NE1617A View Datasheet(PDF) - Philips Electronics
Part Name
Description
Manufacturer
NE1617A Datasheet PDF : 17 Pages
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Philips Semiconductors
Temperature monitor for microprocessor systems
Product data sheet
NE1617A
PC BOARD LAYOUT CONSIDERATION
Because the NE1617A is used to measure a very small voltage in
the range of microvolts from the remote sensor, care must be taken
to minimize noise induced at the sensor inputs, especially in the
computer motherboard noisy environment. The following
precautions should be considered:
– Place the NE1617A as close as possible to the remote sensor. It
can be from 4 to 8 inches, as long as the worst noise sources
such as clock generator, data and address buses, CRTs are
avoided.
– Route the D+ and D– lines in parallel and close together with
ground guards enclosed (refer to Figure 12).
– Leakage currents due to PC board contamination could affect the
temperature accuracy and must be considered. Error can be
introduced by the leakage current as shown on the characteristics
curve (Figure 5: Temperature Error vs. PC Board Resistance).
– Use wide tracks to reduce inductance and noise pickup that may
be introduced by narrow ones. The width of 10 mil and space of
10 mil are recommended.
GND
D+
D–
GND
Figure 12. PCB layout for D+ and D–
SL01218
– Place a bypass capacitor of 0.1 µF close to the VDD pin and an
input filter capacitor of 2200 pF close to the D+ and D– pins.
– If the remote sensor is operating in a noisy environment and
located several feet away from the NE1617A, a shielded twisted
pair cable is recommended. Make sure the shield of the cable is
connected to the NE1617A ground pin, and leave the shield at the
remote end unconnected. Shield connecting to ground of both
ends could create a ground loop (refer to Figure 13) and defeat
the purpose of the shielded cable. Also, cold soldered joints and
damaged cable could introduce series resistance and reslult in
measurement error. For instance, a 1 Ω resistance can introduce
a change of temperature of about 0.5 °C.
SHIELDED TWISTED PAIR
REMOTE
SENSOR
D+
NE1617A
D–
GND
SL02149
Figure 13. Using shielded twisted pair
2004 Oct 05
14
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