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參數(shù)資料
| 型號(hào)： | ADS7822C |
| 英文描述： | CMOS Dual 4-Input NOR Gate 14-TSSOP -55 to 125 |
| 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(yè)數(shù)： | 8/12頁(yè) |
| 文件大?。?/td> | 146K |
| 代理商： | ADS7822C |
8
ADS7822
REFERENCE INPUT
The external reference sets the analog input range. The
ADS7822 will operate with a reference in the range of 50mV
to V
CC
. There are several important implications of this.
As the reference voltage is reduced, the analog voltage
weight of each digital output code is reduced. This is often
referred to as the LSB (least significant bit) size and is equal
to the reference voltage divided by 4096. This means that any
offset or gain error inherent in the A/D converter will appear
to increase, in terms of LSB size, as the reference voltage is
reduced.
The noise inherent in the converter will also appear to
increase with lower LSB size. With a 2.5V reference, the
internal noise of the converter typically contributes only 0.32
LSB peak-to-peak of potential error to the output code. When
the external reference is 50mV, the potential error contribu-
tion from the internal noise will be 50 times larger—16
LSBs. The errors due to the internal noise are gaussian in
nature and can be reduced by averaging consecutive conver-
sion results.
For more information regarding noise, consult the typical
performance curves “Effective Number of Bits vs Reference
Voltage” and “Peak-to-Peak Noise vs Reference Voltage.”
Note that the effective number of bits (ENOB) figure is
calculated based on the converter’s signal-to-(noise + distor-
tion) ratio with a 1kHz, 0dB input signal. SINAD is related
to ENOB as follows
SINAD = 6.02 ENOB + 1.76
With lower reference voltages, extra care should be taken to
provide a clean layout including adequate bypassing, a clean
power supply, a low-noise reference, and a low-noise input
signal. Because the LSB size is lower, the converter will also
be more sensitive to external sources of error such as nearby
digital signals and electromagnetic interference.
DIGITAL INTERFACE
SIGNAL LEVELS
The digital inputs of the ADS7822 can accommodate logic
levels up to 6V regardless of the value of V
CC
. Thus, the
ADS7822 can be powered at 3V and still accept inputs from
logic powered at 5V.
The CMOS digital output (D
OUT
) will swing 0V to V
CC
. If
V
CC
is 3V and this output is connected to a 5V CMOS logic
input, then that IC may require more supply current than
normal and may have a slightly longer propagation delay.
SERIAL INTERFACE
The ADS7822 communicates with microprocessors and other
digital systems via a synchronous 3-wire serial interface as
shown in Figure 1 and Table I. The DCLOCK signal syn-
chronizes the data transfer with each bit being transmitted on
the falling edge of DCLOCK. Most receiving systems will
capture the bitstream on the rising edge of DCLOCK. How-
ever, if the minimum hold time for D
OUT
is acceptable, the
system can use the falling edge of DCLOCK to capture each
bit.
FIGURE 1. ADS7822 Basic Timing Diagrams.
CS/SHDN
D
OUT
DCLOCK
t
DATA
t
SUCS
t
CYC
t
CONV
Power
Down
t
SMPL
Note: (1) After completing the data transfer, if further clocks are applied with CS
LOW, the A/D will output LSB-First data then followed with zeroes indefinitely.
B11
(MSB)
B10 B9
B8
B7
B6
B5
B4
B3
B2
B1 B0
(1)
Null
Bit
Hi-Z
Hi-Z
B11 B10
B9
B8
Null
Bit
CS/SHDN
D
OUT
DCLOCK
t
CONV
t
DATA
t
SUCS
t
CSD
Hi-Z
t
CYC
Power Down
t
SMPL
Note: (1) After completing the data transfer, if further clocks are applied with CS
LOW, the A/D will output zeroes indefinitely.
t
: During this time, the bias current and the comparator power down and the reference input
becomes a high impedance node, leaving the CLK running to clock out LSB-First data or zeroes.
B11
(MSB)
B10 B9
B8
B7
B6
B5
B4
B4
B3
B3
B2
B2
B1
B1
B0
Null
Bit
Hi-Z
B5
B6
B7
B8
B9
B10 B11
(1)
t
CSD
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| 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 |
| ADS7823E250 | 12-Bit, Sampling A/D Converter with I2C?? INTERFACE |
| ADS7823 | CONN, M HDR 2X20 NO LATCH |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 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 |
| ADS7822E/250G4 | 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 |
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