參數(shù)資料
型號(hào)： AD7864
廠商： Analog Devices, Inc.
英文描述： Four Channel, Simultaneous Sampling, High Speed, 12-Bit ADC(四通道,同時(shí)采樣高速12位A/D轉(zhuǎn)換器)
中文描述： 四通道，同步采樣，高速，12位ADC（四通道，同時(shí)采樣高速12位的A / D轉(zhuǎn)換器）
文件頁(yè)數(shù)： 13/20頁(yè)
文件大小： 394K
代理商： AD7864
AD7864
–13–
REV. 0
CONVST
BUSY
EOC
RD
1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 2 3 4 5 6
7 8 9 10 11 12 13 14 1 2
13 14
CLK
FRSTDATA
FIRST CONVERSION
COMPLETE
LAST CONVERSION
COMPLETE
Figure 9. Using an External Clock
Standby Mode Operation
The AD7864 has a Standby Mode whereby the device can be
placed in a low current consumption mode (5
μ
A typ). The
AD7864 is placed in standby by bringing the logic input
STBY
low. The AD7864 can be powered up again for normal opera-
tion by bringing
STBY
logic high. The output data buffers are
still operational while the AD7864 is in standby. This means
the user can still continue to access the conversion results while
the AD7864 is in standby. This feature can be used to reduce
the average power consumption in a system using low through-
put rates. To reduce the average power consumption the AD7864
can be placed in standby at the end of each conversion sequence,
i.e., when BUSY goes low and taken out of standby again prior
the start of the next conversion sequence. The time it takes the
AD7864 to come out of standby is called the “wake up” time.
This wake-up time will limit the maximum throughput rate at
which the AD7864 can be operated when powering down be-
tween conversion sequences. The AD7864 will wake-up in
approximately 2
μ
s when using an external reference. The
“wake up” time is also 2
μ
s when the standby time is less than
1 millisecond while using the internal reference. Figure 11
shows the wake-up time of the AD7864 for standby times
greater than 1 millisecond. Note when the AD7864 is left in
standby for periods of time greater than 1 millisecond the part
will require more than 2
μ
s to wake up. For example after initial
power up, using the internal reference the AD7864 takes 6 ms
to power up. The maximum throughput rate that can be achieved
when powering down between conversions is 1/(t
BUSY
+ 2
μ
s) =
100 kSPS approximately. When operating the AD7864 in a
standby mode between conversions the power savings can be
significant. For example with a throughput rate of 10 kSPS the
AD7864 will be powered down (I
DD
= 5
μ
A) for 90
μ
s out of
every 100
μ
s. See Figure 10. Therefore the average power con-
sumption drops to (125/10) mW or 12.5 mW approximately.
STANDBY TIME – sec
1
0.9
0
0.0001
10
0.001
0.01
0.1
1
0.6
0.3
0.2
0.1
0.8
0.7
0.4
0.5
P
Figure 11. Power-Up Time vs. Standby Time Using the
On-Chip Reference
Accessing the Output Data Registers
There are four Output Data Registers, one for each of the four
possible conversion results from a conversion sequence. The
result of the first conversion in a conversion sequence is placed
in Register 1 and the second result is placed in Register Number
2 and so on. For example if the conversion sequence VIN1,
VIN3 and VIN4 is selected (see Conversion Sequence Selec-
tion) then the results of the conversion on VIN1, VIN3 and
VIN4 are placed in Registers 1 to 3 respectively. The Output
Data register pointer is reset to point to Register 1 and the end
of the first conversion in the sequence, just prior to
EOC
going
CONVST
BUSY
STBY
100
m
s
m
s
t
BUSY
I
DD
= 20
m
A
t
BUSY
m
t
WAKEUP
Figure 10. Power-Down Between Conversion Sequences
相關(guān)PDF資料
PDF描述
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AD7864_09 制造商:AD 制造商全稱:Analog Devices 功能描述:4-Channel, Simultaneous Sampling, High Speed, 12-Bit ADC
AD7864AS 制造商:AD 制造商全稱:Analog Devices 功能描述:IC-SM-12-BIT ADC
AD7864AS-1 制造商:Analog Devices 功能描述: 制造商:Analog Devices 功能描述:IC 12BIT ADC SMD 7864 LQFP44
AD7864AS-2 制造商:Analog Devices 功能描述:ADC Single SAR 520ksps 12-bit Parallel 44-Pin MQFP 制造商:Rochester Electronics LLC 功能描述:4 CH.SIMULTANEOUS SAMPL.500 KSPS ADC I.C - Bulk 制造商:Analog Devices 功能描述:IC 12-BIT ADC
AD7864AS-2REEL 制造商:Analog Devices 功能描述:ADC Single SAR 520ksps 12-bit Parallel 44-Pin MQFP T/R
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