pc87591l National Semiconductor Corporation, pc87591l Datasheet - Page 189

• Manufacturer Part Number: pc87591l
• Description: Lpc Mobile Embedded Controllers
• Manufacturer: National Semiconductor Corporation

Revision 1.07
Embedded Controller Modules
Twisted Pair and Shielded Cables
For remote sensor distances longer than 8 inches or in particularly noisy environments, a twisted pair cable 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 such as that used for audio microphones. Connect the twist-
ed pair to DP and DN and the shield to AGND close to the PC87591x, and leave the remote end of the shield unterminated.
For very long cable runs, the cable parasitic capacitance adds a delay to the Temperature Channel. You should add the
cable capacitance to the value of the C
delay setting accordingly.
Cable resistance also affects remote sensor accuracy. A 1 series resistance introduces about +1.0˚C to +0.5˚C error.
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D
(see “Calculating the Temperature Channel Delay” on page 188) and correct the
Figure 65. DP and DN, PCB Traces
(Continued)
AGND
AGND
DP
DN
189
10 mil
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Minimum
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