ADM1025

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品牌:ONSEMI
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ADM1025 概述

Low Cost PC Hardware Monitor ASIC 低成本的PC硬件监控ASIC

ADM1025 数据手册

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Low Cost PC  
Hardware Monitor ASIC  
ADM1025/ADM1025A  
Preliminary Technical Data  
FEATURES  
Up to 8 measurement channels  
5 inputs to measure supply voltages  
PRODUCT DESCRIPTION  
The ADM1025/ADM1025A1 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  
monitored. The ADM1025A has open-drain VID inputs while  
the ADM1025 has on-chip 100 kΩ pull-ups on the VID inputs.  
V
CC monitored internally  
External temperature measurement with remote diode  
On-chip temperature sensor  
5 digital inputs for VID bits  
Integrated 100 kΩ pull-ups on VID pins (ADM1025 only)  
LDCM support  
I2C® compatible system management bus (SMBus)  
Programmable  
Programmable  
Configurable offset for internal/external channel  
Shutdown mode to minimize power consumption  
Limit comparison of all monitored values  
RST  
INT  
output pin  
output pin  
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  
undervoltage, overvoltage, and overtemperature conditions.  
APPLICATIONS  
Network servers and personal computers  
Microprocessor-based office equipment  
Test equipment and measuring instruments  
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  
Figure 1.  
1 Patent Pending. Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the  
Philips I 2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips.  
©2008 SCILLC. All rights reserved.  
February 2008 – Rev. P5  
Publication Order Number:  
ADM1025/D  
ADM1025/ADM1025A  
Preliminary Technical Data  
TABLE OF CONTENTS  
Features...............................................................................................1  
Internal Temperature Measurement ........................................13  
External Temperature Measurement........................................13  
Layout Considerations ...................................................................14  
Limit Values.................................................................................14  
Status Registers............................................................................14  
Monitoring Cycle Time..............................................................14  
Input Safety..................................................................................14  
Layout and Grounding...............................................................15  
RST/INT Output.........................................................................15  
Applications .......................................................................................1  
Product Description .........................................................................1  
Functional Block Diagram...............................................................1  
Revision History................................................................................2  
Specifications .....................................................................................3  
Absolute Maximum Ratings ............................................................5  
Thermal Characteristics...............................................................5  
ESD Caution ..................................................................................5  
Pin Configuration and Function Descriptions .............................6  
Typical Performance Characteristics..............................................7  
General Description..........................................................................9  
Measurement Inputs.....................................................................9  
Sequential Measurement..............................................................9  
Processor Voltage ID ....................................................................9  
ADD/RST/INT/NTO ...................................................................9  
Internal Registers of the ADM1025/ADM1025A.....................9  
Serial Bus Interface .......................................................................9  
Measurement Inputs...................................................................11  
A/D Converter.............................................................................11  
Input Circuits...............................................................................12  
Temperature Measurement System ..............................................13  
Genterating an  
SMBALERT  
......................................................15  
NAND Tree Tests........................................................................16  
Using the ADM1025/ADM1025A................................................17  
Power-On Reset ..........................................................................17  
Initialization ................................................................................17  
Using the Configuration Register.............................................17  
Using the Offset Register ...........................................................17  
Starting Conversion....................................................................17  
Reduced Power and Shutdown Mode......................................17  
5 V Operation..............................................................................17  
Registers ...........................................................................................18  
Outline Dimensions........................................................................21  
Ordering Guide...........................................................................21  
REVISION HISTORY  
02/08—Rev P5: Conversion to ON Semiconductor  
x/07—Rev. C to Rev. D  
4/03—Rev. B to Rev. C  
10/02—Rev. A to Rev. B  
11/99—Revision 0: Initial Version  
Rev. P5 | Page 2 of 21| www.onsemi.com  
Preliminary Technical Data  
ADM1025/ADM1025A  
SPECIFICATIONS  
TA = TMIN to TMAX, VCC = VMIN to VMAX, unless otherwise noted.  
Table 1.  
Parameter  
Min  
Typ  
Max  
Unit  
Test Conditions/Comments  
POWER SUPPLY  
Supply Voltage, VCC  
Supply Current, ICC  
1
3.0  
3.30  
1.4  
32  
5.5  
2.5  
500  
V
mA  
μA  
2
Interface Inactive, ADC Active  
Standby Mode  
TEMPERATURE-TO-DIGITAL CONVERTER  
Internal Sensor Accuracy  
Resolution  
3
°C  
°C  
°C  
°C  
°C  
μA  
μA  
1
External Diode Sensor Accuracy  
5
3
60°C ≤ TA ≤ 100°C; VCC = 3.3 V  
Resolution  
Remote Sensor Source Current  
1
180  
11  
High Level  
Low Level  
ANALOG-TO-DIGITAL CONVERTER (INCLUDING MUX AND  
ATTENUATORS)  
Total Unadjusted Error, TUE3  
Differential Nonlinearity, DNL  
Power Supply Sensitivity  
Conversion Time (Analog Input or Internal Temperature)4  
Conversion Time (External Temperature)4  
2
1
%
LSB  
%/V  
ms  
ms  
kΩ  
1
11.6  
34.8  
140  
Input Resistance (2.5 V, 3.3 V, 5 V, 12 V, VCCPIN  
)
80  
250  
OPEN-DRAIN DIGITAL OUTPUT ADD/  
Output Low Voltage, VOL  
/
/NTO  
RST INT  
0.4  
1
45  
V
μA  
ms  
IOUT = −6.0 mA; VCC = 3 V  
VOUT = VCC; VCC = 3 V  
High Level Output Leakage Current, IOH  
Pulsewidth  
0.1  
20  
RST  
OPEN-DRAIN SERIAL DATABUS OUTPUT (SDA)  
Output Low Voltage, VOL  
High Level Output Leakage Current, IOH  
SERIAL BUS DIGITAL INPUTS (SCL, SDA)  
Input High Voltage, VIH  
0.4  
1
V
μA  
IOUT = –6.0 mA; VCC = 3 V  
VOUT = VCC  
0.1  
2.1  
V
Input Low Voltage, VIL  
0.8  
V
Hysteresis  
500  
mV  
DIGITAL INPUT LOGIC LEVELS (ADD, VID0–VID4, NTI)5  
VID0–VID3 Input Resistance  
VID4 Input Resistance  
100  
300  
100  
kΩ  
kΩ  
kΩ  
V
ADM1025 Only  
ADM1025 Only  
ADM1025A  
6
Input High Voltage, VIH  
Input Low Voltage, VIL  
2.1  
−1  
6
0.8  
+1  
V
DIGITAL INPUT LEAKAGE CURRENT  
Input High Current, IIH  
Input Low Current, IIL  
μA  
μA  
pF  
VIN = VCC  
VIN = 0  
Input Capacitance, CIN  
5
Rev. P5 | Page 3 of 21| www.onsemi.com  
ADM1025/ADM1025A  
Preliminary Technical Data  
Parameter  
Min  
Typ  
Max  
Unit  
Test Conditions/Comments  
SERIAL BUS TIMING  
Clock Frequency, fSCLK  
Glitch Immunity, tSW  
Bus Free Time, tBUF  
Start Setup Time, tSU:STA  
Start Hold Time, tHD:STA  
Stop Condition Setup Time, tSU:STO  
SCL Low Time, tLOW  
SCL High Time, tHIGH  
SCL, SDA Rise Time, tR  
SCL, SDA Fall Time, tF  
Data Setup Time, tSU:DAT  
Data Hold Time, tHD:DAT  
400  
kHz  
ns  
μs  
ns  
ns  
ns  
μs  
μs  
ns  
ns  
ns  
ns  
See Figure 2  
See Figure 2  
See Figure 2  
See Figure 2  
See Figure 2  
See Figure 2  
See Figure 2  
See Figure 2  
See Figure 2  
See Figure 2  
See Figure 2  
See Figure 2  
50  
1.3  
600  
600  
600  
1.3  
0.6  
300  
300  
100  
300  
1 All voltages are measured with respect to GND, unless otherwise specified.  
2 Typicals are at TA = 25°C and represent most likely parametric norm. Shutdown current typ is measured with VCC = 3.3 V.  
3 TUE (Total Unadjusted Error) includes Offset, Gain, and Linearity errors of the ADC, multiplexer, and on-chip input attenuators, including an external series input  
protection resistor value between zero and 1 kΩ.  
4 Total monitoring cycle time is nominally 114.4 ms. Monitoring Cycle consists of 6 Voltage + 1 Internal Temperature + 1 External Temperature readings.  
5 ADD is a three-state input that may be pulled high, low, or left open-circuit.  
6 Timing specifications are tested at logic levels of VIL = 0.8 V for a falling edge and VIH = 2.2 V for a rising edge.  
Rev. P5 | Page 4 of 21| www.onsemi.com  
Preliminary Technical Data  
ADM1025/ADM1025A  
ABSOLUTE MAXIMUM RATINGS  
Table 2.  
Stresses above those listed under Absolute Maximum Ratings  
may cause permanent damage to the device. This is a stress  
rating only; functional operation of the device at these or any  
other conditions above those indicated in the operational  
section of this specification is not implied. Exposure to absolute  
maximum rating conditions for extended periods may affect  
device reliability.  
Parameter  
Rating  
Positive Supply Voltage (VCC  
Voltage on 12 V VIN Pin  
)
6.5 V  
20 V  
Voltage on Any Input or Output Pin  
Input Current at Any Pin  
Package Input Current  
−0.3 V to +6.5 V  
5 mA  
20 mA  
THERMAL CHARACTERISTICS  
16-Lead QSOP Package:  
θJA = 105°C/W  
Maximum Junction Temperature (TJ max)  
Storage Temperature Range  
Lead Temperature, Soldering  
Vapor Phase 60 sec  
Infrared 15 sec  
ESD Rating All Pins  
150°C  
–65°C to +150°C  
215°C  
200°C  
2000 V  
θ
JC = 39°C/W  
ESD CAUTION  
Figure 2. Diagram for Serial Bus Timing  
Rev. P5 | Page 5 of 21| www.onsemi.com  
ADM1025/ADM1025A  
Preliminary Technical Data  
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS  
Figure 3.Pin Configuration  
Table 3. Pin Function Descriptions  
Pin  
No.  
Mnemonic  
Description  
1
SDA  
Digital I/O. Serial bus bidirectional data. Open-drain output.  
2
3
4
SCL  
GND  
VCC  
Digital Input. Serial bus clock.  
System Ground  
Power. Can be powered by 3.3 V standby power if monitoring in low power states is required. This pin also  
serves as the analog input to monitor VCC  
.
5
6
7
8
9
VID0  
Digital Input. Core voltage ID readouts from the processor. This value is read into the VID0−VID3 Status  
Register. It has an on-chip 100 kΩ pull-up resistor (ADM1025 only).  
VID1  
Digital Input. Core voltage ID readouts from the processor. This value is read into the VID0−VID3 Status  
Register. It has an on-chip 100 kΩ pull-up resistor (ADM1025 only).  
VID2  
Digital Input. Core voltage ID readouts from the processor. This value is read into the VID0−VID3 Status  
Register. It has an on-chip 100 kΩ pull-up resistor (ADM1025 only).  
VID3  
Digital Input. Core voltage ID readouts from the processor. This value is read into the VID0−VID3 Status  
Register. It has an on-chip 100 kΩ pull-up resistor (ADM1025 only).  
D−/NTI  
Analog/Digital Input. Connected to cathode of external temperature sensing diode. If held high at power-up, it  
initiates NAND tree test mode.  
10  
11  
D+  
12VIN/VID4  
Analog Input. Connected to anode of external temperature sensing diode.  
Programmable Analog/Digital Input. Defaults to 12 VIN analog input at power-up but may be pro-grammed as  
VID4 Core Voltage ID readout from the processor. This value is read into the VID4 Status Register. In analog 12  
V
IN mode, it has an on-chip voltage attenuator. In VID4 mode, it has an on-chip 300 kΩ pull-up resistor.  
12  
13  
14  
15  
16  
5VIN  
Analog Input. Monitors 5 V supply.  
Analog Input. Monitors 3.3 V supply.  
Analog Input. Monitors 2.5 V supply.  
3.3VIN  
2.5VIN  
VCCPIN  
Analog Input. Monitors processor core voltage (0 V to 3.0 V).  
ADD/  
/
/NTO Programmable Digital I/O. The lowest order programmable bit of the SMBus Address, sampled on SMB activity  
as a three-state input. Can also be configured to give a minimum 20 ms low reset output pulse. Alternatively, it  
can be programmed as an interrupt output for temperature/voltage interrupts. Functions as the output of the  
NAND tree in NAND tree test mode.  
RST INT  
Rev. P5 | Page 6 of 21| www.onsemi.com  
Preliminary Technical Data  
ADM1025/ADM1025A  
TYPICAL PERFORMANCE CHARACTERISTICS  
Figure 4. Temperature Error vs. PC Board Track Resistance  
Figure 7. Pentium II® Temperature Measurement vs. ADM1025/ADM1025A  
Reading  
Figure 5. Temperature Error vs. Power Supply Noise Frequency  
Figure 8. Temperature Error vs. Capacitance between D+ and D−  
Figure 6. Temperature Error vs. Common-Mode Noise Frequency  
Figure 9. Temperature Error vs. Differential-Mode Noise Frequency  
Pentium II is a registered trademark of Intel Corporation  
Rev. P5 | Page 7 of 21| www.onsemi.com  
ADM1025/ADM1025A  
Preliminary Technical Data  
Figure 10. Standby Current vs. Temperature  
Rev. P5 | Page 8 of 21| www.onsemi.com  
Preliminary Technical Data  
ADM1025/ADM1025A  
GENERAL DESCRIPTION  
The ADM1025/ADM1025A is a complete system hardware  
monitor for microprocessor-based systems. The device  
communicates with the system via a serial System Management  
Bus. The serial bus controller has a hardwired address line for  
device selection (Pin 16), a serial data line for reading and  
writing addresses and data (Pin 1), and an input line for the  
serial clock (Pin 2). All control and programming functions of  
the ADM1025/ADM1025A are performed over the serial bus.  
bits of the serial bus address. During board-level, NAND tree  
connectivity testing, this pin functions as the output of the  
NAND tree. During normal operation, Pin 16 may be  
programmed as a reset output to provide a low going 20 ms  
reset pulse when enabled, or it may be programmed as an  
interrupt output for out-of-limit temperature and/or voltage  
events. These functions are described in more detail later.  
INTERNAL REGISTERS OF THE  
ADM1025/ADM1025A  
MEASUREMENT INPUTS  
The device has six measurement inputs, five for voltage and one  
for temperature. It can also measure its own supply voltage and  
can measure ambient temperature with its on-chip temperature  
sensor.  
A brief description of the ADM1025/ADM1025A’s principal  
internal registers is given below. More detailed information on  
the function of each register is given in Table 8 to Table 18.  
Configuration Register: Provides control and configuration.  
Pins 11 through 15 are analog inputs with on-chip attenuators  
configured to monitor 12 V, 5 V, 3.3 V, 2.5 V, and the processor  
core voltage, respectively. Pin 11 may alternatively be  
programmed as a digital input for Bit 4 of the processor voltage  
ID code.  
Address Pointer Register: This register contains the address  
that selects one of the other internal registers. When writing to  
the ADM1025/ADM1025A, the first byte of data is always a  
register address, which is written to the Address Pointer  
Register.  
Power is supplied to the chip via Pin 4, and the system also  
monitors the voltage on this pin.  
Status Registers: Two registers to provide status of each limit  
comparison.  
Remote temperature sensing is provided by the D+ and D−  
inputs, to which a diode-connected, external temperature-  
sensing transistor may be connected.  
VID Registers: The status of the VID0 to VID4 pins of the  
processor can read from these registers.  
Value and Limit Registers: The results of analog voltage inputs  
and temperature measurements are stored in these registers,  
along with their limit values.  
An on-chip band gap temperature sensor monitors system  
ambient temperature.  
SEQUENTIAL MEASUREMENT  
Offset Register: Allows either an internal or external  
temperature channel reading to be offset by a twos complement  
value written to this register.  
When the ADM1025/ADM1025A monitoring sequence is  
started, it cycles sequentially through the measurement of  
analog inputs and the temperature sensors. Measured values  
from these inputs are stored in Value Registers. These can be  
read out over the serial bus or can be compared with  
programmed limits stored in the Limit Registers. The results of  
out-of-limit comparisons are stored in the Status Registers,  
which can be read over the serial bus to flag out of limit  
conditions.  
SERIAL BUS INTERFACE  
Control of the ADM1025/ADM1025A is carried out via the  
serial bus. The ADM1025/ADM1025A is connected to this bus  
as a slave device, under the control of a master device or master  
controller.  
The ADM1025/ADM1025A has a 7-bit serial bus address.  
When the device is powered up, it will do so with a default  
serial bus address. The five MSBs of the address are set to  
01011; the two LSBs are determined by the logical states of Pin  
16 at power-up. This is a three-state input that can be grounded,  
connected to VCC, or left open-circuit to give three different  
addresses:  
PROCESSOR VOLTAGE ID  
Five digital inputs (VID4 to VID0—Pins 5 to 8 and 11) read the  
processor voltage ID code and store it in the VID registers, from  
which it can be read out by the management system over the  
serial bus. If Pin 11 is configured as a 12 V analog input (power-  
up default), the VID4 bit in the VID4 register will default to 0.  
Table 4. Address Selection  
ADD Pin  
GND  
The VID pins have internal 100 kΩ pull-up resistors (ADM1025  
only).  
A1  
0
A0  
0
ADD/ /NTO  
/
RST INT  
No Connect  
VCC  
1
0
Pin 16 is a programmable digital I/O pin. After power-up, at the  
first sign of SMBus activity, it is sampled to set the lowest two  
0
1
Rev. P5 | Page 9 of 21| www.onsemi.com  
ADM1025/ADM1025A  
Preliminary Technical Data  
If ADD is left open-circuit, the default address will be 0101110.  
ADD is sampled only after power-up, so any changes made will  
have no effect, unless power is cycled.  
transmitted over the serial bus in a single READ or  
WRITE operation is limited only by what the master and  
slave devices can handle.  
The facility to make hardwired changes to A1 and A0 allows the  
user to avoid conflicts with other devices sharing the same  
serial bus if, for example, more than one ADM1025/  
ADM1025A is used in a system. However, as previously  
mentioned, the ADD pin may also function as a reset output or  
interrupt output. Use of these functions may restrict the  
addresses that can be set. See the sections on RST and INT for  
further information.  
3)  
When all data bytes have been read or written, STOP  
conditions are established. In WRITE mode, the master will  
pull the data line high during the 10th clock pulse to assert a  
STOP condition. In READ mode, the master device will  
override the Acknowledge Bit by pulling the data line high  
during the low period before the 9th clock pulse. This is  
known as No Acknowledge. The master will then take the  
data line low during the low period before the 10th clock  
pulse, then high during the 10th clock pulse to assert a STOP  
condition.  
The serial bus protocol operates as follows.  
1) The master initiates data transfer by establishing a START  
condition, defined as a high-to-low transition on the serial  
data line SDA while the serial clock line SCL remains high.  
This indicates that an address/data stream will follow. All  
slave peripherals connected to the serial bus respond to the  
START condition and shift in the next eight bits, consisting  
of a 7-bit address (MSB first) plus an R/W bit, which  
determines the direction of the data transfer, i.e., whether  
data will be written to or read from the slave device.  
Any number of bytes of data may be transferred over the serial  
bus in one operation, but it is not possible to mix read and write  
in one operation because the type of operation is determined at  
the beginning and cannot subsequently be changed without  
starting a new operation.  
In the case of the ADM1025/ADM1025A, write operations  
contain either one or two bytes, and read operations contain  
one byte and perform the following functions.  
To write data to one of the device data registers or read data  
from it, the Address Pointer Register must be set so that the  
correct data register is addressed; data can then be written into  
that register or read from it. The first byte of a write operation  
always contains an address that is stored in the Address Pointer  
Register. If data is to be written to the device, the write  
operation contains a second data byte that is written to the  
register selected by the Address Pointer Register.  
The peripheral whose address corresponds to the  
transmitted address responds by pulling the data line low  
during the low period before the ninth clock pulse, known  
as the Acknowledge Bit. All other devices on the bus now  
remain idle while the selected device waits for data to be  
read from or written to it. If the R/W bit is a 0, the master  
will write to the slave device. If the R/W bit is a 1, the  
master will read from the slave device.  
This is illustrated in Figure 11. The device address is sent over  
the bus followed by R/W set to 0. This is followed by two data  
bytes. The first data byte is the address of the internal data  
register to be written to, which is stored in the Address Pointer  
Register. The second data byte is the data to be written to the  
internal data register.  
2) Data is sent over the serial bus in sequences of nine clock  
pulses, eight bits of data followed by an Acknowledge Bit  
from the slave device. Transitions on the data line must  
occur during the low period of the clock signal and remain  
stable during the high period, since a low-to-high  
transition when the clock is high may be interpreted as a  
STOP signal. The number of data bytes that can be  
Figure 11. Writing a Register Address to the Address Pointer Register, then Writing Data to the Selected Register  
Rev. P5 | Page 10 of 21| www.onsemi.com  
Preliminary Technical Data  
ADM1025/ADM1025A  
Figure 12. Writing to the Address Pointer Register Only  
Figure 13. Reading Data from a Previously Selected Register  
When reading data from a register there are two possibilities:  
4. If Reset or interrupt functionality is required, the address  
pin cannot be strapped to GND, since this would keep the  
ADD/RST/INT/NTO pin permanently low.  
1. If the ADM1025/ADM1025A’s Address Pointer Register  
value is unknown or not the desired value, it is first  
necessary to set it to the correct value before data can be  
read from the desired data register. This is done by  
performing a write to the ADM1025/ADM1025A as  
before, but only the data byte containing the register  
address is sent, since data should not be written to the  
register. This is shown in Figure 12.  
MEASUREMENT INPUTS  
The ADM1025/ADM1025A has six external measurement  
inputs, five for voltage and one (two pins) for temperature.  
Internal measurements are also carried out on VCC and the on-  
chip temperature sensor.  
A/D CONVERTER  
A read operation is then performed consisting of the serial  
bus address, R/W bit set to 1, followed by the data byte  
read from the data register. This is shown in Figure 13.  
These inputs are multiplexed into the on-chip, successive-  
approximation, analog-to-digital converter. This has a  
resolution of eight bits. The basic input range is 0 V to 2.5 V, but  
the inputs have built-in attenuators to allow measurement of  
2.5 V, 3.3 V, 5 V, 12 V, and the processor core voltage VCCP  
without any external components. To allow for the tolerance of  
these supply voltages, the A/D converter produces an output of  
¾ full scale (decimal 192) for the nominal input voltage and so  
has adequate headroom to cope with overvoltages. Table 5  
shows the input ranges of the analog inputs and output codes of  
the A/D converter.  
2. If the Address Pointer Register is known to be already at  
the desired address, data can be read from the  
corresponding data register without first writing to the  
Address Pointer Register, so Figure 12 can be omitted.  
NOTES  
1. Although it is possible to read a data byte from a data  
register without first writing to the Address Pointer  
Register, if the Address Pointer Register is already at the  
correct value, it is not possible to write data to a register  
without writing to the Address Pointer Register because  
the first data byte of a write is always written to the  
Address Pointer Register.  
When the ADC is running, it samples and converts an input  
every 11.6 ms, except for the external temperature (D+ and D−)  
input. This has special input signal conditioning and is averaged  
over 16 conversions to reduce noise; a measurement on this  
input takes nominally 34.8 ms.  
2. In Figure 11 to Figure 13, the serial bus address is shown as  
the default value 01011(A1)(A0), where A1 and A0 are set  
by the three-state ADD pin.  
3. In addition to supporting the Send Byte and Receive Byte  
protocols, the ADM1025/ADM1025A also supports the  
Read Byte protocol (see System Management Bus  
specifications Rev. 1.1 for more information).  
Rev. P5 | Page 11 of 21| www.onsemi.com  
ADM1025/ADM1025A  
Preliminary Technical Data  
INPUT CIRCUITS  
The internal structure for the analog inputs is shown in  
Figure 14. Each input circuit consists of an input protection  
diode, an attenuator, plus a capacitor to form a first order low-  
pass filter that gives the input immunity to high frequency  
noise.  
Figure 14. Structure of Analog Inputs  
Table 5. A/D Output Code vs. VIN  
Input Voltage  
A/D Output  
12 VIN  
<0.062  
5 VIN  
<0.026  
VCC/3.3 VIN  
<0.0172  
2.5 VIN  
<0.013  
VCCPIN  
<0.012  
Decimal  
Binary  
0
1
2
3
4
5
6
7
8
0000 0000  
0000 0001  
0000 0010  
0000 0011  
0000 0100  
0000 0101  
0000 0110  
0000 0111  
0000 1000  
0.062−0.125  
0.125–0.188  
0.188−0.250  
0.250−0.313  
0.313−0.375  
0.375−0.438  
0.438−0.500  
0.500−0.563  
0.026–0.052  
0.052−0.078  
0.078−0.104  
0.104−0.130  
0.130−0.156  
0.156−0.182  
0.182−0.208  
0.208−0.234  
0.017–0.034  
0.034−0.052  
0.052−0.069  
0.069−0.086  
0.086−0.103  
0.103−0.120  
0.120−0.138  
0.138−0.155  
0.013–0.026  
0.026−0.039  
0.039−0.052  
0.052−0.065  
0.065−0.078  
0.078−0.091  
0.091−0.104  
0.104−0.117  
0.012–0.023  
0.023−0.035  
0.035−0.047  
0.047−0.058  
0.058−0.070  
0.070−0.082  
0.082−0.093  
0.093−0.105  
4.000−4.063  
8.000−8.063  
12.000−12.063  
1.666−1.692  
3.330−3.560  
5.000−5.026  
1.100−1.117  
2.200−2.217  
3.300−3.317  
0.833−0.846  
1.667−1.680  
0.749−0.761  
1.499−1.511  
2.249−2.261  
64 (1/4 Scale)  
128 (1/2 Scale)  
192 (3/4 Scale)  
0100 0000  
1000 0000  
1100 0000  
2.500−2.513  
15.312−15.375  
15.375−15.437  
15.437−15.500  
15.500−15.563  
15.625−15.625  
15.625−15.688  
15.688−15.750  
15.750−15.812  
15.812−15.875  
15.875−15.938  
>15.938  
6.380−6.406  
6.406−6.432  
6.432−6.458  
6.458−6.484  
6.484−6.510  
6.510−6.536  
6.536−6.562  
6.562−6.588  
6.588−6.615  
6.615−6.640  
>6.640  
4.210−4.230  
4.230−4.245  
4.245−4.263  
4.263−4.280  
4.280−4.300  
4.300−4.314  
4.314−4.330  
4.331−4.348  
4.348−4.366  
4.366−4.383  
>4.383  
3.190−3.203  
3.203−3.216  
3.216−3.229  
3.229−3.242  
3.242−3.255  
3.255−3.268  
3.268−3.281  
3.281−3.294  
3.294−3.307  
3.307−3.320  
>3.320  
2.869−2.881  
2.881−2.893  
2.893−2.905  
2.905−2.916  
2.916−2.928  
2.928−2.940  
2.940−2.951  
2.951−2.964  
2.964−2.975  
2.975−2.987  
>2.988  
245  
246  
247  
248  
249  
250  
251  
252  
253  
254  
255  
1111 0101  
1111 0110  
1111 0111  
1111 1000  
1111 1001  
1111 1010  
1111 1011  
1111 1100  
1111 1101  
1111 1110  
1111 1111  
Rev. P5 | Page 12 of 21| www.onsemi.com  
Preliminary Technical Data  
ADM1025/ADM1025A  
TEMPERATURE MEASUREMENT SYSTEM  
INTERNAL TEMPERATURE MEASUREMENT  
The ADM1025/ADM1025A contains an on-chip band gap  
temperature sensor whose output is digitized by the on-chip  
ADC. The temperature data is stored in the Local Temperature  
Value Register (Address 27h). As both positive and negative  
temperatures can be measured, the temperature data is stored in  
twos complement format, as shown in Table 6. Theoretically,  
the temperature sensor and ADC can measure temperatures  
from −128°C to +127°C with a resolution of 1°C, although  
temperatures below 0°C and above +100°C are outside the  
operating temperature range of the device.  
Figure 15. Signal Conditioning for External Diode Temperature Sensors  
EXTERNAL TEMPERATURE MEASUREMENT  
Table 6. Temperature Data Format  
Temperature  
−128°C  
−125°C  
−100°C  
−75°C  
−50°C  
−25°C  
0°C  
+10°C  
+25°C  
+50°C  
+75°C  
+100°C  
+125°C  
+127°C  
Digital Output  
1000 0000  
1000 0011  
1001 1100  
1011 0101  
1100 1110  
1110 0111  
0000 0000  
0000 1010  
0001 1001  
0011 0010  
0100 1011  
0110 0100  
0111 1101  
0111 1111  
The ADM1025/ADM1025A can measure temperature using an  
external diode sensor or diode-connected transistor connected  
to Pins 9 and 10.  
The forward voltage of a diode or diode-connected transistor,  
operated at a constant current, exhibits a negative temperature  
coefficient of about −2 mV/°C. Unfortunately, the absolute  
value of VBE, varies from device to device, and individual  
calibration is required to null this out, so the technique is  
unsuitable for mass production.  
The technique used in the ADM1025/ADM1025A is to measure  
the change in VBE when the device is operated at two different  
currents. This is given by:  
ΔVBE = KT / q × In(N)  
where:  
To prevent ground noise interfering with the measurement, the  
more negative terminal of the sensor is not referenced to  
ground but is biased above ground by an internal diode at the  
D− input.  
K is Boltzmann’s constant.  
q is the charge on the carrier.  
T is the absolute temperature in Kelvins.  
N is the ratio of the two currents.  
If the sensor is used in a very noisy environment, a capacitor of  
value up to 1 nF may be placed between the D+ and D– inputs  
to filter the noise.  
Figure 15 shows the input signal conditioning used to measure  
the output of an external temperature sensor. This figure shows  
the external sensor as a substrate transistor provided for  
temperature monitoring on some microprocessors, but it could  
equally well be a discrete transistor.  
To measure ΔVBE, the sensor is switched between operating  
currents of I and N × I. The resulting waveform is passed  
through a 65 kHz low-pass filter to remove noise, then to a  
chopperstabilized amplifier that performs the functions of  
amplification and rectification of the waveform to produce a dc  
voltage proportional to ΔVBE. This voltage is measured by the  
ADC to give a temperature output in 8-bit twos complement  
format. To further reduce the effects of noise, digital filtering is  
performed by averaging the results of 16 measurement cycles.  
An external temperature measurement takes nominally 34.8 ms.  
If a discrete transistor is used, the collector will not be grounded  
and should be linked to the base. If a PNP transistor is used, the  
base is connected to the D− input and the emitter to the D+  
input. If an NPN transistor is used, the emitter is connected to  
the D− input and the base to the D+ input.  
Bit 6 of Status Register 2 (42h) is set if a remote diode fault is  
detected. The ADM1025/ADM1025A detects shorts from D+ to  
GND or supply, as well as shorts/opens between D+/D−.  
Rev. P5 | Page 13 of 21| www.onsemi.com  
ADM1025/ADM1025A  
Preliminary Technical Data  
LAYOUT CONSIDERATIONS  
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.  
Digital boards can be electrically noisy environments and care  
must be taken to protect the analog inputs from noise,  
particularly when measuring the very small voltages from a  
remote diode sensor. The following precautions should be  
taken:  
Cable resistance can also introduce errors. 1 Ω series resistance  
introduces about 0.5°C error.  
1. Place the ADM1025/ADM1025A as close as possible to the  
remote sensing diode. Provided that the worst noise  
LIMIT VALUES  
sources, such as clock generators, data/address buses, and  
CRTs, are avoided, this distance can be four to eight inches.  
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.  
2. Route the D+ and D− tracks close together, in parallel,  
with grounded guard tracks on each side. Provide a ground  
plane under the tracks if possible.  
STATUS REGISTERS  
3. Use wide tracks to minimize inductance and reduce noise  
pickup. 10 mil track minimum width and spacing is  
recommended.  
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  
register 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.  
Figure 16. Arrangement of Signal Tracks  
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.  
MONITORING CYCLE TIME  
The monitoring cycle begins when a 1 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 completed 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.  
Thermocouple effects should not be a major problem as  
1°C corresponds to about 240 μV, and thermocouple  
voltages are about 3 μV/°C of temperature difference.  
Unless there are two thermocouples with a big temperature  
differential between them, thermocouple voltages should  
be much less than 200 μV.  
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, since the most recently measured value of any input  
can be read out at any time.  
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 eight  
inches, the use of twisted pair cable is recommended. This  
will work up to about 6 to 12 feet.  
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, it 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 supplies together.  
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.  
Rev. P5 | Page 14 of 21| www.onsemi.com  
Preliminary Technical Data  
ADM1025/ADM1025A  
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 Ω, and the accuracy will remain  
within specification for any value from zero to 1 kΩ, so a  
standard 510 Ω resistor is suitable.  
1
1
0
1
Voltage Interrupt Only  
Voltage and Thermal Interrupts  
Note that Bit 7 of VID register should be zero, and that Bits 2 to  
7 of Test Register must be zeros.  
When Pin 16 is used as a RST or INT output, it is open-drain  
and requires an external pull-up resistor. This will restrict the  
address function on Pin 16 to being high at power-up. If the  
RST or INT function is required and two ADM1025/  
ADM1025As are to be used on the same serial bus, A1/A0 can  
be set to 10 by using a high value pull-up on Pin 16 (100 kΩ or  
greater). This will not override the “floating” condition of ADD  
during power-up.  
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.  
Note, however, that the RST/INT outputs of two or more  
devices cannot be wire-ORd, since the devices would then have  
the same address. If the RST/INT outputs need to be connected  
to a common interrupt line, they can be ORd together using the  
circuit of Figure 17.  
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.  
If the RSTor INT functionality is not required, a third address  
may be used by setting A1/A0 to 00 by using a 1 kΩ pull-down  
resistor on Pin 16. Note that this address should not be used if  
RSTor INT is required, since using this address will cause the  
device to appear to be generating resets or interrupts, since  
Pin 16 will be permanently tied low.  
/
OUTPUT  
RST INT  
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 temperature/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 7. 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 voltage measurement goes outside its respective  
high or low limit, the INT output will go low. It will remain low  
until Status Register 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.  
Figure 17. Using Two ADM1025/ADM1025As on the Same Bus with a  
Common Interrupt  
GENTERATING AN  
SMBALERT  
The INT output can be used as an interrupt output or can be  
used as an SMBALERT. One or more INT outputs can be  
connected to a common SMBALERT line connected to the  
master. If a device’s INT line goes low, the following procedure  
occurs:  
Table 7. Controlling the Operation of INT  
1. SMBALERTis pulled low.  
Test Register  
2. Master initiates a read operation and sends the Alert  
Response Address (ARA = 0001 100). This is a general call  
address that must not be used as a specific device address.  
Bit 1  
0
0
Bit 0  
0
1
Function  
Interrupts Disabled  
Thermal Interrupt Only  
Rev. P5 | Page 15 of 21| www.onsemi.com  
ADM1025/ADM1025A  
Preliminary Technical Data  
In NAND test mode, all digital inputs may be tested as  
illustrated below. ADD/RST/INT/NTO will become the NAND  
test output pin.  
3. The device whose INT output is low responds to the Alert  
Response Address, and the master reads its device address.  
The address of the device is now known and it can be  
interrogated in the usual way.  
To perform a NAND tree test, all pins are initially driven low.  
The test vectors set all inputs low, then one-by-one toggle them  
high (keeping them high). Exercising the test circuit with this  
“walking one” pattern, starting with the input closest to the  
output of the tree, cycling toward the farthest, causes the output  
of the tree to toggle with each input change. Allow for a typical  
propagation delay of 500 ns. The structure of the NAND tree is  
shown in Figure 18.  
4. If more than one device’s INT output is low, the one with  
the lowest device address will have priority, in accordance  
with normal SMBus arbitration.  
5. Once the ADM1025/ADM1025A has responded to the  
Alert Response Address, it will reset its INT output;  
however, if the error condition that caused the interrupt  
persists, INT will be reasserted on the next monitoring  
cycle.  
NAND TREE TESTS  
A NAND tree is provided in the ADM1025/ADM1025A for  
Automated Test Equipment (ATE) board level connectivity  
testing. The device is placed into NAND Test Mode by  
powering up with Pin 9 (D-/NTI) held high. This pin is  
automatically sampled after power-up, and if it is connected  
high, the NAND test mode is invoked.  
Figure 18. NAND Tree  
Note: If any of the inputs shown in Figure 18 are unused, they  
should not be connected directly to ground but via a resistor  
such as 10 kΩ. This will allow the ATE to drive every input high  
so that the NAND tree test can be properly carried out. Refer to  
Table 19 for Test Vectors.  
Rev. P5 | Page 16 of 21| www.onsemi.com  
Preliminary Technical Data  
ADM1025/ADM1025A  
USING THE ADM1025/ADM1025A  
Bit 7 of the Configuration Register is used to start a  
Configuration Register Initialization when it is set to 1.  
POWER-ON RESET  
When power is first applied, the ADM1025/ADM1025A  
performs a “power- on reset” on several of its registers.  
Registers whose power-on values are not shown have power-on  
conditions that are indeterminate. Value and limit registers are  
reset to 00h on power-up. The ADC is inactive. In most  
applications, usually the first action after power-on would be to  
write limits into the Limit Registers.  
USING THE OFFSET REGISTER  
This register contains a twos complement value that is added  
(or subtracted if the number is negative) to either the internal  
or external temperature reading. Note that the default value in  
the offset register is zero, so zero is always added to the  
temperature reading. The offset register is configured for the  
external temperature channel by default. It may be switched to  
the internal channel by setting Bit 0 of the Test Register to 1,  
setting Bit 6 of the VID Register to 1, and clearing Bit 7 of the  
VID Register.  
Power-on reset clears or initializes the following registers (the  
initialized values are shown in Table 9):  
– Configuration Register  
– Status Registers #1 and #2  
– VID0-3 Register  
STARTING CONVERSION  
The monitoring function of the ADM1025/ADM1025A is  
started by writing to the Configuration Register and setting  
Start (Bit 0) high. Limit values should be written into the Limit  
Registers before starting the ADC to avoid spurious out-of-limit  
conditions. The time taken to complete the analog  
measurements depends on how they are configured, as  
described elsewhere. Once the measurements have been  
completed, the results can be read from the Value Registers at  
any time.  
– VID4 Register  
Test Register  
INITIALIZATION  
Configuration Register Initialization performs a similar, but not  
identical, function to power-on reset.  
Configuration Register Initialization is accomplished by setting  
Bit 7 of the Configuration Register high. This bit automatically  
clears after being set.  
REDUCED POWER AND SHUTDOWN MODE  
USING THE CONFIGURATION REGISTER  
The ADM1025/ADM1025A can be placed in a low power mode  
by setting Bit 0 of the Configuration Register to 0. This disables  
the internal ADC. Full shutdown mode may then be achieved  
by setting Bit 7 of the VID Register to 1 and Bit 0 of the Test  
Register to 1. This turns off power to all analog circuits and  
stops the monitoring cycle, if running, but it does not affect the  
condition of any of the registers. The device will return to its  
previous state when these bits are reset to zero.  
Control of the ADM1025/ADM1025A is provided through the  
configuration register. The Configuration Register is used to  
start and stop the ADM1025/ADM1025A, program the  
operating modes of Pins 11 and 16, and provide the  
initialization function described above.  
Bit 0 of the Configuration Register controls the monitoring loop  
of the ADM1025/ADM1025A. Setting Bit 0 low stops the  
monitoring loop and puts the ADM1025/ADM1025A into a  
low power mode thereby reducing power consumption. Serial  
bus communication is still possible with any register in the  
ADM1025/ADM1025A while in low power mode. Setting Bit 0  
high starts the monitoring loop.  
5 V OPERATION  
The ADM1025/ADM1025A may be operated with VCC  
connected to any supply voltage between 3.0 V and 5.5 V, but it  
should be noted that the device has been optimized for 3.3 V  
operation. In particular, the internal voltage divider used to  
measure the supply voltage is optimized for 3.3 V. Powering the  
device from 5 V will cause the VCC Reading Register (Register  
25h) to overrange. In this case, the 5 V measurement should be  
read from the 5 V Reading Register (Register 23h), instead of  
the VCC Reading Register. Note also that when the 12 VIN/VID4  
pin is programmed to read VID4, due to its internal voltage  
divider, it will only read VIH = 2.1 V on the 12 VIN/VID4 pin as  
logic high if the device is being powered from the 3.3 V supply.  
Bit 4 of the Configuration Register causes a low going 20 ms  
(typ) pulse at the RST pin (Pin 16) when set. This bit is self-  
clearing.  
Bit 5 of the Configuration Register selects the operating mode  
of Pin 11 between the default of 12 V analog input (Bit 5 = 0)  
and VID4 (Bit 5 = 1).  
Rev. P5 | Page 17 of 21| www.onsemi.com  
ADM1025/ADM1025A  
Preliminary Technical Data  
REGISTERS  
Table 8. Address POINTER Register  
Table 10. Register 40h – Configuration Register  
Bit Name R/ Description  
Bit  
Name  
R/  
Description  
W
W
7–0 Address Pointer  
Write Address of ADM1025/  
ADM1025A Registers. See  
the tables below for detail.  
0
START  
Read/Write Logic 1 enables startup of  
monitor ASIC, and Logic 0  
places the ASIC in standby  
mode. At startup, limit  
checking functions and  
scanning begins. Note, all  
HIGH and LOW LIMITS should  
be set into the ADM1025/  
ADM1025A prior to turning  
on this bit. (Power-up Default  
= 0.)  
Table 9. List of Registers  
Address  
A7–A0  
Power On Value of  
Registers: <7:0>  
0000 1000  
Register Name  
in Hex  
Configuration  
Register  
40h  
1
2
3
4
Reserved  
Reserved  
Reserved  
RESET  
Read  
Read  
Read  
Status Register 1  
Status Register 2  
VID Register  
41h  
42h  
47h  
0000 0000  
0000 0000  
<7:4> = 0000, <3:0> = VID3–  
VID0  
<0> = VID4; Default = 1000  
000 (VID4)  
Read/Write Setting this bit generates a  
minimum 20 ms low pulse on  
Pin 16 if the function is  
VID4 Register  
49h  
enabled.  
5
+12/VID4  
Select  
Read/Write Selects whether Pin 11 acts  
as a 12 V analog input  
Value and Limit  
Registers  
15–3Dh  
monitoring pin, or as a VID[4]  
input. This pin defaults to the  
12 V analog input. (Default =  
0.)  
Company ID  
Stepping  
3Eh  
3Fh  
0100 0001  
0010 (Bits 3:0 Version  
Number)  
6
7
Reserved  
Read  
Initialization Read/Write Logic 1 restores power-up  
default values to the  
Configuration Register and  
Status Registers. This bit  
automatically clears itself and  
the power-on default is zero.  
Rev. P5 | Page 18 of 21| www.onsemi.com  
Preliminary Technical Data  
ADM1025/ADM1025A  
Table 11. Register 41h – Status Register 1 (Power-On Default  
<7:0> = 00h)  
Table 13. Register 47h – VID REGISTER (Power-On Default  
= 0000 (VID[3:0]))  
Bit Name  
R/  
Description  
Bit  
Name  
R/  
Description  
W
W
0
1
2
3
4
+2.5 V_Error Read-  
Only  
A 1 indicates a high or low limit  
has been exceeded.  
0–3  
VID[3:0]  
Read-Only  
The VID[3:0] inputs from  
Pentium/PRO power  
supplies to indicate the  
operating voltage (e.g.,  
1.3 V to 2.9 V).  
VCCP_Error  
Read-  
Only  
A 1 indicates a high or low limit  
has been exceeded.  
A 1 indicates a high or low limit  
has been exceeded.  
A 1 indicates a high or low limit  
has been exceeded.  
A 1 indicates a high or a low  
temperature limit has been  
exceeded.  
+3.3 V_Error Read-  
Only  
4–5  
6
Reserved Read-Only  
Offset  
Config  
Undefined  
Read/Write  
Configures offset register  
to be used with internal  
or external channel. If Bit  
0 of Test Register = 1 and  
Bit 7 of VID Register = 0,  
then setting this bit to 1  
configures tHhe Offset  
Register to the internal  
temperature channel.  
Clearing this bit  
configures the Offset  
Register to the external  
temperature channel.  
(Default = 0.)  
+5 V_Error  
Read-  
Only  
Local Temp  
Error  
Read-  
Only  
5
Remote  
Temp Error  
Read-  
Only  
A 1 indicates a high or low  
Remote temperature limit has  
been exceeded.  
6
7
Reserved  
Reserved  
Table 12. Register 42h – Status Register 2 (Power-On Default  
<7:0> = 00h)  
Bit Name  
7
RST  
ENABLE  
Read/Write  
When set to 1, enables  
the  
output function  
RST  
R/  
Description  
W
on Pin 16. This bit  
defaults to 0 on power-  
0
1
2
3
4
5
6
+12 V_Error Read-  
Only  
A 1 indicates a high or low limit  
has been exceeded.  
up. (  
Disabled.)  
RST  
VCC_Error  
Reserved  
Reserved  
Reserved  
Reserved  
Remote  
Read-  
Only  
Read-  
Only  
Read-  
Only  
Read-  
Only  
A 1 indicates a high or low limit  
has been exceeded.  
Table 14. Register 49h – VID4 Register (Power-On Default =  
1000 000(VID4))  
Undefined  
Undefined  
Undefined  
Undefined  
Bit  
Name  
R/  
Description  
W
0
VID4  
Read  
VID4 Input (If Selected)  
(Defaults to 0)  
1–7  
Reserved  
Read  
Read-  
Only  
Read-  
A one indicates either a short or  
open circuited fault on the  
Diode Fault Only  
remote thermal diode inputs.  
7
Reserved  
Read-  
Only  
Undefined  
Rev. P5 | Page 19 of 21| www.onsemi.com  
ADM1025/ADM1025A  
Preliminary Technical Data  
Table 15. Registers 15h–3Dh – Value and Limit Registers  
Table 17. Register 3Eh – Company ID  
Address  
R/  
Description  
W
Value  
(Bits  
7:0)  
15h  
1Fh  
20h  
21h  
22h  
23h  
24h  
25h  
26h  
Read/Write  
Read/Write  
Read-Only  
Read-Only  
Read-Only  
Read-Only  
Read-Only  
Read-Only  
Read-Only  
Manufacturers Test Register  
Offset Register  
2.5 V Reading  
VCCP Reading  
3.3 V Reading  
5 V Reading  
12 V Reading  
VCC Reading  
Remote Diode Temperature  
Reading  
R/  
W
Description  
0100  
0001  
Read-  
Only  
This location contains the company  
identification number that may be used by  
software to determine the manufacturer’s  
device. This register is read-only.  
Table 18. Register 3Fh – Stepping  
Value (Bits 7:0)  
R/  
W
Description  
0010 [Version]  
Read-Only  
Stepping ID Number and  
Version  
27h  
2Bh  
2Ch  
2Dh  
2Eh  
2Fh  
30h  
31h  
32h  
33h  
34h  
35h  
36h  
37h  
38h  
39h  
3Ah  
Read-Only  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Read/Write  
Local Temperature Reading  
2.5 V High Limit  
2.5 V Low Limit  
VCCP High Limit  
VCCP Low Limit  
3.3 V High Limit  
3.3 V Low Limit  
5 V High Limit  
5 V Low Limit  
12 V High Limit  
12 V Low Limit  
VCC High Limit  
VCC Low Limit  
Remote Temperature High Limit  
Remote Temperature Low Limit  
Local Temperature High Limit  
Local Temperature Low Limit  
Table 19. NAND Tree Test Vectors  
ADD/  
/
RST  
Vector  
/NTO  
INT  
No.  
SDA SCL VID0 VID1 VID2 VID3  
1
0
0
0
0
0
0
1
2
3
4
5
6
7
0
0
0
0
0
1
0
0
0
0
1
1
0
0
0
1
1
1
0
0
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
0
1
0
1
0
1
For the high limits of the voltages, the device is doing a greater-than  
comparison. For the low limits, however, it is doing a less-than or equal  
comparison.  
Table 16. Register 15h – Manufacturers Test Register  
Bit  
Name  
R/  
Description  
W
0
Read/Write Used to select  
or  
RST INT  
functions. Refer to  
/
RST INT  
Output section.  
1
Read/Write Used to select RST or  
INT  
functions. Refer to  
Output section.  
/
RST INT  
2–7 Reserved Read/Write Reserved. Only values written  
to these bits should be zeros.  
Rev. P5 | Page 20 of 21| www.onsemi.com  
Preliminary Technical Data  
ADM1025/ADM1025A  
OUTLINE DIMENSIONS  
Figure 19. 16-Lead Shrink Small Outline Package [QSOP]  
(RQ-16)  
Dimensions shown in inches  
ORDERING GUIDE  
Model  
Temperature Range  
Package Description  
16-Lead QSOP  
16-Lead QSOP  
16-Lead QSOP  
16-Lead QSOP  
16-Lead QSOP  
16-Lead QSOP  
16-Lead QSOP  
16-Lead QSOP  
Package Option  
Option  
ADM1025ARQ  
0°C to 100°C  
0°C to 100°C  
0°C to 100°C  
0°C to 100°C  
0°C to 100°C  
0°C to 100°C  
0°C to 100°C  
0°C to 100°C  
RQ-16  
RQ-16  
RQ-16  
RQ-16  
RQ-16  
RQ-16  
RQ-16  
RQ-16  
Integrated 100 kΩ VID Pull-Ups  
Integrated 100 kΩ VID Pull-Ups  
Integrated 100 kΩ VID Pull-Ups  
Integrated 100 kΩ VID Pull-Ups  
Integrated 100 kΩ VID Pull-Ups  
Integrated 100 kΩ VID Pull-Ups  
Open-Drain VID Inputs  
ADM1025ARQ-REEL  
ADM1025ARQ-REEL7  
ADM1025ARQZ1  
ADM1025ARQZ-REEL1  
ADM1025ARQZ-R71  
ADM1025AARQ  
ADM1025AARQZ1  
1 Z = RoHS Compliant Part.  
Open-Drain VID Inputs  
ON Semiconductor and  
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any  
products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising  
out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. “Typical”  
parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating  
parameters, including “Typicals” must be validated for each customer application by customer's technical experts. SCILLC does not convey any license under its patent rights nor the  
rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to  
support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or  
use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors  
harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such  
unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action  
Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.  
PUBLICATION ORDERING INFORMATION  
LITERATURE FULFILLMENT:  
N. American Technical Support: 800-282-9855  
Toll Free USA/Canada  
Europe, Middle East and Africa Technical Support:  
Phone: 421 33 790 2910  
Japan Customer Focus Center  
Phone: 81-3-5773-3850  
ON Semiconductor Website: www.onsemi.com  
Order Literature: http://www.onsemi.com/orderlit  
Literature Distribution Center for ON Semiconductor  
P.O. Box 5163, Denver, Colorado 80217 USA  
Phone: 303-675-2175 or 800-344-3860 Toll Free USA/Canada  
Fax: 303-675-2176 or 800-344-3867 Toll Free USA/Canada  
Email: orderlit@onsemi.com  
For additional information, please contact your local  
Sales Representative  
Rev. P5 | Page 21 of 21| www.onsemi.com  

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