f75386 Feature Integration Technology Inc., f75386 Datasheet - Page 22

• Manufacturer Part Number: f75386
• Description: Dual ?1o C Accuracy Temperature Sensor Ic With Fan Speed Control
• Manufacturer: Feature Integration Technology Inc.

F75386
1. Place the F75386 as close as practical to the remote sensing diode. In noisy environments, such as a
2. Route the D+ and Pin5 GND(D-) tracks close together, in parallel, with grounded guard tracks on each
3. Use wide tracks to minimize inductance and reduce noise pickup. 10 mil track minimum width and
4. Try to minimize the number of copper/solder joints, which can cause thermocouple effects. Where
5. Place a 0.1µF bypass capacitor close to the V
6. If the distance to the remote sensor is more than 8 inches, the use of twisted pair cable is
7. Because the measurement technique uses switched current sources, excessive cable and/or filter
computer main-board, the distance can be 4 to 8 inches. (typ). This length can be increased if the worst
noise sources are avoided. Noise sources generally include clock generators, CRTs, memory buses
and PCI/ISA bus etc.
side. Provide a ground plane under the tracks if possible. Do not route D+ & Pin5 GND(D-) lines next to
the deflection coil of the CRT. And also don’t route the trace across fast digital signals which can easily
induce bigger error.
spacing is recommended.
copper/solder joints are used, make sure that they are in both the D+ and Pin5 GND(D-) path and at
the same temperature. Thermocouple effects should not be a major problem as 1
about 200µV. It means that a copper-solder thermocouple exhibits 3µV/℃, and takes about 200µV of
the voltage error at D+ & Pin5 GND(D-) to cause a 1℃ measurement error. Adding a few
thermocouples causes a negligible error.
3300pF input filter capacitors across D+, Pin5 GND(D-) close to the F75386.
recommended. It will work up to around 6 to 12 feet.
capacitance will affect the measurement accuracy. When using long cables, the filter capacitor may be
reduced or removed. Cable resistance can also induce errors. 1 Ω series resistance introduces about
MINIMUM
10MILS
10MILS
-18-
Pin5 GND(D-)
DD
pin. In very noisy environments, place an external
GND
GND
D+
10MILS
10MILS
℃
corresponds to
F75386
July,
V0.27P
2007