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| 型号： | ADT7476AARQZ-R |
| 厂商： | ON Semiconductor |
| 文件页数： | 25/66页 |
| 文件大小： | 945K |
| 描述： | IC REMOTE THERMAL CTLR 24QSOP |
| 产品变化通告： | MFG CHG Notification ADI to ON Semi QSOP 24ld Pkg (MSL) Change 17/Jun/2010 |
| 标准包装： | 2,500 |
| 系列： | dBCool® |
| 功能： | 风扇控制，温度监控器 |
| 传感器类型： | 内部和外部 |
| 感应温度： | -40°C ~ 125°C |
| 精确度： | ±2.5% |
| 拓扑： | ADC，比较器，风扇速度计数器，多路复用器，寄存器库 |
| 输出类型： | SMBus? |
| 输出警报： | 无 |
| 输出风扇： | 是 |
| 电源电压： | 3 V ~ 3.6 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 24-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 24-QSOP |
| 包装： | 带卷 (TR) |
| 其它名称： | ADT7476AARQZ-R-ND ADT7476AARQZ-ROSTR |
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ADT7476A
http://onsemi.com
25
below the thermal limit. Because the temperature for that
channel is measured only once for every monitoring cycle,
after THERM
asserts, it is guaranteed to remain low for at
least one monitoring cycle.
The THERM
pin can be configured to assert low, if the
Remote 1, local, or Remote 2 THERM
temperature limits
are exceeded by 0.25癈. The THERM
temperature limit
registers are at Register 0x6A, Register 0x6B, and
Register 0x6C, respectively. Setting Bits [5:7] of
Configuration Register 5 (0x7C) enables the THERM
output feature for the Remote 1, local, and Remote 2
temperature channels, respectively. Figure 34 shows how
the THERM
pin asserts low as an output in the event of a
critical overtemperature.
Figure 34. Asserting THERM
as an Output, Based on
Tripping THERM
Limits
THERM
LIMIT
MONITORING
CYCLE
TEMP
THERM
0.255C
THERM
LIMIT
An alternative method of disabling THERM
is to program
the THERM
temperature limit to 63癈 or less in Offset 64
mode, or 128癈 or less in twos complement mode; that is,
for THERM
temperature limit values less than 63癈 or
128癈, respectively, THERM
is disabled.
Enabling and Disabling THERM on individual Channels
THERM
can be enabled/disabled for individual or
combinations of temperature channels using Bits [7:5] of
Configuration Register 5 (0x7C).
THERM
Hysteresis
Setting Bit 0 of Configuration Register 7 (0x11) disables
THERM
hysteresis.
If THERM
hysteresis is enabled and THERM
is disabled
(Bit 2 of Configuration Register 4, 0x7D), the THERM
pin
does not assert low when a THERM
event occurs. If
THERM
hysteresis is disabled and THERM
is disabled
(Bit 2 of Configuration Register 4, 0x7D) and assuming the
appropriate pin is configured as THERM
), the THERM
pin
asserts low when a THERM
event occurs.
If THERM
and THERM
hysteresis are both enabled, the
THERM
output asserts as expected.
THERM
Operation in Manual Mode
In manual mode, THERM
events do not cause fans to go
to full speed, unless Bit 3 of Configuration Register 6
(0x10) is set to 1.
Additionally, Bit 3 of Configuration Register 4 (0x7D)
can be used to select the PWM speed on a THERM
event
(100% or maximum PWM).
Bit 2 in Configuration Register 4 (0x7D) can be set to
disable THERM
events from affecting the fans.
Fan Drive Using PWM Control
The ADT7476A 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 ADT7476A PWM frequency can be set to a selection
of low frequencies or a single high PWM frequency. The
low frequency options are used for 3-wire fans, while the
high frequency option is usually used with 4-wire fans.
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 and the input capacitance of the FET. Because a
10 kW (or greater) resistor must be used as a PWM pullup,
an FET with large input capacitance can cause the PWM
output to become distorted and adversely affect the fan
control range. This is a requirement only when using high
frequency PWM mode.
Typical notebook fans draw a nominal 170 mA, so SOT
devices can be used where board space is a concern. In
desktops, fans 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 should have a gate voltage drive,
V
GS
< 3.3 V, for direct interfacing to the PWM output pin.
The MOSFET should also have a low on resistance to ensure
that there is not a 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 35. Driving a 3-wire Fan Using an N-channel
MOSFET
ADT7476A
TACH
PWM
Q1
NDT3055L
12 V
FAN
3.3 V
12 V
12 V
10 kW
4.7 kW
10 kW
10 kW
TACH
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| ADT7476AARQZ-REEL | 功能描述:IC REMOTE THERMAL CTRLR 24-QSOP 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 |
| ADT7476AARQZ-REEL7 | 功能描述:IC REMOTE THERMAL CTRLR 24-QSOP 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 |
| ADT7476AARQZ-RL7 | 功能描述:板上安装温度传感器 MONITORS 5V/4 FANS 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 |
| ADT7476ARQH | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:dBCOOL Remote Thermal Controller and Voltage Monitor |
| ADT7476ARQH-REEL | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:dBCOOL Remote Thermal Controller and Voltage Monitor |
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