SA56004X Datasheet, PDF (19/23 Pages) NXP Semiconductors – 1 Degrees Celcious accurate, SMBus-compatible, 8-pin, remote/local digital temperature sensor with over temperature alarms

Philips Semiconductors
±1 °C accurate, SMBus-compatible, 8-pin, remote/local
digital temperature sensor with over temperature alarms
Product data sheet
SA56004X
Printed Circuit Board layout considerations
Care must be taken in PCB layout to minimize noise induced at the
remote temperature sensor inputs, especially in extremely noisy
environments, such as a computer motherboard. Noise induced in
the traces running between the device sensor inputs and the remote
diode can cause temperature conversion errors. Typical sensor
signal levels to the SA56004X is a few microvolts. The following
guidelines are recommended:
1. Place the SA56004X 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.
2. Route the D+ and D– lines parallel and close together with
ground guards enclosing them (see ‘Ideal diode trace layout’,
Figure 18).
3. Leakage currents due to PC board contamination must be
considered. Error can be introduced by these leakage currents.
4. Use wide traces to reduce inductance and noise pickup. Narrow
traces more readily pickup noise. The minimum width of 10 mil
and space of 10 mil are recommended.
5. Place a bypass capacitor of 10 nF close to the V_DD pin and an
input filter capacitor of 2200 pF close to the D+ and D– pins.
6. A shielded twisted pair is recommended if remote sensor is
located several feet away from the temperature sensor. Under
this circumstance, connect the shield of the cable at the device
side to the SA56004X GND pin and leave the shield at the
remote end unconnected to avoid ground loop currents. Also
notice that the series resistance of the cable may introduce
measurement error; 1 Ω can introduce about 0.5 °C.
GND
D+
D–
GND
Figure 18. D+ and D– trace layout.
SL02017
PACKING METHOD
The SA56004X is packed in reels, as shown in Figure 19.
GUARD
BAND
TAPE
REEL
ASSEMBLY
BARCODE
LABEL
TAPE DETAIL
COVER TAPE
CARRIER TAPE
BOX
Figure 19. Tape and reel packing method
SL01305
2004 Oct 06
19