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EMC1182-1-AC3-TR 参数 Datasheet PDF下载

EMC1182-1-AC3-TR图片预览
型号: EMC1182-1-AC3-TR
PDF下载: 下载PDF文件 查看货源
内容描述: 双通道1C温度传感器,带有beta补偿和1.8V的SMBus通信 [Dual Channel 1C Temperature Sensor with Beta Compensation and 1.8V SMBus Communications]
分类和应用: 传感器温度传感器通信
文件页数/大小: 48 页 / 565 K
品牌: SMSC [ SMSC CORPORATION ]
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Dual Channel 1°C Temperature Sensor with Beta Compensation and 1.8V SMBus Communications  
Datasheet  
in. The ALERT / THERM2 pin will remain asserted until all temperatures drop below the corresponding  
high limit minus the Therm Hysteresis value.  
When the ALERT / THERM2 pin is asserted in comparator mode, the corresponding high limit status  
bits will be set. Reading these bits will not clear them until the ALERT / THERM2 pin is deasserted.  
Once the ALERT pin is deasserted, the status bits will be automatically cleared.  
The MASK_ALL bit will not block the ALERT / THERM2 pin in this mode; however, the individual  
channel masks (see Section 6.10) will prevent the respective channel from asserting the ALERT/  
THERM2 pin.  
5.6  
Temperature Measurement  
The EMC1182 can monitor the temperature of one externally connected diode.  
The device contains programmable High, Low, and Therm limits for all measured temperature  
channels. If the measured temperature goes below the Low limit or above the High limit, the ALERT  
pin can be asserted (based on user settings). If the measured temperature meets or exceeds the  
Therm Limit, the THERM pin is asserted unconditionally, providing two tiers of temperature detection.  
5.6.1  
Beta Compensation  
The EMC1182 is configured to monitor the temperature of basic diodes (e.g., 2N3904) or CPU thermal  
diodes. For External Diode 1, it automatically detects the type of external diode (CPU diode or diode  
connected transistor) and determines the optimal setting to reduce temperature errors introduced by  
beta variation. Compensating for this error is also known as implementing the transistor or BJT model  
for temperature measurement.  
For discrete transistors configured with the collector and base shorted together, the beta is generally  
sufficiently high such that the percent change in beta variation is very small. For example, a 10%  
variation in beta for two forced emitter currents with a transistor whose ideal beta is 50 would contribute  
approximately 0.25°C error at 100°C. However for substrate transistors where the base-emitter junction  
is used for temperature measurement and the collector is tied to the substrate, the proportional beta  
variation will cause large error. For example, a 10% variation in beta for two forced emitter currents  
with a transistor whose ideal beta is 0.5 would contribute approximately 8.25°C error at 100°C.  
5.6.2  
5.6.3  
Resistance Error Correction (REC)  
Parasitic resistance in series with the external diodes will limit the accuracy obtainable from  
temperature measurement devices. The voltage developed across this resistance by the switching  
diode currents cause the temperature measurement to read higher than the true temperature.  
Contributors to series resistance are PCB trace resistance, on die (i.e. on the processor) metal  
resistance, bulk resistance in the base and emitter of the temperature transistor. Typically, the error  
caused by series resistance is +0.7°C per ohm. The EMC1182 automatically corrects up to 100 ohms  
of series resistance.  
Programmable External Diode Ideality Factor  
The EMC1182 is designed for external diodes with an ideality factor of 1.008. Not all external diodes,  
processor or discrete, will have this exact value. This variation of the ideality factor introduces error in  
the temperature measurement which must be corrected for. This correction is typically done using  
programmable offset registers. Since an ideality factor mismatch introduces an error that is a function  
of temperature, this correction is only accurate within a small range of temperatures. To provide  
maximum flexibility to the user, the EMC1182 provides a 6-bit register for each external diode where  
the ideality factor of the diode used is programmed to eliminate errors across all temperatures.  
SMSC EMC1182  
21  
Revision 1.0 (07-11-13)  
DATASHEET