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PDF ADM1025 Data sheet ( Hoja de datos )

Número de pieza ADM1025
Descripción Low-Cost PC Hardware Monitor ASIC
Fabricantes Analog Devices 
Logotipo Analog Devices Logotipo



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a
Low-Cost PC
Hardware Monitor ASIC
ADM1025/ADM1025A*
FEATURES
Up to Eight Measurement Channels
Five Inputs to Measure Supply Voltages
VCC Monitored Internally
External Temperature Measurement with Remote Diode
On-Chip Temperature Sensor
Five Digital Inputs for VID Bits
Integrated 100 kPull-Ups on VID Pins (ADM1025 Only)
LDCM Support
I2C®-Compatible System Management Bus (SMBus)
Programmable RESET Output Pin
Programmable INT Output Pin
Configurable Offset for Internal/External Channel
Shutdown Mode to Minimize Power Consumption
Limit Comparison of all Monitored Values
APPLICATIONS
Network Servers and Personal Computers
Microprocessor-Based Office Equipment
Test Equipment and Measuring Instruments
PRODUCT DESCRIPTION
The ADM1025/ADM1025A is a complete system hardware
monitor for microprocessor-based systems, providing measure-
ment and limit comparison of various system parameters. Five
voltage measurement inputs are provided, for monitoring 2.5 V,
3.3 V, 5 V and 12 V power supplies and the processor core
voltage. The ADM1025/ADM1025A can monitor a sixth power
supply voltage by measuring its own VCC. One input (two pins) is
dedicated to a remote temperature-sensing diode, and an on-chip
temperature sensor allows ambient temperature to be moni-
tored. The ADM1025A has open-drain VID inputs while the
ADM1025 has on-chip 100 kpull-ups on the VID inputs.
Measured values and in/out of limit status can be read out via
an I2C-compatible serial System Management Bus. The device
can be controlled and configured over the same serial bus. The
device also has a programmable INT output to indicate under-
voltage, overvoltage and over-temperature conditions.
The ADM1025/ADM1025A’s 3.0 V to 5.5 V supply voltage
range, low supply current, and I2C-compatible interface make
it ideal for a wide range of applications. These include hardware
monitoring and protection applications in personal computers,
electronic test equipment, and office electronics.
FUNCTIONAL BLOCK DIAGRAM
VID0
VID1
VID2
VID3
12VIN/VID4
VCC
VDD
VID0–3
REGISTER
100k
300kPULLUPS
VID4
REGISTER
POWER TO CHIP
SERIAL BUS
INTERFACE
ADM1025/
ADM1025A
VALUE AND
LIMIT
REGISTERS
ADD/RST/INT/NTO
SDA
SCL
VCCPIN
2.5VIN
3.3VIN
5VIN
D+
D–/NTI
BANDGAP
TEMPERATURE
SENSOR
INPUT
ATTENUATORS
AND
ANALOG
MULTIPLEXER
ADDRESS
POINTER
REGISTER
ADC
2.5V
BANDGAP
REFERENCE
LIMIT
COMPARATORS
MEASUREMENT
STATUS
REGISTERS
OFFSET
REGISTER
CONFIGURATION
REGISTER
GND
*Patent Pending.
I2C is a registered trademark of Philips Corporation.
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2000

1 page




ADM1025 pdf
Typical Performance Characteristics–ADM1025/ADM1025A
30
20
10
DXP TO GND
0
10
DXP TO VCC (5V)
20
30
40
50
60
1
3.3 10
30
LEAKAGE RESISTANCE M
100
Figure 2. Temperature Error vs. PC Board Track Resistance
120
100
90
80
70
60
50
40
30
20
10
0
0 10 20 30 40 50 60 70 80 90 100 110
MEASURED TEMPERATURE
Figure 5. Pentium II ® Temperature Measurement vs.
ADM1025/ADM1025A Reading
6
5
4
250mV p-p REMOTE
3
2
1
100mV p-p REMOTE
0
1
50
500
5k 50k 500k
FREQUENCY Hz
5M 50M
Figure 3. Temperature Error vs. Power Supply Noise
Frequency
25
20
15
10
5
0
5
1 2.2 3.2 4.7 7 10
DXP-DXN CAPACITANCE nF
Figure 6. Temperature Error vs. Capacitance Between D+
and D–
25
20
100mV p-p
15
10
50mV p-p
5
0 25mV p-p
5
50
500
5k 50k 500k
FREQUENCY Hz
5M 50M
Figure 4. Temperature Error vs. Common-Mode Noise
Frequency
10
9
8
7
10mV SQ. WAVE
6
5
4
3
2
1
0
50 500 5k 50k 100k 500k 5M 25M 50M
FREQUENCY Hz
Figure 7. Temperature Error vs. Differential-Mode Noise
Frequency
Pentium II is a registered trademark of Intel Corporation.
REV. A
–5–

5 Page





ADM1025 arduino
ADM1025/ADM1025A
4. Try to minimize the number of copper/solder joints, which
can cause thermocouple effects. Where copper/solder joints
are used, make sure that they are in both the D+ and D–
path and at the same temperature.
Thermocouple effects should not be a major problem as 1°C
corresponds to about 240 µV, and thermocouple voltages are
about 3 µV/oC of temperature difference. Unless there are two
thermocouples with a big temperature differential between
them, thermocouple voltages should be much less than 200 µV.
5. Place 0.1 µF bypass and 1 nF input filter capacitors close to
the ADM1025/ADM1025A.
6. If the distance to the remote sensor is more than 8 inches, the
use of twisted pair cable is recommended. This will work up
to about 6 to 12 feet.
7. For really long distances (up to 100 feet) use shielded twisted
pair such as Belden #8451 microphone cable. Connect the
twisted pair to D+ and D– and the shield to GND close to
the ADM1025/ADM1025A. Leave the remote end of the
shield unconnected to avoid ground loops.
Because the measurement technique uses switched current
sources, excessive cable and/or filter capacitance can affect the
measurement. When using long cables, the filter capacitor may
be reduced or removed.
Cable resistance can also introduce errors. 1 series resistance
introduces about 0.5°C error.
LIMIT VALUES
High and low limit values for each measurement channel are
stored in the appropriate limit registers. As each channel is
measured, the measured value is stored and compared with the
programmed limit.
STATUS REGISTERS
The results of limit comparisons are stored in Status Registers 1
and 2. The Status Register bit for a particular measurement
channel reflects the status of the last measurement and limit
comparison on that channel. If a measurement is within limits
the corresponding Status Register bit will be cleared to “0.” If
the measurement is out of limits the corresponding status regis-
ter bit will be set to “1.”
The state of the various measurement channels may be polled
by reading the Status Registers over the serial bus. Reading the
Status Registers does not affect their contents. Out-of-limit
temperature/voltage events may also be used to generate an
interrupt, so that remedial action such as turning on a cooling
fan may be taken immediately. This is described in the section
on RST and INT.
MONITORING CYCLE TIME
The monitoring cycle begins when a one is written to the Start
Bit (Bit 0) of the Configuration Register. The ADC measures
each analog input in turn and as each measurement is com-
pleted the result is automatically stored in the appropriate value
register. This “round-robin” monitoring cycle continues until it
is disabled by writing a 0 to Bit 0 of the Configuration Register.
As the ADC will normally be left to free-run in this manner, the
time taken to monitor all the analog inputs will normally not be
of interest, as the most recently measured value of any input can
be read out at any time.
INPUT SAFETY
Scaling of the analog inputs is performed on-chip, so external
attenuators are normally not required. However, since the power
supply voltages will appear directly at the pins, its is advisable to
add small external resistors in series with the supply traces to the
chip to prevent damaging the traces or power supplies should
an accidental short such as a probe connect two power sup-
plies together.
As the resistors will form part of the input attenuators, they will
affect the accuracy of the analog measurement if their value is
too high. The analog input channels are calibrated assuming an
external series resistor of 500 , and the accuracy will remain
within specification for any value from zero to 1 k, so a stan-
dard 510 resistor is suitable.
The worst such accident would be connecting 0 V to 12 V—a
total of 12 V difference, with the series resistors this would draw
a maximum current of approximately 12 mA.
LAYOUT AND GROUNDING
Analog inputs will provide best accuracy when referred to a
clean ground. A separate, low impedance ground plane for
analog ground, which provides a ground point for the voltage
dividers and analog components, will provide best performance
but is not mandatory.
The power supply bypass, the parallel combination of 10 µF
(electrolytic or tantalum) and 0.1 µF (ceramic) bypass capacitors
connected between Pin 9 and ground, should also be located as
close as possible to the ADM1025/ADM1025A.
RST/INT OUTPUT
As previously mentioned, Pin 16 is a multifunction pin. Its state
after power-on is latched to set the lowest two bits of the serial
bus address. During NAND tree board-level connectivity testing
it functions as the output of the NAND tree. It may also be used
as a reset output, or as an interrupt output for out-of-limit tem-
perature/voltage events.
Pin 16 is programmed as a reset output by clearing bit 0 of the
Test Register and setting Bit 7 of the VID Register. A low going,
20 ms, reset output pulse can then be generated by setting Bit 4
of the Configuration Register.
If Bit 7 of the VID Register is cleared, Pin 16 can be programmed
as an interrupt output for out-of-limit temperature/voltage events
(INT). Desired interrupt operation is achieved by changing the
values of Bits 1 and 0 of the Test Register as shown in Table IV.
Note, however, that Bits 2 to 7 of the Test Register must be
zeros (not don’t cares). If, for example, INT is programmed for
thermal and voltage interrupts, then if any temperature or volt-
age measurement goes outside its respective high or low limit,
the INT output will go low. It will remain low until Status Reg-
ister 1 is read, when it will be cleared. If the temperature or
voltage remains out of limit, INT will be reasserted on the next
monitoring cycle. INT can also be cleared by issuing an Alert
Response Address Call.
REV. A
–11–

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