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PDF LM78CCVF-J Data sheet ( Hoja de datos )
| Número de pieza | LM78CCVF-J | |
| Descripción | Microprocessor System Hardware Monitor | |
| Fabricantes | National Semiconductor | |
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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
virtually any microprocessor based system. In a PC, the
LM78 can be used to monitor power supply voltages, tem-
peratures, 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 interrupt 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.
Applications
n System Hardware Monitoring for Servers and PCs
n Office Electronics
n Electronic Test Equipment and Instrumentation
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 I2C™ Serial Bus interfaces
Key Specifications
j Voltage monitoring
accuracy
j Temperature Accuracy
−10˚C to +100˚C
j Supply Voltage
j Supply Current
j ADC Resolution
Operating:
Shutdown:
±1% (max)
±3˚C (max)
5V
1 mA typ
10 µA typ
8 Bits
Typical Application
# indicates Active Low (”Not“)
I2C® is a registered trademark of the Phillips Corporation.
© 2001 National Semiconductor Corporation DS012873
DS012873-1
www.national.com
1 page  
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 (VCC)
Voltage on Any Input or Output Pin
Ground Difference (GNDD–GNDA)
Input Current at any Pin (Note 3)
Package Input Current (Note 3)
Maximum Junction Temperature
(TJ max)
ESD Susceptibility(Note 5)
Human Body Model
Machine Model
Soldering Information
PQFP Package (Note 6) :
6.5V
−0.3V to (VCC+0.3V)
±300 mV
±5 mA
±20 mA
150˚C
2000V
175V
Vapor Phase (60 seconds)
Infrared (15 seconds)
Storage Temperature
215˚C
220˚C
−65˚C to +150˚C
Operating Ratings(Notes 1, 2)
Operating Temperature Range
TMIN ≤ TA ≤ TMAX
LM78
−55˚C ≤ TA ≤ +125˚C
Specified Temperature Range
TMIN ≤ TA ≤ TMAX
LM78
−10˚C ≤ TA ≤ +100˚C
Junction to Ambient Thermal Resistance (θJA(Note 4) )
NS Package ID: VGZ44A
62˚C/W
Supply Voltage (VCC)
Ground Difference
(IGNDD–GNDAI)
+4.25V to +5.75V
≤100 mV
VIN Voltage Range
−0.05V to VCC + 0.05V
DC Electrical Characteristics(Note 7)
The following specifications apply for +4.25 VDC ≤VCC ≤ +5.75 VDC, fSYSCLK = 8.33 MHz, RS = 25Ω, unless otherwise speci-
fied. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C.
Symbol
Parameter
Conditions
Typical
Limits
Units
(Note 8) (Note 9) (Limits)
POWER SUPPLY CHARACTERISTICS
ICC Supply Current
Interface Inactive
Shutdown Mode
1.0 2 mA (max)
10 µA
TEMPERATURE-TO-DIGITAL CONVERTER CHARACTERISTICS
Accuracy
Resolution
−10˚C ≤ TA ≤ +100˚C
±3 ˚C (max)
1 ˚C (min)
ANALOG-TO-DIGITAL CONVERTER CHARACTERISTICS
Resolution (8 bits with full-scale at 4.096V)
16 mV
TUE
Total Unadjusted Error
(Note 10)
±1 % (max)
DNL
Differential Non-Linearity
±1 LSB
PSS
Power Supply Sensitivity
±1 %/V
tC Total Monitoring Cycle Time
OP AMP CHARACTERISTICS
(Note 11)
1.0 1.5 sec (max)
Output Current (Sourcing)
50 µA
Input Offset Voltage
Input Bias Current
IOUT = 50 µA
±1
±0.1
mV
nA
PSRR
60 dB
DC Open Loop Gain
70 dB
Gain Bandwidth Product
500 kHz
MULTIPLEXER/ADC INPUT CHARACTERISTICS
On Resistance
400
2000
Ω (max)
Off Channel Leakage Current
±0.1
nA
Input Current (On Channel Leakage Current)
±0.1
nA
FAN RPM-TO-DIGITAL CONVERTER
Accuracy
Full-scale Count
+25˚C ≤ TA ≤ +75˚C
−10˚C ≤ TA ≤ +100˚C
±10 % (max)
±15 % (max)
255 (max)
5 www.national.com
5 Page 
Test Circuit
DS012873-8
FIGURE 5. Digital Output Load Circuitry
Functional Description
1.0 GENERAL DESCRIPTION
The LM78 provides 7 analog inputs, a temperature sensor, a
Delta-Sigma ADC (Analog-to-Digital Converter), 3 fan speed
counters, WATCHDOG registers, and a variety of inputs and
outputs on a single chip. Interfaces are provided for both the
ISA parallel bus or Serial Bus. The LM78 performs power
supply, temperature, and fan monitoring for personal com-
puters.
The LM78 continuously converts analog inputs to 8-bit digital
words with a 16 mV LSB (Least Significant Bit) weighting,
yielding input ranges of from 0V to 4.096V. The two negative
analog inputs provide inverting op amps, with their
non-inverting input referred to ground. With additional exter-
nal feedback components, these inputs provide measure-
ments of negative voltages (such as -5V and -12V power
supplies). The analog inputs are useful for monitoring sev-
eral power supplies present in a typical computer. Tempera-
ture is converted to an 8-bit two’s-complement digital word
with a 1˚C LSB.
Fan inputs measure the period of tachometer pulses from
the fans, providing a higher count for lower fan speeds. The
fan inputs are digital inputs with an acceptable range of 0V to
5V and a transition level of approximately 1.4V. Full scale fan
counts are 255 (8-bit counter) and this represents a stopped
or very slow fan. Nominal speeds, based on a count of 153,
are programmable from 1100 to 8800 RPM on FAN1 and
FAN2, with FAN3 fixed at 4400 RPM. Signal conditioning
circuitry is included to accommodate slow rise and fall times.
The LM78 provides a number of internal registers, as de-
tailed in Figure 6. These include:
• Configuration Register: Provides control and con-
figuration.
• Interrupt Status Registers: Two registers to provide
status of each WATCHDOG limit or Interrupt event.
• Interrupt Mask Registers: Allows masking of indi-
vidual Interrupt sources, as well as separate masking for
each of both hardware Interrupt outputs.
• VID/Fan Divisor Registers: A register to read the sta-
tus of the VID input lines. The high bits of this register
contain the divisor bits for FAN1 and FAN2 inputs.
• Serial Bus Address Register: Contains the Serial Bus
address. At power on it assumes the default value of
0101101 binary, and can be altered via the ISA or Serial
Bus interface.
• Chip Reset/ID Register: Allows reseting of all the reg-
isters to the default power-on reset value. Provides a bit
for identification between the current version of this de-
vice and an older version which does not have this reset
capability.
• POST RAM: FIFO RAM to store up to 32 bytes of 8-bit
POST codes. Overflow of the POST RAM will set an
Interrupt. The POST RAM, located at base address x0h
and x4h, allows for easy decoding to address 80h and
84h, the normal addresses for outputting of POST codes.
Interrupt will only be set when writing to port x0h or x4h.
The POST RAM can be read via ports 85h and 86h.
• Value RAM: The monitoring results: temperature, volt-
ages, fan counts, and WATCHDOG limits are all con-
tained in the Value RAM. The Value RAM consists of a
total of 64 bytes. The first 11 bytes are all of the results,
the next 19 bytes are the WATCHDOG limits, and are
located at 20h-3Fh, including two unused bytes in the
upper locations. The next 32 bytes, located at 60h-7Fh,
mirror the first 32 bytes with identical contents. The only
difference in the upper bytes are that they auto-increment
the LM78 Internal Address Register when read from or
written to via the ISA bus (auto-increment is not available
for Serial Bus communications).
When the LM78 is started, it cycles through each measure-
ment in sequence, and it continuously loops through the
sequence approximately once every second. Each mea-
sured value is compared to values stored in WATCHDOG, or
Limit registers. When the measured value violates the pro-
grammed limit the LM78 will set a corresponding Interrupt in
the Interrupt Status Registers. Two hardware Interrupt lines,
SMI and NMI/IRQ, are fully programmable with separate
masking of each Interrupt source, and masking of each
output. In addition, the Configuration Register has control
bits to enable or disable the hardware Interrupts.
Additional digital inputs are provided for chaining of SMI
(System Management Interrupt), outputs of multiple external
LM75 temperature sensors via the BTI (Board Temperature
Interrupt) input, and a Chassis Intrusion input. The Chassis
Intrusion input is designed to accept an active high signal
from an external circuit that latches when the case is re-
moved from the computer.
11 www.national.com
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