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參數(shù)資料
| 型號： | MAX6639YAEE+T |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 模擬信號調(diào)理 |
| 英文描述： | 2-Channel Temperature Monitor with Dual, Automatic, PWM Fan-Speed Controller |
| 中文描述： | SPECIALTY ANALOG CIRCUIT, PDSO16 |
| 封裝： | 0.150 INCH, 0.025 INCH PITCH, ROHS COMPLIANT, MO-137AB, QSOP-16 |
| 文件頁數(shù)： | 10/24頁 |
| 文件大小： | 393K |
| 代理商： | MAX6639YAEE+T |
MAX6639
Quick-Start Guide for 8000RPM 4-Pole
(2 Pulses per Revolution) Fan in Automatic
RPM Mode Using the Circuit of Figure 7
1) Write 02h to register 11h to set the PWM output to
drive the n-channel MOSFET.
2) Write 4Bh to register 22h to set the minimum RPM
to 3200.
3) Write 5Eh to register 24h to set the pulses per revo-
lution to 2 and to set the maximum RPM speed to
8000RPM.
4) Write 19h to register 28h to set the fan-start temper-
ature to +25°C.
5) Write D2h to register 10h to start automatic
RPM mode.
Remote-Diode Considerations
Temperature accuracy depends upon having a good-
quality, diode-connected, small-signal transistor.
Accuracy has been experimentally verified for all the
devices listed in Table 12. The MAX6639 can also
directly measure the die temperature of CPUs and
other ICs with on-board temperature-sensing diodes.
The transistor must be a small-signal type with a rela-
tively high forward voltage. This ensures that the input
voltage is within the A/D input voltage range. The for-
ward voltage must be greater than 0.25V at 10A at the
highest expected temperature. The forward voltage
must be less than 0.95V at 100A at the lowest expect-
ed temperature. The base resistance has to be less
than 100
. Tight specification of forward-current gain
(+50 to +150, for example) indicates that the manufac-
turer has good process control and that the devices
have consistent characteristics.
Effect of Ideality Factor
The accuracy of the remote temperature measurements
depends on the ideality factor (n) of the remote diode
(actually a transistor). The MAX6639 is optimized for n
= 1.008, which is the typical value for the Intel
Pentium III and the AMD Athlon MP model 6. If a
sense transistor with a different ideality factor is used,
the output data is different. Fortunately, the difference
is predictable.
Assume a remote-diode sensor designed for a nominal
ideality factor nNOMINAL is used to measure the tem-
perature of a diode with a different ideality factor, n1.
The measured temperature TM can be corrected using:
where temperature is measured in Kelvin.
As mentioned above, the nominal ideality factor of the
MAX6639 is 1.008. As an example, assume the
MAX6639 is configured with a CPU that has an ideality
factor of 1.002. If the diode has no series resistance,
the measured data is related to the real temperature
as follows:
For a real temperature of +85°C (358.15K), the mea-
sured temperature is +82.91°C (356.02K), which is an
error of -2.13°C.
TT
n
TT
ACTUAL
M
NOMINAL
MM
=
=
=
1
1 008
1 002
1 00599
.
(.
)
TT
n
M
ACTUAL
NOMINAL
=
1
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
18
______________________________________________________________________________________
FIGURE
DESCRIPTION
PULSE STRETCHING
PWM FREQUENCY
PWM POLARITY
6
High-side PWM drive
Yes
Low
Negative
7
Low-side PWM drive
Yes
Low
Positive
8
High-side PWM drive with keep-alive supply
No
Low
Negative
9
High-side linear supply
No
High
Positive
10
4-wire fan with PWM speed-control input
No
High
Positive
Table 11. Summary of Fan-Drive Options
MANUFACTURER
MODEL NO.
Central Semiconductor (USA)
CMPT3906
Rohm Semiconductor (USA)
SST3906
Samsung (Korea)
KST3906-TF
Siemens (Germany)
SMBT3906
Table 12. Remote-Sensor Transistor
Manufacturers
Intel and Pentium are registered trademarks of Intel Corp.
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| MAX6639AEE+ | 2-Channel Temperature Monitor with Dual, Automatic, PWM Fan-Speed Controller |
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