ADM1023ARQ [ONSEMI]

SPECIALTY ANALOG CIRCUIT, PDSO16, MO-137AB, QSOP-16;
ADM1023ARQ
型号: ADM1023ARQ
厂家: ONSEMI    ONSEMI
描述:

SPECIALTY ANALOG CIRCUIT, PDSO16, MO-137AB, QSOP-16

光电二极管
文件: 总18页 (文件大小:246K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
ACPI-Compliant, High Accuracy  
Microprocessor System Temperature Monitor  
ADM1023  
FEATURES  
GENERAL DESCRIPTION  
The ADM10231 is a 2-channel digital thermometer and under-  
and overtemperature alarm for use in personal computers and  
other systems requiring thermal monitoring and management.  
Optimized for the Pentium® III, the higher accuracy allows  
Next generation upgrade of ADM1021  
On-chip and remote temperature sensing  
Offset registers for system calibration  
1°C accuracy and resolution on local channel  
0.125°C resolution/1°C accuracy on remote channel  
Programmable over/under temperature limits  
Programmable conversion rate  
systems designers to safely reduce temperature guard banding  
and increase system performance. The device can measure the  
temperature of a microprocessor using a diode-connected PNP  
transistor, which may be provided on-chip with the Pentium III  
or similar processors; or it can be a low-cost, discrete NPN/PNP  
device such as the 2N3904/2N3906. A novel measurement  
technique cancels out the absolute value of the transistors base  
emitter voltage so that no calibration is required. The second  
measurement channel measures the output of an on-chip  
temperature sensor to monitor the temperature of the device  
and its environment.  
ALERT  
Supports system management bus (SMBus)  
2-wire SMBus serial interface  
200 μA max operating current (0.25 conversions/second)  
1 μA standby current  
3 V to 5.5 V supply  
Small 16-lead QSOP package  
APPLICATIONS  
The ADM1023 communicates over a 2-wire serial interface  
compatible with SMBus standards. Under- and overtemperature  
limits can be programmed into the device over the serial bus,  
and an ALERT output signals when the on-chip or remote  
temperature is out of range. This output can be used as an  
interrupt or as an SMBus ALERT.  
Desktop computers  
Notebook computers  
Smart batteries  
Industrial controllers  
Telecomm equipment  
Instrumentation  
FUNCTIONAL BLOCK DIAGRAM  
ADDRESS POINTER  
REGISTER  
ONE-SHOT  
REGISTER  
CONVERSION RATE  
REGISTER  
OFFSET  
REGISTERS  
ON-CHIP  
TEMPERATURE  
SENSOR  
LOCAL TEMPERATURE  
LOW-LIMIT REGISTER  
LOCAL TEMPERATURE  
VALUE REGISTER  
LOCAL TEMPERATURE  
LOW-LIMIT COMPARATOR  
LOCAL TEMPERATURE  
HIGH-LIMIT COMPARATOR  
LOCAL TEMPERATURE  
HIGH-LIMIT REGISTER  
3
4
D+  
D–  
A-TO-D  
CONVERTER  
ANALOG  
MUX  
REMOTE TEMPERATURE  
LOW-LIMIT COMPARATOR  
REMOTE TEMPERATURE  
LOW-LIMIT REGISTERS  
BUSY RUN/STANDBY  
REMOTE TEMPERATURE  
HIGH-LIMIT COMPARATOR  
REMOTE TEMPERATURE  
VALUE REGISTERS  
REMOTE TEMPERATURE  
HIGH-LIMIT REGISTERS  
CONFIGURATION  
REGISTER  
15  
11  
STBY  
EXTERNAL DIODE OPEN-CIRCUIT  
INTERRUPT  
MASKING  
ALERT  
STATUS REGISTER  
ADM1023  
SMBus INTERFACE  
1
2
5
7
8
9
13  
16  
12  
14  
10  
6
NC  
V
NC GND GND NC  
NC  
NC  
SDATA  
SCLK  
ADD0  
ADD1  
DD  
NC = NO CONNECT  
Figure 1.  
1 Protected by U.S. Patents 5,195,827; 5,867,012; 5,982,221; 6,097,239; 6,133,753; 6,169,442; other patents pending.  
©2008 SCILLC. All rights reserved.  
January 2008 – Rev. 8  
Publication Order Number:  
ADM1023/D  
ADM1023  
TABLE OF CONTENTS  
Specifications .....................................................................................3  
Serial Bus Interface .....................................................................12  
Address Pins ................................................................................12  
Absolute Maximum Ratings ............................................................4  
Thermal Characteristics...............................................................4  
ESD Caution ..................................................................................4  
Pin Configuration and Function Description...............................5  
Typical Performance Characteristics..............................................6  
Theory of Operation.........................................................................8  
Functional Description ................................................................8  
Measurement Method ..................................................................9  
ALERT  
Output ............................................................................14  
Low Power Standby Modes .......................................................15  
Sensor Fault Detection...............................................................15  
Applications .....................................................................................16  
Factors Affecting Accuracy .......................................................16  
Layout Considerations ...............................................................16  
Application Circuits....................................................................17  
Outline Dimensions........................................................................18  
Ordering Guide...........................................................................18  
Sources of Errors on Thermal Transistors Measurement  
Method ...........................................................................................9  
Temperature Data Format..........................................................10  
Register Functions ......................................................................10  
REVISION HISTORY  
01/08 - Rev 8: Conversion to ON Semiconductor  
4/03—Rev. D to Rev. E  
Added ESD Caution ......................................................................... 3  
Updated Outline Dimensions ....................................................... 13  
7/05—Rev. G to Rev. H  
Changes to Table 1 ............................................................................ 3  
9/02—Rev. C to Rev. D  
Outline Dimensions updated .......................................................... 13  
2/05—Rev. F to Rev. G  
Updated Format ..................................................................Universal  
Changes to Specifications................................................................. 3  
Changes to Absolute Maximum Ratings........................................ 4  
Changes to Figure 14 ........................................................................ 8  
Changes to Figure 21 ...................................................................... 17  
Changes to Ordering Guide........................................................... 18  
5/02—Rev. B to Rev. C  
Figures 2 to 11 changed to TPCs 1–10, renumbered figures  
accordingly......................................................................................... 4  
Text change to Figure 9 (TPC 8) ..................................................... 5  
Callouts in text added for Tables IV–VI ........................................ 8  
Change to Serial Bus Interface section........................................... 9  
4/03—Rev. E to Rev. F  
Added Reference to Figure 1 ........................................................... 2  
4/00—Revision 0: Initial Version  
Rev. 8 | Page 2 of 18 | www.onsemi.com  
ADM1023  
SPECIFICATIONS  
TA = TMIN to TMAX1, VDD = 3.0 V to 3.6 V, unless otherwise noted.  
Table 1.  
Parameter  
Min  
Typ  
Max Unit Test Conditions/Comments  
POWER SUPPLY AND ADC  
Temperature Resolution, Local Sensor  
Temperature Resolution, Remote Sensor  
Temperature Error, Local Sensor  
1
°C  
°C  
°C  
°C  
°C  
°C  
°C  
V
V
mV  
V
mV  
μA  
μA  
μA  
μA  
ms  
Guaranteed no missed codes  
Guaranteed no missed codes  
TA = 60°C to 100°C  
0.125  
−1.5  
−3  
−1  
−3  
0.5  
1
+1.5  
+3  
+1  
TA = 0°C to 120°C  
Temperature Error, Remote Sensor  
TA, TD = 60°C to 100°C2  
TA, TD = 0°C to 120°C2  
TA = 60°C to 100°C  
+3  
Relative Accuracy  
Supply Voltage Range3  
0.25  
3.6  
2.8  
3
2.55  
Undervoltage Lockout Threshold  
Undervoltage Lockout Hysteresis  
Power-On Reset Threshold  
POR Threshold Hysteresis  
Standby Supply Current  
2.7  
25  
1.7  
50  
1
VDD input, disables ADC, rising edge  
VDD, falling edge4  
0.9  
2.2  
5
VDD = 3.3 V, no SMBus activity  
SCLK at 10 kHz  
0.25 conversions/sec rate  
2 conversions/sec rate  
From stop bit to conversion complete  
(both channels) D+ forced to D− + 0.65 V  
4
Average Operating Supply Current  
Autoconvert Mode, Averaged Over 4 Sec  
Conversion Time  
130  
225  
115  
200  
370  
170  
65  
Remote Sensor Source Current  
120  
7
205  
12  
0.7  
50  
300  
16  
μA  
μA  
V
High level4  
Low level4  
D-Source Voltage  
Address Pin Bias Current (ADD0, ADD1)  
SMBus INTERFACE  
μA  
Momentary at power-on reset  
See Figure 3  
Logic Input High Voltage, VIH  
2.2  
V
V
VDD = 3 V to 5.5 V  
, SCLK, SDATA  
STBY  
Logic Input Low Voltage, VIL  
, SCLK, SDATA  
0.8  
VDD = 3 V to 5.5 V  
STBY  
SMBus Output Low Sink Current  
ALERT  
6
1
mA  
mA  
μA  
pF  
kHz  
μs  
μs  
μs  
μs  
μs  
SDATA forced to 0.6 V  
ALERT  
Output Low Sink Current  
forced to 0.4 V  
Logic Input Current, IIH, IIL  
SMBus Input Capacitance, SCLK, SDATA  
SMBus Clock Frequency  
SMBus Clock Low Time, tLOW  
SMBus Clock High Time, tHIGH  
SMBus Start Condition Setup Time, tSU:STA  
SMBus Start Condition Hold Time, tHD:STA  
SMBus Stop Condition Setup Time, tSU:STO  
SMBus Data Valid to SCLK Rising Edge Time, tSU:DAT  
SMBus Bus Free Time, tBUF  
−1  
+1  
5
400  
1.3  
0.6  
0.6  
0.6  
0.6  
100  
1.3  
tLOW between 10% points  
tHIGH between 90% points  
Time from 10% of SDATA to 90% of SCLK  
Time from 90% of SCLK to 10% of SDATA  
Time for 10% or 90% of SDATA to 10% of SCLK  
Between start/stop condition  
Master clocking in data  
ns  
μs  
ns  
ns  
SCLK SDATA Rise Time, tR MAX  
SCLK SDATA Fall Time, tF MAX  
300  
300  
VDD = 0 V  
1 TMAX = 120°C, TMIN = 0°C.  
2 TD is the temperature of the remote thermal diode; TA, TD = 60°C to 100°C.  
3 Operation at VDD = 5 V guaranteed by design; not production tested.  
4 Guranteed by design; not production tested.  
Rev. 8 | Page 3 of 18 | www.onsemi.com  
ADM1023  
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.  
Parameters  
Ratings  
Positive Supply Voltage (VDD) to GND  
D+, ADD0, ADD1  
D− to GND  
−0.3 V to +6 V  
−0.3 V to VDD + 0.3 V  
−0.3 V to +0.6 V  
−0.3 V to +6 V  
50 mA  
ALERT STBY  
SCLK, SDATA,  
Input Current  
,
Input Current, D−  
1 mA  
ESD Rating, All Pins (Human Body Model) 2000 V  
Continuous Power Dissipation  
THERMAL CHARACTERISTICS  
Up to 70°C  
650 mW  
16-lead QSOP package:  
θJA = 105°C/W  
Derating Above 70°C  
6.7 mW/°C  
−55°C to +125°C  
150°C  
−65°C to +150°C  
300°C  
Operating Temperature Range  
Maximum Junction Temperature (TJ MAX  
Storage Temperature Range  
Lead Temperature (Soldering 10 sec)  
IR Reflow Peak Temperature  
θ
JC = 39°C/W  
)
220°C  
IR Reflow Peak Temperature for Pb-Free  
260°C  
ESD CAUTION  
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate  
on the human body and test equipment and can discharge without detection. Although this product  
features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to  
high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid  
performance degradation or loss of functionality.  
Rev. 8 | Page 4 of 18 | www.onsemi.com  
ADM1023  
PIN CONFIGURATION AND FUNCTION DESCRIPTION  
1
2
3
4
5
6
7
8
16  
15  
14  
13  
12  
11  
10  
9
NC  
NC  
V
STBY  
SCLK  
NC  
DD  
D+  
ADM1023  
TOP VIEW  
(Not to Scale)  
D–  
NC  
SDATA  
ALERT  
ADD0  
NC  
ADD1  
GND  
GND  
NC = NO CONNECT  
Figure 2. Pin Configuration  
Table 3. Pin Function Descriptions  
Pin No.  
1, 5, 9, 13, 16  
Mnemonic  
NC  
Description  
No Connect.  
2
VDD  
Positive Supply, 3 V to 5.5 V.  
3
4
6
7, 8  
10  
11  
12  
14  
15  
D+  
D−  
ADD1  
GND  
ADD0  
ALERT  
SDATA  
SCLK  
STBY  
Positive Connection to Remote Temperature Sensor.  
Negative Connection to Remote Temperature Sensor.  
Three-State Logic Input, Higher Bit of Device Address.  
Supply 0 V Connection.  
Three-State Logic Input, Lower Bit of Device Address.  
Open-Drain Logic Output Used as Interrupt or SMBus  
ALERT  
.
Logic Input/Output, SMBus Serial Data. Open-drain output.  
Logic Input, SMBus Serial Clock.  
Logic Input Selecting Normal Operation (High) or Standby Mode (Low).  
tHD;STA  
tR  
tLOW  
tF  
SCL  
SDA  
tHD;DAT  
tSU;STA  
tSU;DAT  
tHD;STA  
tHIGH  
tSU;STO  
tBUF  
S
P
P
S
Figure 3. Diagram for Serial Bus Timing  
Rev. 8 | Page 5 of 18 | www.onsemi.com  
ADM1023  
TYPICAL PERFORMANCE CHARACTERISTICS  
20  
3
2
15  
D+ TO GND  
10  
UPPER SPEC LEVEL  
LOWER SPEC LEVEL  
5
0
1
–5  
0
–10  
D+ TO V  
DD  
–1  
–2  
–3  
–15  
–20  
–25  
–30  
1
10  
LEAKAGE RESISTANCE (MΩ)  
100  
50  
60  
70  
80  
90  
100  
110  
120  
TEMPERATURE (°C)  
Figure 4. Temperature Error vs. Resistance from Track to VDD and GND  
Figure 7. Temperature Error of ADM1023 vs. Pentium III Temperature  
5
14  
12  
10  
4
250mV p-p REMOTE  
8
6
4
3
2
100mV p-p REMOTE  
1
2
0
0
100  
–2  
1k  
10k  
100k  
1M  
10M  
100M  
2
4
6
8
10  
12  
14  
16  
18  
20  
22  
24  
FREQUENCY (Hz)  
CAPACITANCE (nF)  
Figure 5. Remote Temperature Error vs. Supply Noise Frequency  
Figure 8. Temperature Error vs. Capacitance Between D+ and D−  
9
70  
60  
50  
40  
100mV p-p  
8
7
6
5
4
V
= 3.3V  
DD  
30  
20  
10  
0
3
50mV p-p  
2
1
V
= 5V  
DD  
25mV p-p  
1M 10M  
0
1
10  
100  
1k  
10k  
100k  
100M  
1
5
10  
25  
50  
75  
100 250 500 750 1000  
FREQUENCY (Hz)  
SCLK FREQUENCY (kHz)  
Figure 6. Temperature Error vs. Common-Mode Noise Frequency  
Figure 9. Standby Supply Current vs. SCLK Frequency  
Rev. 8 | Page 6 of 18 | www.onsemi.com  
ADM1023  
4
3
2
1
100  
80  
60  
40  
20  
0
10mV p-p  
0
–20  
100k  
1M  
10M  
FREQUENCY (Hz)  
100M  
1G  
0
0.5  
1.0  
1.5  
2.0  
2.5  
3.0  
3.5  
4.0  
4.5  
5.0  
SUPPLY VOLTAGE (V)  
Figure 10. Temperature Error vs. Differential-Mode Noise Frequency  
Figure 12. Standby Supply Current vs. Supply Voltage  
550  
500  
450  
400  
350  
300  
250  
125  
100  
75  
50  
25  
0
REMOTE  
TEMPERATURE  
INT  
TEMPERATURE  
200  
3.3V  
150  
100  
5V  
50  
0.0625 0.1250 0.2500 0.5000 1.0000 2.0000 4.0000 8.0000  
CONVERSION RATE (Hz)  
0
1
2
3
4
5
6
7
8
9
10  
TIME (Seconds)  
Figure 11. Operating Supply Current vs. Conversion Rate, VDD = 5 V and 3.3 V  
Figure 13. Response to Thermal Shock  
Rev. 8 | Page 7 of 18 | www.onsemi.com  
ADM1023  
THEORY OF OPERATION  
FUNCTIONAL DESCRIPTION  
limits as 11-bit values. Out-of-limit comparisons generate flags  
that are stored in the status register, and one or more out-of-  
limit results cause the ALERT output to pull low.  
The ADM1023 contains a two-channel analog-to-digital  
converter (ADC) with special input-signal conditioning to  
enable operation with remote and on-chip diode temperature  
sensors. When the ADM1023 is operating normally, the ADC  
operates in a free-running mode. The analog input multiplexer  
alternately selects either the on-chip temperature sensor to  
measure its local temperature or the remote temperature sensor.  
These signals are digitized by the ADC, and the results are  
stored in the local and remote temperature value registers. Only  
the eight most significant bits (MSBs) of the local temperature  
value are stored as an 8-bit binary word. The remote tempera-  
ture value is stored as an 11-bit binary word in two registers.  
The eight MSBs are stored in the remote temperature value  
high byte register at Address 0x01. The three least significant  
bits (LSBs) are stored, left justified, in the remote temperature  
value low byte register at Address 0x10.  
Registers can be programmed, and the device controlled and  
configured, via the serial system management bus (SMBus).  
The contents of any register can also be read back via the  
SMBus.  
Control and configuration functions consist of  
Switching the device between normal operation  
and standby mode.  
Masking or enabling the ALERT output.  
Selecting the conversion rate.  
On initial power-up, the remote and local temperature values  
default to −128°C. The device normally powers up converting,  
making a measure of local and remote temperature. These  
values are then stored before making a comparison with the  
stored limits. However, if the part is powered up in standby  
mode (STBY pin pulled low), no new values are written to the  
register before a comparison is made. As a result, both RLOW  
and LLOW are tripped in the status register, thus generating an  
ALERT output. This may be cleared in one of two ways:  
Error sources such as PCB track resistance and clock noise  
can introduce offset errors into measurements on the remote  
channel. To achieve the specified accuracy on this channel,  
these offsets must be removed, and two offset registers are  
provided for this purpose at Address 0x11 and Address 0x12.  
An offset value may automatically be added to or subtracted  
from the measurement by writing an 11-bit, twos complement  
value to Register 0x11 (high byte) and Register 0x12 (low byte,  
left-justified).  
Change both the local and remote lower limits to –128°C  
and read the status register (which in turn clears the  
ALERT output).  
The offset registers default to 0 at power-up and have  
no effect if nothing is written to them.  
Take the part out of standby and read the status register  
(which in turn clears the ALERT output). This works only  
when the measured values are within the limit values.  
The measurement results are compared with local and remote,  
high and low temperature limits, stored in six on-chip limit  
registers. As with the measured value, the local temperature  
limits are stored as 8-bit values and the remote temperature  
V
DD  
I
N × I  
I
BIAS  
D+  
1
V
OUT+  
C1  
TO ADC  
REMOTE  
SENSING  
TRANSISTOR  
BIAS  
DIODE  
V
D–  
OUT–  
LOW-PASS FILTER  
fC = 65kHz  
1
CAPACITOR C1 IS OPTIONAL. IT IS ONLY NECESSARY IN NOISY ENVIRONMENTS.  
C1 = 1000pF MAX.  
Figure 14. Input Signal Conditioning  
Rev. 8 | Page 8 of 18 | www.onsemi.com  
ADM1023  
MEASUREMENT METHOD  
SOURCES OF ERRORS ON THERMAL TRANSISTORS  
MEASUREMENT METHOD  
A simple method of measuring temperature is to exploit the  
negative temperature coefficient of a diode, or the base emitter  
voltage of a transistor, operating at constant current. Thus, the  
temperature may be obtained from a direct measurement of VBE  
where  
The Effect Of Ideality Factor (n)  
The effects of ideality factor (n) and beta (β) of the temperature  
measured by a thermal transistor are described in this section.  
For a thermal transistor implemented on a submicron process,  
such as the substrate PNP used on a Pentium III processor, the  
temperature errors due to the combined effect of the ideality  
factor and beta are shown to be less than 3°C. Equation 2 is  
optimized for a substrate PNP transistor (used as a thermal  
diode) usually found on CPUs designed on submicron CMOS  
processes such as the Pentium III processor. There is a thermal  
diode on board each of these processors. The n in Equation 2  
represents the ideality factor of this thermal diode. This ideality  
factor is a measure of the deviation of the thermal diode from  
ideal behavior.  
(
IC  
IS  
)
nKT  
q
(1)  
VBE  
=
×1n  
This technique, however, requires calibration to nullify the effect  
of the absolute value of VBE, which varies from device to device.  
The technique used in the ADM1023 is to measure the change in  
VBE when the device is operated at two different collector currents.  
This is given by  
nKT  
(2)  
Δ VBE  
=
×1n  
(N )  
q
According to Pentium III processor manufacturing specifications,  
measured values of n at 100°C are  
where:  
K is Boltzmann’s constant.  
nMIN = 1.0057 < nTYPICAL = 1.008 < nMAX = 1.0125  
q is the charge on the electron (1.6 × 10–19 Coulombs).  
T is the absolute temperature in Kelvins.  
The ADM1023 takes this ideality factor into consideration  
when calculating temperature TTD of the thermal diode. The  
ADM1023 is optimized for nTYPICAL = 1.008; any deviation  
on n from this typical value causes a temperature error that  
is calculated below for the nMIN and nMAX of a Pentium III  
processor at TTD = 100°C.  
N is the ratio of the two collector currents.  
n is the ideality factor of the thermal diode (TD).  
To measure ΔVBE, the sensor is switched between operating  
1.0057 1.008  
Δ TMIN  
=
×
(
273.15 Kelvin + 100oC  
)
)
= −0.85oC  
currents of I and NI. The resulting waveform is passed through a  
low-pass filter to remove noise, then to a chopper-stabilized  
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, which gives a  
temperature output in binary format. To further reduce the effects  
of noise, digital filtering is performed by averaging the results of 16  
measurement cycles. Signal conditioning and measurement of the  
internal temperature sensor are performed in a similar manner.  
1.008  
1.0125 1.008  
Δ TMAX  
=
×
(
273.15 Kelvin + 100oC  
= +1.67oC  
1.008  
Thus, the temperature error due to variation on n of the  
thermal diode for a Pentium III processor is about 2.5°C.  
In general, this additional temperature error of the thermal  
diode measurement due to deviations on n from its typical  
value is given by  
Figure 14 shows the input signal conditioning used to measure the  
output of an external temperature sensor. This figure shows the  
external sensor as a substrate PNP transistor, provided for  
temperature monitoring on some microprocessors, but it could  
equally well be a discrete transistor. If a discrete transistor is used,  
the collector is not grounded and should be connected to the base.  
To prevent ground noise from 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. If the sensor is operating in a noisy environment, C1 may  
optionally be added as a noise filter. Its value is 1000 pF maximum.  
See the Layout Considerations section for more information on  
C1.  
n 1.008  
Δ T =  
×
(
273.15 Kelvin + TTD  
)
1.008  
where TTD is in °C.  
Beta of Thermal Transistor (β)  
In Figure 14, the thermal diode is a substrate PNP transistor where  
the emitter current is forced into the device. The derivation of  
Equation 2 assumed that the collector currents were scaled by N as  
the emitter currents were also scaled by N. Thus, this assumes that  
beta (β) of the transistor is constant for various collector currents.  
Figure 15 shows typical β variation vs. collector current for  
Pentium III processors at 100°C. The maximum β is 4.5 and varies  
less than 1% over the collector current range from 7 μA to 300 μA.  
Rev. 8 | Page 9 of 18 | www.onsemi.com  
ADM1023  
β
< 4.5  
MAX  
Table 5. Extended Temperature Resolution  
(Remote Temperature Low Byte)  
I
E
Δβ  
Extended Resolution (°C)  
Remote Temperature Low Byte  
β
β
0.000  
0.125  
0.250  
0.375  
0.500  
0.625  
0.750  
0.875  
0000 0000  
0010 0000  
0100 0000  
0110 0000  
1000 0000  
1010 0000  
1100 0000  
1110 0000  
I
=
I
E
C
β+1  
I
(mA)  
C
7
300  
Figure 15. Variation of β with Collector Currents  
Expressing the collector current in terms of the emitter current  
IC = IE [β/(β + 1)]  
where:  
REGISTER FUNCTIONS  
The ADM1023 contains registers that are used to store the  
results of remote and local temperature measurements and high  
and low temperature limits, and to configure and control the  
device. A description of these registers follows, and further  
details are given in Table 6 to Table 10. Most of the registers  
for the ADM1023 are dual-port and have different addresses  
for read and write operations. Attempting to write to a read  
address or to read from a write address produces an invalid  
result. Register addresses above 0x14 are reserved for future  
use or factory test purposes and should not be written to.  
Address Pointer Register  
The address pointer register does not have, nor does it require,  
an address, because it is the register to which the first data byte  
of every write operation is automatically written. This data byte  
is an address pointer that sets up one of the other registers for  
the second byte of the write operation or for a subsequent read  
operation.  
β(300 μA) = β(7 μA)(1 + ε ).  
ε = Δβ/β and β = β(7 μA).  
Rewriting the equation for ΔVBE, to include the ideality factor,  
n, and beta, β yields  
(
1 + ε  
)
×
)
(
β + 1  
)
nKT  
q
(3)  
Δ VBE  
=
× ln  
× N  
(1 + ε β + 1  
All β variations of less than 1% (ε < 0.01) contribute to  
temperature errors of less than 0.4°C.  
TEMPERATURE DATA FORMAT  
One LSB of the ADC corresponds to 0.125°C, so the ADM1023  
can measure from 0°C to 127.875°C. The temperature data  
format and extended temperature resolution are shown in  
Table 4 and Table 5.  
Value Registers  
Table 4. Temperature Data Format  
The ADM1023 has three registers to store the results of local  
and remote temperature measurements. These registers are  
written to by the ADC and can only be read over the SMBus.  
The Offset Register  
Two offset registers are provided at Address 0x11 and  
Address 0x12. These are provided so that the user may remove  
errors from the measured values of remote temperature. These  
errors may be introduced by clock noise and PCB track resis-  
tance. See Table 7 for an example of offset values.  
The offset value is stored as an 11-bit, twos complement value  
in Register 0x11 (high byte) and Register 0x12 (low byte, left  
justified). The value of the offset is negative if the MSB of  
Register 0x11 is 1, and it is positive if the MSB of Register 0x11  
is 0. This value is added to the remote temperature. These  
registers default to 0 at power-up and have no effect if nothing  
is written to them. The offset register can accept values from  
−128.875°C to +127.875°C. The ADM1023 detects overflow so  
the remote temperature value register does not wrap around  
+127°C or −128°C.  
(Local Temperature and Remote Temperature High Byte)  
Temperature (°C)1  
Digital Output  
0 000 0000  
0 000 0001  
0 000 1010  
0 001 1001  
0 011 0010  
0 100 1011  
0 110 0100  
0 111 1101  
0 111 1111  
0
1
10  
25  
50  
75  
100  
125  
127  
1 The ADM1023 differs from the ADM1021 in that the temperature resolution  
of the remote channel is improved from 1°C to 0.125°C, but it cannot  
measure temperatures below 0°C. If negative temperature measurement is  
required, the ADM1021 should be used.  
The results of the local and remote temperature measurements  
are stored in the local and remote temperature value registers  
and are compared with limits programmed into the local and  
remote high and low limit registers.  
Rev. 8 | Page 10 of 18 | www.onsemi.com  
ADM1023  
Table 6. List of ADM1023 Registers  
Read Address (Hex)  
Write Address (Hex)  
Name  
Power-On Default  
Not applicable  
Not applicable  
Address pointer  
Undefined  
00  
01  
02  
Not applicable  
Not applicable  
Not applicable  
Local temperature value  
Remote temperature value high byte  
Status  
1000 0000 (0x80) (−128°C)  
1000 0000 (0x80) (−128°C)  
Undefined  
03  
09  
Configuration  
0000 0000 (0x00)  
04  
0A  
Conversion rate  
0000 0010 (0x02)  
05  
06  
07  
08  
0B  
0C  
0D  
0E  
0F1  
Local temperature high limit  
Local temperature low limit  
Remote temperature high limit high byte  
Remote temperature low limit high byte  
One-shot  
0111 1111 (0x7F) (+127°C)  
1100 1001 (0xC9) (−55°C)  
0111 1111 (0x7F) (+127°C)  
1100 1001 (0xC9) (−55°C)  
Not applicable  
10  
11  
12  
13  
14  
19  
20  
FE  
FF  
Not applicable  
11  
12  
13  
Remote temperature value low byte  
Remote temperature offset high byte  
Remote temperature offset low byte  
Remote temperature high limit low byte  
Remote temperature low limit low byte  
Reserved  
Reserved  
Manufacturer device ID  
Die revision code  
0000 0000  
0000 0000  
0000 0000  
0000 0000  
0000 0000  
0000 0000  
Undefined  
0100 0001 (0x41)  
0011 xxxx (0x3x)  
14  
Not applicable  
21  
Not applicable  
Not applicable  
1 Writing to Address 0F causes the ADM1023 to perform a single measurement. It is not a data register as such; thus, it does not matter what data is written to it.  
While a limit comparator is tripped due to a value register  
containing an out-of-limit measurement or the sensor is open-  
circuit, the corresponding flag bit cannot be reset. A flag bit can  
be reset only if the corresponding value register contains an in-  
limit measurement, or the sensor is good.  
Table 7. Offset Values  
Remote  
Temperature  
(With  
Remote  
Temperature  
(Without  
Offset)  
18°C  
18°C  
18°C  
18°C  
18°C  
Offset Registers  
Offset  
Value  
−4°C  
−1°C  
−0.125°C  
0°C  
+0.125°C  
+1°C  
+4°C  
0x11  
0x12  
Offset)  
14°C  
17°C  
17.875°C  
18°C  
18.125°C  
19°C  
1111 1100  
1111 1111  
1111 1111  
0000 0000  
0000 0000  
0000 0001  
0000 0100  
0000 0000  
0000 0000  
1110 0000  
0000 0000  
0010 0000  
0000 0000  
0000 0000  
The ALERT interrupt latch is not reset by reading the status  
register, but it resets when the  
output has been serviced  
ALERT  
by the master reading the device address, provided the error  
condition has gone away and the status register flag bits have  
been reset.  
18°C  
18°C  
22°C  
Table 8. Status Register Bit Assignments  
Status Register  
Bit  
Name  
Function  
Bit 7 of the status register (see Table 8) indicates that the ADC is  
busy converting when it is high. Bit 6 to Bit 3 are flags indicating  
the results of the limit comparisons.  
If the local and/or remote temperature measurement is above  
the corresponding high temperature limit or below the corre-  
sponding low temperature limit, one or more of these flags will  
be set. Bit 2 is a flag that is set if the remote temperature sensor  
is open-circuit. These five flags are NORd together, so that if  
7
6
5
4
3
2
BUSY  
At 1 when ADC converting  
LHIGH1  
LLOW1  
RHIGH1  
RLOW1  
OPEN1  
At 1 when local high temp limit tripped  
At 1 when local low temp limit tripped  
At 1 when remote high temp limit tripped  
At 1 when remote low temp limit tripped  
At 1 when remote sensor open-circuit  
Reserved  
1 to 0  
1 These flags stay high until the status register is read or they are reset by POR.  
any of them are high, the  
interrupt latch is set, and the  
ALERT  
output goes low.  
ALERT  
Reading the status register clears the five flag bits, provided the  
error conditions that caused the flags to be set have gone away.  
Rev. 8 | Page 11 of 18 | www.onsemi.com  
ADM1023  
perform a > comparison, while the low limit registers perform  
a < comparison. For example, if the high limit register is  
programmed as a limit of 80°C, measuring 81°C results in an  
alarm condition. Even though the temperature range is 0 to  
127°C, it is possible to program the limit register with negative  
values. This is for backward-compatibility with the ADM1021.  
One-Shot Register  
The one-shot register is used to initiate a single conversion and  
comparison cycle when the ADM1023 is in standby mode, after  
which the device returns to standby. This is not a data register  
as such, and it is the write operation that causes the one-shot  
conversion. The data written to this address is irrelevant and  
is not stored.  
Configuration Register  
Two bits of the configuration register are used. If Bit 6 is 0,  
which is the power-on default, the device is in operating mode  
with the ADC converting (see Table 9). If Bit 6 is set to 1, the  
device is in standby mode and the ADC does not convert.  
Standby mode can also be selected by taking the STBY pin low.  
In standby mode, the values of remote and local temperature  
remain at the value they were before the part was placed in  
standby mode.  
Bit 7 of the configuration register is used to mask the  
output. If Bit 7 is 0, which is the power-on default, the  
output is enabled. If Bit 7 is set to 1, the  
ALERT  
ALERT  
output is  
ALERT  
disabled.  
SERIAL BUS INTERFACE  
Table 9. Configuration Register Bit Assignments  
Control of the ADM1023 is carried out via the serial bus. The  
ADM1023 is connected to this bus as a slave device, under the  
control of a master device. Note that the SMBus SDA and SCLK  
pins are three-stated when the ADM1023 is powered down, and  
they do not pull down the SMBus.  
Bit  
7
Name  
MASK1  
Function  
Power-On Default  
0
0 =  
1 =  
Enabled  
Masked  
ALERT  
ALERT  
6
/STOP 0 = Run  
RUN  
0
0
1 = Standby  
Reserved  
ADDRESS PINS  
5 to 0  
In general, every SMBus device has a 7-bit device address  
(except for some devices that have extended, 10-bit addresses).  
When the master device sends a device address over the bus,  
the slave device with that address responds. The ADM1023  
has two address pins, ADD0 and ADD1, to allow selection of  
the device address, so that several ADM1023s can be used on  
the same bus and to avoid conflict with other devices. Although  
only two address pins are provided, these pins are three-state  
and can be grounded, left unconnected, or tied to VDD, so that a  
total of nine different addresses are possible, as shown in Table 11.  
Conversion Rate Register  
The lowest three bits of this register are used to program the  
conversion rate by dividing the ADC clock by 1, 2, 4, 8, 16, 32,  
64, or 128, to give conversion times from 125 ms (Code 0x07)  
to 16 seconds (Code 0x00). This register can be written to and  
read back over the SMBus. The higher five bits of this register  
are unused and must be set to 0. Use of slower conversion times  
greatly reduces the devices power consumption, as shown in  
Table 10.  
Table 10. Conversion Rate Register Code  
Note that the state of the address pins is sampled only at power-  
up, so changing them after power-up has no effect.  
Table 11. Device Addresses1  
Average Supply Current  
μA Typ at VCC = 3.3 V  
Data  
0x00  
Conversion/Sec  
0.0625  
150  
150  
150  
150  
150  
150  
160  
180  
ADD0  
0
0
0
NC  
NC  
NC  
1
1
1
ADD1  
0
NC  
1
0
NC  
1
0
NC  
1
Device Address  
0011 000  
0011 001  
0011 010  
0101 001  
0101 010  
0101 011  
1001 100  
1001 101  
1001 110  
0x01  
0.125  
0x02  
0.25  
0x03  
0.5  
0x04  
1
0x05  
2
0x06  
4
0x07  
8
0x08 to 0xFF  
Reserved  
Limit Registers  
The ADM1023 has six limit registers to store local and remote,  
high and low temperature limits. These registers can be written  
to and read back over the SMBus. The high limit registers  
1 ADD0 and ADD1 are sampled at power-up only.  
The serial bus protocol operates as follows:  
Rev. 8 | Page 12 of 18 | www.onsemi.com  
ADM1023  
the slave device. Transitions on the data line must occur  
1. The master initiates data transfer by establishing a start  
condition, defined as a high-to-low transition on the serial  
data line, SDATA, while the serial clock line, SCLK, 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 8 bits. These bits  
consist of a 7-bit address (MSB first) plus an R/W bit, which  
determines the direction of the data transfer, that is, whether  
data is written to, or read from, the slave device.  
during the low period of the clock signal and remain stable  
during the high period, because 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 transmitted over the  
serial bus in a single read or write operation is limited only  
by what the master and slave devices can handle.  
3. When all data bytes have been read or written, stop condi-  
tions are established. In write mode, the master pulls the  
data line high during the 10th clock pulse to assert a stop  
condition. In read mode, the master device overrides the  
Acknowledge bit by pulling the data line high during the  
low period before the ninth clock pulse. This is known as  
No Acknowledge. The master then takes 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 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 Acknowl-  
edge bit. All other devices on the bus remain idle while the  
selected device waits for data to be read from or written to it.  
If the R/W bit is 0, the master writes to the slave device. If the  
R/W bit is 1, the master reads from the slave device.  
2. Data is sent over the serial bus in sequences of nine clock  
pulses, 8 bits of data followed by an Acknowledge bit from  
1
9
1
9
SCLK  
0
1
0
1
1
A1  
A0  
D7  
D6  
D5  
D4  
D3  
D2  
D1  
SDATA  
START BY  
D0  
R/W  
ACK. BY  
ACK. BY  
ADM1023  
MASTER  
ADM1023  
FRAME 1  
SERIAL BUS ADDRESS BYTE  
FRAME 2  
ADDRESS POINTER REGISTER BYTE  
1
9
SCLK (CONTINUED)  
SDATA (CONTINUED)  
D7  
D6  
D5  
D4  
D3  
D2  
D1  
D0  
ACK. BY  
STOP BY  
ADM1023 MASTER  
FRAME 3  
DATA BYTE  
Figure 16. Writing a Register Address to the Address Pointer Register, then Writing Data to the Selected Register  
1
0
9
1
9
SCLK  
D6  
D4  
D2  
SDATA  
1
0
1
1
A1  
A0  
R/W  
D7  
D5  
D3  
D1  
D0  
START BY  
MASTER  
ACK. BY  
ADM1023  
ACK. BY  
ADM1023  
STOP BY  
MASTER  
FRAME 1  
SERIAL BUS ADDRESS BYTE  
FRAME 2  
ADDRESS POINTER REGISTER BYTE  
Figure 17. Writing to the Address Pointer Register Only  
1
9
1
9
SCLK  
R/W  
A5  
A1  
A0  
D2  
A6  
A4  
A3  
A2  
D7  
D5  
D4  
D3  
D1  
SDATA  
D6  
D0  
NO ACK.  
ACK. BY  
ADM1023  
STOP BY  
START BY  
MASTER  
BY MASTER MASTER  
FRAME 1  
SERIAL BUS ADDRESS BYTE  
FRAME 2  
DATA BYTE FROM ADM1023  
Figure 18. Reading Data from a Previously Selected Register  
Rev. 8 | Page 13 of 18 | www.onsemi.com  
ADM1023  
NOTES  
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.  
It is possible to read a data byte from a data register with-  
out first writing to the address pointer register. However,  
it is not possible to write data to a register without writing  
to the address pointer register even if the address pointer  
register is already at the correct value. This is because the  
first data byte of a write is always written to the address  
pointer register.  
For the ADM1023, write operations contain either one or two  
bytes, while 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 a valid 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.  
Do not forget that ADM1023 registers have different  
addresses for read and write operations. The write address  
of a register must be written to the address pointer if data  
is to be written to that register, but it is not possible to read  
data from that address. The read address of a register must  
be written to the address pointer before data can be read  
from that register.  
OUTPUT  
ALERT  
This is illustrated in Figure 16. The device address is sent over  
The ALERT output goes low whenever an out-of-limit measure-  
ment is detected or if the remote temperature sensor is open-  
circuit. It is an open drain and requires a 10 kΩ pull-up to VDD  
Several outputs can be wire-ANDed together, so that  
the common line goes low if one or more of the  
goes low.  
the bus followed by R/ set to 0. This is followed by two data  
W
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.  
.
ALERT  
outputs  
ALERT  
When reading data from a register, there are two possibilities:  
The ALERT output can be used as an interrupt signal to a  
processor, or it may be used as an . Slave devices  
on the SMBus normally cannot signal to the master that they  
want to talk, but the SMBALERT function allows them to do so.  
1. If the ADM1023s address pointer register value is unknown  
or not the desired value, it is 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 ADM1023 as  
before, but only the data byte containing the register read  
address is sent, as data is not to be written to the register.  
This is shown in Figure 17.  
SMBALERT  
One or more ALERT outputs are connected to a common  
SMBALERT  
SMBALERT  
line connected to the master. When the  
line is pulled low by one of the devices, the  
procedure shown in Figure 19 occurs.  
A read operation is then performed consisting of the serial  
MASTER  
RECEIVES  
SMBALERT  
bus address, R/ bit set to 1, followed by the data byte read  
W
from the data register. This is shown in Figure 18.  
ALERT RESPONSE  
DEVICE  
ADDRESS  
NO  
ACK  
START  
RD ACK  
STOP  
ADDRESS  
2. If the address pointer register is known to be at the desired  
address already, data can be read from the corresponding  
data register without first writing to the address pointer  
register.  
MASTER SENDS  
ARA AND READ  
COMMAND  
DEVICE SENDS  
ITS ADDRESS  
Figure 19. Use of SMBALERT  
Rev. 8 | Page 14 of 18 | www.onsemi.com  
ADM1023  
SMBALERT Process  
SENSOR FAULT DETECTION  
1. SMBALERT pulled low.  
The ADM1023 has a fault detector at the D+ input that detects  
if the external sensor diode is open-circuit. This is a simple  
voltage comparator that trips if the voltage at D+ exceeds  
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.  
V
CC − 1 V (typical). The output of this comparator is checked  
when a conversion is initiated and sets Bit 2 of the status  
3. The device whose ALERT output is low responds  
to the ARA and the master reads its device address.  
The address of the device is now known, and it can  
be interrogated in the usual way.  
register if a fault is detected.  
If the remote sensor voltage falls below the normal measuring  
range, for example, due to the diode being short-circuited,  
the ADC outputs –128°C (1000 0000 000). Because the normal  
operating temperature range of the device extends only down  
to 0°C, this output code is never seen in normal operation and  
can be interpreted as a fault condition.  
4. If more than one device’s ALERT output is low, the one  
with the lowest device address has priority, in accordance  
with normal SMBus arbitration.  
5. Once the ADM1023 has responded to the ARA, it resets its  
In this respect, the ADM1023 differs from, and improves upon,  
competitive devices that output 0 if the external sensor goes  
short-circuit. Unlike the ADM1023, these other devices can  
misinterpret a genuine 0°C measurement as a fault condition.  
output, provided that the error condition that caused  
ALERT  
the ALERT no longer exists. If the SMBALERT line remains  
low, the master sends ARA again, and so on until all devices  
whose  
outputs were low have responded.  
ALERT  
If the external diode channel is not being used and is shorted  
out, the resulting ALERT may be cleared by writing 0x80  
(−128°C) to the low limit register.  
LOW POWER STANDBY MODES  
The ADM1023 can be put into a low power standby mode using  
hardware or software, that is, by taking the STBY input low or  
by setting Bit 6 of the configuration register. When  
is  
STBY  
high or Bit 6 is low, the ADM1023 operates normally. When  
is pulled low or Bit 6 is high, the ADC is inhibited, and  
STBY  
any conversion in progress is terminated without writing the  
result to the corresponding value register.  
The SMBus is still enabled. Power consumption in the standby  
mode is reduced to less than 10 μA if there is no SMBus activity,  
or 100 μA if there are clock and data signals on the bus.  
These two modes are similar but not identical. When STBY is  
low, conversions are completely inhibited. When Bit 6 is set,  
but STBY is high, a one-shot conversion of both channels can  
be initiated by writing any data value to the one-shot register  
(Address 0x0F).  
Rev. 8 | Page 15 of 18 | www.onsemi.com  
ADM1023  
APPLICATIONS  
FACTORS AFFECTING ACCURACY  
LAYOUT CONSIDERATIONS  
Remote Sensing Diode  
Digital boards can be electrically noisy environments, and the  
ADM1023 is measuring very small voltages from the remote  
sensor; therefore, care must be taken to minimize noise induced  
at the sensor inputs. The following precautions are needed:  
The ADM1023 is designed to work with substrate transistors  
built into processors or with discrete transistors. Substrate  
transistors are generally PNP types with the collector connected  
to the substrate. Discrete types can be either PNP or NPN,  
connected as a diode (base-shorted to collector). If an NPN  
transistor is used, the collector and base are connected to D+  
and the emitter to D−. If a PNP transistor is used, the collector  
and base are connected to D− and the emitter to D+.  
Place the ADM1023 as close as possible to the remote  
sensing diode. Provided that the worst noise sources, such as  
clock generators, data/address buses, and CRTs, are avoided,  
this distance can be 4 to 8 inches.  
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 (see Figure 20).  
The user has no choice with substrate transistors, but if a  
discrete transistor is used, the best accuracy is achieved  
by choosing devices according to the following criteria:  
Use wide tracks to minimize inductance and reduce noise  
pickup. 10 mil track minimum width and spacing is  
recommended.  
Base emitter voltage greater than 0.25 V at 6 μA, at the  
highest operating temperature.  
10MIL  
10MIL  
10MIL  
10MIL  
10MIL  
10MIL  
10MIL  
GND  
Base emitter voltage less than 0.95 V at 100 μA, at the  
lowest operating temperature.  
D+  
Base resistance less than 100 Ω.  
Small variation in hfe (approximately 50 to 150),  
which indicates tight control of VBE characteristics.  
D–  
GND  
Transistors such as 2N3904, 2N3906, or equivalents in SOT-23  
packages are suitable devices to use.  
Figure 20. Arrangement of Signal Tracks  
Thermal Inertia and Self-Heating  
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.  
Accuracy depends on the temperature of the remote-sensing  
diode and/or the internal temperature sensor being at the same  
temperature as that being measured, and a number of factors  
can affect this. Ideally, the sensor should be in good thermal  
contact with the part of the system being measured, such as the  
processor, for example. If it is not in good thermal contact, the  
thermal inertia caused by the mass of the sensor causes a lag in  
the response of the sensor to a temperature change. With the  
remote sensor, this should not be a problem, as it will be either  
a substrate transistor in the processor or a small package device,  
such as SOT-23, placed in close proximity to it.  
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 240 μV.  
Place a 0.1 μF bypass capacitor close to the VDD pin and  
1000 pF input filter capacitors across D+, D− close to the  
ADM1023.  
The on-chip sensor, however, is often remote from the proces-  
sor and monitors only the general ambient temperature around  
the package. The thermal time constant of the QSOP-16  
package is about 10 seconds.  
If the distance to the remote sensor is more than 8 inches, the  
use of twisted pair cable is recommended. This is effective  
up to approximately 6 to 12 feet.  
In practice, the package has electrical, and hence thermal,  
connection to the printed circuit board. Therefore, the  
temperature rise due to self-heating is negligible.  
Rev. 8 | Page 16 of 18 | www.onsemi.com  
ADM1023  
For longer distances (up to 100 feet), use shielded, twisted-  
pair cable such as Belden #8451 microphone cable. Connect  
the twisted pair to D+ and D−, and connect the shield to  
GND close to the ADM1023. Leave the remote end of the  
shield unconnected to avoid ground loops.  
The SCLK and SDATA pins of the ADM1023 can be interfaced  
directly to the SMBus of an I/O chip. Figure 22 shows how the  
ADM1023 might be integrated into a system using this type of  
I/O controller.  
D–  
ADM1023  
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.  
PROCESSOR  
D+  
SYSTEM BUS  
Cable resistance can also introduce errors. A 1 Ω series  
resistance introduces about 1°C error.  
DISPLAY  
SYSTEM  
MEMORY  
GMCH  
DISPLAY  
CACHE  
PCI SLOTS  
APPLICATION CIRCUITS  
HARD  
DISK  
CD ROM  
Figure 21 shows a typical application circuit for the ADM1023,  
using a discrete sensor transistor connected via a shielded,  
twisted-pair cable. The pull-ups on SCLK, SDATA, and ALERT  
are required only if they are not already provided elsewhere in  
the system.  
PCI BUS  
ICH I/O  
CONTROLLER  
HUB  
2 IDE PORTS  
SMBUS  
SUPER I/O  
USB USB  
FWH  
(FIRMWARE  
HUB)  
2 USB PORTS  
0.1μF  
3V  
V
DD  
TO 5.5V  
ADM1023  
Figure 22. System Using ADM1023 and I/O Controller  
10kΩ 10kΩ 10kΩ  
IN  
D+  
1000pF  
SHIELD  
SCLK  
D–  
TO  
CONTROL  
CHIP  
SDATA  
I/O  
OUT  
2N3904  
ALERT  
ADD0  
SET TO  
REQUIRED  
ADDRESS  
ADD1  
GND  
Figure 21. Typical Application Circuit  
Rev. 8 | Page 17 of 18 | www.onsemi.com  
ADM1023  
OUTLINE DIMENSIONS  
0.193  
BSC  
16  
1
9
8
0.154  
BSC  
0.236  
BSC  
PIN 1  
0.069  
0.053  
0.065  
0.049  
8°  
0°  
0.010  
0.004  
COPLANARITY  
0.004  
0.025  
BSC  
0.012  
0.008  
0.050  
0.016  
SEATING  
PLANE  
0.010  
0.006  
COMPLIANT TO JEDEC STANDARDS MO-137-AB  
Figure 23. 16-Lead Shrink Small Outline Package [QSOP]  
(RQ-16)  
Dimensions shown in inches  
ORDERING GUIDE  
Model  
Temperature Range  
Package Description  
Package Option  
RQ-16  
RQ-16  
RQ-16  
RQ-16  
ADM1023ARQ  
0°C to 120°C  
0°C to 120°C  
0°C to 120°C  
0°C to 120°C  
0°C to 120°C  
0°C to 120°C  
16-Lead Shrink Small Outline Package [QSOP]  
16-Lead Shrink Small Outline Package [QSOP]  
16-Lead Shrink Small Outline Package [QSOP]  
16-Lead Shrink Small Outline Package [QSOP]  
16-Lead Shrink Small Outline Package [QSOP]  
16-Lead Shrink Small Outline Package [QSOP]  
Evaluation Board  
ADM1023ARQ-REEL  
ADM1023ARQ-REEL7  
ADM1023ARQZ1  
ADM1023ARQZ-REEL1  
ADM1023ARQZ-R71  
EVAL-ADM1023EB  
RQ-16  
RQ-16  
1 Z = Pb-free part.  
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  
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Rev. 8 | Page 18 of 18 | www.onsemi.com  

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