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參數資料
| 型號： | ADT7460 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | dB COOL?? Remote Thermal Controller and Fan Controller |
| 中文描述： | 分貝很酷吧？？遠程熱控制器和風扇控制器 |
| 文件頁數： | 26/48頁 |
| 文件大小： | 695K |
| 代理商： | ADT7460 |
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REV. 0
–26–
ADT7460
Fan TACH Limit Registers
The Fan TACH Limit Registers are 16-bit values consisting of
two bytes.
Reg. 0x54
TACH1 Minimum Low Byte
= 0xFF default
Reg. 0x55
TACH1 Minimum High Byte
= 0xFF default
Reg. 0x56
TACH2 Minimum Low Byte
= 0xFF default
Reg. 0x57
TACH2 Minimum High Byte
= 0xFF default
Reg. 0x58
TACH3 Minimum Low Byte
= 0xFF default
Reg. 0x59
TACH3 Minimum High Byte
= 0xFF default
Reg. 0x5A
TACH4 Minimum Low Byte
= 0xFF default
Reg. 0x5B
TACH4 Minimum High Byte
= 0xFF default
Fan Speed Measurement Rate
The Fan TACH readings are normally updated once every
second.
The FAST bit (Bit 3) of Configuration Register 3 (Reg. 0x78),
when set, updates the Fan TACH readings every 250 ms.
If any of the fans are not being driven by a PWM channel but
are powered directly from 5 V or 12 V, its associated dc bit in
Configuration Register 3 should be set. This allows TACH
readings to be taken on a continuous basis for fans connected
directly to a dc source.
Calculating Fan Speed
Assuming a fan with a two pulses/revolution (and two pulses/rev
being measured) fan speed is calculated by:
Fan Speed (RPM) = (90,000 60)/Fan Tach Reading
where:
Fan Tach Reading
= 16-bit Fan Tachometer Reading
Example:
TACH1 High Byte (Reg 0x29) = 0x17
TACH1 Low Byte (Reg 0x28) = 0xFF
What is Fan 1 speed in RPM
Fan 1 TACH reading = 0x17FF = 6143 decimal
RPM = (f 60)/Fan 1 TACH reading
RPM = (90000 60)/6143
Fan Speed = 879 RPM
Fan Pulses Per Revolution
Different fan models can output either 1, 2, 3, or 4 TACH pulses
per revolution. Once the number of fan TACH pulses has been
determined, it can be programmed into the Fan Pulses Per
Revolution Register (Reg. 0x7B) for each fan. Alternatively, this
register can be used to determine the number or pulses/revolution
output by a given fan. By plotting fan speed measurements at
100% speed with different pulses/rev setting, the smoothest graph
with the lowest ripple determines the correct pulses/rev value.
Fan Pulses Per Revolution Register
<1:0> FAN1 default = 2 pulses per rev.
<3:2> FAN2 default = 2 pulses per rev.
<5:4> FAN3 default = 2 pulses per rev.
<7:6> FAN4 default = 2 pulses per rev.
00 = 1 pulse per rev.
01 = 2 pulses per rev.
10 = 3 pulses per rev.
11 = 4 pulses per rev.
2-Wire Fan Speed Measurements
The ADT7460 is capable of measuring the speed of 2-wire fans,
i.e., fans without TACH outputs. To do this, the fan must be
interfaced as shown in the Fan Drive Circuitry section of the
data sheet. In this case, the TACH inputs need to be repro-
grammed as analog inputs, AIN.
CONFIGURATION REGISTER 2 (REG. 0x73)
Bit 3 (AIN4) = 1,
Pin 9 is reconfigured to measure the speed
of a 2-wire fan using an external sensing resistor and coupling
capacitor.
Bit 2 (AIN3) = 1,
Pin 4 is reconfigured to measure the speed
of a 2-wire fan using an external sensing resistor and coupling
capacitor.
Bit 1 (AIN2) = 1,
Pin 7 is reconfigured to measure the speed
of a 2-wire fan using an external sensing resistor and coupling
capacitor.
Bit 0 (AIN1) = 1,
Pin 6 is reconfigured to measure the speed
of a 2-wire fan using an external sensing resistor and coupling
capacitor.
AIN Switching Threshold
Having configured the TACH inputs as AIN inputs for 2-wire
measurements, you can select the sensing threshold for the
AIN signal.
CONFIGURATION REGISTER 4 (REG. 0x7D)
<3:2> AINL
These two bits define the input threshold for
2-wire fan speed measurements.
00 = 20 mV
01 = 40 mV
10 = 80 mV
11 = 130 mV
Fan Spin-Up
The ADT7460 has a unique fan spin-up function. It will spin
the fan at 100% PWM duty cycle until two TACH pulses are
detected on the TACH input. Once two pulses have been
detected, the PWM duty cycle will go to the expected running
value, e.g., 33%. The advantage of this is that fans have dif-
ferent spin-up characteristics and will take different times to
overcome inertia. The ADT7460 just runs the fans fast enough
to overcome inertia and will be quieter on spin-up than fans
programmed to spin-up for a given spin-up time.
Fan Start-Up Timeout
To prevent false interrupts being generated as a fan spins up
(since it is below running speed), the ADT7460 includes a Fan
Start-Up Timeout function. This is the time limit allowed for two
TACH pulses to be detected on spin-up. For example, if 2 seconds
Fan Start-Up Timeout is chosen and no TACH pulses occur
within 2 seconds of the start of spin-up, a fan fault is detected
and flagged in the Interrupt Status Registers.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| ADT7460ARQ | 功能描述:IC REMOTE THRML/FAN CTRLR 16QSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 熱管理 系列:dBCool® 標準包裝:1 系列:- 功能:溫度監控系統（傳感器） 傳感器類型:內部和外部 感應溫度:-40°C ~ 125°C，外部傳感器 精確度:±2.5°C 本地（最大值），±5°C 遠程（最大值） 拓撲:ADC，比較器，寄存器庫 輸出類型:2 線 SMBus? 輸出警報:無 輸出風扇: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 供應商設備封裝:SOT-23-8 包裝:Digi-Reel® 其它名稱:296-22675-6 |
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| ADT7460ARQ-REEL7 | 功能描述:IC SENSOR TEMP FAN-CTRL 16QSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 熱管理 系列:dBCool® 標準包裝:1 系列:- 功能:溫度監控系統（傳感器） 傳感器類型:內部和外部 感應溫度:-40°C ~ 125°C，外部傳感器 精確度:±2.5°C 本地（最大值），±5°C 遠程（最大值） 拓撲:ADC，比較器，寄存器庫 輸出類型:2 線 SMBus? 輸出警報:無 輸出風扇: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 供應商設備封裝:SOT-23-8 包裝:Digi-Reel® 其它名稱:296-22675-6 |
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| ADT7460ARQZ-R7 | 制造商:ON Semiconductor 功能描述:Temp Sensor Digital Serial (3-Wire) 16-Pin QSOP T/R |
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