adm1027 Analog Devices, Inc., adm1027 Datasheet - Page 28

• Manufacturer Part Number: adm1027
• Description: Dbcool? Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

ADM1027
Step 1
Determine the Hardware Configuration
Essentially this means choosing whether to use Pin 10 as a PWM2
output or as an SMBALERT output and deciding which SMBus
address is to be used. To set Pin 10 as SMBALERT, set Bit 0
of Configuration Register 3 (Addr = 0x78) equal to 1. The
default state is PWM2, where this bit equals 0.
It also refers to the layout recommendations of the ADM1027
on a motherboard, for example.
ADM1027 Placement Considerations
Motherboards are electrically noisy environments, and care must
be taken to protect the analog inputs from noise, particularly the
D+/D– lines of a remote diode sensor. The following precautions
should be taken:
1. Place the ADM1027 as close as possible to the remote sensing
2. Route the D+ and D– tracks close together, in parallel, with
diode. Provided that the worst noise sources such as clocks
and data/address buses are avoided, this distance can be
4 inches to 8 inches.
grounded guard tracks on each side. Provide a ground plane
under the tracks if possible. Do NOT run the D+/D– lines in
different directions.
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3. Use wide tracks to minimize inductance and reduce noise
4. Try to minimize the number of copper/solder joints, which
5. Place a 0.1 mF supply bypass capacitor close to the ADM1027.
6. If the distance to the remote sensor is more than 8 inches,
Because the measurement technique uses switched current
sources, excessive cable (adds resistance) and/or filter capacitance
can affect the measurement. A 1 W series resistance introduces
about 0.8
pickup. A 10 mil track minimum width and spacing is
recommended.
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. Avoid routing D+/D–
on multiple layers or through vias if possible. These increase
series resistance that will cause temperature error.
the use of shielded twisted pair cable is recommended. This
will work up to 100 feet. Connect the twisted pair to D+/D–
and the shield to GND close to the ADM1027. Leave the
remote end of the shield unconnected to avoid ground loops.
o
C error.
REV. A