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| 型号： | LM80CIMTX-32 |
| 厂商： | National Semiconductor Corporation |
| 英文描述： | Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor |
| 中文描述： | 串行接口ACPI的兼容微处理器系统硬件监视器 |
| 文件页数： | 6/29页 |
| 文件大小： | 412K |
| 代理商： | LM80CIMTX-32 |
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Functional Description (Continued)
6.0 FAN INPUTS
Inputs are provided for signals from fans equipped with ta-
chometer outputs. These are logic-level inputs with an ap-
proximate threshold of V
+/2. Signal conditioning in the LM80
accommodates the slow rise and fall times typical of fan ta-
chometer outputs. The maximum input signal range is 0 to
V
+. In the event these inputs are supplied from fan outputs
which exceed 0 to V+, either resistive division or diode
clamping must be included to keep inputs within an accept-
able range, as shown in
Figure 7. R2 is selected so that it
does not develop excessive error voltage due to input leak-
age. R1 is selected based on R2 to provide a minimum input
of 2V and a maximum of V
+. R1 should be as low as possible
to provide the maximum possible input up to V
+ for best
noise immunity. Alternatively, use a shunt reference or zener
diode to clamp the input level.
If fans can be powered while the power to the LM80 is off,
the LM80 inputs will provide diode clamping. Limit input cur-
rent to the Input Current at Any Pin specification shown in the
ABSOLUTE MAXIMUM RATINGS section. In most cases,
open collector outputs with pull-up resistors inherently limit
this current. If this maximum current could be exceeded, ei-
ther a larger pull up resistor should be used or resistors con-
nected in series with the fan inputs.
The Fan Inputs gate an internal 22.5 kHz oscillator for one
period of the Fan signal into an 8-bit counter (maximum
count = 255). The default divisor, located in the VID/Fan Di-
visor Register, is set to 2 (choices are 1, 2, 4, and 8) provid-
ing a nominal count of 153 for a 4400 rpm fan with two
pulses per revolution. Typical practice is to consider 70% of
normal RPM a fan failure, at which point the count will be
219.
Determine the fan count according to:
Note that Fan 1 and Fan 2 Divisors are programmable via
the Fan Divisor/RST_OUT/OS Register.
FAN1 and FAN2 inputs can also be programmed to be level
sensitive digital inputs.
Fans that provide only one pulse per revolution would re-
quire a divisor set twice as high as fans that provide two
pulses, thus maintaining a nominal fan count of 153. There-
fore the divisor should be set to 4 for a fan that provides 1
pulse per revolution with a nominal RPM of 4400.
www.national.com
14
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM80CIMTX-5 | 功能描述:监控电路 RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel |
| LM80CIMTX-5/NOPB | 功能描述:监控电路 RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel |
| LM80CIMTX-52 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor |
| LM80EVAL | 功能描述:EVALUATION BOARD FOR LM80 RoHS:是 类别:编程器，开发系统 >> 评估演示板和套件 系列:PowerWise® 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:- 主要目的:电源管理，电池充电器 嵌入式:否 已用 IC / 零件:MAX8903A 主要属性:1 芯锂离子电池 次要属性:状态 LED 已供物品:板 |
| LM81 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor |
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