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參數(shù)資料
| 型號： | ADS7822B |
| 英文描述： | 12-Bit High Speed 2.7V microPower Sampling ANALOG-TO-DIGITAL CONVERTER |
| 中文描述： | 12位高速2.7微采樣模擬到數(shù)字轉(zhuǎn)換器 |
| 文件頁數(shù)： | 10/12頁 |
| 文件大?。?/td> | 146K |
| 代理商： | ADS7822B |
10
ADS7822
POWER DISSIPATION
The architecture of the converter, the semiconductor fabrica-
tion process, and a careful design allow the ADS7822 to
convert at up to a 75kHz rate while requiring very little
power. Still, for the absolute lowest power dissipation, there
are several things to keep in mind.
The power dissipation of the ADS7822 scales directly with
conversion rate. So, the first step to achieving the lowest
power dissipation is to find the lowest conversion rate that
will satisfy the requirements of the system.
In addition, the ADS7822 is in power down mode under two
conditions: when the conversion is complete and whenever
CS is HIGH (see Figure 1). Ideally, each conversion should
occur as quickly as possible, preferably, at a 1.2MHz clock
rate. This way, the converter spends the longest possible time
in the power down mode. This is very important as the
converter not only uses power on each DCLOCK transition
(as is typical for digital CMOS components) but also uses
some current for the analog circuitry, such as the comparator.
The analog section dissipates power continuously, until the
power down mode is entered.
Figure 3 shows the current consumption of the ADS7822
versus sample rate. For this graph, the converter is clocked at
1.2MHz regardless of the sample rate—CS is HIGH for the
remaining sample period. Figure 4 also show current con-
sumption versus sample rate. However, in this case, the
DCLOCK period is 1/16th of the sample period—CS is
HIGH for one DCLOCK cycle out of every 16.
There is an important distinction between the power down
mode that is entered after a conversion is complete and the
full power down mode which is enabled when CS is HIGH.
While both shutdown the analog section, the digital section
is completely shutdown only when CS is HIGH. Thus, if CS
is left LOW at the end of a conversion and the converter is
continually clocked, the power consumption will not be as
low as when CS is HIGH. See Figure 5 for more information.
Power dissipation can also be reduced by lowering the power
supply voltage and the reference voltage. The ADS7822 will
operate over a V
CC
range of 2.0V to 5.25V. However, at
voltages below 2.7V, the converter will not run at a 75kHz
sample rate. See the typical performance curves for more
information regarding power supply voltage and maximum
sample rate.
SHORT CYCLING
Another way of saving power is to utilize the CS signal to
short cycle the conversion. Because the ADS7822 places the
latest data bit on the D
OUT
line as it is generated, the
converter can easily be short cycled. This term means that the
conversion can be terminated at any time. For example, if
only 8 bits of the conversion result are needed, then the
conversion can be terminated (by pulling CS HIGH) after the
8th bit has been clocked out.
FIGURE 3. Maintaining f
CLK
at the Highest Possible Rate
Allows Supply Current to Drop Linearly with
Sample Rate.
FIGURE 4. Scaling f
CLK
Reduces Supply Current Only
Slightly with Sample Rate.
1000
100
10
1
S
μ
A
0.1
1
10
100
Sample Rate (kHz)
T
A
= 25
°
C
V
CC
= 2.7V
V
REF
= 2.5V
f
CLK
= 16 f
SAMPLE
FIGURE 5. Shutdown Current with CS HIGH is 50nA
Typically, Regardless of the Clock. Shutdown
Current with CS LOW Varies with Sample
Rate.
10.0
8.0
6.0
4.0
2.0
0.0
0.00
S
μ
A
0.1
1
10
100
Sample Rate (kHz)
0.050
T
A
= 25
°
C
V
CC
= 2.7V
V
REF
= 2.5V
f
CLK
= 16 f
SAMPLE
CS LOW (GND)
CS HIGH (V
CC
)
1000
100
10
1
S
μ
A
0.1
1
10
100
Sample Rate (kHz)
V
CC
= 5.0V
V
REF
= 5.0V
V
CC
= 2.7V
V
REF
= 2.5V
T
A
= 25
°
C
f
CLK
= 1.2MHz
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| ADS7822C | CMOS Dual 4-Input NOR Gate 14-TSSOP -55 to 125 |
| ADS7822E | CMOS Dual 4-Input NOR Gate 14-TSSOP -55 to 125 |
| ADS7822EB | 12-Bit, High-Speed, 2.7V microPower Sampling ANALOG-TO-DIGITAL CONVERTER |
| ADS7822EC | CMOS Dual 4-Input NOR Gate 14-CDIP -55 to 125 |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADS7822C | 制造商:BB 制造商全稱:BB 功能描述:12-Bit High Speed 2.7V microPower Sampling ANALOG-TO-DIGITAL CONVERTER |
| ADS7822CIDGKRAN | 制造商:Texas Instruments 功能描述: |
| ADS7822E | 制造商:TI 制造商全稱:Texas Instruments 功能描述:12-Bit, High-Speed, 2.7V microPower Sampling ANALOG-TO-DIGITAL CONVERTER |
| ADS7822E/250 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit Hi-Speed 2.7V MicroPower Sampling RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS7822E/250 | 制造商:Texas Instruments 功能描述:Analog/Digital Converter IC Number of Bi |
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