f75393 Feature Integration Technology Inc., f75393 Datasheet - Page 12

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f75393

Manufacturer Part Number
f75393
Description
?1 C Temperature Sensor With ? Compensation
Manufacturer
Feature Integration Technology Inc.
Datasheet

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F75393
6.11 Resistor Cancelled Function
6.12 PCB Layout Guide
auto-adjust I
accurate temperature. This algorithm of beta compensation is suitable for substrate transistor or new generational CPU (i.e. 45nm
CPU) because small beta and high proportional beta variation. The default value of register CR3Bh bit7 is enabled for measure
substrate transistor. If user would like to detect discrete transistor and the beta is big enough, please disable this bit for detecting.
About this section application, please refer the register description for detail.
The F75393 can cancel resistor effect from CPU internal circuit or PCB circuit.
PCB can be electrically noisy environments, and the F75393 is measuring very small voltage from the remote sensor, so care must
be taken to minimize noise which is occurred at the sensor inputs. The following guideline should be taken to reduce the
measurement error of the temperature sensors:
1.
2.
3.
4.
5.
Place the F75393 as close as practical to the remote sensing diode. In noisy environments, such as a 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.
Route the D+ and D- tracks close together, in parallel, with grounded guard tracks on each side. Provide a ground plane under
the tracks if possible. Do not route D+ & 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.
Use wide tracks to minimize inductance and reduce noise pickup. 10 mil track minimum width and spacing is recommended.
Try to minimize the number of copper/solder joints, which can cause thermocouple effects. Where copper/solder joints are used,
make sure that they are in both the D+ and D- path and at the same temperature. Thermocouple effects should not be a major
problem as 1
200µV of the voltage error at D+ & D- to cause a 1 ℃ measurement error. Adding a few thermocouples causes a negligible
error.
Place a 0.1µF bypass capacitor close to the VCC pin. In very noisy environments, place an external 2200pF input filter
capacitors across D+, D- close to the F75393.
E
(I
E1
and I
corresponds to about 200µV
E2
) current and feedback I
MINIMUM
10MILS
10MILS
B
. It means that a copper-solder thermocouple exhibits 3µV/ ℃ , and takes about
(I
B1
and I
-8-
B2
) promptly for getting proper I
GND
DXP
DXN
GND
C
proportion (I
10MILS
10MILS
C1
/ I
C2
), then calculates the
F75393
May, 2008
V0.16P

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