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參數(shù)資料
| 型號： | ADT7473ARQZ-1REEL7 |
| 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), 2.50Cel, RECTANGULAR, SURFACE MOUNT |
| 封裝： | ROHS COMPLIANT, MO-137AB, QSOP-16 |
| 文件頁數(shù)： | 21/72頁 |
| 文件大?。?/td> | 1494K |
| 代理商： | ADT7473ARQZ-1REEL7 |
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ADT7473/ADT7473-1
Rev. C | Page 28 of 72
Reading Fan Speed from the ADT7473/ADT7473-1
The measurement of fan speeds involves a 2-register read for
each measurement. The low byte should be read first. This
causes the high byte to be frozen until both high and low byte
registers have been read, preventing erroneous TACH readings.
The fan tachometer reading registers report back the number
of 11.11 μs period clocks (90 kHz oscillator) gated to the fan
speed counter, from the rising edge of the first fan TACH pulse
to the rising edge of the third fan TACH pulse (assuming two
pulses per revolution are being counted). Because the device is
essentially measuring the fan TACH period, the higher the
count value, the slower the fan is actually running. A 16-bit
fan tachometer reading of 0xFFFF indicates either the fan has
stalled or is running very slowly (<100 RPM).
High Limit > Comparison Performed
Because the actual fan TACH period is measured, falling below
a fan TACH limit by 1 sets the appropriate status bit and can be
used to generate an SMBALERT.
Measuring Fan TACH
When the ADT7473/ADT7473-1 starts up, TACH measure-
ments are locked. In effect, an internal read of the low byte has
been made for each TACH input. The net result of this is that all
TACH readings are locked until the high byte is read from the
corresponding TACH registers. All TACH related interrupts are
also ignored until the appropriate high byte is read.
Once the corresponding high byte has been read, TACH
measurements are unlocked and interrupts are processed as
normal.
Fan TACH Limit Registers
The fan TACH limit registers are 16-bit values consisting of
two bytes.
Register 0x54, TACH1 Minimum Low Byte = 0xFF default
Register 0x55, TACH1 Minimum High Byte = 0xFF default
Register 0x56, TACH2 Minimum Low Byte = 0xFF default
Register 0x57, TACH2 Minimum High Byte = 0xFF default
Register 0x58, TACH3 Minimum Low Byte = 0xFF default
Register 0x59, TACH3 Minimum High Byte = 0xFF default
Register 0x5A, TACH4 Minimum Low Byte = 0xFF default
Register 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 (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, their 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. For optimal results, the associated dc bit
should always be set when using 4-wire fans.
Calculating Fan Speed
Assuming a fan has two pulses per revolution (and two pulses
per revolution being measured), fan speed is calculated by
Fan Speed (RPM) = (90,000 × 60)/Fan TACH Reading
where Fan TACH Reading is the 16-bit fan tachometer reading.
Example
TACH1 High Byte (Register 0x29) = 0x17
TACH1 Low Byte (Register 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 one, two, three, or four
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 (Register 0x7B) for each fan.
Alternatively, this register can be used to determine the number
or pulses per revolution output by a given fan. By plotting fan
speed measurements at a 100% speed with different pulses per
revolution setting, the smoothest graph with the lowest ripple
determines the correct pulses per revolution value.
TACH Pulses per Revolution Register
Bits [1:0] Fan 1 default = 2 pulses per revolution
Bits [3:2] Fan 2 default = 2 pulses per revolution
Bits [5:4] Fan 3 default = 2 pulses per revolution
Bits [7:6] Fan 4 default = 2 pulses per revolution
00 = 1 pulse per revolution
01 = 2 pulses per revolution
10 = 3 pulses per revolution
11 = 4 pulses per revolution
Fan Spin-Up
The ADT7473/ADT7473-1 has a unique fan spin-up function.
It spins the fan at 100% PWM duty cycle until two TACH pulses
are detected on the TACH input. Once two TACH pulses are
detected, the PWM duty cycle goes to the expected running
value, for example, 33%. The advantage is that fans have
different spin-up characteristics and take different times to
overcome inertia. The ADT7473/ADT7473-1 runs the fans just
fast enough to overcome inertia and is quieter on spin-up than
fans programmed for a given spin-up time.
Fan Startup Timeout
To prevent the generation of false interrupts as a fan spins up
(because it is below running speed), the ADT7473/ADT7473-1
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PDF描述 |
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| ADT7473ARQZ-1REEL | DIGITAL TEMP SENSOR-SERIAL, 8BIT(s), 2.50Cel, RECTANGULAR, SURFACE MOUNT |
| ADT7476ARQZ-REEL7 | DIGITAL TEMP SENSOR-SERIAL, 10BIT(s), 2.50Cel, RECTANGULAR, SURFACE MOUNT |
| ADT7482ARMZ-RL | DIGITAL TEMP SENSOR-SERIAL, 11BIT(s), 2.5Cel, SQUARE, SURFACE MOUNT |
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| ADT7485ARMZ-REEL | DIGITAL TEMP SENSOR-SERIAL, 16BIT(s), 1Cel, SQUARE, SURFACE MOUNT |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADT7473ARQZ-1RL | 功能描述:板上安裝溫度傳感器 FAN CNTRLR/INT MON RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準確性:+/- 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: 安裝風格: 封裝 / 箱體: 設備功能:Temperature and Humidity Sensor |
| ADT7473ARQZ-REEL | 功能描述:板上安裝溫度傳感器 FAN CNTRLR/INT MON RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準確性:+/- 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: 安裝風格: 封裝 / 箱體: 設備功能:Temperature and Humidity Sensor |
| ADT7473ARQZ-REEL7 | 功能描述:IC REMOTE THERMAL CTRLR 16QSOP RoHS:是 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(jiān)控系統(tǒng)（傳感器） 傳感器類型:內(nèi)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 |
| ADT7473ARQZ-RL7 | 功能描述:板上安裝溫度傳感器 FAN CNTRLR/INT MON RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準確性:+/- 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: 安裝風格: 封裝 / 箱體: 設備功能:Temperature and Humidity Sensor |
| ADT7473EBZEVB | 功能描述:EVALUATION BOARD ADT7473 制造商:on semiconductor 系列:* 零件狀態(tài):在售 標準包裝:1 |
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