TI1 LM81BIMT-3/NOPB Serial interface acpi-compatible microprocessor system hardware monitor Datasheet

LM81
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SNAS011E – JUNE 1999 – REVISED FEBRUARY 2002
LM81 Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor
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FEATURES
APPLICATIONS
•
•
•
1
2
•
•
•
•
•
•
•
Temperature Sensing
6 Positive Voltage Inputs with Scaling
Resistors to Monitor +5V, +12V, +3.3V, +2.5V,
Vccp Power Supplies Directly
8-Bit DAC Output for Controlling Fan Speed
2 Fan Speed Monitoring Inputs
Chassis Intrusion Detector Input
WATCHDOG Comparison of all Monitored
Values
SMBus 1.0 (LM81C) and 1.1 (LM81B) Serial
Bus Interface Compatibility
LM81B has Improved Voltage Monitoring
Accuracy
VID0-VID4 Monitoring Inputs
KEY SPECIFICATIONS
•
•
•
•
•
•
Voltage Monitoring Error: +2% or ±1.2% (max)
Temperature Error
– −40˚C to +125˚C ± 3˚C (max)
Supply Voltage Range: 2.8V to 3.8V
Supply Current: 0.4 mA (typ)
ADC and DAC Resolution: 8 Bits
Temperature Resolution: 0.5˚C
•
•
System Thermal and Hardware Monitoring for
Servers and PCs
Office Electronics
Electronic Test Equipment and
Instrumentation
DESCRIPTION
The LM81 is a highly integrated data acquisition
system for hardware monitoring of servers, Personal
Computers, or virtually any microprocessor-based
system. In a PC, the LM81 can be used to monitor
power supply voltages, temperatures, and fan
speeds. Actual values for these inputs can be read at
any time. Programmable WATCHDOG limits in the
LM81 activate a fully programmable and maskable
interrupt system with two outputs (INT and T_CRIT_).
The LM81 has an on-chip digital output temperature
sensor with 9-bit or 12-bit resolution, a 6 analog input
ADC with 8-bit resolution and an 8-bit DAC. Two fan
tachometer outputs can be measured with the LM81’s
FAN1 and FAN2 inputs. The DAC, with a 0 to 1.25V
output voltage range, can be used for fan speed
control. Additional inputs are provided for Chassis
Intrusion detection circuits, and VID monitor inputs.
The LM81 has a Serial Bus interface that is
compatible with SMBus. Serial Bus Timing Diagram
TYPICAL APPLICATION
Figure 1.
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 © 1999–2002, Texas Instruments Incorporated
LM81
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This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
Figure 2. CONNECTION DIAGRAM
2
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Figure 3. BLOCK DIAGRAM
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Table 1. PIN DESCRIPTIONS
Pin Name(s)
Pin Number
Number of Pins
Type
Description
A0/NTEST_OUT
1
1
Digital I/0
The lowest order programmable bit of the serial
bus address. This pin functions as an output
during NAND Tree tests (board-level connectivity
testing). Refer to the NAND TREE TESTS section.
A1
2
1
Digital Input
The highest order programmable bit of the serial
bus address.
SMBData
3
1
Digital I/O
Serial Bus bidirectional Data. Open-drain output.
SMBCLK
4
1
Digital Input
Serial Bus Clock.
FAN1-FAN2
6-May
2
Digital Inputs
Schmitt Trigger fan tachometer inputs.
CI
7
1
Digital I/O
An active high input from an external circuit which
latches a Chassis Intrusion event. This line can go
high without any clamping action regardless of the
powered state of the LM81. There is also an
internal open-drain output on this line, controlled
by Bit 6 of the Configuration Register (40h) or Bit 7
CI Clear Register (46h), to provide a minimum 20
ms reset pulse. See the USING THE
CONFIGURATION REGISTER and THE LM81
INTERRUPT STRUCTURE sections.
T_CRIT_A
8
1
Digital Output
Critical Temperature Alarm active low open-drain
output. This pin can be grounded when not used.
V+ (+2.8V to +3.8V)
9
1
POWER
+3.3V V+ power. Bypass with the parallel
combination of 10 µF (electrolytic or tantalum) and
0.1 µF (ceramic) bypass capacitors.
INT
10
1
Digital Output
Interrupt active low open-drain output. This output
is enabled when Bit 1 in the Configuration Register
is set to 1. The default state is disabled.
DACOut/NTEST_IN
11
1
Analog Output/Digital
Input
0V to +1.25V amplitude 8-bit DAC output. When
forced high by an external voltage the NAND Tree
Test mode is enabled which provides board-level
connectivity testing. Refer to the NAND TREE
TESTS section.
RESET
12
1
Digital I/O
Master Reset, 5 mA driver (open-drain), active low
output with a 20 ms minimum pulse width.
Available when enabled via Bit 4 in the
Configuration register. It acts as an active low
power on RESET input.
GND
13
1
GROUND
Internally connected to all circuitry. The ground
reference for all analog inputs and the DAC output.
This pin needs to be connected to a low noise
analog ground plane for optimum performance of
the DAC output.
Vccp2
14
1
Analog Input
Analog input for monitoring −12V or Vccp2.
Selectable by choosing the appropriate external
resistor divider values such that the input to the
LM81 is scaled to +2.5V. See the ANALOG
INPUTS section.
+12Vin
15
1
Analog Input
Analog input for monitoring +12V.
+5Vin
16
1
Analog Input
Analog input for monitoring +5V.
+3.3Vin
17
1
Analog Input
Analog input for monitoring +3.3V.
+2.5Vin
18
1
Analog Input
Analog input for monitoring +2.5V.
Vccp1
19
1
Analog Input
Analog input for monitoring Vccp, a processor
voltage that is nominally at +2.5V.
VID4-VID0
20-24
5
Digital Inputs
Supply Voltage readouts from the Pentium/PRO
power supplies that indicate the operating voltage
or the processor (e.g. 1.5V to 2.9V). The values
are read in the VID/Fan Divisor Register and the
VID4 Register.
TOTAL PINS
4
24
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ABSOLUTE MAXIMUM RATINGS (1) (2) (3)
MIN
Positive Supply Voltage
Voltage on Any Input or Output Pin:
+15.0
V
A0, A1, DACOut
−0.3
(V++ 0.3)
V
Input Current at any Pin (5)
Package Input Current (5)
Maximum Junction Temperature
(TJ max)
ESD Susceptibility (5)
Human Body Model
(3)
(4)
(5)
(6)
See
(4)
−0.3
+6.0
V
-5.0
+5.0
mA
-20
+20
mA
150
°C
2000
V
Machine Model
200
V
Vapor Phase (60
seconds)
215
°C
Infrared (15 seconds)
235
°C
+150
°C
−65
Storage Temperature
(2)
V
-0.3
All other pins
(1)
UNIT
+6.0
+12Vin, T_CRIT_A
+2.5Vin, +3.3Vin
Soldering Information, VSSOP Package (6)
MAX
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
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 the
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.
All voltages are measured with respect to GND, unless otherwise specified.
The Absolute maximum input range for :
(a) +2.5Vin - −0.3V to (1.4 x V+ + 0.42V or 6V, whichever is smaller
(b) +3.3Vin - −0.3V to (1.8 x V+ + 0.55V or 6V, whichever is smaller.
The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF
capacitor discharged directly into each pin.
See www.ti.com for other methods of soldering surface mount devices.
RECOMMENDED OPERATING CONDITIONS (1) (2)
TMIN ≤ TA ≤ TMAX
Operating Temperature Range
−40°C ≤ TA ≤ +125°C
LM81
TMIN ≤ TA ≤ TMAX
Specified Temperature Range
−40°C ≤ TA ≤ +125°C
LM81
Junction to Ambient Thermal Resistance
(θJA (3))
TI Package Number: PW24A
Supply Voltage (V+)
VIN Voltage Range:
FAN1-FAN2
+2.8V to +3.8V
+12Vin
−0.05V to +15V
+5Vin
−0.05V to +6.8V
+3.3Vin
−0.05V to +4.6V
+2.5Vin
−0.05V to +3.6V
LM84B VID0 - VID4, Vccp,
−0.05V to +6.0V
LM84C VID0 - VID4, Vccp
All other inputs
(1)
(2)
(3)
95°C/W
−0.05V to +6.0V
−0.05V to (V+ + 0.05V)
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 the
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.
All voltages are measured with respect to GND, unless otherwise specified.
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 = (TJ max−TA)/θJA.
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DC ELECTRICAL CHARACTERISTICS (1)
The following specifications apply for +2.8VDC ≤ V+ ≤ +3.8VDC, RS = 500Ω, unless otherwise specified. Boldface limits
apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C.
SYMBOL
PARAMETER
TEST CONDITIONS
TYPICAL (2)
LIMITS
LIMITS
LM81BIM (3) LM81CIM (3)
UNIT
POWER SUPPLY CHARACTERISTICS
I+
Supply Current
Interface Inactive
0.4
1.4
0.9
mA
(max)
±3
±3
˚C
(max)
0.5
0.5
˚C
(min)
0.0625
0.0625
˚C
(min)
+1.2
+2
%
(max)
−1.2
+0.8
%
(min)
+1.2
+2.4
%
(max)
−1.2
0
%
(min)
+1.2
+3.1
%
(max)
−1.2
+1.2
%
(min)
±1
±1
LSB
(max)
TEMPERATURE-TO-DIGITAL CONVERTER CHARACTERISTICS
−40˚C ≤ TA ≤ +125˚C
Error
Resolution
9-bit mode
12-bit mode
LM81 ANALOG-TO-DIGITAL CONVERTER CHARACTERISTICS
Resolution
TUE
Total Unadjusted
Error
8
+2.5Vin
(See (4) and
(5)
)
+3.3Vin
bits
+5Vin
Vccp1, Vccp2
+12Vin
DNL
Differential Non-Linearity
PSS
Power Supply Sensitivity
tC
Total Monitoring Cycle Time
(See (4))
(See (4) and
(5)
)
(See (6))
±0.4
%/V
0.4
sec
9-bit Temp Resolution
0.82
0.82
sec
(max)
12-bit Temp Resolution
1.2
1.2
sec
(max)
90
90
kΩ
(min)
ADC INPUT CHARACTERISTICS
Input Resistance (All analog inputs
except Vccp1 and Vccp2)
115
ADC INPUT CHARACTERISTICS
Vccp1 and Vccp2 DC Input Current
±1
µA
8
bits
ADC INPUT CHARACTERISTICS
DAC CHARACTERISTICS
Resolution
(1)
(2)
(3)
(4)
(5)
(6)
6
Parasitics and or ESD protection circuitry are shown in the figure below for the LM81’s pins. The nominal breakdown voltage of the
zener D3 is 6.5V. Care should be taken not to forward bias the parasitic diode, D1, present on pins: A0/NTEST_OUT, A1 and
DACOut/NTEST_IN. Doing so by more than 50 mV may corrupt a temperature or voltage measurement.
Typicals are at TJ = TA = 25˚C and represent most likely parametric norm.
Limits are ensured to TI’s AOQL (Average Outgoing Quality Level). Each 9-bit temperature and 8-bit input voltage conversion takes 50
ms typical and 56 ms maximum. Twelve bit temperature conversion takes 400 ms. Fan tachometer readings take 20 ms typical, at 4400
rpm, and 200 ms maximum.
TUE (Total Unadjusted Error) includes Offset, Gain and Linearity errors of the ADC.
Ensured at 3/4 scale ±15%.
Total Monitoring Cycle Time includes temperature conversion, 6 analog input voltage conversions and 2 tachometer readings.
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DC ELECTRICAL CHARACTERISTICS(1) (continued)
The following specifications apply for +2.8VDC ≤ V+ ≤ +3.8VDC, RS = 500Ω, unless otherwise specified. Boldface limits
apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C.
SYMBOL
PARAMETER
DAC Error
TEST CONDITIONS
TYPICAL (2)
LIMITS
LIMITS
LM81BIM (3) LM81CIM (3)
V+ = 3.3V
UNIT
±5
±5
%
(max)
±62.5
±62.5
mV
(max)
±10
%
(max)
±125
mV
(max)
DAC Error Temperature Sensitivity
100
100
DAC Error Power Supply
Sensitivity
0.5
0.725
%
(max)
625
625
Ω
(min)
20
20
pF
(max)
+25˚C ≤ TA ≤ +75˚C
±10
±10
%
(max)
−10˚C ≤ TA ≤ +100˚C
±15
±15
%
(max)
−40˚C ≤ TA ≤ +125˚C
±20
±20
%
(max)
255
255
(max)
RL
Output Load Resistance
CL
Output Load Capacitance
VO = 1.25V
ppm/˚C
(max)
FAN RPM-TO-DIGITAL CONVERTER
Fan RPM Error
Full-scale Count
FAN1 and FAN2 Nominal Input
RPM (See the FAN INPUTS
section)
Internal Clock Frequency
Divisor = 1, Fan Count = 153
(See (7))
8800
RPM
Divisor = 2, Fan Count = 153
(See (7))
4400
RPM
Divisor = 3, Fan Count = 153
(See (7))
2200
RPM
Divisor = 4, Fan Count = 153
(See (7))
1100
RPM
+25˚C ≤ TA ≤ +75˚C
22.5
−10˚C ≤ TA ≤ +100˚C
−40˚C ≤ TA ≤ +125˚C
22.5
22.5
20.2
20.2
kHz
(min)
24.8
24.8
kHz
(max)
19.1
19.1
kHz
(min)
25.9
25.9
kHz
(max)
18
18
kHz
(min)
27
27
kHz
(max)
DIGITAL OUTPUTS (NTEST_OUT)
VOUT(1)
Logical “1” Output Voltage
IOUT = ±3.0 mA at V+ = +2.8V
2.4
2.4
V
(min)
VOUT(0)
Logical “0” Output Voltage
IOUT = ±3.0 mA at V+ = +3.8V
0.4
0.4
V
(max)
OPEN- DRAIN DIGITAL OUTPUTS (SMBData, RESET, CI, INT, T_CRIT_A)
(7)
The total fan count is based on 2 pulses per revolution of the fan tachometer output.
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DC ELECTRICAL CHARACTERISTICS(1) (continued)
The following specifications apply for +2.8VDC ≤ V+ ≤ +3.8VDC, RS = 500Ω, unless otherwise specified. Boldface limits
apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C.
SYMBOL
PARAMETER
TEST CONDITIONS
VOUT(0)
Logical “0” Output Voltage
IOUT = −3.0 mA
IOH
High Level Output Current
VOUT = V+
TYPICAL (2)
RESET and Chassis Intrusion
Pulse Width
LIMITS
LIMITS
LM81BIM (3) LM81CIM (3)
UNIT
0.4
0.4
V
(min)
0.1
100
100
µA
(max)
45
20
20
ms
(min)
DIGITAL INPUTS: VID0–VID4, NTEST_IN, A0/NTEST_OUT, A1, Chassis Intrusion (CI)
VIN(1)
Logical “1” Input Voltage
2.0
2.0
V
(min)
VIN(0)
Logical “0” Input Voltage
0.8
0.8
V
(max)
SMBus DIGITAL INPUTS (SMBCLK, SMBData)
VIN(1)
Logical “1” Input Voltage
2.1
1.4
V
(min)
VIN(0)
Logical “0” Input Voltage
0.8
0.6
V
(max)
Tach Pulse Logic Inputs (FAN1, FAN2)
VIN(1)
Logical “1” Input Voltage
0.7 x V+
0.7 x V+
V
(min)
VIN(0)
Logical “0” Input Voltage
0.3 x V+
0.3 x V+
V
(max)
−0.005
-1
-1
µA
(min)
0.005
1
1
µA
(max)
ALL DIGITAL INPUTS
IIN(1)
Logical “1” Input Current
VIN = V+
IIN(0)
Logical “0” Input Voltage
VIN = 0 VDC
CIN
Digital Input Capacitance
8
20
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AC ELECTRICAL CHARACTERISTICS
The following specifications apply for +2.8VDC ≤ V+ ≤ +3.8VDC on SMBCLK and SMBData, unless otherwise specified.
Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C. (See (1))
SYMBOL
TYP (2)
PARAMETER
LIMITS (3)
UNIT
SERIAL BUS TIMING CHARACTERISTICS
t1
SMBCLK (Clock) Period
trise
SMBCLK and SMBData Rise Time
2.5
tfall
SMBCLK and SMBData Fall Time
300
t2
Data In Setup Time to SMBCLK High
100
t3
Data Out Stable After SMBCLK Low
t4
SMBData Low Setup Time to SMBCLK Low (start)
100
t5
SMBData High Hold Time After SMBCLK High (stop)
100
tTIMEOUT
SMBData or SMBCLK low time required to reset the Serial Bus Interface to the Idle State
1
0
31
ms
25 ms (min)
35 ms (max)
CL
(1)
(2)
(3)
Capacitive Load on SMBCLK and SMBData
400 pF (max)
Timing specifications are tested at the specified logic levels, VIL for a falling edge and VIH for a rising edge.
Typicals are at TJ = TA = 25˚C and represent most likely parametric norm.
Limits are ensured to TI’s AOQL (Average Outgoing Quality Level). Each 9-bit temperature and 8-bit input voltage conversion takes 50
ms typical and 56 ms maximum. Twelve bit temperature conversion takes 400 ms. Fan tachometer readings take 20 ms typical, at 4400
rpm, and 200 ms maximum.
Figure 4. Serial Bus Timing Diagram
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Table 2.
Pin Name
D2
D3
R1
R2
INT
D1
x
x
D4
0
∞
CI
x
x
0
∞
FAN1–FAN2
x
0
∞
SMBCLK
x
0
∞
x
x
0
∞
SMBData
x
x
0
∞
A0/NTEST_OUT
x
x
x
0
∞
A1
x
x
x
0
∞
+12Vin
x
x
RESET
Vccp1, Vccp2
x
+5Vin
x
x
+3.3Vin, +2.5Vin
x
x
T_CRIT_A
x
VID4–VID0
x
x
DACOut/NTEST_I
N
x
R1+R2 ∼120k
x
x
∞
0
R1+R2 ∼120k
x
R1+R2 ∼120k
x
0
∞
x
0
∞
x
0
∞
x
Figure 5. ESD Protection Input Structure
10
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TEST CIRCUIT
Figure 6. Digital Output Load Test Circuitry
FUNCTIONAL DESCRIPTION
GENERAL DESCRIPTION
The LM81 provides 6 analog inputs, a temperature sensor, a Delta-Sigma ADC (Analog-to-Digital Converter), a
DAC output, 2 fan speed counters, WATCHDOG registers, and a variety of inputs and outputs on a single chip. A
two wire Serial Bus interface is included. The LM81 performs power supply, temperature, fan control and fan
monitoring for personal computers.
The analog inputs are useful for monitoring several power supplies present in a typical computer. The LM81
includes internal resistor dividers that scale and/or offset external Vccp, +2.5V, +3.3V, +5.0V and +12V power
supply voltages to a 3/4 scale nominal ADC output. The LM81 ADC then continuously converts the scaled inputs
to 8-bit digital words. Measurement of negative voltages (such as -5V and -12V power supplies) can be
accommodated with an external resistor divider applied to the Vccp2 input. Temperature is converted to a 9-bit or
12-bit two’s-complement digital word with a 0.5˚C LSB or 0.0625˚C LSB, respectively.
Fan inputs measure the period of tachometer pulses from the fans, providing a higher count for lower fan
speeds. The fan inputs are Schmitt-Trigger digital inputs with an acceptable range of 0V to V+ and a transition
level of approximately V+/2. Full scale fan counts are 255 (8-bit counter) and this represents a stopped or very
slow fan. Nominal speeds, based on a count of 153, are programmable from 1100 to 8800 RPM on FAN1 and
FAN2. Schmitt-Trigger input circuitry is included to accommodate slow rise and fall times. A 0V to 1.25V DAC
output voltage range can be used for control of fan speed.
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The LM81 has several internal registers, as shown in Figure 7, Table 3 and the REGISTERS AND RAM section.
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 the two hardware Interrupt outputs.
• CI Clear Register: Allows transmitting a 20 ms low pulse on the chassis intrusion pin (CI).
• VID/Fan Divisor Register: This register contains the state of the VID0-VID3 input lines and the divisor bits
for FAN1 and FAN2 inputs.
• Serial Bus Address Register: Contains the Serial Bus address. At power on it assumes the default value of
01011XX binary, and can be altered by the state of A0 and A1.
• VID4 Register: Contains the state of the VID4 input.
• Temperature Configuration Register: Selects the interrupt mode and contains the 0.5˚C LSB of the
temperature reading.
• Extended Mode Registers: Enable and control the Extended Mode which includes the LSBs of the 12-bit
temperature reading, T_CRIT, and THYST
• Value RAM: The DAC digital input, monitoring results (temperature, voltages, fan counts), WATCHDOG
limits, and Company/Stepping IDs are all contained in the Value RAM. The Value RAM consists of a total of
34 bytes, addresses 15h - 3Fh, containing:
– byte 1 at address 15h a manufacturers test register
– locations 16h - 18h are unassigned and do not have associated registers
– byte 2 at address 19h contains the DAC Data Register
– locations 1Ah - 1Fh are unassigned and do not have associated registers
– the next 10 bytes at addresses 20h -29h contain all of the results, with address 26h reserved
– the next 18 bytes at addresses 2Bh-3Ch are the WATCHDOG limits
– the last 2 bytes at addresses 3Eh and 3Fh contain the Company ID and Stepping ID numbers,
respectively
When the LM81 is started, it cycles through each measurement in sequence, and it continuously loops through
the sequence approximately once every 400 ms. Each measured value is compared to values stored in
WATCHDOG, or Limit registers. When the measured value violates the programmed limit the LM81 will set a
corresponding Interrupt in the Interrupt Status Registers. The hardware Interrupt line INT is fully programmable
with separate masking of each Interrupt source. In addition, the Configuration Register has a control bit to enable
or disable the hardware Interrupt.
Another hardware Interrupt line available T_CRIT_A (Critical Temperature Alarm Output) is used to signal a
catastrophic overtemperature event. Having a dedicated interrupt for this purpose allows for the fastest possible
response time to a thermal runaway event. This output can be enabled by setting bit 4 of Extended Mode
Register 1.
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.
12
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INTERFACE
Figure 7. LM81 Register Structure
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INTERNAL REGISTERS OF THE LM81
Table 3. Internal Registers and Their Corresponding Internal LM81 Addresses
Register
LM81 Internal Hex Address
Power On Value
Notes
Configuration Register
40h
0000 1000
Interrupt Status Register 1
41h
0000 0000
Interrupt Status Register 2
42h
0000 0000
Interrupt Mask Register 1
43h
0000 0000
Interrupt Mask Register 2
44h
0000 0000
CI Clear Register
46h
0000 0000
VID/Fan Divisor Register
47h
0101 XXXX
The upper four bits set the divisor
for Fan Counters 1 and 2. The
lower four bits reflect the state of
the VID0-VID3 inputs.
Serial Bus Address Register
48h
0010 11XX
The lower 2 bits reflect the state
of A1 and A0, the Serial Bus
address input pins.
VID4 Register
49h
1000 000X
The lower bit reflects the state of
VID4 input.
Temperature Configuration
Register
4Bh
0000 0001
Extended Mode Register 1
4Ch
0100 0100
Extended Mode Register 2
4Dh
0000 0000
Value RAM DAC Data Register
19h
1111 1111
Value RAM
20h-3Fh
Contains: monitoring results
(temperature, voltages, fan
counts), WATCHDOG limits, and
Company/Stepping IDs
SERIAL BUS INTERFACE
Serial Bus Timing
Figure 8. Serial Bus Write to the Internal Address Register followed by the Data Byte
14
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Figure 9. Serial Bus Write to the Internal Address Register Only
Figure 10. Serial Bus Read from a Register with the Internal Address Register Preset to Desired Location
The Serial Bus control lines consist of the SMBData (serial data), SMBCLK (serial clock) and A0-A1 (address)
pins. The LM81 can operate only as a slave. The SMBCLK line only controls the serial interface, all other clock
functions within LM81 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 LM81 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 already be at the desired Address, simply read the LM81 with the
Serial Bus Interface Address byte, followed by the data byte read from the LM81.
2. If the Internal Address Register value is unknown, or if it is not the desired value, write to the LM81 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 LM81.
The default Serial Bus address of the LM81 is set to 010 11(A1)(A0). All bits, except for A0 and A1, can be
changed by writing to the Serial Bus address register. A0 and A1 will always reflect the state of the A0 and A1
input pins.
All of these communications are depicted in the Serial Bus Interface Timing Diagrams as shown in the Serial Bus
Timing section.
Serial Bus Timeout can be initiated by holding the SMBCLK and/or SMBData lines low for greater than tTIMEOUT
(35 ms max). Serial Bus Timeout resets the serial bus interface circuitry to the idle state and readies the LM81
for a new serial bus communication.
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USING THE LM81
POWER ON
When power is first applied, the LM81 performs a “power on reset” on several of its registers. The power on
condition of the LM81’s registers in shown in Table 1 Registers whose power on values are not shown have
power on conditions that are indeterminate (this includes the value RAM ,exclusive of the DAC data, and
WATCHDOG limits). When power is first applied the ADC is inactive. In most applications, usually the first action
after power on is usually to write WATCHDOG limits into the Value RAM. Register values can be returned to
their default values after power is applied to the LM81 by taking RESET low for at least 50 ns.
RESETS
Configuration Register INITIALIZATION accomplishes the same function as power on reset on most registers.
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 3:
• Configuration Register
• Interrupt Status Register 1
• Interrupt Status Register 2
• INT Mask Register 1
• INT Mask Register 2
• VID/Fan Divisor Register
• Serial Bus Address Register (Power on reset only, not reset by Configuration Register INITIALIZATION)
• VID4 Register
• Temperature Configuration Register
• Extended Mode Register 1
• Extended Mode Register 2
Configuration Register INITIALIZATION is accomplished by setting Bit 7 of the Configuration Register high. This
bit automatically clears after being set.
USING THE CONFIGURATION REGISTER
The Configuration Register controls the LM81 operation. At power on, the ADC is stopped and INT_Clear is
asserted, clearing the INT hardwire output. The Configuration Register starts and stops the LM81, enables and
disables interrupt output, and provides the Reset function described in the RESETS section.
Bit 0 of the Configuration Register controls the monitoring loop of the LM81. Setting Bit 0 low stops the LM81
monitoring loop and puts the LM81 in shutdown mode, reducing power consumption. Serial Bus communication
can take place with any register in the LM81 although activity on the SMBData and SMBCLK 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 3 of the Configuration Register clears the INT output when set high, without affecting the contents of the
Interrupt Status Registers. The LM81 will stop monitoring. It will resume upon clearing of this bit.
Bit 4 of the Configuration Register provides an active low 20 ms pulse at the RESET output when set high.
The CI_Clear provides an active low 20 ms pulse at the CI output pin when set high. This is intended for
resetting the Chassis Intrusion circuitry.
The INITIALIZATION bit resets the internal registers of the LM81 as described in the RESETS section.
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STARTING CONVERSIONS
The monitoring function (Analog inputs, temperature, and fan speeds) in the LM81 is started by writing to the
Configuration Register and setting INT_Clear (Bit 3), low, and Start (bit 0), high. The LM81 then performs a
“round-robin” monitoring of all analog inputs, temperature, and fan speed inputs approximately once every 400
ms. The sequence of items being monitored corresponds to locations in the Value RAM and is:
1. Temperature
2. Vccp2
3. +12Vin
4. +5Vin
5. +3.3Vin
6. Vccp1
7. +2.5Vin
8. Fan 1
9. Fan 2
DACOut immediately changes after the DAC Data Register in the Value RAM has been updated. For a zero to
full scale transition DACOut will typically settle within 100 µsec of the stop by master in the write to the DAC Data
Register Serial Bus transaction. The DAC Data Register is not reset by the INITIALIZATION bit found in the
Configuration Register.
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 it is read, reads of
any single value should not be done more often than once every 56 ms. When reading all values, allow at least
0.82 seconds between reading groups of values. Reading more frequently than once every 0.82 seconds can
also prevent complete updates of Interrupt Status Registers and Interrupt Outputs.
A typical sequence of events upon power on of the LM81 would consist of:
1. Set WATCHDOG Limits
2. Set Interrupt Masks
3. Start the LM81 monitoring process
DIGITAL COMMUNICATION NOISE CONSIDERATIONS
The SMBData and SMBCLK logic input levels were changed in the SMBus 1.1 specification. SMBus 1.0 levels
were set to 1.4V for a logic high and 0.6V for a logic low. In SMBus 1.1 they were changed to 2.1V for a logic
high and 0.8V for a logic low. Devices that meet the SMBus 1.0 specification have issues in that the logic levels
did not allow for enough noise immunity for some pcb layouts. This has changed with the SMBus 1.1
specification because the higher logic levels allow for more hysteresis in the schmitt trigger inputs stages and
thus more noise immunity. It may be required in some cases to add a series 5.1kΩ resistor connected at the
SMBCLK pin of the LM81C to improve its noise immunity. In addition to meeting the SMBus 1.1 logic levels, the
LM81B has a built-in glitch filter that rejects 100MHz or greater to make it impervious to noise.
ANALOG INPUTS
All analog input voltages are digitized to 8-bits of resolution. All analog inputs, except for Vccp1 and Vccp2,
include internal resistor attenuators. The theoretical LSB size, theoretical voltage input required for an ADC
reading of 192 (3/4 scale) and 255 (full scale) for each analog input is detailed in the table below:
Input
LSB size
Vin for 192
Vin for 255
2.5 Vin
13 mV
2.5V
3.320V
3.3 Vin
17.2 mV
3.3V
4.383V
5 Vin
26 mV
5V
6.641V
12 Vin
62.5 mV
12V
15.93V
Vccp1, Vccp2
14.1 mV
2.7V
3.586V
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Thus monitoring power supplies within a system can be easily accomplished by tying the Vccp, +2.5 Vin, +3.3
Vin, +5 Vin and +12 Vin analog inputs to the corresponding system supply. A digital reading can be converted to
a voltage by simply multiplying the decimal value of the reading by the LSB size.
For inputs with attenuators the input impedance is greater than 90 kΩ. Vccp inputs do not have resistor
attenuators and are are directly tied to the ADC, therefore having a much larger input impedance.
A negative power supply voltage can be applied to a Vccp input through a resistor divider referenced to a known
positive DC voltage as show in Figure 11. The resistor values shown in the table below for the circuit of
Figure 11 will provide approximately 1.25V at the Vccp analog inputs of the LM81 for a nominal reading of 89.
Voltage Measurements
(VS)
R2 (1)
R1 (1)
V+
Voltage at Analog Inputs (ADC code
89)
−12V
40 kΩ
141 kΩ
+5V
+1.25V
−5V
40 kΩ
66.7 kΩ
+5V
+1.25V
(1)
Resistor values shown in table provide approximately 1.25V at the Vccp inputs.
Figure 11. Input Examples
The resistors were selected by setting R2 = 40 kΩ and then calculating R2 using the following equation:
R1 = [(1.25V − VS) ÷ (V+ − 1.25V)] x 40 kΩ
(1)
The maximum R1 can be is restricted by the DC input current of a Vccp input.
Inputs with internal resistor dividers (+2.5 Vin, +3.3 Vin or +5 Vin, +12 Vin) can have voltage applied that
exceeds the power supply up to: 3.6V for +2.5 Vin, 4.6V for +3.3 Vin, 6.8V for +5 Vin, and 15V for +12 Vin. The
Vccp inputs have a parasitic diode to the positive supply, so care should be taken not to forward bias this diode.
All analog inputs have internal diodes that clamp the input voltage when going below ground thus limiting the
negative analog input voltage range to −50 mV. Violating the analog input voltage range of any analog input has
no detrimental effect on the other analog inputs. External resistors should be included to limit input currents to
the values given in the ABSOLUTE MAXIMUM RATINGS (2) (3) (4) section for Input Current At Any Pin whenever
exceeding the analog input voltage range, even on an un-powered LM81. Inputs with external attenuator
networks will usually meet these requirements. If it is possible for inputs without attenuators (such as Vccp1 and
Vccp2) to be turned on while LM81 is powered off, additional resistors of about 10 kΩ should be added in series
with the inputs to limit the input current.
(2)
(3)
(4)
18
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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 the
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.
All voltages are measured with respect to GND, unless otherwise specified.
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ANALOG INPUT INTERRUPTS
A WATCHDOG window comparison on the analog inputs can activate the INT interrupt output. A converted input
voltage that is above its respective HIGH limit or less than or equal to its LOW limit will cause a flag to be set in
its Interrupt Status Register. This flag will activate the INT output when its mask bit is set low. Mask bits are
found in the Interrupt Mask Registers.
LAYOUT AND GROUNDING
A separate, low-impedance ground plane for analog ground, which provides a ground point for both GND pins,
voltage dividers and other 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 LM81.
The power supply bypass, the parallel combination of 10 μF (electrolytic or tantalum) and 0.1 μF (ceramic)
bypass capacitors connected between pin 12 and ground, should also be located as close as possible to the
LM81.
FAN INPUTS
The FAN1 and FAN2 inputs accept signals from fans equipped with tachometer outputs. These are logic-level
inputs with an approximate threshold of V+/2. Signal conditioning in the LM81 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 the ALTERNATIVES FOR FAN INPUTS section. R2 is
selected so that it does not develop excessive 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 LM81 is off, the LM81 inputs will provide diode clamping. Limit
input current to the Input Current at Any Pin specification shown in the ABSOLUTE MAXIMUM RATINGS (5) (6) (7)
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:
Count
1.35 u 106
RPM u Divisor
(2)
Note that Fan 1 and Fan 2 Divisors are programmable via the VID/Fan Divisor Register.
Fan tachometer outputs that provide one pulse per revolution should use a divisor setting twice that of outputs
that provide two pulses per revolution. For example, a 4400 RPM fan that provides one pulse per revolution
should have the divisor set to 4 such that the nominal counter output is 153.
(5)
(6)
(7)
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
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 the
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.
All voltages are measured with respect to GND, unless otherwise specified.
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ALTERNATIVES FOR FAN INPUTS
Figure 12. Fan with Tach Pull-Up to +5V
Figure 13. Fan with Tach Pull-Up to +12V, or
Totem-Pole Output and Resistor Attenuator
Figure 14. Fan with Tach Pull-Up to +12V and
Diode Clamp
Figure 15. Fan with Strong Tach Pull-Up or Totem
Pole Output and Diode Clamp
NOTE
Counts are based on 2 pulses per revolution tachometer outputs.
20
RPM
Time per Revolution
Counts for “Divide by 2”
(Default) in Decimal
Comments
4400
13.64 ms
153 counts
Typical RPM
3080
19.48 ms
219 counts
70% RPM
2640
22.73 ms
255 counts (maximum counts)
60% RPM
Mode Select
Nominal RPM
Time per
Revolution
Counts for the Given Speed
in Decimal
70% RPM
Divide by 1
Divide by 2
8800
6.82 ms
153
6160
9.74 ms
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
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Time per Revolution for
70% RPM
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DAC OUTPUT
The LM81 provides an 8-bit DAC (Digital-to-Analog Converter) with an output range of 0 to 1.25 volts (4.88 mV
LSB). This DAC can be used in any way, but in most applications of the LM81 the DAC will be used for fan
control. Typically the DAC output would be amplified to provide the up to 12 volt drive required by the fan. At
power-on the DAC provides full output, insuring that full fan speed is the default condition. Care should be taken
such that the analog circuitry tied to this pin does not drive this pin above 2.5V. Doing so will place the LM81 in
NAND tree test mode which will make all pins inputs, thus disabling any response from the LM81.
Fans do not start reliably at reduced voltages, so operation at a reduced voltage should be preceded by a brief
(typically 1 second) excursion to full operating voltage, then reduce the voltage. Most fans do not operate at all
below 5 to 7 volts. At those lower voltages the fan will simply consume current, dissipate power, and not operate
and such conditions should be avoided.
The output of the amplifier can be configured to provide a high or low side pass transistor. A high side pass
transistor simplifies the coupling of tachometer outputs to the tachometer inputs of the LM81 since the fan
remains grounded. Low side drive will require AC coupling along with clamping at the LM81 input to prevent
negative excursions.
A typical circuit for fan drive is shown in Figure 16. R4 is used when a negative power supply is available to
eliminate offset in the amplifier and provide a 0 to 11.5 volt output (actually 12 volts less saturation). Omitting R4
will create a “dead zone” between approximately 0 to 6 volts output (a potentially unusable region anyway). In
many applications protecting the pass transistor Q2 from faults such as a shorted fan can be accomplished by
taking advantage of the current limit already existing on the 12 volt supply. Q2 will have to be heat-sunk
accordingly. Otherwise, use the suggested current limit circuit as shown.
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Figure 16. Amplifier Circuit for Connection Between DAC Output and Fan
TEMPERATURE MEASUREMENT SYSTEM
The LM81 temperature sensor and ADC produce 9-bit or 12-bit two’s-complement temperature data. A digital
comparator compares the temperature data to the user-programmable High, Low, Critical setpoints and
Hysteresis values.
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Figure 17. 9-bit Temperature-to-Digital Transfer Function
Figure 18. 12-bit Temperature-to-Digital Transfer Function
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TEMPERATURE DATA FORMAT
Temperature data can be read from the Temperature, THIGH setpoint, THIHYST setpoint, TLOW setpoint, TC setpoint
and THYST Offset registers; and written to the THIGH setpoint, THIHYST, TLOW setpoint, T_CRIT setpoint and THYST
offset registers. THIGH setpoint, TLOW setpoint, T_CRIT setpoint temperature data 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
−40˚C
1101 1000
D8h
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
−40˚C
1 1011 0000
1 B0h
In the extended mode temperature Register data can also be represented by a 12-bit two’s complement digital
word with an 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
0 00h
−0.0625˚C
1111 1111 1111
F FFh
−1.0˚C
1111 1111 0000
F F0h
−25˚C
1110 0111 0000
E 70h
−40˚C
1101 1000 0000
D 80h
THYST Offset temperature data is represented by a 3-bit word with an LSB (Least Significant Bit) equal to 1˚C.
TEMPERATURE INTERRUPTS
INT and T_CRIT_A outputs are provided for temperature interrupt. Temperature interrupts have a normal and an
extended option of operation. Each option has three different modes of operation: Repetitive Interrupt, One-Time
Interrupt and Comparator.
24
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Normal Repetitive Interrupt Mode is shown in Figure 19 and operates in the following way: T_CRIT_A is
disabled. Exceeding THIGH causes an interrupt that will remain active indefinitely until reset by reading Interrupt
Status Register 1. Once reset if the temperature remains above the THIHYST setpoint the interrupt will again be
activated at the completion of another conversion cycle. If temperature is less than or equal to THIHYST the
interrupt will not be activated.
Figure 19. Normal Repetitive Interrupt Response Diagram
Normal One-Time Interrupt Mode is shown in Figure 20 and operates in the following way: T_CRIT_A is
disabled. Exceeding THIGH causes an interrupt that will remain active indefinitely until reset by reading Interrupt
Status Register 1. Another interrupt will not occur until the temperature drops to less than or equal to THIHYST and
then exceeds THIGH during a subsequent conversion. After power up this mode is selected as default.
Figure 20. One-Time Interrupt Response Diagram
Normal Comparator Mode is shown in Figure 21 and operates in the following way: T_CRIT_A is disabled.
Exceeding THIGH causes an interrupt that will remain activated until the temperature is less than or equal to THIGH.
TLOW is disabled.
Figure 21. Normal Comparator Mode
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Extended Repetitive Interrupt Mode is shown in Figure 22 and operates in the following way: Once activated,
all interrupts remain activated until reset by a read of the Interrupt Status Register 1. Once activated all
T_CRIT_A interrupts remain activated until reset by a read of the Extended Mode Register 1. Temperature
conversion data less than or equal to TLOW will activate interrupt. Interrupt will continue to be activated until the
temperature data exceeds (TLOW + THYST). Exceeding THIGH activates interrupt. Interrupt will continue to be
activated at the end of a conversion until the temperature data is less than or equal to (THIGH − THYST). T_CRIT_A
interrupts are activated when the temperature exceeds T_CRIT. T_CRIT_A interrupts will no longer be activated
if the temperature data at the end of a conversion is less than or equal to( T_CRIT − THYST).
Figure 22. Extended Repetitive Interrupt Mode
Extended One-Time Interrupt Mode is shown in Figure 23 and operates in the following way: Once activated all
interrupts remain activated until reset by a read of the Interrupt Status Register 1. Once activated all T_CRIT_A
interrupts remain activated until reset by a read of the Extended Mode Register 1. An interrupt will be activated
when the data of a temperature conversion is less than or equal to TLOW. Interrupt cannot again be activated until
the data from a temperature conversion is greater than (TLOW + THYST). An interrupt will be activated when the
data of a temperature conversion is greater than THIGH. Interrupt cannot again be activated until the data of a
temperature conversion is less than or equal to (THIGH − THYST). T_CRIT_A interrupt is activated when the data
from a temperature conversion is greater than T_CRIT. Activation of an T_CRIT_A interrupt cannot occur until
the data from a temperature conversion is less than or equal to ( T_CRIT − THYST).
Figure 23. Extended One-Time Interrupt
Extended Comparator Mode is shown in Figure 24 and operates in the following way: Interrupt is activated
when the data from a temperature conversion is less than or equal to TLOW. Interrupt is reset when the data from
a temperature conversion exceeds (TLOW + THIGH). Exceeding THIGH will activate interrupt. This interrupt will be
reset when data from a temperature conversion is less than or equal to (THIGH − THYST). T_CRIT_A interrupt is
activated when the temperature exceeds T_CRIT. T_CRIT_A remains active until the data from a temperature
conversion is less than or equal to (T_CRIT − THYST) resets it.
26
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Figure 24. Extended Comparator Mode
(1)
(1)
Interrupt resets occur only when interrupt Status Register 1 is read.
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THE LM81 INTERRUPT STRUCTURE
Figure 25. Interrupt Structure
Figure 25 depicts the Interrupt Structure of the LM81. The LM81 can generate Interrupts as a result of each of its
internal WATCHDOG registers on the analog, temperature, and fan inputs.
28
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External Interrupts can come from the following source. 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:
• 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 LM81 is expected to latch the event. The design of the LM81 allows this input to go high even with no
power applied to the LM81, and no clamping or other interference with the line will occur. This line can also
be pulled low for at least 20 ms by the LM81 to reset a typical Chassis Intrusion circuit. Accomplish this reset
by setting Bit 7 of CI Clear Register (45h) high. The bit in the Register is self-clearing.
All interrupts are indicated in the two Interrupt Status Registers. The INT output has two mask registers, and
individual masks for each Interrupt. As described in the USING THE CONFIGURATION REGISTER section, the
hardware Interrupt line can also be enabled/disabled in the Configuration Register.
T_CRIT_A interrupt is dedicated to temperature and is indicated in Extended Mode Register 1. Extended Mode
Register 1 controls T_CRIT_A.
INTERRUPT CLEARING
Reading a 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
820 ms to allow all Registers to be updated between reads. In summary, the Interrupt Status Register clears
upon being read, and requires at least 400 ms to be updated. When the Interrupt Status Register clears, the
hardware interrupt line will also clear until the Registers are updated by the monitoring loop. The hardware
Interrupt line (INT) is cleared with the INT_Clear bit, which is Bit 3 of the Configuration Register. When this bit is
high, the LM81 monitoring loop will stop. It will resume when the bit is low.
RESET I/O
RESET is intended to provide a master reset to devices connected to this line. INT Mask Register 2, Bit 7, must
be set high to enable this function. Setting Bit 4 in the Configuration Register high outputs a least 20 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 RESET capability is not needed it can be used for any type
of digital control that requires a 20 ms active low open-drain output.
RESET operates as an input when not activated by the Configuration Register. Setting this line low will reset all
of the registers in the LM81 to their power on default state. All Value RAM locations will not be affected except
for the DAC Data Register.
NAND TREE TESTS
A NAND tree is provided in the LM81 for Automated Test Equipment (ATE) board level connectivity testing.
DACOut/ NTEST_IN, T_CRIT_A, V+ and GND pins are excluded from NAND tree testing. Taking
DACOut/NTEST_IN high before the first write to the configuration register activates the NAND Tree test mode.
After the first write to the configuration register the NAND Tree test mode cannot be reactivated. To perform a
NAND tree test all pins included in the NAND tree should be driven to 1 forcing the A0/ NTEST_OUT high. Each
individual pin starting with A1 and concluding with SMBData (excluding DACOut/NTEST_IN, T_CRIT_A, V+ and
GND) can be taken low with the resulting toggle observed on the A0/NTEST_OUT pin. Allow for a typical
propagation delay of 500 ns.
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Figure 26.
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
(60 mm sq. X 20 mm)
9-16
2410ML
2.36 in sq. X 0.98 in
(60 mm sq. X 25 mm)
14-25
3108NL
3.15 in sq. X 0.79 in
(80 mm sq. X 20 mm)
25-42
3110KL
3.15 in sq. X 0.98 in
(80 mm sq. X 25 mm)
25-40
Mechatronics
Inc. P.O. Box 20
Mercer Island, WA 98040
800 453-4569 Various sizes available with tach output option.
Sanyo Denki America, Inc.
468 Amapola Ave.
Torrance, CA 90501
310 783-5400
30
Model Number
Frame Size
Airflow CFM
109P06XXY601
2.36 in sq. X 0.79 in
(60 mm sq. X 20 mm)
11-15
109R06XXY401
2.36 in sq. X 0.98 in
(60 mm sq. X 25 mm)
13-28
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Model Number
Frame Size
Airflow CFM
109P08XXY601
3.15 in sq. X 0.79 in
(80 mm sq. X 20 mm)
23-30
109R08XXY401
3.15 in sq. X 0.98 in
(80 mm sq. X 25 mm)
21-42
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
Write
Address of RAM and Registers. See the tables below for more
details.
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
A2
A1
A0
Address Pointer (Power On default 00h)
A7
A6
A5
A4
A3
13.2 ADDRESS POINTER INDEX (A7–A0)
Registers and RAM
A6–A0 in Hex
Power On Value of Registers:
<7:0> in Binary
Notes
Configuration Register
40h
0000 1000
Interrupt Status Register 1
41h
0000 0000
Interrupt Status Register 2
42h
0000 0000
Interrupt Mask Register 1
43h
0000 0000
Interrupt Mask Register 2
44h
0000 0000
CI Clear Register
46h
0000 0000
VID/Fan Divisor Register
47h
<7:4> = 0101;
<3:0> = VID3–VID0
Serial Bus Address Register
48h
<7:2> =0010 11; <1:0>
=(A!)(A0)
VID4 Register
49h
<7:1> =1000 000;
<0> =VID4
Temperature Configuration
Register
4Bh
0000 0001
Extended Mode Register 1
4Ch
0100 0100
Extended Mode Register 2
4Dh
0000 0000
Value RAM
19h–3Dh
Company ID
3Eh
0000 0001
This default designates Texas
Instruments.
Stepping
3Fh
0000 0011
Revisions of this device will start
with 1 and increment by one.
Address 19h default=1111 1111
CONFIGURATION REGISTER — ADDRESS 40H
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. (1)
At start up, limit checking functions and scanning begin. (2)
(1)
(2)
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.
All limits should be set in the Value RAM before setting this bit HIGH.
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Power on default - <7:0> = 00001000 binary
Bit
Name
Read/Write
Description
1
INT Enable
Read/Write
A one enables the INT Interrupt output.
2
Reserved
Read/Write
3
INT_Clear
Read/Write
A one disables the INT output 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 20 ms active low reset signal at
RESET. This bit is cleared once the pulse has gone
inactive.
5
Reserved
Read/Write
6
CI_Clear
Read/Write
A one outputs a minimum 20 ms active low pulse on the CI
pin. The register bit self clears after the pulse has been
output. This bit is mirrored in the CI Clear Register bit 7.
7
INITIALIZATION
Read/Write
A one restores power on default value to the Configuration
Register, Interrupt Status Registers, Interrupt Mask
Registers, CI Clear Register, VID/Fan Divisor Register,
VID4, Temperature Configuration Register, and the
Extended Mode Registers. This bit clears itself since the
power on default is zero.
INTERRUPT STATUS REGISTER 1 — ADDRESS 41H
Power on default - <7:0> = 00001000 binary
Bit
Name
Read/Write
Description
0
+2.5Vin
Read Only
A one indicates a High or Low limit has been exceeded.
1
Vccp1
Read Only
A one indicates a High or Low limit has been exceeded.
2
+3.3Vin
Read Only
A one indicates a High or Low limit has been exceeded.
3
+5Vin
Read Only
A one indicates a High or Low limit has been exceeded.
4
Temperature
Read Only
A one indicates a HIGH or HIHYST temperature error, see
the TEMPERATURE INTERRUPTS section.
5
Reserved
Read Only
6
FAN1
Read Only
A one indicates the fan count limit has been exceeded.
7
FAN2
Read Only
A one indicates the fan count limit has been exceeded.
INTERRUPT STATUS REGISTER 2 — ADDRESS 42H
Power on default - <7:0> = 00001000 binary
32
Bit
Name
Read/Write
Description
0
+12Vin
Read Only
A one indicates a High or Low limit has been exceeded.
1
Vccp2
Read Only
A one indicates a High or Low limit has been exceeded.
2
Reserved
Read Only
3
Reserved
Read Only
4
CI
Read Only
5
Reserved
Read Only
6
Reserved
Read Only
7
TLOW
Read Only
A one indicates CI (Chassis Intrusion) has gone high.
A one indicates LOW temperature error in EXTENDED
MODE ONLY, see the TEMPERATURE INTERRUPTS
section.
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INTERRUPT MASK REGISTER 1 — ADDRESS 43H
Power on default - <7:0> = 00001000 binary
Bit
Name
Read/Write
Description
0
+2.5Vin
Read/Write
A one disables the corresponding interrupt status bit for
INT interrupt.
1
Vccp1
Read/Write
A one disables the corresponding interrupt status bit for
INT interrupt.
2
+3.3Vin
Read/Write
A one disables the corresponding interrupt status bit for
INT interrupt.
3
+5Vin
Read/Write
A one disables the corresponding interrupt status bit for
INT interrupt.
4
Temperature
Read/Write
A one disables the corresponding interrupt status bit for
INT interrupt.
5
Reserved
Read/Write
6
FAN1
Read/Write
A one disables the corresponding interrupt status bit for
INT interrupt.
7
FAN2
Read/Write
A one disables the corresponding interrupt status bit for
INT interrupt.
INTERRUPT MASK REGISTER 2 — ADDRESS 44H
Power on default - <7:0> = 00001000 binary
Bit
Name
Read/Write
Description
0
+12Vin
Read/Write
A one disables the corresponding interrupt status bit for
INT interrupt.
1
Vccp2
Read/Write
A one disables the corresponding interrupt status bit for
INT interrupt.
2
Reserved
Read/Write
3
Reserved
Read/Write
4
Chassis Intrusion
Read/Write
5
Reserved
Read/Write
6
Reserved
Read/Write
7
RESET Enable
Read/Write
A one disables the corresponding interrupt status bit for
INT interrupt.
<7> = 1 in INT Mask Register 2 enables the RESET in
the Configuration Register.
RESERVED REGISTER — ADDRESS 45H
Power on default - <7:0> = 00h. Read/Write for backwards compatibility
CI CLEAR REGISTER — ADDRESS 46H
Power on default - <7:0> = 00001000 binary
Bit
Name
Read/Write
0-6
Reserved
Read/Write
7
CI Clear
Read/Write
Description
A one outputs a minimum 20 ms active low pulse on the
Chassis Intrusion pin. The register bit self clears after the
pulse has been output. This bit is mirrored in
Configuration Register bit 6.
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VID/FAN DIVISOR REGISTER — ADDRESS 47H
Power on default - <7:4> is 0101, and <3:0> is mapped to VID <3:0>
Bit
Name
Read/Write
Description
0-3
VID <3:0>
Read Only
The VID <3:0> inputs from the Pentium/PRO power
supplies that indicate the operating voltage (e.g. 1.5V to
2.9V).
4-5
FAN1 RPM Control
Read/Write
FAN1 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.
6-7
FAN2 RPM Control
Read/Write
FAN2 Speed Control.
<7:6> = 00 - divide by 1;
<7:6> = 01 - divide by 2;
<7:6> = 10 - divide by 4;
<7:6> = 11 - divide by 8.
SERIAL BUS ADDRESS REGISTER — ADDRESS 48H
Power on default - Serial Bus address <6:0> = 010
11(A1)(A0) and <7> = 0 binary
Bit
Name
Read/Write
Description
0-1
Serial Bus Address
Read Only
Serial Bus address <1:0> = A1 A0
2-6
Serial Bus Address
Read/Write
Serial Bus address <6:2> = 010 11
7
Reserved
Read/Write
VID4 REGISTER — ADDRESS 49H
Power on default - <7:1> = 100 000, <0> = VID4
Bit
Name
Read/Write
Description
0
VID4
Read Only
VID4 input from Pentium/PRO power supply that indicate
the operating voltage of the processor (e.g. 1.5V to 2.9V).
1-7
Reserved
Read/Write
TEMPERATURE CONFIGURATION REGISTER — ADDRESS 4BH
Power on default - <7:0> = 0000 0001 binary
Bit
Name
Read/Write
Description
0-1
Temperature Interrupt
Mode Select Bits
Read/Write
The state of these bits select the interrupt mode for INT
as described below.
<1:0> = 00 or <1:0> = 11: Repetitive Interrupt Mode
<1:0> = 01: One-Time Interrupt Mode
<1:0> = 10: Comparator Mode
2-6
Reserved
Read/Write
7
Temperature
Resolution
Read Only
For 8-bit plus sign temperature resolution: <7> = LSB
(0.5˚C)
EXTENDED MODE REGISTER 1 — ADDRESS 4CH
Power on default - <7:0> = 0100 0100 binary
34
Bit
Name
Read/Write
Description
0
Extended Mode
Enable
Read/Write
A one enables the Extended Interrupt Modes, the
T_CRIT_A output and all the functions listed in the
Extended Mode Registers. Bit 7 of the Interrupt Status
register will be activated to reflect the interrupt status of
the LOW limit comparison result.
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Power on default - <7:0> = 0100 0100 binary
Bit
Name
Read/Write
Description
1
LOW Limit Mask Bit
Read/Write
A mask bit for the LOW limit Interrupt. A one disables the
interrupt from propagating to the INT pin.
2-3
T_CRIT_A Interrupt
Mode Select
Read/Write
The state of these bits select the interrupt mode for
T_CRIT_A as described below.
<3:2> = 00 or <3:2> = 11: Repetitive Interrupt Mode
<3:2> = 01: One-Time Interrupt Mode
<3:2> = 10: Comparator Mode
4
T_CRIT_A Enable
Read/Write
A one enables the T_CRIT_A pin.
5
T_CRIT_A Polarity
Read/Write
A one sets the T_CRIT_A pin active HIGH. A zero sets
the T_CRIT_A pin active LOW.
6
T_CRIT_A Mask
Enable
Read/Write
A one prevents the T_CRIT_A interrupt from propagating
to the INT output pin.
7
T_CRIT_A Status Bit
Read
A one indicates that a T_CRIT_A interrupt has occurred.
EXTENDED MODE REGISTER 2 — ADDRESS 4DH
Power on default - <7:0> = 0000 0000 binary
Bit
Name
Read/Write
Description
0-2
Hysteresis Offset
Value
Read/Write
THYST value.
3
12-bit Temperature
Resolution Enable
Read/Write
A one sets the temperature resolution to 12 bits.
4-7
12-bit Temperature
Data
Read Only
12-bit temperature data least significant bits. Bit 7
mirrors bit 7 in the temperature configuration register
(4Bh) and has a weight of 0.5˚C; bits 6-4 have a weight
of 0.25, 0.125, and 0.0625˚C, respectively.
VALUE RAM — ADDRESS 15H–3FH
Address A6–A0 (1)
(1)
(2)
Description
(1)
15h
Manufacturers Test Register
19h
DAC data register; power on default <7:0> =1111 1111 binary
20h
+2.5Vin reading
21h
Vccp1 reading
22h
+3.3Vin reading
23h
+5Vin reading
24h
+12Vin reading
25h
Vccp2 reading
26h
Reserved reading
27h
Temperature reading (8 MSBs)
28h
FAN1 reading (2)
29h
FAN2 reading (2)
2Ah
Reserved
2Bh
+2.5Vin High Limit
2Ch
+2.5Vin Low Limit
2Dh
Vccp1 High Limit
2Eh
Vccp1 Low Limit
2Fh
+3.3Vin High Limit
30h
+3.3Vin Low Limit
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.
This location stores the number of counts of the internal clock per revolution.
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Address A6–A0 (1)
Description
31h
(1)
+5Vin High Limit
32h
+5Vin Low Limit
33h
+12Vin High Limit
34h
+12Vin Low Limit
35h
Vccp2 High Limit
36h
Vccp2 Low Limit
37h
T_CRIT Limit (Extended Mode)
38h
LOW Limit (Extended Mode)
39h
HIGH Temperature Limit
3Ah
HIHYST Temperature Limit
3Bh
FAN1 Fan Count Limit (3)
3Ch
FAN2 Fan Count Limit (3)
3Dh
Reserved
3Eh
Company Identification. The number in this register identifies Texas Instruments (0000 0001)
3Fh
Stepping Register:
LM81CIM revision number 03h (0000 0011)
LM81BIM revision number 04h (0000 0100)
(3)
36
It is the number of counts of the internal clock for the Low Limit of the fan speed.
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TYPICAL APPLICATION
In the following PC application, the LM81 monitors temperature, fan speed for 2 fans, and 6 power supply
voltages. It also monitors an optical chassis intrusion detector. The LM81 provides a DAC output that can be
used to control fan speed.
Figure 27.
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PACKAGE OPTION ADDENDUM
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7-Oct-2013
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
(2)
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
LM81BIMT-3/NOPB
ACTIVE
TSSOP
PW
24
61
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
LM81
BIMT-3
LM81BIMTX-3/NOPB
ACTIVE
TSSOP
PW
24
2500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
LM81
BIMT-3
LM81CIMT-3/NOPB
ACTIVE
TSSOP
PW
24
61
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
LM81
CIMT-3
LM81CIMTX-3/NOPB
ACTIVE
TSSOP
PW
24
2500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
LM81
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.
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
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
7-Oct-2013
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.
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.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
23-Sep-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
LM81BIMTX-3/NOPB
TSSOP
PW
24
2500
330.0
16.4
6.95
8.3
1.6
8.0
16.0
Q1
LM81CIMTX-3/NOPB
TSSOP
PW
24
2500
330.0
16.4
6.95
8.3
1.6
8.0
16.0
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
23-Sep-2013
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LM81BIMTX-3/NOPB
TSSOP
PW
24
2500
367.0
367.0
35.0
LM81CIMTX-3/NOPB
TSSOP
PW
24
2500
367.0
367.0
35.0
Pack Materials-Page 2
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