt Status Register clears upon being read, and requires at least 1.5 seconds to be updated. When the
Interrupt Status Register clears, the hardwire interrupt line will also clear until the Registers are updated by the
monitoring loop. The hardware Interrupt lines are cleared with the INT_Clear bit, which is Bit 3 of the
Configuration Register, without affecting the contents of the Interrupt (INT) Status Registers. When this bit is
high, the LM80 monitoring loop will stop. It will resume when the bit is low.
RST and GPO OUTPUTS
In PC applications the open drain GPO provides a gate drive signal to an external P-channel MOSFET power
switch. This external MOSFET then would keep power turned on regardless of the state of front panel power
switches when software power control is used. In any given application this signal is not limited to the function
described by its label. For example, since the LM80 incorporates temperature sensing, the GPO output could
also be utilized to control power to a cooling fan. Take GPO active low by setting Bit 6 in the Configuration
Register low.
RST is intended to provide a master reset to devices connected to this line. The RST_OUT/OS Control bit in Fan
Divisor/RST_OUT/OS Register, Bit 7, must be set high to enable this function. Setting Bit 4 in the Configuration
Register high outputs a least 10 ms low on this line, at the end of which Bit 4 in the Configuration Register
automatically clears. Again, the label for this pin is only its suggested use. In applications where the RST
capability is not needed it can be used for any type of digital control that requires a 10 ms active low open drain
output.
NAND TREE TESTS
A NAND tree is provided in the LM80 for Automated Test Equipment (ATE) board level connectivity testing. If the
user applies a logic zero to the NTEST_IN/Reset_IN input pin, the device will be in the NAND tree test mode.
A0/NTEST_OUT will become the NAND tree output pin. To perform a NAND tree test all pins included in the
NAND tree should be driven to 1. Beginning with IN0 and working clockwise around the chip, each pin can be
toggled and a resulting toggle can be observed on A0/NTEST_OUT. The following pins are excluded from the
NAND tree test: GNDA (analog ground), GND (digital ground), V + (power supply), A0/NTEST_OUT,
NTEST_IN/Reset_IN and RST_OUT/OS. Allow for a typical propagation delay of 500 ns.
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FAN MANUFACTURERS
Manufacturers of cooling fans with tachometer outputs are listed below:
NMB Tech
9730 Independence Ave.
Chatsworth, California 91311
818 341-3355
818 341-8207
Model Number Frame Size Airflow CFM
2408NL 2.36 in sq. X 0.79 in 9-16
(60 mm sq. X 20 mm)
2410ML 2.36 in sq. X 0.98 in 14-25
(60 mm sq. X 25 mm)
3108NL 3.15 in sq. X 0.79 in 25-42
(80 mm sq. X 20 mm)
3110KL 3.15 in sq. X 0.98 in 25-40
(80 mm sq. X 25 mm)
Mechatronics Inc.
P.O. Box 20
Mercer Island, WA 98040
800 453-45698
Various sizes available with tach output option.
Sanyo Denki America, Inc.
468 Amapola Ave.
Torrance, CA 90501
310 783-5400
Model Number Frame Size Airflow CFM
109P06XXY601 2.36 in sq. X 0.79 in 11-15
(60 mm sq. X 20 mm)
109R06XXY401 2.36 in sq. X 0.98 in 13-28
(60 mm sq. X 25 mm)
109P08XXY601 3.15 in sq. X 0.79 in 23-30
(80 mm sq. X 20 mm)
109R08XXY401 3.15 in sq. X 0.98 in 21-42
(80 mm sq. X 25 mm)
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REGISTERS AND RAM
Address Register
The main register is the ADDRESS Register. The bit designations are as follows:
Bit Name Read/Write Description
7-0 Address Pointer Read/Write Address of RAM and Registers. See the tables below for detail.
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Address Pointer (Power On default 00h)
A7 A6 A5 A4 A3 A2 A1 A0
Address Pointer Index (A7–A0)
Registers and RAM A6–A0 in Hex Power On Value of Registers:
<7:0> in Binary
Configuration Register 00h 0000 1000
Interrupt Status Register 1 01h 0000 0000
Interrupt Status Register 2 02h 0000 0000
Interrupt Mask Register 1 03h 0000 0000
Interrupt Mask Register 2 04h 0000 0000
Fan Divisor/RST_OUT/OS 05h 0001 0100
OS Configuration/Temperature Resolution 06h 0000 0001
Register
Value RAM 20h–3Fh
Configuration Register—Address 00h
Power on default <7:0> = 00001000 binary
Bit Name Read/Write Description
0 Start Read/Write A one enables startup of monitoring operations, a zero puts the part in standby mode.
Note: The outputs of Interrupt pins will not be cleared if the user writes a zero to this location after
an interrupt has occurred unlike “INT_Clear” bit.At start up, limit checking functions and scanning
begin. Note, all limits should be set in the Value RAM before setting this bit HIGH.
1 INT Enable Read/Write A one enables the INT Interrupt output.
2 INT polarity select Read/Write A one selects an active high open source output while a zero selects an active low open drain
output.
3 INT_Clear Read/Write A one disables the INT and RST_OUT/OS outputs without affecting the contents of Interrupt Status
Registers. The device will stop monitoring. It will resume upon clearing of this bit.
4 RESET Read/Write A one outputs at least a 10 ms active low reset signal at RESET, if <7> = 1 and <6> = 0 in the Fan
Divisor/RST_OUT/OS Register. This bit is cleared once the pulse has gone inactive.
5 Chassis Clear Read/Write A one clears the CI (Chassis Intrusion) pin. This bit clears itself after the CI pins cleared.
6 GPO Read/Write A one in this bit drives a one on GPO (General Purpose Output) pin.
7 INITIALIZATION Read/Write A one restores power on default value to the Configuration Register, Interrupt Status Registers,
Interrupt Mask Registers, Fan Divisor/RST_OUT/OSRegister, and the OS
Configuration/Temperature Resolution Register. This bit clears itself since the power on default is
zero.
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Interrupt Status Register 1—Address 01h
Power on default <7:0> = 0000 0000 binary
Bit Name Read/Write Description
0 IN0 Read Only A one indicates a High or Low limit has been exceeded.
1 IN1 Read Only A one indicates a High or Low limit has been exceeded.
2 IN2 Read Only A one indicates a High or Low limit has been exceeded.
3 IN3 Read Only A one indicates a High or Low limit has been exceeded.
4 IN4 Read Only A one indicates a High or Low limit has been exceeded.
5 IN5 Read Only A one indicates a High or Low limit has been exceeded.
6 IN6 Read Only A one indicates a High or Low limit has been exceeded.
7 INT_IN Read Only A one indicates that a Low has been detected on the INT_IN.
Interrupt Status Register 2—Address 02h
Power on default <7:0> = 0000 0000 binary
Bit Name Read/Write Description
0 Hot Temperature Read Only A one indicates a High or Low limit has been exceeded. Only “One-Time Interrupt” and
“Default Interrupt” modes are supported. The mode is set by bit-6 of the Interrupt Mask
Register 2.
1 BTI Read Only A one indicates that an interrupt has occurred from the Board Temperature Interrupt (BTI)
input pin. BTI can be tied to the OS output of multiple LM75 chips.
2 FAN1 Read Only A one indicates that a fan count limit has been exceeded.
3 FAN2 Read Only A one indicates that a fan count limit has been exceeded.
4 CI (Chassis Read Only A one indicates CI (Chassis Intrusion) has gone high.
Intrusion)
5 OS bit Read Only A one indicates a High or a Low OS Temperature limit has been exceed. Only “One-Time
Interrupt” and “Default Interrupt” modes are supported (see Temperature Interrupts and
Interrupt Outputs). The mode is set by bit-7 of the Interrupt Mask Register 2.
6 Reserved Read Only
7 Reserved Read Only
Interrupt Mask Register 1—Address 03h
Power on default <7:0> = 0000 0000 binary
Bit Name Read/Write Description
0 IN0 Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
1 IN1 Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
2 IN2 Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
3 IN3 Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
4 IN4 Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
5 IN5 Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
6 IN6 Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
7 INT_IN Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
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Interrupt Mask Register 2—Address 04h
Power on default <7:0> = 0000 0000 binary
Bit Name Read/Write Description
0 Hot Temperature Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
1 BTI Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
2 FAN1 Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
3 FAN2 Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
4 CI (Chassis Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
Intrusion)
5 OS bit Read/Write A one disables the corresponding interrupt status bit for INT interrupt.
6 Hot Temperature Read/Write A zero selects the default interrupt mode which gives the user an interrupt if the temperature
Interrupt mode goes above the hot limit. The interrupt will be cleared once the status register is read, but it will
select again be generated when the next conversion has completed. It will continue to do so until the
temperature goes below the hysteresis limit.
A one selects the one time interrupt mode which only gives the user one interrupt when it goes
above the hot limit. The interrupt will be cleared once the status register is read. Another interrupt
will not be generated until the temperature goes below the hysteresis limit. It will also be cleared
if the status register is read. No more interrupts will be generated until the temperature goes
above the hot limit again. The corresponding bit will be cleared in the status register every time it
is read but may not set again when the next conversion is done (See Figure 12).
7 OS bit Interrupt Read/Write A zero selects the default interrupt mode which gives the user an interrupt if the temperature
mode select goes above the hot limit. The interrupt will be cleared once the status register is read, but it will
again be generated when the next conversion has completed. It will continue to do so until the
temperature goes below the hysteresis limit.
A one selects the one time interrupt mode which only gives the user one interrupt when it goes
above the hot limit. The interrupt will be cleared once the status register is read. Another interrupt
will not be generated until the temperature goes below the hysteresis limit. It will also be cleared
if the status register is read. No more interrupts will be generated until the temperature goes
above the hot limit again. The corresponding bit will be cleared in the status register every time it
is read but may not set again when the next conversion is done (See Figure 12).
Fan Divisor Register/RST_OUT/OS—Address 05h
Power on – <7:4> is 0101, and <3:0>is mapped to VID <3:0>
Bit Name Read/Write Description
0 FAN1 Mode Select Read/Write A one selects the level sensitive input mode while a zero selects Fan count mode for the FAN1
input pin.
1 FAN2 Mode Select Read/Write A one selects the level sensitive input mode while a zero selects Fan count mode for the FAN2
input pin.
2-3 FAN1 RPM Control Read/Write FAN1 Speed Control.
<3:2> = 00 - divide by 1;
<3:2> = 01 - divide by 2;
<3:2> = 10 - divide by 4;
<3:2> = 11 - divide by 8.
If level sensitive input is selected: >2< = 1 selects and active-low input (An interrupt will be
generated if the FAN2 input is Low), >2< = 0 selects an active-high input (an interrupt will be
generated if the FAN2 input is High).
4-5 FAN2 RPM Control Read/Write FAN2 Speed Control.
<5:4> = 00 - divide by 1;
<5:4> = 01 - divide by 2;
<5:4> = 10 - divide by 4;
<5:4> = 11 - divide by 8.
If level sensitive input is selected: <2> = 1 selects and active-low input (An interrupt will be
generated if the FAN2 input is Low), <2> = 0 selects an active-high input (an interrupt will be
generated if the FAN2 input is High).
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Bit Name Read/Write Description
6 OS pin enable Read/Write A one enables OS mode on the RST_OUT/OS output pin, while Bit 7 of this register is set to
zero. If bits 6 and 7 of this register are set to zero the RST_OUT/OS pin is disabled.
7 RST enable Read/Write A one sets the RST_OUT/OS pin in the RST mode. In the RST mode, bit 7 of the Fan
Divisor/RST_OUT/OS Register has to be set to one. If bits 6 and 7 of this register are set to
zero the RST_OUT/OS pin is disabled.
OS Configuration/Temperature Resolution Register—Address 06h
Power on default Serial Bus address <7:0> = 0000 0001 binary
Bit Name Read/Write Description
0 OS status Read only Status of the OS.This bit mirrors the state of the RST_OUT/OS pin when in the OS mode.
1 OS Polarity Read/Write A zero selects OS to be active-low, while a one selects OS to be active high. OS is an open-
drain output.
2 OS mode select Read/Write A one selects the one time interrupt mode for OS, while a zero selects comparator mode for
OS. (See in Temperature Measurement System)
3 Temperature Read/Write A zero selects the default 8-bit plus sign resolution temperature conversions while a one selects
Resolution Control 11-bit plus sign resolution temperature conversions. 8-bit plus sign conversions time is
approximately 100 ms, while 11-bit plus sign conversion time is approximately 2 seconds.
4-7 Temp [3:0] Read/Write The lower nibble (4 LSBs) of the 11-bit plus sign temperature data. <4> = Temp [0] (nibble LSB,
0.0625°C), <5> = Temp [1], <6> = Temp [2], <7> = Temp 3 (nibble MSB, 0.5°C). For 8-bit plus
sign temperature resolution, <7> = Temp [0] (LSB, 0.5°C) while <4:6> are undefined.
Value RAM—Address 20h–3Fh
Address A7–A0 Description
20h IN0 reading
21h IN1 reading
22h IN2 reading
23h IN3 reading
24h IN4 reading
25h IN5 reading
26h IN6 reading
27h Temperature reading
28h FAN1 reading
Note: This location stores the number of counts of the internal clock per revolution.
29h FAN2 reading
Note: This location stores the number of counts of the internal clock per revolution.
2Ah IN0 High Limit
2Bh IN0 Low Limit
2Ch IN1 High Limit
2Dh IN1 Low Limit
2Eh IN2 High Limit
2Fh IN2 Low Limit
30h IN3 High Limit
31h IN3 Low Limit
32h IN4 High Limit
33h IN4 Low Limit
34h IN5 High Limit
35h IN5 Low Limit
36h IN6 High Limit
37h IN6 Low Limit
38h Hot Temperature Limit (High)
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SNIS102F –JUNE 1999–REVISED MARCH 2013
www.ti.com
Address A7–A0 Description
39h Hot Temperature Hysteresis Limit (Low)
3Ah OS Temperature Limit (High)
3Bh OS Temperature Hysteresis Limit (Low)
3Ch FAN1 Fan Count Limit
Note: It is the number of counts of the internal clock for the Low Limit of the fan speed.
3Dh FAN2 Fan Count Limit
Note: It is the number of counts of the internal clock for the Low Limit of the fan speed.
3Eh-3Fh Reserved
NOTE
Setting all ones to the high limits for voltages and fans (0111 1111 binary for temperature)
means interrupts will never be generated except the case when voltages go below the low
limits.
For voltage input high limits, the device is doing a greater than comparison. For low limits,
however, it is doing a less than or equal to comparison.
Typical Application
Figure 13. Typical Application Diagram
In this PC application the LM80 monitors temperature, fan speed for 2 fans, and 7 power
supply voltages. It also monitors an optical chassis intrusion detector.
28 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated
Product Folder Links: LM80
LM80
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SNIS102F –JUNE 1999–REVISED MARCH 2013
REVISION HISTORY
Changes from Revision E (March 2013) to Revision F Page
• Changed layout of National Data Sheet to TI format .......................................................................................................... 28
Copyright © 1999–2013, Texas Instruments Incorporated Submit Documentation Feedback 29
Product Folder Links: LM80
PACKAGE OPTION ADDENDUM
www.ti.com 1-Nov-2013
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LM80CIMT-3/NOPB NRND TSSOP PW 24 61 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -25 to 125 LM80
CIMT-3
LM80CIMTX-3/NOPB NRND TSSOP PW 24 2500 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -25 to 125 LM80
CIMT-3
(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) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
PACKAGE OPTION ADDENDUM
www.ti.com 1-Nov-2013
Addendum-Page 2
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LM80CIMTX-3/NOPB TSSOP PW 24 2500 330.0 16.4 6.95 8.3 1.6 8.0 16.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 8-Apr-2013
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LM80CIMTX-3/NOPB TSSOP PW 24 2500 367.0 367.0 35.0
PACKAGE MATERIALS INFORMATION
www.ti.com 8-Apr-2013
Pack Materials-Page 2
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