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| 型号： | ADM1024 |
| 厂商： | Analog Devices, Inc. |
| 英文描述： | System Hardware Monitor with Remote Diode Thermal Sensing |
| 中文描述： | 系统硬件监控与远程二极管温度传感器 |
| 文件页数： | 13/28页 |
| 文件大小： | 285K |
| 代理商： | ADM1024 |
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ADM1024
–13–
REV. 0
10MIL
10MIL
10MIL
10MIL
10MIL
10MIL
10MIL
GND
D+
D
–
GND
Figure 15. Arrangement of Signal Tracks
4. Try to minimize the number of copper/solder joints, which
can cause thermocouple effects. Where copper/solder joints
are used, make sure that they are in both the D+ and D–
path and at the same temperature.
Thermocouple effects should not be a major problem as 1
°
C
corresponds to about 240
μ
V, and thermocouple voltages are
about 3
μ
V/
o
C of temperature difference. Unless there are
two thermocouples with a big temperature differential between
them, thermocouple voltages should be much less than 200 mV.
5. Place 0.1
μ
F bypass and 2200 pF input filter capacitors close
to the ADM1024.
6. If the distance to the remote sensor is more than 8 inches, the
use of twisted pair cable is recommended. This will work up
to about 6 feet to 12 feet.
7. For really long distances (up to 100 feet) use shielded twisted
pair such as Belden #8451 microphone cable. Connect the
twisted pair to D+ and D– and the shield to GND close to the
ADM1024. Leave the remote end of the shield unconnected
to avoid ground loops.
Because the measurement technique uses switched current
sources, excessive cable and/or filter capacitance can affect the
measurement. When using long cables, the filter capacitor may
be reduced or removed.
Cable resistance can also introduce errors. One
series resis-
tance introduces about 0.5
°
C error.
LIMIT VALUES
Limit values for analog measurements are stored in the appro-
priate limit registers. In the case of voltage measurements, high
and low limits can be stored so that an interrupt request will be
generated if the measured value goes above or below acceptable
values. In the case of temperature, a Hot Temperature or High
Limit can be programmed, and a Hot Temperature Hyster-
esis or Low Limit, which will usually be some degrees lower.
This can be useful as it allows the system to be shut down when
the hot limit is exceeded, and restarted automatically when it has
cooled down to a safe temperature.
MONITORING CYCLE TIME
The monitoring cycle begins when a one is written to the
Start Bit (Bit 0), and a zero to the
INT
_Clear Bit (Bit 3) of
the Configuration Register.
INT
_Enable (Bit 1) should be set
to one to enable the
INT
output. The ADC measures each analog
input in turn, as each measurement is completed the result is
automatically stored in the appropriate value register. This “round-
robin” monitoring cycle continues until it is disabled by writing
a 0 to Bit 0 of the Configuration Register.
As the ADC will normally be left to free-run in this manner, the
time taken to monitor all the analog inputs will normally not be
of interest, as the most recently measured value of any input can
be read out at any time.
For applications where the monitoring cycle time is important,
it can be calculated as follows:
m
×
t
1
×
n
×
t
2
where:
m
is the number of inputs configured as analog inputs, plus the
internal V
CC
measurement and internal temperature sensor.
t
1
is the time taken for an analog input conversion, nominally
755
μ
s.
n
is the number of inputs configured as external temperature
inputs.
t
2
is the time taken for a temperature conversion, nominally
33.24 ms.
This rapid sampling of the analog inputs ensures a quick response
in the event of any input going out of limits, unlike other moni-
toring chips that employ slower ADCs.
FAN MONITORING CYCLE TIME
When a monitoring cycle is started, monitoring of the fan speed
inputs begins at the same time as monitoring of the analog inputs.
However, the two monitoring cycles are not synchronized in any
way. The monitoring cycle time for the fan inputs is dependent
on fan speed and is much slower than for the analog inputs. For
more details see Fan Speed Measurement section.
INPUT SAFETY
Scaling of the analog inputs is performed on chip, so external
attenuators are normally not required. However, since the power
supply voltages will appear directly at the pins, its is advisable to
add small external resistors in series with the supply traces to the
chip to prevent damaging the traces or power supplies should a
accidental short such as a probe connect two power supplies
together.
As the resistors will form part of the input attenuators, they will
affect the accuracy of the analog measurement if their value is
too high. The analog input channels are calibrated assuming an
external series resistor of 500
, and the accuracy will remain
within specification for any value from zero to 1 k
, so a stan-
dard 510
resistor is suitable.
The worst such accident would be connecting –12 V to +12 V—
a total of 24 V difference, with the series resistors this would draw
a maximum current of approximately 24 mA.
ANALOG OUTPUT
The ADM1024 has a single analog output from a unsigned 8-bit
DAC which produces 0 V–2.5 V. The analog output register
defaults to FF during power-on reset, which produces maximum
fan speed. The analog output may be amplified and buffered
with external circuitry such as an op amp and transistor to provide
fan speed control.
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| ADM1024ARU | 功能描述:IC MONITOR SYS TEMP/VOLT 24TSSOP RoHS:否 类别:集成电路 (IC) >> 接口 - 专用 系列:- 标准包装:3,000 系列:- 应用:PDA，便携式音频/视频，智能电话 接口:I²C，2 线串口 电源电压:1.65 V ~ 3.6 V 封装/外壳:24-WQFN 裸露焊盘 供应商设备封装:24-QFN 裸露焊盘（4x4） 包装:带卷 (TR) 安装类型:表面贴装 产品目录页面:1015 (CN2011-ZH PDF) 其它名称:296-25223-2 |
| ADM1024ARU-REEL | 功能描述:IC MONITOR SYS TEMP/VOLT 24TSSOP RoHS:否 类别:集成电路 (IC) >> 接口 - 专用 系列:- 标准包装:3,000 系列:- 应用:PDA，便携式音频/视频，智能电话 接口:I²C，2 线串口 电源电压:1.65 V ~ 3.6 V 封装/外壳:24-WQFN 裸露焊盘 供应商设备封装:24-QFN 裸露焊盘（4x4） 包装:带卷 (TR) 安装类型:表面贴装 产品目录页面:1015 (CN2011-ZH PDF) 其它名称:296-25223-2 |
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| ADM1024ARUZ-R7 | 功能描述:板上安装温度传感器 +/-2 C / +/-3 C Digital 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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