LM85
Hardware Monitor with Integrated Fan Control
General Description
The LM85, hardware monitor, has a two wire digital interface
compatible with SMBus 2.0. Using an 8-bit
ADC, the
LM85 measures:
the temperature of two remote diode connected transis-
tors as well as its own die
the V
CCP
, 2.5V, 3.3VSBY, 5.0V, and 12V supplies (inter-
nal scaling resistors).
To set fan speed, the LM85 has three PWM outputs that are
each controlled by one of three temperature zones. The
LM85 includes a digital filter that can be invoked to smooth
temperature readings for better control of fan speed. The
LM85 has four tachometer inputs to measure fan speed.
Limit and status registers for all measured values are in-
cluded.
Features
n
2-wire, SMBus 2.0 compliant, serial digital interface
n
8-bit
ADC
n
Monitors V
CCP
, 2.5V, 3.3 VSBY, 5.0V, and 12V
motherboard/processor supplies
n
Monitors 2 remote thermal diodes
n
Programmable autonomous fan control based on
temperature readings
n
Noise filtering of temperature reading for fan control
n
1.0C digital temperature sensor resolution
n
3 PWM fan speed control outputs
n
4 fan tachometer inputs
n
Monitors 5 VID control lines
n
24-pin QSOP package
n
XOR-tree test mode
Key Specifications
n
Voltage Measurement Accuracy
2% FS (max)
n
Resolution
8-bits, 1C
n
Temperature Sensor Accuracy
3C (max)
n
Temperature Range
-- LM85 Operational
0C to +85C
-- Remote Temp Accuracy
0C to +125C
n
Power Supply Voltage
+3.0V to +3.6V
n
Power Supply Current
0.53 mA
Applications
n
Desktop PC
n
Microprocessor based equipment
(e.g. Base-stations, Routers, ATMs, Point of Sales)
Block Diagram
20035301
March 2003
LM85
Hardware
Monitor
with
Integrated
Fan
Control
2003 National Semiconductor Corporation
DS200353
www.national.com
Connection Diagram
24 Pin QSOP
20035302
NS Package MQA24
Top View
LM85BIMQ or LM85CIMQ (55 units per rail), or
LM85BIMQX or LM85CIMQX (2500 units per tape and reel)
Information on the differences between the LM85BIMQ and LM85CIMQ can be found in Section 6.0. It is highly recommended
that all new designs use the LM85BIMQ.
Pin Descriptions
Symbol
Pin
Typ
Name and Function/Connection
SMBus
SMBDAT
1
Digital I/O
(Open-Drain)
System Management Bus Data. Open-drain output. 5V tolerant,
SMBus 2.0 compliant.
SMBCLK
2
Digital Input
System Management Bus Clock. Tied to Open-drain output. 5V
tolerant, SMBus 2.0 compliant.
Processor
VID
Lines
VID0
5
Digital Input
Voltage identification signal from the processor. This value is read
in the VID0VID4 Status Register.
VID1
6
Digital Input
Voltage identification signal from the processor. This value is read
in the VID0VID4 Status Register.
VID2
7
Digital Input
Voltage identification signal from the processor. This value is read
in the VID0VID4 Status Register.
VID3
8
Digital Input
Voltage identification signal from the processor. This value is read
in the VID0VID4 Status Register.
VID4
19
Digital Input
Voltage identification signal from the processor. This value is read
in the VID0VID4 Status Register.
Power
3.3V
4
POWER
+3.3V pin. Can be powered by +3.3V Standby power if monitoring
in low power states is required. This pin also serves as the analog
input to monitor the 3.3V supply. This pin should be bypassed
with a 0.1f capacitor in parallel with 100pf. A bulk capacitance of
approximately 10f needs to be in the near vicinity of the LM85.
GND
3
GROUND
Ground for all analog and digital circuitry.
Voltage
Inputs
5V
20
Analog Input
Analog input for +5V monitoring.
12V
21
Analog Input
Analog input for +12V monitoring.
2.5V
22
Analog Input
Analog input for +2.5V monitoring.
V
CCP
23
Analog Input
Analog input for +V
CCP
(processor voltage) monitoring.
LM85
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2
Pin Descriptions
(Continued)
Symbol
Pin
Typ
Name and Function/Connection
Remote
Remote1+
18
Remote Thermal
Diode Positive
Input
Positive input (current source) from the first remote thermal diode.
Serves as the positive input into the A/D. Connected to
THERMDA pin of Pentium processor or the base of a diode
connected MMBT3904 NPN transistor.
Remote1-
17
Remote Thermal
Diode Negative
Input
Negative input (current sink) from the first remote thermal diode.
Serves as the negative input into the A/D. Connected to
THERMDC pin of Pentium processor or the emmiter of a diode
connected MMBT3904 NPN transistor.
Remote2+
16
Remote Thermal
Diode Positive
Output
Positive input (current source) from the first remote thermal diode.
Serves as the positive input into the A/D. Connected to
THERMDA pin of Pentium processor or the base of a diode
connected MMBT3904 NPN transistor.
Remote2-
15
Remote Thermal
Diode Negative
Input
Negative input (current sink) from the first remote thermal diode.
Serves as the negative input into the A/D. Connected to
THERMDC pin of Pentium processor or the emmiter of a diode
connected MMBT3904 NPN transistor.
Fan
Tachometer
Inputs
TACH1
11
Digital Input
Input for monitoring tachometer output of fan 1.
TACH2
12
Digital Input
Input for monitoring tachometer output of fan 2.
TACH3
9
Digital Input
Input for monitoring tachometer output of fan 3.
TACH4/Address
Select
14
Digital Input
Input for monitoring tachometer output of fan 4. If in Address
Select Mode, determines the SMBus address of the LM85.
Fan
Control
PWM1/xTest
Out
24
Digital Open-Drain
Output
Fan speed control 1. When in XOR tree test mode, functions as
XOR Tree output.
PWM2
10
Digital Open-Drain
Output
Fan speed control 2.
PWM3/Address
Enable
13
Digital Open-Drain
Output
Fan speed control 3. Pull to ground at power on to enable
Address Select Mode (Address Select pin controls SMBus
address of the device).
LM85
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3
Absolute Maximum Ratings
(Notes 1,
2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage, V+
-0.5V to 6.0V
Voltage on Any Digital Input or
Output Pin
-0.5V to 6.0V
Voltage on 12V Analog Input
-0.5V to 16V
Voltage on 5V Analog Input
-0.5V to 6.66V
Voltage on Remote1+, Remote2+, -0.5V to (V+ + 0.05V)
Current on Remote1-, Remote2-
1 mA
Voltage on Other Analog Inputs
-0.5V to 6.0V
Input Current on Any Pin (Note 3)
5 mA
Package Input Current (Note 3)
20 mA
Package Dissipation at T
A
= 25C
See (Note 5)
ESD Susceptibility (Note 4)
Human Body Model
2500V
Machine Model
250V
Soldering Temperature, Infrared,
10 seconds (Note 6)
235C
Storage Temperature
-65C to +150C
Operating Ratings
(Notes 1, 2)
LM85 Operating Temperature Range
0C
T
A
+85C
Remote Diode Temperature Range
0C
T
D
+125C
Supply Voltage (3.3V nominal)
+3.0V to +3.6V
V
IN
Voltage Range
+12V V
IN
-0.05V to 16V
+5V V
IN
-0.05V to 6.66V
+3.3V V
IN
3.0V to 4.4V
V
CCP
and All Other Inputs
-0.05V to (V+ + 0.05V)
VID0VID4
-0.05V to 5.5V
Typical Supply Current
0.53 mA
DC Electrical Characteristics
The following specifications apply for V+ = 3.0V to 3.6V, and all analog input source impedance R
S
= 50
unless otherwise
specified in conditions. Boldface limits apply for T
A
= T
MIN
to T
MAX
; all other limits T
A
= 25C.
Symbol
Parameter
Conditions
Typical
(Note 7)
Limits
(Note 8)
Units
(Limits)
POWER SUPPLY CHARACTERISTICS
Supply Current (Note 9)
Converting, Interface and
Fans Inactive, Peak
Current
1.8
3.5
mA (max)
Converting, Interface and
Fans Inactive, Average
Current
0.53
mA
Power-On Reset Threshold Voltage
1.6
V (min)
2.8
V (max)
TEMPERATURE TO DIGITAL CONVERTER CHARACTERISTICS
Resolution
1
8
C
Bits
Temperature Accuracy (See (Note 10) for Thermal
Diode Processor Type)
At 25C
2.5
C (max)
0C to 100C
3
C (max)
100C to 125C
4
C (max)
Temperature Accuracy using Internal Diode (Note
11)
0C to 85C
3
C (max)
I
DS
External Diode Current Source
High Level
188
280
A (max)
Low Level
11.75
A
External Diode Current Ratio
16
ANALOG TO DIGITAL CONVERTER CHARACTERISTICS
TUE
Total Unadjusted Error(Note 12)
LM85CIMQ
-0.5/+3.5 %FS (max)
LM85BIMQ
2
%FS
(max)
DNL
Differential Non-linearity
1
LSB
Power Supply Sensitivity
1
%/V
Total Monitoring Cycle Time (Note 13)
All Voltage and
Temperature readings
182
200
ms (max)
LM85
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DC Electrical Characteristics
(Continued)
The following specifications apply for V+ = 3.0V to 3.6V, and all analog input source impedance R
S
= 50
unless otherwise
specified in conditions. Boldface limits apply for T
A
= T
MIN
to T
MAX
; all other limits T
A
= 25C.
Symbol
Parameter
Conditions
Typical
(Note 7)
Limits
(Note 8)
Units
(Limits)
Input Resistance, all analog inputs
210
140
k
(min)
400
k
(max)
DIGITAL OUTPUT: PWM1, PWM2, PWM3, XTESTOUT
I
OL
Logic Low Sink Current
LM85CIMQ
V
OL
=0.55V
8
mA (min)
LM85BIMQ
V
OL
=0.4V
8
mA (min)
V
OL
Logic Low Level
LM85CIMQ
I
OUT
= +3 mA
0.4
V (max)
I
OUT
= +8 mA
0.55
V (max)
LM85BIMQ
I
OUT
= +8 mA
0.4
V (max)
SMBUS OPEN-DRAIN OUTPUT: SMBDAT
V
OL
Logic Low Output Voltage
I
OUT
= +4 mA
0.4V
V (max)
I
OH
High Level Output Current
V
OUT
= V+
0.1
10
A (max)
SMBUS INPUTS: SMBCLK. SMBDAT
V
IH
Logic Input High Voltage
2.1
V (min)
V
IL
Logic Input Low Voltage
0.8
V (max)
V
HYST
Logic Input Hysteresis Voltage
300
mV
DIGITAL INPUTS: ALL
V
IH
Logic Input High Voltage
2.1
V (min)
V
IL
Logic Input Low Voltage
0.8
V (max)
V
TH
Logic Input Threshold Voltage
1.5
V
I
IH
Logic High Input Current
V
IN
= V+
0.005
10
A (max)
I
IL
Logic Low Input Current
V
IN
= GND
-0.005
-10
A (max)
C
IN
Digital Input Capacitance
20
pF
AC Electrical Characteristics
The following specifications apply for V+ = 3.0V to 3.6V unless otherwise specified in conditions. Boldface limits apply for T
A
= T
MIN
to T
MAX
; all other limits T
A
= 25C.
Symbol
Parameter
Conditions
Typical
(Note 7)
Limits
(Note 8)
Units
(Limits)
TACHOMETER ACCURACY
Fan Count Accuracy
10
% (max)
Fan Full-Scale Count
65536
(max)
Fan Counter Clock Frequency
90
kHz
Fan Count Conversion Time
0.7
1.4
sec (max)
FAN PWM OUTPUT
Frequency Setting Accuracy
10
% (max)
Frequency Range
10
94
Hz
Hz
Duty-Cycle Range
0 to 100
% (max)
Duty-Cycle Resolution (8-bits)
0.390625
%
Spin-Up Time Interval Range
100
4000
ms ms
Spin-Up Time Interval Accuracy
10
% (max)
SPIKE SMOOTHING FILTER
Time Interval Deviation
10
% (max)
Time Interval Range
35
0.8
sec
sec
LM85
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