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Part: LM85
Category:
Description: Hardware Monitor With Integrated Fan Control
Company: National Semiconductor Corporation
Datasheet: Download LM85 datasheet File size : 135 kB
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LM85 Hardware Monitor with Integrated Fan Control
March 2003
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 transistors as well as its own die the VCCP, 2.5V, 3.3VSBY, 5.0V, and 12V supplies (internal 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 included. n n n n n n n Noise filtering of temperature reading for fan control 1.0°C digital temperature sensor resolution 3 PWM fan speed control outputs 4 fan tachometer inputs Monitors 5 VID control lines 24-pin QSOP package XOR-tree test mode
Key Specifications
Voltage Measurement Accuracy Resolution Temperature Sensor Accuracy Temperature Range -- LM85 Operational -- Remote Temp Accuracy n Power Supply Voltage n Power Supply Current n n n n
± 2% FS (max)
8-bits, 1°C
± 3°C (max)
0°C to +85°C 0°C to +125°C +3.0V to +3.6V 0.53 mA
Features
n 2-wire, SMBus 2.0 compliant, serial digital interface n 8-bit ADC n Monitors VCCP, 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
Applications
n Desktop PC n Microprocessor based equipment (e.g. Base-stations, Routers, ATMs, Point of Sales)
Block Diagram
20035301
© 2003 National Semiconductor Corporation
DS200353
www.national.com
LM85
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 SMBus SMBDAT SMBCLK VID0 VID1 Processor VID Lines VID2 VID3 VID4 3.3V Power Pin 1 2 5 6 7 8 19 4 Typ Digital I/O (Open-Drain) Digital Input Digital Input Digital Input Digital Input Digital Input Digital Input POWER Name and Function/Connection System Management Bus Data. Open-drain output. 5V tolerant, SMBus 2.0 compliant. System Management Bus Clock. Tied to Open-drain output. 5V tolerant, SMBus 2.0 compliant. Voltage identification signal from the processor. This value is read in the VID0 VID4 Status Register. Voltage identification signal from the processor. This value is read in the VID0 VID4 Status Register. Voltage identification signal from the processor. This value is read in the VID0 VID4 Status Register. Voltage identification signal from the processor. This value is read in the VID0 VID4 Status Register. Voltage identification signal from the processor. This value is read in the VID0 VID4 Status Register. +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 0.1µf capacitor in parallel with 100pf. A bulk capacitance of approximately 10µf needs to be in the near vicinity of the LM85. Ground for all analog and digital circuitry. Analog input for +5V monitoring. Analog input for +12V monitoring. Analog input for +2.5V monitoring. Analog input for +VCCP (processor voltage) monitoring.
GND Voltage Inputs 5V 12V 2.5V VCCP
3 20 21 22 23
GROUND Analog Input Analog Input Analog Input Analog Input
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2
LM85
Pin Descriptions
Symbol Remote1+
(Continued) Pin 18 Typ Name and Function/Connection
Remote Thermal Positive input (current source) from the first remote thermal diode. Diode Positive Serves as the positive input into the A/D. Connected to Input THERMDA pin of Pentium processor or the base of a diode connected MMBT3904 NPN transistor. Remote Thermal Negative input (current sink) from the first remote thermal diode. Diode Negative Serves as the negative input into the A/D. Connected to Input THERMDC pin of Pentium processor or the emmiter of a diode connected MMBT3904 NPN transistor. Remote Thermal Positive input (current source) from the first remote thermal diode. Diode Positive Serves as the positive input into the A/D. Connected to Output THERMDA pin of Pentium processor or the base of a diode connected MMBT3904 NPN transistor. Remote Thermal Negative input (current sink) from the first remote thermal diode. Diode Negative Serves as the negative input into the A/D. Connected to Input THERMDC pin of Pentium processor or the emmiter of a diode connected MMBT3904 NPN transistor. Digital Input Digital Input Digital Input Digital Input Input for monitoring tachometer output of fan 1. Input for monitoring tachometer output of fan 2. Input for monitoring tachometer output of fan 3. Input for monitoring tachometer output of fan 4. If in Address Select Mode, determines the SMBus address of the LM85.
Remote1-
17
Remote
Remote2+
16
Remote2-
15
Fan Tachometer Inputs
TACH1 TACH2 TACH3 TACH4/Address Select PWM1/xTest Out
11 12 9 14 24 10 13
Digital Open-Drain Fan speed control 1. When in XOR tree test mode, functions as Output XOR Tree output. Digital Open-Drain Fan speed control 2. Output Digital Open-Drain Fan speed control 3. Pull to ground at power on to enable Output Address Select Mode (Address Select pin controls SMBus address of the device).
Fan Control
PWM2 PWM3/Address Enable
3
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