参数资料
| 型号： | ADT7475EBZEVB |
| 厂商： | ON Semiconductor |
| 文件页数： | 13/58页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION FOR ADT7475 |
| 产品变化通告： | MFG CHG Notification ADI to ON Semi |
| 标准包装： | 1 |
| 系列： | dBCool® |
| 类型： | 温度传感器 |
| 适用于相关产品： | ADT7475 |
| 所含物品： | 评估板 |
| 其它名称： | EVAL-ADT7475EB EVAL-ADT7475EB-ND |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页当前第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页第33页第34页第35页第36页第37页第38页第39页第40页第41页第42页第43页第44页第45页第46页第47页第48页第49页第50页第51页第52页第53页第54页第55页第56页第57页第58页
ADT7475
Temperature Measurement Method
Local Temperature Measurement
The ADT7475 contains an on-chip band gap temperature
sensor whose output is digitized by the on-chip, 10-bit ADC.
The 8-bit MSB temperature data is stored in the temperature
registers (0x25, 0x26, and 0x27). Because both positive and
negative temperatures can be measured, the temperature
data is stored in Offset 64 format or twos complement
format, as shown in Table 11 and Table 12.
Theoretically, the temperature sensor and ADC can
measure temperatures from ? 128 ° C to +127 ° C (or ? 64 ° C to
+191 ° C in the extended temperature range) with a
resolution of 0.25 ° C.
However, this exceeds the operating temperature range of
the device, so local temperature measurements outside the
ADT7475 operating temperature range are not possible.
Remote Temperature Measurement
The ADT7475 can measure the temperature of two remote
diode sensors or diode-connected transistors connected to
Pin 10 and Pin 11 or to Pin 12 and Pin 13.
The forward voltage of a diode or diode-connected
transistor operated at a constant current exhibits a negative
temperature coefficient of about –2 mV/ ° C. Because the
absolute value of V BE varies from device to device and
individual calibration is required to null this out, the
technique is unsuitable for mass production.
CPU
THERMDA
D+
I
N × I
I BIAS
V DD
V OUT+
REMOTE
SENSING
TRANSISTOR
THERMDC
D ?
BIAS
To ADC
V OUT ?
DIODE
LOW-PASS FILTER
f C = 65 kHz
Figure 20. Signal Conditioning for Remote Diode Temperature Sensors
The technique used in the ADT7475 is to measure the
change in V BE when the device is operated at two different
currents.
To measure D V BE , the sensor is switched between
operating currents of I and N × I. The resulting waveform is
passed through a 65 kHz low-pass filter to remove noise and
This is given by:
where:
D V BE + kT q
ln(N)
(eq. 1)
to a chopper stabilized amplifier that performs the functions
of amplification and rectification of the waveform to
produce a dc voltage proportional to D V BE . This voltage is
measured by the ADC to give a temperature output in 10-bit,
k is Boltzmann’s constant.
q is the charge on the carrier.
T is the absolute temperature in Kelvins.
N is the ratio of the two currents.
Figure 20 shows the input signal conditioning used to
measure the output of a remote temperature sensor. This
figure shows the external sensor as a substrate transistor,
provided for temperature monitoring on some
microprocessors. It could also be a discrete transistor such
as a 2N3904/2N3906.
If a discrete transistor is used, the collector is not grounded
and should be linked to the base. If a PNP transistor is used,
the base is connected to the D ? input and the emitter to the
D+ input. If an NPN transistor is used, the emitter is
connected to the D ? input and the base to the D+ input.
Figure 21 and Figure 22 show how to connect the ADT7475
to an NPN or PNP transistor for temperature measurement.
To prevent ground noise from interfering with the
measurement, the more negative terminal of the sensor is not
referenced to ground but is biased above ground by an
twos complement format. To further reduce the effects of
noise, digital filtering is performed by averaging the results
of 16 measurement cycles.
A remote temperature measurement takes nominally
38 ms. The results of remote temperature measurements are
stored in 10-bit, twos complement format, as shown in
Table 11. The extra resolution for the temperature
measurements is held in the Extended Resolution Register 2
(0x77). This gives temperature readings with a resolution of
0.25 ° C.
Noise Filtering
For temperature sensors operating in noisy environments,
previous practice was to place a capacitor across the D+ pin
and D ? pin to help combat the effects of noise. However,
large capacitance’s affect the accuracy of the temperature
measurement, leading to a recommended maximum
capacitor value of 1,000 pF.
This capacitor reduces the noise but does not eliminate it.
Sometimes, this sensor noise is a problem in a very noisy
environment. In most cases, a capacitor is not required
internal diode at the D input.
http://onsemi.com
13
相关PDF资料 |
PDF描述 |
|---|---|
| ADT7476EBZEVB | BOARD EVALUATION FOR ADT7476 |
| ADT7490ZEVB | BOARD EVALUATION FOR ADT7490 |
| ADZS-21262-1-EZEXT | BOARD DAUGHTER FOR ADSP-21262 |
| ADZS-BF-EZEXT-1 | BOARD DAUGHTER ADSP-BF533/561KIT |
| ADZS-BFAV-EZEXT | BOARD DAUGHT ADSP-BF533,37,61KIT |
相关代理商/技术参数 |
参数描述 |
|---|---|
| ADT7476 | 制造商:AD 制造商全称:Analog Devices 功能描述:dBCool Remote Thermal Controller and Voltage Monitor |
| ADT7476A | 制造商:AD 制造商全称:Analog Devices 功能描述:dBCool Remote Thermal Controller and Voltage Monitor |
| ADT7476AARQZ | 功能描述:马达/运动/点火控制器和驱动器 MONITORS 5V/4 FANS 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 |
| ADT7476AARQZ-R | 功能描述:板上安装温度传感器 MONITORS 5V/4 FANS 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 |
| ADT7476AARQZ-REEL | 功能描述:IC REMOTE THERMAL CTRLR 24-QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 热管理 系列:dBCool® 标准包装:1 系列:- 功能:温度监控系统（传感器） 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:±2.5°C 本地（最大值），±5°C 远程（最大值） 拓扑:ADC，比较器，寄存器库 输出类型:2 线 SMBus? 输出警报:无 输出风扇:无 电源电压:2.7 V ~ 5.5 V 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:SOT-23-8 供应商设备封装:SOT-23-8 包装:Digi-Reel® 其它名称:296-22675-6 |
发布紧急采购，3分钟左右您将得到回复。