ADM1023 Ver la hoja de datos (PDF) - Analog Devices
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ADM1023 Datasheet PDF : 12 Pages
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ADM1023
around the package. The thermal time constant of the QSOP-16
package is about 10 seconds.
In practice, the package will have electrical, and hence thermal,
connection to the printed circuit board, so the temperature rise
due to self-heating will be negligible.
LAYOUT CONSIDERATIONS
Digital boards can be electrically noisy environments, and the
ADM1023 is measuring very small voltages from the remote
sensor, so care must be taken to minimize noise induced at the
sensor inputs. The following precautions should be taken:
1. 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 four to eight inches.
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.
3. Use wide tracks to minimize inductance and reduce noise
pickup. 10 mil track minimum width and spacing is
recommended.
APPLICATION CIRCUITS
Figure 19 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.
The SCLK and SDATA pins of the ADM1023 can be interfaced
directly to the SMBus of an I/O chip. Figure 20 shows how the
ADM1023 might be integrated into a system using this type of
I/O controller.
2200pF
2N3904 SHIELD
VDD
ADM1023
D+
SCLK
D–
SDATA
ALERT
0.1F
10k⍀ 10k⍀
3V
TO 5.5V
10k⍀
IN
I/O
OUT
TO
CONTROL
CHIP
ADD0
ADD1
GND
SET TO
REQUIRED
ADDRESS
Figure 19. Typical ADM1023 Application Circuit
GND
D+
10MIL
10MIL
10MIL
PROCESSOR
D–
D+
ADM1023
D–
GND
10MIL
10MIL
10MIL
10MIL
Figure 18. Arrangement of Signal Tracks
DISPLAY
DISPLAY
CACHE
HARD
CD ROM DISK
SYSTEM BUS
GMCH
SYSTEM
MEMORY
PCI SLOTS
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.
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.
5. Place a 0.1 µF bypass capacitor close to the VDD pin and
2200 pF input filter capacitors across D+, D– close to the
ADM1023.
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.
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 ADM1023. Leave the remote end of the shield uncon-
nected to avoid ground loops.
2 IDE PORTS
USB USB
2 USB PORTS
ICH I/O
CONTROLLER
HUB
FWH
(FIRMWARE
HUB)
PCI BUS
SUPER I/O
SMBUS
Figure 20. Typical System Using ADM1023
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
16-Lead QSOP
(RQ-16)
0.197 (5.00)
0.189 (4.80)
16
0.157 (3.99)
0.150 (3.81)
1
9
0.244 (6.20)
0.228 (5.79)
8
Because the measurement technique uses switched current sources,
excessive cable and/or filter capacitance can affect the measure-
ment. When using long cables, the filter capacitor may be reduced
or removed.
PIN 1
0.059 (1.50)
MAX
Cable resistance can also introduce errors. 1 Ω series resistance
introduces about 1°C error.
0.010 (0.25)
0.004 (0.10)
0.025
(0.64)
BSC
–12–
0.069 (1.75)
0.053 (1.35)
8؇
0.012 (0.30) SEATING 0.010 (0.20) 0؇
0.008 (0.20) PLANE 0.007 (0.18)
0.050 (1.27)
0.016 (0.41)
REV. A
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