ADM1031ARQ-REEL7 ON Semiconductor, ADM1031ARQ-REEL7 Datasheet - Page 10

• Manufacturer Part Number: ADM1031ARQ-REEL7
• Description: IC SENSOR 2-TEMP/FAN CTRL 16QSOP
• Manufacturer: ON Semiconductor

Specifications of ADM1031ARQ-REEL7

• Rohs Status: RoHS non-compliant
• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: 0°C ~ 100°C, External Sensor
• Output Type: SMBus™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: 0°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP

grounded, and is 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.
ADM1031 can theoretically measure temperatures from
–127°C to +127.75°C, although –127°C is outside the
operating range for the device. The extended temperature
resolution data format is shown in Table 3 and Table 4.
TRANSISTOR
Table 2. Temperature Data Format − (Local
Temperature and Remote Temperature High Bytes)
Table 3. Remote Sensor Extended Temperature
Resolution
If a discrete transistor is used, then the collector is not
One LSB of the ADC corresponds to 0.125°C, so the
Extended Resolution
SENSING
REMOTE
Temperature (5C)
0.000°C
0.125°C
0.250°C
0.375°C
0.500°C
0.625°C
0.750°C
0.875°C
−128°C
−125°C
−100°C
+100°C
+125°C
+127°C
D+
D–
−75°C
−50°C
−25°C
+10°C
+25°C
+50°C
+75°C
Figure 18. Signal Conditioning
+1°C
−1°C
0°C
I
DIODE
BIAS
N × I
I
BIAS
Remote Temperature Low Bits
LOW−PASS
f
C
FILTER
= 65kHz
V
DD
Digital Output
1000 0000
1000 0011
1001 1100
1011 0101
0000 0000
0000 0001
0000 1010
0001 1001
0011 0010
0100 1011
0110 0100
000
001
010
100
101
1100 1110
0111 1101
011
110
111
1110 0111
0111 1111
1111 1111
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V
V
OUT+
OUT–
ADC
TO
10
remote channels is stored in the extended temperature
resolution register (Register 0×06), and is outlined in Table 27.
measurement, the more negative terminal of the sensor is not
referenced to ground, but biased above ground by an internal
diode at the D– input. If the sensor is used in a very noisy
environment, a capacitor of value up to 1000 pF can be
placed between the D+ and D– inputs to filter the noise.
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 chopper−stabilized amplifier that performs the
functions of amplification and rectification of the waveform
to produce a dc voltage proportional to DV
is measured by the ADC to give a temperature output in
11−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 nominally takes 9.6 ms.
Layout Considerations
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:
Table 4. Local Sensor Extended Temperature
Resolution
The extended temperature resolution for the local and
To
To measure DV
Digital boards can be electrically noisy environments and
Extended Resolution
1. Place the ADM1031 as close as possible to the
2. Route the D+ and D– tracks close together, in
3. Use wide tracks to minimize inductance and
GND
GND
D+
D–
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.
parallel, with grounded guard tracks on each side.
Provide a ground plane under the tracks if possible.
reduce noise pickup. Ten mil track minimum
width and spacing is recommended.
prevent
Figure 19. Arrangement of Signal Tracks
0.00°C
0.25°C
0.50°C
0.75°C
ground
BE
, the sensor is switched between
noise
Local Temperature Low Bits
interfering
00
01
10
11
BE
. This voltage
10MIL
10MIL
10MIL
10MIL
10MIL
10MIL
10MIL
with
the