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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 Σ∆ 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 Σ∆ 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 1.0˚C 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, 1˚C

n Temperature Sensor Accuracy

3˚C (max)

n Temperature Range

— LM85 Operational 0˚C to +85˚C

— Remote Temp Accuracy 0˚C to +125˚C

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

Summary of content (26 pages)

PAGE 1
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 Σ∆ 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.
PAGE 2
4 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. Symbol Pin Typ 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.
PAGE 3
Remote Fan Tachometer Inputs Fan Control LM85 Pin Descriptions (Continued) Symbol Pin Remote1+ 18 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. Typ Name and Function/Connection Remote1− 17 Remote Thermal Negative input (current sink) from the first remote thermal diode.
PAGE 4
LM85 Absolute Maximum Ratings Machine Model (Notes 1, Soldering Temperature, Infrared, 10 seconds (Note 6) 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.
PAGE 5
(Continued) The following specifications apply for V+ = 3.0V to 3.6V, and all analog input source impedance RS = 50Ω unless otherwise specified in conditions. Boldface limits apply for TA = TMIN to TMAX; all other limits TA = 25˚C. Symbol Parameter Conditions Input Resistance, all analog inputs Typical (Note 7) Limits (Note 8) Units (Limits) 210 140 kΩ (min) 400 kΩ (max) 8 mA (min) DIGITAL OUTPUT: PWM1, PWM2, PWM3, XTESTOUT IOL Logic Low Sink Current LM85CIMQ LM85BIMQ VOL=0.
PAGE 6
LM85 AC Electrical Characteristics (Continued) The following specifications apply for V+ = 3.0V to 3.6V unless otherwise specified in conditions. Boldface limits apply for TA = TMIN to TMAX; all other limits TA = 25˚C. Symbol Parameter Conditions Typical (Note 7) Limits (Note 8) Units (Limits) SMBUS TIMING CHARACTERISTICS fSMB SMBus Operating Frequency 10 100 kHz (min) kHz (max) fBUF SMBus Free Time Between Stop And Start Condition 4.
PAGE 7
Note 13: This specification is provided only to indicate how often temperature and voltage data is updated. The LM85 can be read at any time without regard to conversion state (and will yield last conversion result). Note 14: Holding the SMBDAT and/or SMBCLK lines Low for a time interval greater than tTIMEOUT will reset the LM85’s SMBus state machine, therefore setting the SMBDAT pin to a high impedance state. Functional Description 1.
PAGE 8
LM85 Functional Description 1. (Continued) Set limits and parameters (not necessarily in this order): – [5F-61h] Set PWM frequencies and auto fan control range. – [62-63h] Set spike smoothing and min/off. – [5C-5Eh] Set the fan spin-up delays. – [5C-5Eh] Match each fan with a corresponding thermal zone. – [67-69h] Set the fan temperature limits. – [6A-6Ch] Set the temperature absolute limits. – [64-66h] Set the PWM minimum duty cycle. 2. 3. – [6D-6Eh] Set the temperature Hysteresis values.
PAGE 9
LM85 Functional Description (Continued) Register Read/ Register Address Write Name Bit 7 Bit 6 (MSB) Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (LSB) Default Lock? Value 49h R/W 3.
PAGE 10
LM85 Functional Description (Continued) Register Read/ Register Address Write Name Bit 7 Bit 6 (MSB) Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (LSB) RES Default Lock? Value 6Fh R/W XOR Test Tree Enable RES RES RES RES RES RES XEN 00h 74h R/W Tach Monitor Mode RES RES T3/4-1 T3/4-0 T2-1 T2-0 T1-1 T1-0 00h 75h R/W Fan Spin-up Mode RES RES RES PWM3 SU PWM2 SU PWM1 SU 7h RES RES U U Note: Reserved bits will always return 0 when read. 4.
PAGE 11
LM85 Functional Description (Continued) TABLE 1. Temperature vs Register Reading (Continued) Temperature Reading (Dec) Reading (Hex) (SENSOR ERROR) 80h 4.
PAGE 12
LM85 Functional Description (Continued) Current Duty Value (Decimal) Value (Hex) . . . . . . . . . 50.196% 128 80h . . . . . . . . . 100% 255 FFh 4.5 Register 3Eh: Company ID Register Address Read/ Write Register Name Bit 7 (MSB) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (LSB) Default Value 3Eh R Company ID 7 6 5 4 3 2 1 0 01h The company ID register contains the company identification number. For National Semiconductor this is 01h.
PAGE 13
LM85 Functional Description (Continued) Bit Name R/W Default Description 1 LOCK R/W 0 Setting this bit to 1 locks specified limit and parameter registers. Once this bit is set, limit and parameter registers become read only and will remain locked until the device is powered off. This register bit becomes read only once it is set.
PAGE 14
LM85 Functional Description (Continued) Bit Name R/W Default Description 6 Zone 3 Limit Exceeded R 0 The LM85 automatically sets this bit to 1 when the temperature input measured by the Remote2− and Remote2+ inputs is less than or equal to the limit set in the Internal (Zone2) Low Temp register or greater than the limit set in the Remote (Zone3) High Temp register. This bit will be set when a diode fault is detected.
PAGE 15
LM85 Functional Description (Continued) 4.11 Registers 44-4Dh: Voltage Limit Registers Register Address Read/ Write Register Name Bit 7 (MSB) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (LSB) Default Value 44h R/W 2.5V Low Limit 7 6 5 4 3 2 1 0 00h 45h R/W 2.5V High Limit 7 6 5 4 3 2 1 0 FFh 46h R/W VCCP Low Limit 7 6 5 4 3 2 1 0 00h 47h R/W VCCP High Limit 7 6 5 4 3 2 1 0 FFh 48h R/W 3.3V Low Limit 7 6 5 4 3 2 1 0 00h 49h R/W 3.
PAGE 16
LM85 Functional Description (Continued) TABLE 3. Temperature Limits vs Register Settings Temperature Reading (Decimal) Reading (Hex) −127˚C −127 81h . . . . . . . . . −50˚C −50 CEh . . . . . . . . . 0˚C 0 00h . . . . . . . . . 50˚C 50 32h . . . . . . . . . 127˚C 127 7Fh 4.
PAGE 17
LM85 Functional Description (Continued) This register becomes Read Only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect. After power up the default value is used whenever the Ready/Lock/Start/Override register Start bit is cleared even though modifications to this register are possible. Bits [7:5] Zone/Mode Bits [7:5] of the Fan Configuration registers associate each fan with a temperature sensor.
PAGE 18
LM85 Functional Description (Continued) In Auto Fan Mode, when the temperature for a zone is above the Temperature Limit (Registers 67-69h) and below its Absolute Temperature Limit (Registers 6A-6Ch), the speed of a fan assigned to that zone is determined as follows. When the temperature reaches the Fan Temp Limit for a zone, the PWM output assigned to that zone will be Fan PWM Minimum.
PAGE 19
LM85 Functional Description (Continued) RAN [3:0] Range (˚C) 0011 4 0100 5 0101 6.67 0110 8 0111 10 1000 13.33 1001 16 1010 20 1011 26.67 1100 32 1101 40 1110 53.33 1111 80 This register becomes Read Only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect.
PAGE 20
LM85 Functional Description (Continued) 20035307 FIGURE 2. What LM85 Auto Fan Control Sees With and Without Spike Smoothing TABLE 7. Spike Smoothing ZN-X[2:0] Spike Smoothed Over 000 35 seconds 001 17.6 seconds 010 11.8 seconds 011 7.0 seconds 100 4.4 seconds 101 3.0 seconds 110 1.6 seconds 111 .8 seconds TABLE 8. PWM Output Below Limit Depending on Value of Off/Min Off/Min PWM Action 0 At 0% duty below LIMIT 1 At Min PWM Duty below LIMIT 4.
PAGE 21
LM85 Functional Description (Continued) TABLE 9. PWM Duty vs Register Setting Current Duty Value (Decimal) Value (Hex) 0% 0 00h 0.3922% 1 01h . . . . . . . . . 25.098% 64 40h . . . . . . . . . 50.196% 128 80h . . . . . . . . . 100% 255 FFh 4.
PAGE 22
LM85 Functional Description (Continued) 4.
PAGE 23
LM85 Functional Description (Continued) TABLE 12. Hysteresis Settings (Continued) Setting HYSTERESIS . . . . . . 5h 5˚C . . . . . . Fh 15˚C 4.21 Register 6Fh: Test Register Register Address Read/ Write Register Name Bit 7 (MSB) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (LSB) Default Value 6Fh R/W Test Register RES RES RES RES RES RES RES XEN 00h If the XEN bit is set high, the part will be placed into XOR tree test mode.
PAGE 24
LM85 Functional Description (Continued) 23.14 1944 420 30.04 2523 420 38.16 3205 420 47.06 3953 420 61.38 5156 420 94.12 7906 420 This register is not effected when the Ready/Lock/Start/Override register Lock bit is set. After power up the default value is used whenever the Ready/Lock/Start/Override register Start bit is cleared even though modifications to this register are possible. 4.22.
PAGE 25
LM85 Functional Description (Continued) Item No. Description LM85CIMQ 4 Overide bit (register 40h bit 3) function with disabled PWM output (Fan configuration registers 5Ch-5Eh, bits fan_config[7:5]=ZON[2:0]=100 The override bit has no effect when The overide bit has precedance the PWM output is disabled. over all of the PWM output dissable bits. Therefore, if a PWM output is dissabled, setting the override bit will set the PWM output to 100%.
PAGE 26
LM85 Hardware Monitor with Integrated Fan Control Physical Dimensions inches (millimeters) unless otherwise noted 24-Lead Molded QSOP Package, Order Number LM85BIMQ, LM86BIMQX, LM85CIMQ or LM85CIMQX NS Package Number MQA24 LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1.