- 您現(xiàn)在的位置：買賣IC網(wǎng) > Datasheet目錄45 > NCT7491RQR2G (ON Semiconductor)IC REMOTE THERMAL MONITOR 24QSOP Datasheet資料下載
參數(shù)資料
| 型號： | NCT7491RQR2G |
| 廠商： | ON Semiconductor |
| 文件頁數(shù)： | 31/80頁 |
| 文件大?。?/td> | 844K |
| 描述： | IC REMOTE THERMAL MONITOR 24QSOP |
| 標準包裝： | 2,500 |
| 系列： | * |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁當前第31頁第32頁第33頁第34頁第35頁第36頁第37頁第38頁第39頁第40頁第41頁第42頁第43頁第44頁第45頁第46頁第47頁第48頁第49頁第50頁第51頁第52頁第53頁第54頁第55頁第56頁第57頁第58頁第59頁第60頁第61頁第62頁第63頁第64頁第65頁第66頁第67頁第68頁第69頁第70頁第71頁第72頁第73頁第74頁第75頁第76頁第77頁第78頁第79頁第80頁
NCT7491
http://onsemi.com
31
allows TACH readings to be taken on a continuous basis for
fans connected directly to a dc source. For 4wire fans, once
high frequency mode is enabled, the dc bits do not need to
be set because this is automatically done internally.
If any tach channels are not connected then the associated
DC bit should be set for that fan.
Calculating Fan Speed From Register Values
Assuming a fan with a two pulses per revolution, and with
the NCT7491 programmed to measure two pulses per
revolution, fan speed is calculated by Fan Speed (RPM) =
(78,000 x 60)/Fan TACH Reading where Fan TACH
Reading is the 16bit 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 x 60)/Fan 1 TACH Reading
RPM = (78000 x 60)/6143
Fan Speed = 762 RPM
Fan Pulses per Revolution
Different fan models can output 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
TACH pulses per revolution 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 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 0x7B
" Bits [1:0], FAN1 default = 2 pulses per revolution
" Bits [3:2], FAN2 default = 2 pulses per revolution
" Bits [5:4], FAN3 default = 2 pulses per revolution
" Bits [7:6], FAN4 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 SpinUp
The NCT7491 has a unique fan spinup function. It spins
the fan at 100% PWM duty cycle until two TACH pulses are
detected on the TACH input. When two TACH pulses have
been detected, the PWM duty cycle goes to the expected
running value, for example, 33%. The advantage of this is
that fans have different spinup characteristics and take
different times to overcome inertia. The NCT7491 runs the
fans just fast enough to overcome inertia and is quieter on
spinup than fans programmed to spin up for a given
spinup time.
Fan Startup Timeout
To prevent the generation of false interrupts as a fan spins
up, because the fan is below running speed, the NCT7491
includes a fan startup timeout function. During this time, the
NCT7491 looks for two TACH pulses. If two TACH pulses
are not detected, an interrupt is generated. Fan startup
timeout can be disabled by setting Bit 3 (FSPDIS) of
Configuration Register 7 (0x11).
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| NCT75MNR2G | IC SENSOR TEMP DGTL 8DFN |
| NCV8881PWR2G | IC REG TRPL BUCK/LINEAR 16SOIC |
| NE1617ADS,112 | IC TEMP MONITOR 16SSOP |
| NE1619DS,118 | IC TEMP MONITOR 16SSOP |
| NIS5112D1R2G | IC ELECTRONIC FUSE HOTSWAP 8SOIC |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| NCT75DMR2G | 功能描述:板上安裝溫度傳感器 2-Channel Digital Thermometer w/ Alarm 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 |
| NCT75DR2G | 功能描述:板上安裝溫度傳感器 2-Channel Digital Thermometer w/ Alarm 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 |
| NCT75MNR2G | 功能描述:板上安裝溫度傳感器 HAS2MONOJLCC84SPACE 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 |
| NCT7717U TR | 制造商:Nuvoton Technology Corp 功能描述:SMBUS INTERFACE TEMP. SENSOR W 制造商:Nuvoton Technology Corp 功能描述:IC SMBUS TEMP SENSOR 8MSOP |
| NCT7718W TR | 制造商:Nuvoton Technology Corp 功能描述:IC SMBUS TEMP SENSOR 8MSOP |
發(fā)布緊急采購，3分鐘左右您將得到回復。