ADM1021ARQ Fast Delivery |IC PHOENIX CO.,LIMITED

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ADM1021ARQ
Low Cost Microprocessor System Temperature Monitor
REV.0
Low Cost Microprocessor
System Temperature Monitor
FUNCTIONAL BLOCK DIAGRAM
TESTVDDNCGNDNCNCTEST
ALERT
STBY
SDATASCLKADD0ADD1GND
FEATURES
Improved Replacement for MAX1617
On-Chip and Remote Temperature Sensing
No Calibration Necessary
18C Accuracy for On-Chip Sensor
38C Accuracy for Remote Sensor
Programmable Over/Under Temperature Limits
Programmable Conversion Rate
2-Wire SMBus Serial Interface
Supports System Management Bus (SMBus™) Alert
70 mA Max Operating Current
3 mA Standby Current
3 V to 5.5 V Supply
Small 16-Lead QSOP Package
APPLICATIONS
Desktop Computers
Notebook Computers
Smart Batteries
Industrial Controllers
Telecomms Equipment
Instrumentation
PRODUCT DESCRIPTION
The ADM1021 is a two-channel digital thermometer and under/
over temperature alarm, intended for use in personal computers
and other systems requiring thermal monitoring and manage-
ment. The device can measure the temperature of a micropro-
cessor using a diode-connected PNP transistor, which may be
provided on-chip in the case of the Pentium® II or similar pro-
cessors, or 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 transistor’s base emitter voltage, so
that no calibration is required. The second measurement chan-
nel measures the output of an on-chip temperature sensor, to
monitor the temperature of the device and its environment.
The ADM1021 communicates over a two-wire serial interface
compatible with SMBus standards. Under and over temperature
limits can be programmed into the devices 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 inter-
rupt, or as an SMBus alert.
SMBus is a trademark and Pentium is a registered trademark of Intel Corporation.
ADM1021–SPECIFICATIONS(TA = TMIN to TMAX, VDD = 3.0 V to 3.6 V, unless otherwise noted)
NOTESOperation at VDD = +5 V guaranteed by design, not production tested.Guaranteed by design, not production tested.
Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS*
Positive Supply Voltage (VDD) to GND . . . . . . .–0.3 V to +6 V
D+, ADD0, ADD1 . . . . . . . . . . . . . . . .–0.3 V to VDD + 0.3 V
D– to GND . . . . . . . . . . . . . . . . . . . . . . . . . .–0.3 V to +0.6 V
SCLK, SDATA, ALERT, STBY . . . . . . . . . . . .–0.3 V to +6 V
Input Current, SDATA . . . . . . . . . . . . . . . .–1 mA to +50 mA
Input Current, D– . . . . . . . . . . . . . . . . . . . . . . . . . . . . .–1 mA
ESD Rating, all pins (Human Body Model) . . . . . . . .2000 V
Continuous Power Dissipation
Up to +70°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . .650 mW
Derating above +70°C . . . . . . . . . . . . . . . . . . . .6.7 mW/°C
Operating Temperature Range . . . . . . . . . .–55°C to +125°C
Maximum Junction Temperature (TJ max) . . . . . . . . .+150°C
Storage Temperature Range . . . . . . . . . . . .–65°C to +150°C
Lead Temperature, Soldering
Vapor Phase 60 sec . . . . . . . . . . . . . . . . . . . . . . . . .+215°C
Infrared 15 sec . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+200°C
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent 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.
THERMAL CHARACTERISTICS
16-Lead QSOP Package: qJA = 150°C/Watt.
ORDERING GUIDE
PIN FUNCTION DESCRIPTIONS
NOTE
Pins 1 and 16 are reserved for test purposes. Ideally these pins should be left
unconnected. If routing through these pins is required, then both should be at
the same potential (i.e., connected together).
PIN CONFIGURATION
NC = NO CONNECT
TEST
VDD
ADD1
GND
GND
TEST
STBY
SCLK
SDATA
ALERT
ADD0PROTOCOL
SCL
SDA
PROTOCOL
SCL
SDA
tLOWtHIGH1/fSCLtF
BIT 0
(R/W)
Figure 1.Diagram for Serial Bus Timing
ADM1021–Typical Performance Characteristics
LEAKAGE RESISTANCE – MV
TEMPERATURE ERROR – 30
–20
Figure 2.Temperature Error vs. PC Board Track Resistance
FREQUENCY – Hz5050M500
TEMPERATURE ERROR – 50k500k5M
Figure 3.Temperature Error vs. Power Supply Noise
Frequency
FREQUENCY – Hz50M500
TEMPERATURE ERROR – 50k500k5M
Figure 4.Temperature Error vs. Common-Mode Noise
Frequency
MEASURED TEMPERATURE11010
READING304050
100708090100
Figure 5.Pentium II Temperature Measurement vs.
ADM1021 Reading
DXP-DXN CAPACITANCE – nF
TEMPERATURE ERROR –
3.24.77
Figure 6.Temperature Error vs. Capacitance Between
D+ and D–

SCLK FREQUENCY – Hz01M1k
SUPPLY CURRENT – 10k25k50k75k100k250k500k750k
Figure 7.Standby Supply Current vs. Clock Frequency
FREQUENCY – Hz5050M500
TEMPERATURE ERROR – 50k500k5M
100k25M
Figure 8.Temperature Error vs. Differential-Mode Noise
Frequency
CONVERSION RATE – Hz
SUPPLY CURRENT –
120
Figure 9.Operating Supply Current vs. Conversion
Rate
SUPPLY VOLTAGE – Volts
SUPPLY CURRENT –
1.31.51.71.92.12.32.52.72.93.54.5
Figure 10.Standby Supply Current vs. Supply Voltage
TIME – Sec
T = 0T = 10T = 2
TEMPERATURE –
T = 4T = 6T = 8
Figure 11.Response to Thermal Shock
FUNCTIONAL DESCRIPTION
The ADM1021 contains a two-channel A-to-D converter with
special input-signal conditioning to enable operation with remote
and on-chip diode temperature sensors. When the ADM1021 is
operating normally, the A-to-D converter operates in a free-
running mode. The analog input multiplexer alternately selects
either the on-chip temperature sensor to measure its local tem-
perature, or the remote temperature sensor. These signals are
digitized by the ADC and the results stored in the Local and
Remote Temperature Value Registers as 8-bit, twos complement
words.
The measurement results are compared with Local and Remote,
High and Low Temperature Limits, stored in four on-chip regis-
ters. Out-of-limit comparisons generate flags that are stored in
the status register, and one or more out-of-limit results will
cause the ALERT output to pull low.
The limit registers can be programmed, and the device con-
trolled and configured, via the serial System Management Bus.
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.
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, operated at constant current. Unfortu-
nately, this technique requires calibration to null out the effect
of the absolute value of Vbe, which varies from device to device.
The technique used in the ADM1021 is to measure the change
in Vbe when the device is operated at two different currents.
This is given by:Vbe = KT/q · ln (N)
where:
K is Boltzmann’s constant
ADM1021
Figure 12 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 tem-
perature monitoring on some microprocessors, but it could
equally well be a discrete transistor. If a discrete transistor is
used, the collector will not be grounded and should be linked to
the base. To prevent ground noise interfering with the measure-
ment, 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 typi-
cally 2200pF, but should be no more than 3000pF. See the
section on layout considerations for more information on C1.
To measure DVbe, the sensor is switched between operating
currents of I and N · I. The resulting waveform is passed through
a 65kHz low-pass filter to remove noise, thence to a chopper-
stabilized amplifier that performs the functions of amplification
and rectification of the waveform to produce a dc voltage pro-
portional to DVbe. 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.
Signal conditioning and measurement of the internal tempera-
ture sensor is performed in a similar manner.
TEMPERATURE DATA FORMAT
One LSB of the ADC corresponds to 1°C, so the ADC can
theoretically measure from –128°C to +127°C, although the
practical lowest value is limited to –65°C due to device maxi-
mum ratings. The temperature data format is shown in Table I.
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.
REMOTE
SENSING
TRANSISTOR
VOUT+
TO ADC
VOUT–
CAPACITOR C1 IS OPTIONAL. IT IS ONLY NECESSARY IN NOISY ENVIRONMENTS.
C1 = 2.2nF TYPICAL, 3nF MAX.
Figure 12.Input Signal Conditioning
Table I.Temperature Data Format
REGISTERS
The ADM1021 contains nine registers that are used to store the
results of remote and local temperature measurements, high and
low temperature limits, and to configure and control the device.
A description of these registers follows, and further details are
given in Tables II to IV. It should be noted that the ADM1021’s
registers 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, will produce an invalid result. Regis-
ter addresses above 0Fh are reserved for future use or used for
factory test purposes and should not be written to.
Address Pointer Register
The Address Pointer Register itself does not have, nor does it
require, an address, as it is the register to which the first data
byte of every Write operation is written automatically. 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.

Partno	Mfg	Dc	Qty	Available	Descript
ADM1021ARQ	AD	N/a	2400	avai	Low Cost Microprocessor System Temperature Monitor