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參數(shù)資料
| 型號： | ADS828E |
| 英文描述： | 10-Bit, 75MHz Sampling ANALOG-TO-DIGITAL CONVERTER |
| 中文描述： | 10位，75MHz的采樣模擬數(shù)字轉(zhuǎn)換器 |
| 文件頁數(shù)： | 12/12頁 |
| 文件大?。?/td> | 172K |
| 代理商： | ADS828E |
12
ADS828
JitterSNR
t
rmssignaltormsnoise
IN
A
=
20
1
2
log
π
FIGURE 9. Recommended Bypassing for the Supply Pins.
+FS –1LSB (IN = +3V, IN = +2V)
+1/2 Full Scale
Bipolar Zero (IN = IN = CMV)
–1/2 Full Scale
–FS (IN = +2V, IN = +3V)
11 1111 1111
11 0000 0000
10 0000 0000
01 0000 0000
00 0000 0000
STRAIGHT OFFSET BINARY
(SOB)
DIFFERENTIAL INPUT
TABLE II. Coding Table for Differential Input Configuration
and 2Vp-p Full-Scale Range.
+FS –1LSB (IN = REFT)
+1/2 Full Scale
Bipolar Zero (IN = CMV)
–1/2 Full Scale
–FS (IN = REFB)
11 1111 1111
11 0000 0000
10 0000 0000
01 0000 0000
00 0000 0000
SINGLE-ENDED INPUT
(IN = CMV)
STRAIGHT OFFSET BINARY
(SOB)
TABLE I. Coding Table for Single-Ended Input Configura-
tion with IN Tied to the Common-Mode Voltage
(CMV).
given by the following equation. If this value is near your
system requirements, input clock jitter must be reduced.
where:
IN
is input signal frequency
t
A
is rms clock jitter
Special consideration should be given to clock jitter, particu-
larly in undersampling applications. The clock input should
be treated as an analog input in order to achieve the highest
level of performance. Any overshoot or undershoot of the
clock signal may cause degradation of performance. When
digitizing at high sampling rates, the clock should have 50%
duty cycle (t
H
= t
L
), along with fast rise and fall times of 2ns
or less. The clock input of the ADS828 can be driven with
either 3V or 5V logic levels. Using low-voltage logic (3V)
may lead to improved AC performance of the converter.
Digital Outputs
The output data format of the ADS828 is in positive Straight
Offset Binary code, see Tables I and II. This format can
easily be converted into the Binary Two’s Complement code
by inverting the MSB.
It is recommended to keep the capacitive loading on the data
lines as low as possible (
≤
15pF). Higher capacitive loading
will cause larger dynamic currents as the digital outputs are
changing. Those high current surges can feed back to the
analog portion of the ADS828 and affect the performance. If
necessary, external buffers or latches close to the converter’s
output pins may be used to minimize the capacitive loading.
They also provide the added benefit of isolating the ADS828
from any digital noise activities on the bus coupling back
high frequency noise.
Digital Output Driver (VDRV)
The ADS828 features a dedicated supply pin for the output
logic drivers, VDRV, which is not internally connected to
the other supply pins. By setting the voltage at VDRV to
+5V or +3V, the ADS828 produces corresponding logic
levels and can directly interface to the selected logic family.
The output stages are designed to supply sufficient current to
drive a variety of logic families. However, it is recom-
mended to use the ADS828 with +3V logic supply. This will
lower the power dissipation in the output stages due to the
lower output swing and reduce current glitches on the supply
line, which may affect the ac performance of the converter.
In some applications, it might be advantageous to decouple
the VDRV pin with additional capacitors or a pi-filter.
GROUNDING AND DECOUPLING
Proper grounding and bypassing, short lead length, and the
use of ground planes are particularly important for high
frequency designs. Multilayer PC boards are recommended
for best performance since they offer distinct advantages like
minimizing ground impedance, separation of signal layers
by ground layers, etc. The ADS828 should be treated as an
analog component. Whenever possible, the supply pins should
be powered by the analog supply. This will ensure the most
consistent results since digital supply lines often carry high
levels of noise which otherwise would be coupled into the
converter and degrade the achievable performance. All ground
connections on the ADS828 are internally joined together,
obviating the design of split ground planes. The ground pins
(1, 16, 26) should directly connect to an analog ground
plane, which covers the PC board area around the converter.
While designing the layout, it is important to keep the analog
signal traces separated from any digital lines to prevent noise
coupling onto the analog signal path. Because of its high
sampling rate the, ADS828 generates high frequency current
transients and noise (clock feedthrough) that are fed back
into the supply and reference lines. This requires that all
supply and reference pins be sufficiently bypassed. Figure 9
shows the recommended decoupling scheme for the ADS828.
In most cases, 0.1
μ
F ceramic chip capacitors at each pin are
adequate to keep the impedance low over a wide frequency
range. Their effectiveness largely depends on the proximity
to the individual supply pin. Therefore, they should be
located as close to the supply pins as possible. In addition,
a larger bipolar capacitor (1
μ
F to 22
μ
F) should be placed on
the PC board in proximity of the converter circuit.
+V
S
27
26
GND
ADS828
+
0.1
μ
F
0.1
μ
F
+V
S
15
16
GND
10
μ
F
+5V
VDRV
28
0.1
μ
F
+3/+5V
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADS828E | 制造商:Texas Instruments 功能描述:IC 10BIT ADC 75MHZ SSOP28 828 制造商:Texas Instruments 功能描述:IC, 10BIT ADC, 75MHZ, SSOP28, 828 |
| ADS828E | 制造商:Texas Instruments 功能描述:IC 10-BIT ADC SAMPLING |
| ADS828E/1K | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10-Bit 75 MSPS SE/Diff Int/Ext Ref 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 |
| ADS828E/1KG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10-Bit 75 MSPS SE/Diff Int/Ext Ref 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 |
| ADS828EG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10-Bit 75 MSPS SE/Diff Int/Ext Ref 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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