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LM87

Serial Interface System Hardware Monitor with Remote

Diode Temperature Sensing

General Description

The LM87 is a highly integrated data acquisition system for

hardware monitoring of servers, Personal Computers, or

virtually any microprocessor-based system. In a PC, the

LM87 can be used to monitor power supply voltages, moth-

erboard and processor temperatures, and fan speeds. Ac-

tual values for these inputs can be read at any time. Pro-

grammable WATCHDOG limits in the LM87 activate a fully

programmable and maskable interrupt system with two out-

puts (INT

and THERM

The LM87 has an on-chip digital output temperature sensor

with 8-bit resolution as well as the capability of monitoring 2

external diode temperatures to 8-bit resolution, an 8 channel

analog input ADC with 8-bit resolution and an 8-bit DAC. A

channel on the ADC measures the supply voltage applied to

the LM87, nominally 3.3 V. Two of the ADC inputs can be

redirected to a counter that can measure the speed of up to

2 fans. A slow speed Σ∆ ADC architecture allows stable

measurement of signals in an extremely noisy environment.

The DAC, witha0to2.5Voutput voltage range, can be

used for fan speed control. Additional inputs are provided for

Chassis Intrusion detection circuits, and VID monitor inputs.

The VID monitor inputs can also be used as IRQ inputs if VID

monitoring is not required. The LM87 has a Serial Bus

interface that is compatible with SMBus

™

and I

™

Features

n Remote diode temperature sensing (2 channels)

n 8 positive voltage inputs with scaling resistors for

monitoring +5 V, +12 V, +3.3 V, +2.5 V, Vccp power

supplies directly

n 2 inputs selectable for fan speed or voltage monitoring

n 8-bit DAC output for controlling fan speed

n Chassis Intrusion Detector input

n WATCHDOG comparison of all monitored values

n SMBus or I

C Serial Bus interface compatibility

n VID0-VID4 or IRQ0-IRQ4 monitoring inputs

n On chip temperature sensor

Key Specifications

Voltage Monitoring Error

2 % (max)

External Temperature Error

4 ˚C (max)

Internal Temperature Error

−40 ˚C to +125 ˚C

3 ˚C (typ)

Supply Voltage Range 2.8 to 3.8 V

Supply Current 0.7 mA (typ)

ADC and DAC Resolution 8 Bits

Temperature Resolution 1.0 ˚C

Applications

n System Thermal and Hardware Monitoring for Servers,

Workstations and PCs

n Networking and Telecom Equipment

n Office Electronics

n Electronic Test Equipment and Instrumentation

Ordering Information

Temperature Range

NS Package

Number

−40 ˚C ≤ T

≤ +125 ˚C

Order Number Device Marking

LM87CIMT

LM87CIMT MTC24B

LM87CIMTX

LM87CIMT MTC24B

Note:

-Rail transport media, 61 parts per rail

-Tape and reel transport media, 2500 parts per reel

Connection Diagram

10099503

SMBus

™

is a trademark of the Intel Corporation.

December 2003

LM87 Serial Interface System Hardware Monitor with Remote Diode Temperature Sensing

Summary of content (32 pages)

PAGE 1
LM87 Serial Interface System Hardware Monitor with Remote Diode Temperature Sensing General Description The LM87 is a highly integrated data acquisition system for hardware monitoring of servers, Personal Computers, or virtually any microprocessor-based system. In a PC, the LM87 can be used to monitor power supply voltages, motherboard and processor temperatures, and fan speeds. Actual values for these inputs can be read at any time.
PAGE 2
LM87 Block Diagram 10099501 Pin Description Pin Name(s) Pin Number Number of Pins ADD/NTEST_OUT 1 1 Digital I/0 This pin normally functions as a three-state input that controls the two LSBs of the Serial Bus Address. When this pin is tied to VCC the two LSBs are 01. When tied to Ground, the two LSBs are 10. If this pin is not connected, the two LSBs are 00. This pin also functions as an output during NAND Tree tests (board-level connectivity testing).
PAGE 3
Pin Name(s) LM87 Pin Description (Continued) Pin Number Number of Pins GND 8 1 GROUND The system ground pin. 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. V+ (+2.8 V to +3.8 V) 9 1 POWER +3.3 V V+ power. Bypass with the parallel combination of 10 µF (electrolytic or tantalum) and 0.1 µF (ceramic) bypass capacitors.
PAGE 4
LM87 Absolute Maximum Ratings Vapor Phase (60 seconds) (Notes 1, 215 ˚C Infrared (15 seconds) 2) Positive Supply Voltage (V+) Operating Temperature Range All other pins NS Package Number: MTC24B ≤ TA ≤ TMAX IN +2.8 V to +3.8 V Voltage Range: +12Vin −0.05 V to +15 V +5Vin −0.05 V to +6.8 V 2500 V +3.3Vin −0.05 V to +4.6 V 150V +2.5Vin −0.05 V to +3.6 V VID0 - VID4, Vccp −0.05 V to +6.
PAGE 5
(Continued) The following specifications apply for +2.8 VDC ≤ V+ ≤ +3.8 VDC, Analog voltage inputs RS = 510 Ω, unless otherwise specified. Boldface limits apply for TA = T J = TMIN to TMAX; all other limits TA = TJ = 25 ˚C.(Note 8) Symbol Parameter Conditions Typical Limits Units (Note 9) (Note 10) (Limits) -3.3 % (min) DAC CHARACTERISTICS DAC Error 0 ˚C ≤ TA ≤ +75 ˚C, V+ = 3.3 V, Code = 255 V+ = 3.3 V, 3/4 Scale, code 192 +3.7 0 ˚C ≤ TA ≤ +75 ˚C, V, V+ = 3.
PAGE 6
LM87 AC Electrical Characteristics The following specifications apply for +2.8 VDC ≤V+ ≤ +3.8 VDC on SMBCLK and SMBData, unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits T A = TJ = 25˚C. (Note 17) Symbol Parameter Conditions Typical Limits Units (Note 9) (Note 10) (Limits) 2.
PAGE 7
D1 D2 D3 R1 R2 R3 R4 INT# x x x 0 ∞ 100k 1M CI x x x 0 ∞ ∞ FAN1–FAN2 x x x 0 ∞ ∞ SMBCLK x x x 0 SMBData x x x 0 RESET# x x x 0 ADD/NTEST_OUT x x x 0 ∞ ∞ 1M ∞ ∞ 1M ∞ 100k 1M ∞ ∞ 1M Pin Name D1 D2 +12Vin x 1M +5Vin 1M D3 R1 R2 R3 x R1+R2 ≈130k ∞ x x R1+R2 ≈130k ∞ +3.3Vin, +2.
PAGE 8
LM87 Test Circuit 10099506 FIGURE 3. Digital Output Load Test Circuitry Typical Performance Characteristics DAC Power Supply Sensitivity 10099536 ages to a 3/4 scale nominal ADC output. Two additional inputs, +AIN1 and +AIN2 (2.5V full scale) are input directly with no resistive dividers. The LM87 ADC continuously converts the scaled inputs to 8-bit digital words.
PAGE 9
The DAC digital output, moni• Value and Limit RAM: toring results (temperature, voltages, fan counts), WATCHDOG limits, and Company/Stepping IDs are all contained in the Value RAM.
PAGE 10
LM87 Functional Description (Continued) 2.0 INTERFACE 10099507 FIGURE 4. LM87 Register Structure www.national.
PAGE 11
LM87 Functional Description (Continued) 2.1 Internal Registers of the LM87 TABLE 1. The internal registers and their corresponding internal LM87 addresses are as follows: Register LM87 Internal Hex Address Power on Value Notes Internal Temp. Hardware High Limit 13h 0100 0110 70 ˚C Default - User adjustable. Lockable by setting bit 1 of register 4Ah. External Temp. Hardware High Limit 14h 0101 0101 85 ˚C Default - User adjustable. Lockable by setting bit 2 of register 4Ah.
PAGE 12
LM87 Functional Description (Continued) 2.2 Serial Bus Interface 10099508 (a) Serial Bus Write to the Internal Address Register followed by the Data Byte 10099509 (b) Serial Bus Write to the Internal Address Register Only 10099510 (c) Serial Bus Read from a Register with the Internal Address Register Preset to Desired Location FIGURE 5. Serial Bus Timing The Serial Bus control lines consist of the SMBData (serial data), SMBCLK (serial clock) and ADD (address) pin.
PAGE 13
3.3 Configuration Registers and Channel Mode Register The Configuration Registers and Channel Mode Register control the LM87 operation. At power on, the ADC is stopped and INT_Clear is asserted, clearing the INT# hardwire output. These registers start and stop the LM87, enable and disable interrupt output, configure the operation of dual function inputs, and provide the Reset functions described in Section 3.2. Bit 0 of Configuration Register 1 controls the monitoring loop of the LM87.
PAGE 14
LM87 Functional Description than once every 0.6 seconds can also prevent complete updates of Interrupt Status Registers and Interrupt Output’s. A typical sequence of events upon power on of the LM87 would consist of: 1. Set WATCHDOG Limits (Continued) Bit 2 of the Channel Mode Register, when set to 0, configures pins 18 and 19 as +2.5V and VCCP2 voltage inputs. When set to 1, pins 18 and 19 are configured as a second remote temperature sensing channel. 2. 3.
PAGE 15
5.0 LAYOUT AND GROUNDING (Continued) A separate, low-impedance ground plane for analog ground, which provides a ground point for the GND pin, 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 LM87. The power supply bypass, the parallel combination of 10 µF (electrolytic or tantalum) and 0.
PAGE 16
LM87 Functional Description (Continued) 10099512 (a) Fan with Tach Pull-Up to +5V 10099513 (b) Fan with Tach Pull-Up to +12V, or Totem-Pole Output and Resistor Attenuator 10099514 10099515 (c) Fan with Tach Pull-Up to +12V and Diode Clamp (d) Fan with Strong Tach Pull-Up or Totem Pole Output and Diode Clamp FIGURE 7. Alternatives for Fan Inputs Counts are based on 2 pulses per revolution tachometer outputs.
PAGE 17
(Continued) Temperature Digital Output Binary 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.
PAGE 18
LM87 Functional Description Make sure the traces to the 2.2 nF capacitor are matched. 2. Ideally, the LM87 should be placed within 10 cm of the Processor diode pins with the traces being as straight, short and identical as possible. (Continued) η from part to part. As an example, assume a temperature sensor has an accuracy specification of ± 3˚C at room temperature of 25˚C and the process used to manufacture the diode has a non-ideality variation of ± 1%.
PAGE 19
LM87 Functional Description (Continued) 9.0 WATCHDOG LIMIT COMPARISONS AND INTERRUPT STRUCTURE 10099531 FIGURE 10. Interrupt Structure the LM87 allows this input to go high even with no power applied to the LM87, 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 LM87 to reset a typical Chassis Intrusion circuit. This reset is activated by setting Bit 7 of CI Clear Register (46h) high. The bit in the Register is self-clearing.
PAGE 20
LM87 Functional Description Voltage, Fan, and Temperature High/Low errors are slightly more complex in their generation of INT# outputs. All of these error bits are stored in the Interrupt Status Registers at 43h, 44h and the Interrupt Status Mirror Registers at 4Ch and 4Dh. These inputs are gated by the Interrupt Mask Registers and processed by the INT# state machine to generate the INT# output.
PAGE 21
INT# Mask bit is set, the interrupt status for internal and external temperature, the THERM# input, and the hardware temperature error comparisons, will continue to be updated every conversion cycle, but will not have any effect on the INT# output. (Continued) 1 (40h) is written to re-Initialize the chip, or power is removed and reapplied. This feature is provided to prevent software from unintentionally overwriting these important limits.
PAGE 22
LM87 Functional Description sient temperature events. The Fault Queue adds a counter between the comparison logic and the Interrupt Status Register and THERM# output circuitry. The Fault Queue has a depth of 3, so three consecutive readings outside of limits is required to set an external temperature Interrupt Status Bit or generate a THERM# output. When the monitored temperature is returning within limits, only one conversion within limits is required to clear the status bit.
PAGE 23
LM87 Functional Description (Continued) 10099533 FIGURE 12. NAND Tree Test Structure Mechatronics Inc. P.O. Box 20 12.0 FAN MANUFACTURERS Manufacturers of cooling fans with tachometer outputs are listed below: NMB Tech 9730 Independence Ave. Chatsworth, California 91311 818 341-3355 818 341-8207 Model Number Frame Size Airflow CFM 2408NL 2.36 in sq. X 0.79 in 9-16 Mercer Island, WA 98040 800 453-4569 Various sizes available with tach output option. Sanyo Denki America, Inc. 468 Amapola Ave.
PAGE 24
LM87 Functional Description (Continued) 13.0 REGISTERS AND RAM 13.1 Address Pointer Register The main register is the Address Pointer Register. The bit designations are as follows: Bit Name 7-0 Address Pointer Bit 7 Read/Write Description Write Address of RAM and Registers. See the tables below for detail. 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.
PAGE 25
LM87 Functional Description (Continued) 13.3 Test Register — Address 15h Power on default – < 7:0 > = 00000000 binary Bit Name Read/Write 0 Shutdown Read/Write 1 Reserved Read/Write 2 Reserved Read/Write 3 Reserved Read/Write 4 Reserved Read/Write 5 Reserved Read/Write 6 Reserved Read/Write 7 Reserved Read/Write Description A one places the LM87 in a lower power "Shutdown" mode. 13.
PAGE 26
LM87 Functional Description (Continued) 13.5 Configuration Register 1 — Address 40h Power on default – < 7:0 > = 00001000 binary Bit 0 Name Read/Write Start Read/Write Description A one enables startup of monitoring operations, a zero puts the part in standby mode. Note: The outputs of Interrupt pins will not be cleared if the user writes a zero to this location after an interrupt has occurred, unlike the “INT_Clear” bit. At start up, limit checking functions and scanning begin.
PAGE 27
LM87 Functional Description (Continued) 13.7 Interrupt Status Register 2 — Address 42h Power on default – < 7:0 > = 0000 0000 binary 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 A one indicates the CI (Chassis Intrusion) input has gone high.
PAGE 28
LM87 Functional Description Bit Name 4-5 FAN1 RPM Control (Continued) Read/Write Read/Write Description FAN1 Speed Control. < 5:4 > < 5:4 > < 5:4 > < 5:4 > 6-7 FAN2 RPM Control Read/Write = 00 - divide by 1; = 01 - divide by 2; = 10 - divide by 4; = 11 - divide by 8. FAN2 Speed Control. < 7:6 > < 7:6 > < 7:6 > < 7:6 > = 00 - divide by 1; = 01 - divide by 2; = 10 - divide by 4; = 11 - divide by 8. 13.13 VID4 Register — Address 49h Power on default – < 7:1 > = 100 000, < 0 > = VID4.
PAGE 29
LM87 Functional Description (Continued) Bit Name 6 FAN1/AIN1 Read Only Read Only A one indicates the fan count limit has been exceeded or an AIN1 High or Low limit has been exceeded. Description 7 FAN2/AIN2 Read Only A one indicates the fan count limit has been exceeded or an AIN2 High or Low limit has been exceeded. 13.
PAGE 30
LM87 Functional Description (Continued) Address A6–A0 Description 2Ah Reserved 2Bh +2.5V High Limit/External Temperature 2 High Limit 2Ch +2.5V Low Limit/External Temperature 2 Low Limit 2Dh Vccp1 High Limit 2Eh Vccp1 Low Limit 2Fh +3.3V High Limit 30h +3.
PAGE 31
LM87 Typical Application 10099523 FIGURE 13. In this PC application the LM87 monitors temperature, fan speed for 2 fans, and 6 power supply voltages. It also monitors an optical chassis intrusion detector. The LM87 provides a DAC output that can be used to control fan speed. 31 www.national.
PAGE 32
LM87 Serial Interface System Hardware Monitor with Remote Diode Temperature Sensing Physical Dimensions inches (millimeters) unless otherwise noted 24-Lead TSSOP Order Number LM87CIMT NS Package Number MTC24B 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.