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參數(shù)資料
| 型號： | ADM1024EVB |
| 廠商： | ON Semiconductor |
| 文件頁數(shù)： | 7/30頁 |
| 文件大?。?/td> | 0K |
| 描述： | BOARD EVAL FOR ADM1024 |
| 標準包裝： | 1 |
| 其它名稱： | EVAL-ADM1024EB EVAL-ADM1024EB-ND |
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ADM1024
http://onsemi.com
15
t1 the time taken for an analog input conversion, nominally
6.044 ms.
n the number of inputs configured as external temperature
inputs.
t2 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 monitoring 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 the 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, it 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 an 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
W, and
the accuracy will remain within specification for any value
from 0 k
W to 1 kW, so a standard 510 W resistor is suitable.
The worst such accident would be connecting 2.0 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 an
unsigned 8-bit DAC that produces 0 V to 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.
When using any of these circuits, the following points should be
noted:
1. All of these circuits will provide an output range
from 0 V to almost 12 V, apart from Figure 25
which loses the baseemitter voltage drop of Q1
due to the emitterfollower configuration.
2. To amplify the 2.5 V range of the analog output up
to 12 V, the gain of these circuits needs to be
around 4.8.
3. Care must be taken when choosing the op amp to
ensure that its input common-mode range and
output voltage swing are suitable.
4. The op amp may be powered from the 12 V rail
alone or from 12 V. If it is powered from 12 V,
then the input common-mode range should include
ground to accommodate the minimum output
voltage of the DAC, and the output voltage should
swing below 0.6 V to ensure that the transistor can
be turned fully off.
5. If the op amp is powered from 12 V, precautions
such as a clamp diode to ground may be needed to
prevent the base-emitter junction of the output
transistor being reverse-biased in the unlikely
event that the output of the op amp should swing
negative for any reason.
Figure 19. Fan Drive Circuit with Op Amp and
Emitter-Follower
AOUT
12V
Q1
2N2219A
1/4
LM324
R1
10k
R2
36k
Figure 20. Fan Drive Circuit with Op Amp and PNP
Transistor
AOUT
12V
Q1
BD136
2SA968
1/4
LM324
R1
10k
R3
1k
R2
39k
R4
1k
Figure 21. Fan Driver Circuit with Op Amp and
P-Channel MOSFET
AOUT
12V
Q1
IRF9620
1/4
LM324
R1
10k
R3
100k
R2
39k
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| ADM1025AARQZ | 功能描述:IC MONITOR SYS/VOLT 5CH 16QSOP RoHS:是 類別:集成電路 (IC) >> 接口 - 專用 系列:- 標準包裝:3,000 系列:- 應用:PDA，便攜式音頻/視頻，智能電話 接口:I²C，2 線串口 電源電壓:1.65 V ~ 3.6 V 封裝/外殼:24-WQFN 裸露焊盤 供應商設備封裝:24-QFN 裸露焊盤（4x4） 包裝:帶卷 (TR) 安裝類型:表面貼裝 產(chǎn)品目錄頁面:1015 (CN2011-ZH PDF) 其它名稱:296-25223-2 |
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