- 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)： | 30/80頁 |
| 文件大?。?/td> | 844K |
| 描述： | IC REMOTE THERMAL MONITOR 24QSOP |
| 標(biāo)準(zhǔn)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頁當(dāng)前第30頁第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
30
TACH Measurement Overview
The fan counter does not count the fan TACH output
pulses directly because the fan speed could be less than 1000
RPM, and it takes several seconds to accumulate a
reasonably large and accurate count. Instead, the period of
the fan revolution is measured by gating an onchip 78 kHz
oscillator into the input of a 16bit counter for N periods of
the fan TACH output (see Figure 21) so the accumulated
count is actually proportional to the fan tachometer period
and inversely proportional to the fan speed. N, the number
of pulses counted, is determined by the settings of the TACH
pulses per revolution register (0x7B). This register contains
two bits for each fan, allowing one, two (default), three, or
four TACH pulses to be counted.
Figure 21. Fan Speed Measurement
Fan Speed Measurement Registers
The fan tachometer registers are 16bit values consisting
of a 2byte read from the NCT7491.
" Register 0x28, TACH1 Low Byte
" Register 0x29, TACH1 High Byte
" Register 0x2A, TACH2 Low Byte
" Register 0x2B, TACH2 High Byte
" Register 0x2C, TACH3 Low Byte
" Register 0x2D, TACH3 High Byte
" Register 0x2E, TACH4 Low Byte
" Register 0x2F, TACH4 High Byte
Reading Fan Speed from the NCT7491
The measurement of fan speeds involves a 2register 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 12.82 us period clocks (78 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 16bit fan tachometer reading of
0xFFFF indicates that either the fan has stalled or is running
very slowly (<100 RPM).
Because the actual fan TACH period is being measured,
falling below a fan TACH limit by 1 sets the appropriate
status bit and can be used to generate an SMBALERT
Fan TACH Limit Registers
The fan TACH limit registers are 16bit 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. When set, the FAST bit (Bit 3) of Configuration
Register 3 (0x78), updates the fan TACH readings every
250 ms.
DC Bits
If any of the fans are not being driven by a PWM channel
but are powered directly from 5.0 V or 12 V, their associated
dc bit in Configuration Register 3 (0x78) should be set. This
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(zhǔn)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(fēng)格: 封裝 / 箱體: 設(shè)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(zhǔn)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(fēng)格: 封裝 / 箱體: 設(shè)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(zhǔn)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(fēng)格: 封裝 / 箱體: 設(shè)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(fù)。