MAX6639 データシートの表示（PDF） - Maxim Integrated

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MAX6639

2-Channel Temperature Monitor with Dual, Automatic, PWM Fan-Speed Controller

Maxim Integrated 

MAX6639/MAX6639F

2-Channel Temperature Monitor with Dual,

Automatic, PWM Fan-Speed Controller

Typical Operating Circuit

5V

VFAN

(5V OR 12V)

3.0V TO 3.6V

5V

CPU

VCC ADD TACH1

DXP1

VFAN

(5V OR 12V)

DXN

PWM1

5V

DXP2

PWM2

MAX6639

3.3V TO 5.5V

GPU

TO SMBus

SDA

MASTER

SCL

3.3V TO 5.5V

TACH2

3.3V TO 5.5V

ALERT

3.3V TO 5.5V

OT

TO SYSTEM SHUTDOWN

3.3V TO 5.5V

TO CLOCK THROTTLE

THERM

FANFAIL

GND

3) Route the DXP and DXN traces parallel and close to

each other, away from any high-voltage traces such

as +12VDC. Avoid leakage currents from PCB cont-

amination. A 20MΩ leakage path from DXP ground

causes approximately +1°C error.

4) Connect guard traces to GND on either side of the

DXP/DXN traces. With guard traces, placing routing

near high-voltage traces is no longer an issue.

5) Route as few vias and crossunders as possible to

minimize copper/solder thermocouple effects.

6) When introducing a thermocouple, make sure that

both the DXP and the DXN paths have matching

thermocouples. In general, PCB-induced thermo-

couples are not a serious problem. A copper solder

thermocouple exhibits 3µV/°C, and it takes approxi-

mately 200µV of voltage error at DXP/DXN to cause

a +1°C measurement error, so most parasitic ther-

mocouple errors are swamped out.

7) Use wide traces. Narrow traces are more inductive

and tend to pick up radiated noise. The 10-mil widths

and spacings recommended are not absolutely nec-

essary (as they offer only a minor improvement in

leakage and noise), but use them where practical.

8) Placing an electrically clean copper ground plane

between the DXP/DXN traces and traces carrying

high-frequency noise signals helps reduce EMI.

20

Maxim Integrated

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