收藏本站
ADT7473
THERM LIMIT
0.25 5 C
12 V
12 V
THERM LIMIT
TEMP
TACH
10 k W
4.7 k W
10 k W
12 V
FAN
THERM
MONITORING
CYCLE
ADT7473/
ADT7473 ? 1
PWM
3.3 V
10 k W
Q1
NDT3055L
Figure 34. Asserting THERM as an Output, Based on
Tripping THERM Limits
Fan Drive Using PWM Control
The ADT7473/ADT7473 ? 1 uses pulse-width modulation
(PWM) to control fan speed. This relies on varying the duty
cycle (or on/off ratio) of a square wave applied to the fan to
vary the fan speed. The external circuitry required to drive a
fan using PWM control is extremely simple. For 4-wire fans,
the PWM drive might need only a pullup resistor. In many
cases, the 4-wire fan PWM input has a built-in pullup resistor.
The ADT7473/ADT7473 ? 1 PWM frequency can be set to
a selection of low frequencies or a single high PWM
frequency. The low frequency options are usually used for
3-wire fans, while the high frequency option is usually used
with 4-wire fans.
Note that care must be taken to ensure that the PWM or
TACH pins are not connected to a pullup supply greater than
3.6 V.
Figure 35. Driving a 3-wire Fan Using
an N-channel MOSFET
Figure 35 uses a 10 k W pullup resistor for the TACH
signal. This assumes that the TACH signal is an
open-collector from the fan. In all cases, the TACH signal
from the fan must be kept below 3.6 V maximum to prevent
damaging the ADT7473/ADT7473 ? 1. If uncertain as to
whether the fan used has an open-collector or totem pole
TACH output, use one of the input signal conditioning
circuits shown in the Fan Speed Measurement section.
Figure 36 shows a fan drive circuit using an NPN
transistor such as a general-purpose MMBT2222. While
these devices are inexpensive, they tend to have much lower
current handling capabilities and higher on resistance than
MOSFETs. When choosing a transistor, care should be taken
to ensure that it meets the fan’s current requirements.
Ensure that the base resistor is chosen so that the transistor
is saturated when the fan is powered on.
Many fans have internal pullups connected to the
12 V
12 V
TACH/PWM pins to a supply greater than 3.6 V. Clamping
or dividing down the voltage on these pins must be done
where necessary. Clamping these pins with a Zener diode
can also help prevent back-EMF related noise from being
coupled into the system.
For 3-wire fans, a single N-channel MOSFET is the only
drive device 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;
TACH
ADT7473/
ADT7473 ? 1
PWM
10 k W
10 k W
TACH
4.7 k W
3.3 V
665 W
12 V
FAN
Q1
MMBT2222
therefore, SOT devices can be used where board space is a
concern. In desktops, fans can typically draw 250 mA to
300 mA each. If you drive several fans in parallel from a
single PWM output or drive larger server fans, the MOSFET
must handle the higher current requirements. The only other
stipulation is that the MOSFET have a gate voltage drive,
V GS < 3.3 V, for direct interfacing to the PWM output. The
MOSFET should also have a low on resistance to ensure that
there is not significant voltage drop across the FET, which
would reduce the voltage applied across the fan and,
therefore, the maximum operating speed of the fan.
Figure 35 shows how to drive a 3 wire fan using PWM
control.
Figure 36. Driving a 3-wire Fan Using
an NPN Transistor
Because 4-wire fans are powered continuously, the fan
speed is not switched on or off as with previous PWM
driven/powered fans. This enables it to perform better than
3-wire fans, especially for high frequency applications.
Figure 37 shows a typical drive circuit for 4-wire fans. As
the PWM input on 4-wire fans is usually internally pulled up
to a voltage greater than 3.6 V (the maximum voltage
allowed on the ADT7473/ADT7473 ? 1 PWM output), the
PWM output should be clamped to 3.3 V using a Zener
diode.
http://onsemi.com
25
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
ADT7475EBZEVB BOARD EVALUATION FOR ADT7475
ADT7476EBZEVB BOARD EVALUATION FOR ADT7476
ADT7490ZEVB BOARD EVALUATION FOR ADT7490
ADZS-21262-1-EZEXT BOARD DAUGHTER FOR ADSP-21262
ADZS-BF-EZEXT-1 BOARD DAUGHTER ADSP-BF533/561KIT
ADZS-BFAV-EZEXT BOARD DAUGHT ADSP-BF533,37,61KIT
ADZS-BFSHUSB-EZEXT BOARD DAUGHTER EZ EXTENDER
ADZS-BRKOUT-EX3 ADZS-BRKOUT-EX3
相关代理商/技术参数
ADT7475 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:dBCOOL Remote Thermal Monitor and Fan Controller
ADT7475_1110 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:dbCOOL Remote Thermal Monitor and Fan Controller
ADT7475ARQZ 功能描述:马达/运动/点火控制器和驱动器 MLTCH TDM FAN CTRLR RoHS:否 制造商:STMicroelectronics 产品:Stepper Motor Controllers / Drivers 类型:2 Phase Stepper Motor Driver 工作电源电压:8 V to 45 V 电源电流:0.5 mA 工作温度:- 25 C to + 125 C 安装风格:SMD/SMT 封装 / 箱体:HTSSOP-28 封装:Tube
ADT7475ARQZ-REEL 功能描述:板上安装温度传感器 MULTICH TDM FAN CTRL RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor
ADT7475ARQZ-REEL7 功能描述:IC REMOTE THERMAL CTRLR 16QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 热管理 系列:dBCool® 标准包装:1 系列:- 功能:温度监控系统（传感器） 传感器类型:内部和外部 感应温度:-40°C ~ 125°C，外部传感器 精确度:±2.5°C 本地（最大值），±5°C 远程（最大值） 拓扑:ADC，比较器，寄存器库 输出类型:2 线 SMBus? 输出警报:无 输出风扇:无 电源电压:2.7 V ~ 5.5 V 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:SOT-23-8 供应商设备封装:SOT-23-8 包装:Digi-Reel® 其它名称:296-22675-6
ADT7475ARQZ-RL7 功能描述:板上安装温度传感器 MLTCH TDM FAN CTRLR RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor
ADT7475EBZEVB 功能描述:BOARD EVALUATION FOR ADT7475 RoHS:否 类别:编程器，开发系统 >> 过时/停产零件编号 系列:dBCool® 标准包装:1 系列:- 传感器类型:CMOS 成像，彩色（RGB） 传感范围:WVGA 接口:I²C 灵敏度:60 fps 电源电压:5.7 V ~ 6.3 V 嵌入式:否 已供物品:成像器板 已用 IC / 零件:KAC-00401 相关产品:4H2099-ND - SENSOR IMAGE WVGA COLOR 48-PQFP4H2094-ND - SENSOR IMAGE WVGA MONO 48-PQFP
ADT7476 制造商:AD 制造商全称:Analog Devices 功能描述:dBCool Remote Thermal Controller and Voltage Monitor