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기능 Low Cost Microprocessor System Temperature Monitor Microcomputer
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ADM1021A 데이터시트, 핀배열, 회로
ADM1021A
Low Cost Microprocessor
System Temperature
Monitor Microcomputer
The ADM1021A is a two-channel digital thermometer and
under/overtemperature alarm, intended for use in personal computers
and other systems requiring thermal monitoring and management. The
device can measure the temperature of a microprocessor using
a diode-connected PNP transistor, which can be provided on-chip with
the PentiumIII or similar processors, 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
channel measures the output of an on-chip temperature sensor to
monitor the temperature of the device and its environment.
The ADM1021A communicates over a two-wire serial interface
compatible with SMBus standards. Under/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.
Features
Alternative to the ADM1021
On-chip and Remote Temperature Sensing
No Calibration Necessary
1C Accuracy for On-chip Sensor
3C Accuracy for Remote Sensor
Programmable Over/Undertemperature Limits
Programmable Conversion rate
2-wire SMBus Serial Interface
Supports System Management Bus (SMBus) Alert
200 mA Max Operating Current
1 mA Standby Current
3.0 V to 5.5 V Supply
Small 16-lead QSOP Package
This Device is Pb-Free, Halogen Free and is RoHS Compliant
Applications
Desktop Computers
Notebook Computers
Smart Batteries
Industrial Controllers
Telecom Equipment
Instrumentation
http://onsemi.com
QSOP 16
CASE 492
PIN ASSIGNMENT
NC 1
VDD 2
D+ 3
D4
NC 5
ADD1 6
GND 7
GND 8
ADM1021A
(Top View)
16 NC
15 STBY
14 SCLK
13 NC
12 SDATA
11 ALERT
10 ADD0
9 NC
NC = No Connect
MARKING DIAGRAM
1021AA
RQZ
YYWWG
1021AARQZ = Specific Device Code
YY = Year
WW = Work Week
G = Pb-Free Package
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 15 of this data sheet.
Semiconductor Components Industries, LLC, 2012
July, 2012 Rev. 9
1
Publication Order Number:
ADM1021A/D




ADM1021A pdf, 반도체, 판매, 대치품
ADM1021A
Table 4. ELECTRICAL CHARACTERISTICS (continued)
(TA = TMIN to TMAX, VDD = 3.0 V to 3.6 V, unless otherwise noted) (Note 1)
Parameter
Test Conditions/Comments
Min Typ Max Unit
SMBus Interface (See Figure 2)
Logic Input High Voltage, VIH
STBY, SCLK, SDATA
VDD = 3.0 V to 5.5 V
2.2 − − V
Logic Input Low Voltage, VIL
STBY, SCLK, SDATA
VDD = 3.0 V to 5.5 V
− − 0.8 V
SMBus Output Low Sink Current
SDATA Forced to 0.6 V
6.0
mA
ALERT Output Low Sink Current
ALERT Forced to 0.4 V
1.0
mA
Logic Input Current, IIH, IIL
SMBus Input Capacitance, SCLK, SDATA
1.0
+1.0
mA
5.0 pF
SMBus Clock Frequency
− − 100 kHz
SMBus Clock Low Time, tLOW
SMBus Clock High Time, tHIGH
SMBus Start Condition Setup Time,
tSU:STA
SMBus Repeat Start Condition
tLOW between 10% Points
tHIGH between 90% Points
4.7
4.0
4.7
250
ms
ms
ms
ns
Setup Time, tSU:STA
SMBus Start Condition Hold Time, tHD:STA
SMBus Stop Condition Setup Time, tSU:STO
SMBus Data Valid to SCLK
Between 90% and 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
250
4.0
4.0
250
ns
ms
ms
ns
Rising Edge Time, tSU:DAT
SMBus Data Hold Time, tBUF:DAT
SMBus Bus Free Time, tBUF
SCLK Falling Edge to SDATA
Time for 10% or 90% of SDATA to 10% of SCLK
Between Start/Stop Condition
Valid Time, tVD:DAT
Master Clocking in Data
1. TMAX = 100C, TMIN = 0C
2. Operation at VDD = 5.0 V guaranteed by design; not production tested.
3. Guaranteed by design; not production tested.
250
0
4.7
ns
ms
ms
1 ms
1 ms
SCLK
SDATA
tBUF
STOP START
t LOW
tR
tHD; STA
tHD; DAT
tF
tHIGH
tSU; DAT
t HD; STA
tSU; STA
START
Figure 2. Serial Bus Timing
tSU; STO
STOP
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ADM1021A 전자부품, 판매, 대치품
ADM1021A
Functional Description
The ADM1021A 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 ADM1021A is operating normally, the
A-to-D converter operates in 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 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 registers. 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
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 powerup, the remote and local temperature
values default to –128C. Since the device normally powers
up converting, a measurement of local and remote
temperature is made, and these values are then stored before
a comparison with the stored limits is made. 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
can be cleared in one of two ways.
1. Change both the local and remote lower limits to
–128C and read the status register (which in turn
clears the ALERT output).
2. Take the part out of standby and read the status
register (which in turn clears the ALERT output).
This works only if the measured values are within
the limit values.
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. Unfortunately, this technique requires calibration to
null the effect of the absolute value of VBE, which varies
from device to device.
I
N I IBIAS
VDD
REMOTE
SENSING
TRANSISTOR
D+
C1*
D
BIAS
DIODE
LOW-PASS FILTER
fC = 65 kHz
VOUT+
To ADC
VOUT
*CAPACITOR C1 IS OPTIONAL. IT IS ONLY NECESSARY IN NOISY ENVIRONMENTS.
C1 = 2.2 nF TYP, 3 nF MAX
Figure 13. Input Signal Conditioning
The technique used in the ADM1021A is to measure the
change in VBE when the device is operated at two different
currents. This is given by:
DVBE + kTńq 1n (N)
(eq. 1)
where:
k is Boltzmann’s constant.
q is the charge on the electron (1.6 10–19 Coulombs).
T is the absolute temperature in Kelvins.
N is the ratio of the two currents.
Figure 13 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 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 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, one can
optionally be added as a noise filter. Its value is typically
2,200 pF, but it should be no more than 3,000 pF. See the
Layout Considerations section for more information.
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ADM1021

Low Cost Microprocessor System Temperature Monitor

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Analog Devices
ADM1021A

Low Cost Microprocessor System Temperature Monitor Microcomputer

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