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參數(shù)資料
| 型號： | ADM1031ARQZ |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 溫度/濕度傳感器 |
| 英文描述： | DIGITAL TEMP SENSOR-SERIAL, 8BIT(s), 3Cel, RECTANGULAR, SURFACE MOUNT |
| 封裝： | LEAD FREE, MO-137AB, QSOP-16 |
| 文件頁數(shù)： | 17/36頁 |
| 文件大?。?/td> | 596K |
| 代理商： | ADM1031ARQZ |
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ADM1031
Rev. B | Page 24 of 36
FAN DRIVE AND SPEED MEASUREMENT
Fans come in a variety of different options. One distinguishing
feature of fans is the number of poles that a fan has internally.
The most common fans available have four, six, or eight poles.
The number of poles the fan has generally affects the number of
pulses per revolution the fan outputs.
If the ADM1031 is used to drive fans other than 4-pole fans that
output 2 tach pulses/revolution, then the fan speed
measurement equation needs to be adjusted to calculate and
display the correct fan speed, and also to program the correct
count value in RPM feedback mode.
FAN SPEED MEASUREMENT EQUATIONS
For a 4-pole fan (2 tach pulses/rev):
Fan RPM = (f × 60)/Count × N
For a 6-pole fan (3 tach pulses/rev):
Fan RPM = (f × 60)/(Count × N × 1.5)
For an 8-pole fan (4 tach pulses/rev):
Fan RPM = (f × 60)/(Count × N × 2)
If in doubt as to the number of poles the fans used have, or the
number of tach output pulses/rev, consult the fan manufacturer’s
data sheet, or contact the fan vendor for more information.
FAN DRIVE USING PWM CONTROL
The external circuitry required to drive a fan using PWM
control is extremely simple. A single NMOS FET is the only
drive transistor required. The specifications of the MOSFET
depend on the maximum current required by the fan being
driven. Typical notebook fans draw a nominal 170 mA, and so
SOT devices can be used where board space is a constraint. If
driving several fans in parallel from a single PWM output, or
driving larger server fans, the MOSFET needs to handle the
higher current requirements. The only other stipulation is that
the MOSFET should have a gate voltage drive, VGS < 3.3 V, for
direct interfacing to the PWM_OUT pin. The MOSFET should
also have a low on-resistance to ensure that there is not significant
voltage drop across the FET. This would reduce the maximum
operating speed of the fan.
Figure 35 shows how a 3-wire fan can be driven using PWM
control.
+V
5V OR 12V
FAN
Q1
NDT3055L
ADM1031
PWM_OUT
TACH/AIN
TACH
10k
Ω
TYPICAL
10k
Ω
TYPICAL
3.3V
02402-035
Figure 35. Interfacing the ADM1031 to a 3-Wire Fan
The NDT3055L n-type MOSFET was chosen since it has 3.3 V
gate drive, low on-resistance, and can handle 3.5 A of current.
Other MOSFETs can be substituted based on the system’s fan
drive requirements.
Figure 36 shows how a 2-wire fan can be connected to the
ADM1031. This circuit allows the speed of the 2-wire fan to be
measured even though the fan has no dedicated Tach signal. A
series RSENSE resistor in the fan circuit converts the fan
commutation pulses into a voltage. This is ac-coupled into the
ADM1031 through the 0.01 μF capacitor. On-chip signal
conditioning allows accurate monitoring of fan speed. For
typical notebook fans drawing approximately 170 mA, a 2 Ω
RSENSE value is suitable. For fans such as desktop or server fans
that draw more current, RSENSE can be reduced. The smaller
RSENSE is, the better, since more voltage is developed across the
fan, and the fan then spins faster.
+V
5V OR 12V
FAN
ADM1031
TACH/AIN
PWM_OUT
TACH
10k
Ω
TYPICAL
0.01
μF
3.3V
Q1
NDT3055L
RSENSE
(2W TYPICAL)
02402-036
Figure 36. Interfacing the ADM1031 to a 2-Wire Fan
Figure 37 shows a typical plot of the sensing waveform at the
TACH/AIN pin. The most important thing is that the negative-
going spikes are more than 250 mV in amplitude. This is the
case for most fans when RSENSE = 2 Ω. The value of RSENSE can be
reduced as long as the voltage spikes at the TACH/AIN pin are
greater than 250 mV. This allows fan speed to be reliably
determined.
02402-037
Figure 37. Fan Speed Sensing Waveform at TACH/AIN Pin
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| ADM1031ARQZ-R7 | 功能描述:IC SENSOR 2TEMP/FAN CTRL 16QSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 熱管理 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 功能:溫度監(jiān)控系統(tǒng)（傳感器） 傳感器類型:內(nèi)部和外部 感應(yīng)溫度:-40°C ~ 125°C，外部傳感器 精確度:±2.5°C 本地（最大值），±5°C 遠(yuǎn)程（最大值） 拓?fù)?ADC，比較器，寄存器庫 輸出類型:2 線 SMBus? 輸出警報:無 輸出風(fēng)扇:無 電源電壓:2.7 V ~ 5.5 V 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-8 供應(yīng)商設(shè)備封裝:SOT-23-8 包裝:Digi-Reel® 其它名稱:296-22675-6 |
| ADM1031ARQZ-REEL | 功能描述:板上安裝溫度傳感器 2 CH TDM PWM FAN CTRL IC RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor |
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