LM78.PDF

February 2000

LM78

Microprocessor System Hardware Monitor

General Description

The LM78 is a highly integrated Data Acquisition system for

hardware monitoring of servers, Personal Computers, or vir-

tually any microprocessor based system. In a PC, the LM78

can be used to monitor power supply voltages, tempera-

tures, and fan speeds. Actual values for these inputs can be

read at any time, and programmable WATCHDOG limits in

the LM78 activate a fully programmable and maskable inter-

rupt system with two outputs.

The LM78 has an on-chip temperature sensor, 5 positive

analog inputs, two inverting inputs (for monitoring negative

voltages), and an 8-bit ADC. An input is provided for the

overtemperature outputs of additional temperature sensors

and this is linked to the interrupt system. The LM78 provides

inputs for three fan tachometer outputs. Additional inputs are

provided for Chassis Intrusion detection circuits, VID monitor

inputs, and chainable interrupt. The LM78 provides both ISA

and Serial Bus interfaces. A 32-byte auto-increment RAM is

provided for POST (Power On Self Test) code storage.

Features

n Temperature sensing

n 5 positive voltage inputs

n 2 op amps for negative voltage monitoring

n 3 fan speed monitoring inputs

n Input for additional temperature sensors

n Chassis Intrusion Detector input

n WATCHDOG comparison of all monitored values

n POST code storage RAM

n ISA and I 2 C ™ Serial Bus interfaces

Key Specifications

j Voltage monitoring

accuracy

± 1% (max)

j Temperature Accuracy

−10˚C to +100˚C

± 3˚C (max)

j Supply Voltage

Applications

n System Hardware Monitoring for Servers and PCs

n Office Electronics

n Electronic Test Equipment and Instrumentation

j Supply Current

Operating:

1 mA typ

Shutdown:

10 µA typ

j ADC Resolution

8 Bits

Typical Application

DS012873-1

# indicates Active Low (”Not“)

I 2 C ® is a registered trademark of the Phillips Corporation.

DS012873

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Ordering Information

Connection Diagram

Temperature Range

Package

−10˚C

T A

+100˚C

Order Number

Device Marking

LM78CCVF

LM78CCVF-J

VGZ44A

DS012873-2

Block Diagram

DS012873-3

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Pin Descriptions

Na me(s)

Number

of Pins

Type

Description

IORD

Digital Input

An active low standard ISA bus I/O Read Control.

IOWR

Digital Input

An active low standard ISA bus I/O Write Control.

SYSCLK

Digital Input

The reference clock for the ISA bus. Typically ranges from 4.167 MHz to

8.33 MHz. The minimum clock frequency this input can handle is 1 Hz.

D7–D0

4–11

Digital I/O

Bi-directional ISA bus Data lines. D0 corresponds to the low order bit,

with D7 the high order bit.

V CC (+5V)

POWER

+5V V CC power. Bypass with the parallel combination of 10 µF

(electolytic or tantalum) and 0.1 µF (ceramic) bypass capacitors.

GNDD

GROUND

Internally c onn ected to all digital circuitry.

SMI__IN

Digital Input

Chainable SMI (System Management Interrupt) Input. This is an active

low input that propagates the SMI signal to the SMI output of the LM78

via SMI Mask Register Bit 6 and SMI enable Bit 1 of the Configuration

Chassis

Intrusion

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 LM78. The LM78 provides an

internal open drain on this line, controlled by Bit 7 of NMI Mask Register

2, to provide a minimum 20 ms reset of this line.

Power

Switch

Bypass

Digital Output An active low push-pull output intended to drive an external P-channel

power MOSFET for software power control.

FAN3–FAN1

17–19

Digital Input

0V to +5V amplitude fan tachometer input.

SCL

Digital Input

Serial Bus Clock.

SDA

Digital I/O

Serial Bus bidirectional Data.

RESET

Digital Output Master Reset, 5 mA driver (open drain), active low output with a 20 ms

minimum pulse width. Available when enabeld via Bit 7 in SMI Mask

NTEST

Test Output

NAND Tree totem-pole output that provides board-level connectivity

testing. Refer to Section 11.0 on NAND Tree testing.

GNDA

GROUND

Internally connected to all analog circuitry. The ground reference for all

analog inputs.

−IN6

Analog Input

Ground-referred inverting op amp input. Refer to Section 4.0, “ANALOG

INPUTS”.

FB6

Analog Output Output of inverting op amp for Input 6. Refer to section 4.0, “ANALOG

INPUTS”.

FB5

Analog Output Output of inverting op amp for Input 5. Refer to section 4.0, “ANALOG

INPUTS”.

−IN5

Analog Input

Ground-referred inverting op amp input. Refer to Section 4.0, “ANALOG

INPUTS”.

IN4–IN0

29–33

Analog Input

0V to 4.096V FSR Analog Inputs.

VID3–VID0

34–37

Digital Input

Voltage Supply readouts from P6. This value is read in the VID/Fan

Divisor Register.

BTI

Digital Input

Board Temperature Interrupt driven by O.S. outputs of additional

temperature sensors such as LM75. Pr ovides internal pu ll-up of 10 k

NMI/IRQ

Digital Output Non-Maskable Interrupt (open source)/Interrupt Request (open drain).

The mode is selected with Bit 5 of the Configuration Register and the

output is enabled when Bit 2 of th e C onfiguration Register is set to 1.

The default state is disabled and IRQ mode.

SMI

Digital Output System Management Interrupt (open drain). This output is enabled when

Bit 1 in the Configuration Register is set to 1. The default state is

disabled.

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Pin Descriptions (Continued)

Name(s)

Number

of Pins

Type

Description

A2–A0

41–43

Digital Input

The three lowest order bits of the 16-bit ISA Address Bus. A0

corresponds to the lowest order bit.

Digital Input

Chip Select input from an external decoder which decodes high order

address bits on the ISA Address Bus. This is an active low input.

TOTAL PINS

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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.

Positive Supply Voltage (V CC )

Vapor Phase (60 seconds)

215˚C

Infrared (15 seconds)

220˚C

Storage Temperature

−65˚C to +150˚C

6.5V

Operating Ratings (Notes 1, 2)

Voltage on Any Input or Output Pin

−0.3V to (V CC +0.3V)

Operating Temperature Range

T MIN

£ T A

£ T MAX

± 300 mV

Ground Difference (GNDD–GNDA)

LM78

−55˚C £ T A

£ +125˚C

± 5mA

Input Current at any Pin (Note 3)

Specified Temperature Range

T MIN

T A

T MAX

Package Input Current (Note 3)

± 20 mA

LM78

−10˚C

T A

+100˚C

Maximum Junction Temperature

(T J max)

150˚C

Junction to Ambient Thermal Resistance (

q JA (Note 4) )

NS Package ID: VGZ44A

62˚C/W

ESD Susceptibility(Note 5)

Human Body Model

2000V

Supply Voltage (V CC )

+4.25V to +5.75V

Ground Difference

(IGNDD–GNDAI)

Machine Model

175V

100 mV

Soldering Information

PQFP Package (Note 6) :

V IN Voltage Range

−0.05V to V CC + 0.05V

DC Electrical Characteristics (Note 7)

The following specifications apply for +4.25 V DC

V CC

+5.75 V DC ,f SYSCLK = 8.33 MHz, R S =25

, unless otherwise speci-

fied. Boldface limits apply for T A =T J =T MIN to T MAX ; all other limits T A =T J = 25˚C.

Symbol

Parameter

Conditions

Typical

Limits

Units

(Note 8)

(Note 9)

(Limits)

POWER SUPPLY CHARACTERISTICS

I CC

Supply Current

Interface Inactive

1.0

mA (max)

Shutdown Mode

µA

TEMPERATURE-TO-DIGITAL CONVERTER CHARACTERISTICS

Accuracy

−10˚C

T A

+100˚C

± 3

˚C (max)

Resolution

˚C (min)

ANALOG-TO-DIGITAL CONVERTER CHARACTERISTICS

Resolution (8 bits with full-scale at 4.096V)

TUE

Total Unadjusted Error

(Note 10)

± 1

% (max)

DNL

Differential Non-Linearity

± 1

LSB

PSS

Power Supply Sensitivity

± 1

%/V

t C

Total Monitoring Cycle Time

(Note 11)

1.0

1.5

sec (max)

OP AMP CHARACTERISTICS

Output Current (Sourcing)

µA

Input Offset Voltage

I OUT =50µA

± 1

Input Bias Current

± 0.1

PSRR

DC Open Loop Gain

Gain Bandwidth Product

500

kHz

MULTIPLEXER/ADC INPUT CHARACTERISTICS

On Resistance

400

2000

(max)

Off Channel Leakage Current

± 0.1

Input Current (On Channel Leakage Current)

± 0.1

FAN RPM-TO-DIGITAL CONVERTER

Accuracy

+25˚C £ T A

£ +75˚C

± 10

% (max)

−10˚C

T A

+100˚C

± 15

% (max)

Full-scale Count

255

(max)

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