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| 型号： | MAX6645ABFAUB+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 12/17页 |
| 文件大小： | 208K |
| 描述： | IC CNTRLR FAN SPEED 10-UMAX |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 功能： | 风扇控制，温度监控器 |
| 传感器类型： | 内部和外部 |
| 感应温度： | -40°C ~ 125°C，外部传感器 |
| 精确度： | ±3.5°C 本地（最大），±3°C 远程（最大） |
| 拓扑： | ADC，PWM 发生器，转速计计数器 |
| 输出类型： | PWM |
| 输出警报： | 是 |
| 输出风扇： | 是 |
| 电源电压： | 3 V ~ 5.5 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 供应商设备封装： | 10-uMAX |
| 包装： | 带卷 (TR) |
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
12 ______________________________________________________________________________________
Effect of Series Resistance
Series resistance in a sense diode contributes addition-
al errors. For nominal diode currents of 10礎 and
100礎, change in the measured voltage is:
Since 1癈 corresponds to 198.6礦, series resistance
contributes a temperature offset of:
Assume that the diode being measured has a series
resistance of 3? The series resistance contributes an
offset of:
The effects of the ideality factor and series resistance
are additive. If the diode has an ideality factor of 1.008
and series resistance of 3? the total offset can be cal-
culated by adding error due to series resistance with
error due to ideality factor:
1.36癈 - 0.66癈 = 0.7癈
for a diode temperature of +60.7癈.
In this example, the effect of the series resistance and
the ideality factor partially cancel each other.
For best accuracy, the discrete transistor should be a
small-signal device with its collector connected to
base, and emitter connected to GND. Table 5 lists
examples of discrete transistors that are appropriate for
use with the MAX6643/MAX6644/MAX6645.
The transistor must have a relatively high forward volt-
age; otherwise, the ADC input voltage range can be vio-
lated. The forward voltage at the highest expected
temperature must be greater than 0.25V at 10礎, and at
the lowest expected temperature, the forward voltage
must be less than 0.95V at 100礎. Large power transis-
tors must not be used. Also, ensure that the base resis-
tance is less than 100? Tight specifications for forward
current gain (50 < ?<150, for example) indicate that the
manufacturer has good process controls and that the
devices have consistent V
BE
characteristics.
ADC Noise Filtering
The integrating ADC has inherently good noise rejec-
tion, especially of low-frequency signals such as
60Hz/120Hz power-supply hum. Micropower operation
places constraints on high-frequency noise rejection.
Lay out the PCB carefully with proper external noise fil-
tering for high-accuracy remote measurements in elec-
trically noisy environments.
Filter high-frequency electromagnetic interference
(EMI) at the DXP pins with an external 2200pF capaci-
tor connected between DXP, DXP1, or DXP2 and
ground. This capacitor can be increased to about
3300pF (max), including cable capacitance. A capaci-
tance higher than 3300pF introduces errors due to the
rise time of the switched-current source.
Twisted Pairs and Shielded Cables
For remote-sensor distances longer than 8in, or in par-
ticularly noisy environments, a twisted pair is recom-
mended. Its practical length is 6ft to 12ft (typ) before
noise becomes a problem, as tested in a noisy electron-
ics laboratory. For longer distances, the best solution is
a shielded twisted pair like that used for audio micro-
phones. For example, Belden 8451 works well for dis-
tances up to 100ft in a noisy environment. Connect the
twisted pair to DXP and GND and the shield to ground,
and leave the shields remote end unterminated. Excess
capacitance at DXP limits practical remote-sensor dis-
tances (see the Typical Operating Characteristics).
For very long cable runs, the cables parasitic capaci-
tance often provides noise filtering, so the recommend-
ed 2200pF capacitor can often be removed or reduced
in value. Cable resistance also affects remote-sensor
accuracy. A 1?series resistance introduces about
+1/2癈 error.
PCB Layout Checklist
1) Place the MAX6643/MAX6644/MAX6645 as close as
practical to the remote diode. In a noisy environment,
such as a computer motherboard, this distance can
be 4in to 8in or more, as long as the worst noise
sources (such as CRTs, clock generators, memory
buses, and ISA/PCI buses) are avoided.
2) Do not route the DXP lines next to the deflection coils
of a CRT. Also, do not route the traces across a fast
memory bus, which can easily introduce +30癈 error,
even with good filtering. Otherwise, most noise
sources are fairly benign.
3
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX6645BAFAUB | 制造商:Maxim Integrated Products 功能描述:AUTOMATIC PWM FAN-SPEED CONTROLLERS WITH OVER - Rail/Tube |
| MAX6645BAFAUB+ | 功能描述:马达/运动/点火控制器和驱动器 Automatic PWM Fan Speed Controller RoHS:否 制造商:STMicroelectronics 产品:Stepper Motor Controllers / Drivers 类型:2 Phase Stepper Motor Driver 工作电源电压:8 V to 45 V 电源电流:0.5 mA 工作温度:- 25 C to + 125 C 安装风格:SMD/SMT 封装 / 箱体:HTSSOP-28 封装:Tube |
| MAX6645BAFAUB+T | 功能描述:马达/运动/点火控制器和驱动器 Automatic PWM Fan Speed Controller RoHS:否 制造商:STMicroelectronics 产品:Stepper Motor Controllers / Drivers 类型:2 Phase Stepper Motor Driver 工作电源电压:8 V to 45 V 电源电流:0.5 mA 工作温度:- 25 C to + 125 C 安装风格:SMD/SMT 封装 / 箱体:HTSSOP-28 封装:Tube |
| MAX6646MUA | 功能描述:板上安装温度传感器 RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
| MAX6646MUA+ | 功能描述:板上安装温度传感器 145C SMBus-Comp Remote/Local Sensor RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
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