THMC10 Datasheet, PDF (15/20 Pages) Texas Instruments – REMOTE/LOCAL TEMPERATURE MONITOR WITH SMBus INTERFACE

THMC10
REMOTE/LOCAL TEMPERATURE MONITOR
WITH SMBus INTERFACE
SLIS089 – DECEMBER 1999
PRINCIPLES OF OPERATION
PC board layout checklist (continued)
10 MILS
10 MILS
GND
DXP
DXN
GND
Figure 7. Recommended PC Board Layout for DXP/DXN Traces
10 MILS
MINIMUM
10 MILS
uses of twisted pair and shielded cables
For remote-sensor distances longer than 8 inches or in particularly noisy environments, a twisted pair is
recommended. Its practical length is 6 feet to 12 feet (typical) before noise becomes a problem, as tested in
a noisy electronics laboratory. For longer distances, the best solution is a shielded twisted pair like that used
for audio microphones. For example, a Belden® #8451 works well for distances up to 100 feet in a noisy
environment. Connect the twisted pair to DXP and DXN and the shield to GND, and leave the shield’s remote
end unterminated. Excess capacitance at DXN limits practical remote sensor distances (see A/D and supply
dc electrical characteristics). For very long cable runs, the cable’s parasitic capacitance often provides noise
filtering; hence, the 2200-pF capacitor can often be removed or reduced in value. Cable resistance also affects
remote-sensor accuracy. A 1-Ω series resistance introduces about 0.5°C error.
Belden is a registered trademark of Belden Corporation.
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