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參數(shù)資料
| 型號： | EVAL-AD7887CB |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | +2.7 V to +5.25 V, Micropower, 2-Channel, 125 kSPS, 12-Bit ADC in 8-Lead uSOIC |
| 中文描述： | 2.7 V至5.25 V，微功耗，2通道，125 kSPS的，12位ADC的8引腳uSOIC |
| 文件頁數(shù)： | 8/16頁 |
| 文件大?。?/td> | 133K |
| 代理商： | EVAL-AD7887CB |
REV. B
AD7887
–8–
PE RFORMANCE CURVE S
Figure 2 shows a typical FFT plot for the AD7887 at 125 kHz
sample rate and 10 kHz input frequency.
6
0
1
1
2
3
3
4
4
5
6
–110
0
–10
–30
–50
–70
–90
4096 POINT FFT
SAMPLING
125kSPS
f
= 10kHz
SNR = 71dB
Figure 2. Dynamic Performance
Figure 3 shows the SNR vs. Frequency for a 5 V supply with a
5 V external reference.
INPUT FREQUENCY – kHz
71.0
0.15
42.14
S
73.0
72.5
72.0
71.5
10.89
31.59
V
= 5V
5V EXT REFERENCE
21.14
Figure 3. SNR vs. Input Frequency
Figure 4 shows the power supply rejection ratio versus fre-
quency for the part. T he power supply rejection ratio is defined
as the ratio of the power in the ADC output at frequency f to
the power of a full-scale sine wave applied to the ADC of fre-
quency f
S
:
PSRR (dB) =
10 log
(
Pf/Pfs
)
Pf
= Power at frequency f in ADC output,
Pfs
= power at fre-
quency f
S
in ADC full-scale input. Here a 100 mV peak-to-peak
sine wave is coupled onto the V
DD
supply. Both the +2.7 V and
+5.5 V supply performances are shown.
INPUT FREQUENCY – kHz
–93
2.65
64.15
P
12.85
33.65
V
DD
= +5.5V/+2.7V
100mV p-p SINE WAVE ON V
DD
REF
IN
= 2.488V EXT REFERENCE
23.15
–91
–89
–87
–85
–83
–81
–79
–77
–75
43.85
54.35
Figure 4. PSRR vs. Frequency
CIRCUIT INFORMAT ION
T he AD7887 is a fast, low power, 12-bit, single supply, single-
channel/dual-channel A/D converter. T he part can be operated
from a +3 V (+2.7 V to +3.6 V) supply or from a +5 V (+4.75 V to
+5.25 V) supply. When operated from either a +5 V or +3 V
supply, the AD7887 is capable of throughput rates of 125 kSPS
when provided with a 2 MHz clock.
T he AD7887 provides the user with an on-chip track/hold, A/D
converter, reference and serial interface housed in an 8-lead
package. T he serial clock input accesses data from the part and
also provides the clock source for the successive approximation
A/D converter. T he part can be configured for single-channel or
dual-channel operation. When configured as a single-channel
part, the analog input range is 0 to V
REF
(where the externally-
applied V
REF
can be between +1.2 V and V
DD
). When the
AD7887 is configured for two input channels, the input range is
determined by internal connections to be 0 to V
DD
.
If single-channel operation is required, the AD7887 can be
operated in a read-only mode by tying the DIN line permanently to
GND. For applications where the user wants to change the
mode of operation or wants to operate the AD7887 as a dual-
channel A/D converter, the DIN line can be used to clock data
into the part’s control register.
CONVE RT E R OPE RAT ION
T he AD7887 is a successive approximation analog-to-digital
converter based around a charge redistribution DAC. Figures 5
and 6 show simplified schematics of the ADC. Figure 5 shows
the ADC during its acquisition phase. SW2 is closed and SW1 is
in position A, the comparator is held in a balanced condition
and the sampling capacitor acquires the signal on AIN.
(REF IN/REF OUT)/2
SAMPLING
CAPACITOR
COMPARATOR
ACQUISITION
PHASE
SW1
A
SW2
AGND
B
AIN
CHARGE
REDISTRIBUTION
DAC
CONTROL
LOGIC
Figure 5. ADC Acquisition Phase
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| EVAL-AD7887CB4 | 制造商:AD 制造商全稱:Analog Devices 功能描述:2.7 V to 5.25 V, Micropower, 2-Channel, 125 kSPS, 12-Bit ADC in 8-Lead MSOP |
| EVAL-AD7887CBZ | 功能描述:BOARD EVAL FOR AD7887 RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - 模數(shù)轉(zhuǎn)換器 (ADC) 系列:* 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標準包裝:1 系列:- ADC 的數(shù)量:1 位數(shù):12 采樣率（每秒）:94.4k 數(shù)據(jù)接口:USB 輸入范圍:±VREF/2 在以下條件下的電源（標準）:- 工作溫度:-40°C ~ 85°C 已用 IC / 零件:MAX11645 已供物品:板，軟件 |
| EVAL-AD7888CB | 制造商:Analog Devices 功能描述:EVAL KIT FOR 2.7 V TO 5.25 V, MICROPWR, 8CH, 125 KSPS, 12-BI - Bulk |
| EVAL-AD7890-2 | 制造商:Analog Devices 功能描述:AD7890 EVAL BOARD |
| EVAL-AD7891-1CB | 制造商:Analog Devices 功能描述:Evaluation Board For LC2MOS 8-Channel, 12-Bit High Speed Data Acquisition System 44PLCC 制造商:Analog Devices 功能描述:EVAL BD FOR LC2MOS 8CH, 12-BIT HS DATA ACQ SYS 44PLCC(P-44A) - Bulk |
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