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參數(shù)資料
| 型號： | ADC12040 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 12-Bit, 40 MSPS, 340 mW A/D Converter with Internal Sample-and-Hold |
| 中文描述： | 12位，40 MSPS的，340毫瓦的A / D轉(zhuǎn)換器，內(nèi)置采樣保持電路 |
| 文件頁數(shù)： | 19/20頁 |
| 文件大?。?/td> | 519K |
| 代理商： | ADC12040 |
Applications Information
(Continued)
speed digital components (e.g., 74F and 74AC devices) to
exhibit overshoot or undershoot that goes above the power
supply or below ground. A resistor of about 50
to 100
in
series with any offending digital input, close to the signal
source, will eliminate the problem.
Do not allow input voltages to exceed the supply voltage,
even on a transient basis. Not even during power up or
power down.
Be careful not to overdrive the inputs of the ADC12040 with
a device that is powered from supplies outside the range of
theADC12040 supply. Such practice may lead to conversion
inaccuracies and even to device damage.
Attempting to drive a high capacitance digital data bus.
The more capacitance the output drivers must charge for
each conversion, the more instantaneous digital current
flows through V
and DR GND. These large charging cur-
rent spikes can couple into the analog circuitry, degrading
dynamic performance. Adequate bypassing and maintaining
separate analog and digital areas on the pc board will reduce
this problem.
Additionally, bus capacitance beyond the specified 20 pF/pin
will cause t
to increase, making it difficult to properly latch
theADC output data. The result could, again, be an apparent
reduction in dynamic performance.
The digital data outputs should be buffered (with 74ACQ541,
for example). Dynamic performance can also be improved
by adding series resistors at each digital output, close to the
ADC12040, which reduces the energy coupled back into the
converter output pins by limiting the output current. A rea-
sonable value for these resistors is 47
to 100
.
Using an inadequate amplifier to drive the analog input.
As explained in Section 1.3, the capacitance seen at the
input alternates between 8 pF and 7 pF, depending upon the
phase of the clock. This dynamic load is more difficult to
drive than is a fixed capacitance.
If the amplifier exhibits overshoot, ringing, or any evidence of
instability, even at a very low level, it will degrade perfor-
mance. A small series resistor at each amplifier output and a
capacitor across the analog inputs (as shown in
Figures 5, 6
)
will improve performance. The CLC409 has been success-
fully used to drive the analog inputs of the ADC12040.
Also, it is important that the signals at the two inputs have
exactly the same amplitude and be exactly 180
o
out of phase
with each other. Board layout, especially equality of the
length of the two traces to the input pins, will affect the
effective phase between these two signals. Remember that
an operational amplifier operated in the non-inverting con-
figuration will exhibit more time delay than will the same
device operating in the inverting configuration.
Operating with the reference pins outside of the speci-
fied range.
As mentioned in Section 1.2, V
REF
should be in
the range of
1.0V
≤
V
REF
≤
2.2V
Operating outside of these limits could lead to performance
degradation.
Using a clock source with excessive jitter, using exces-
sively long clock signal trace, or having other signals
coupled to the clock signal trace.
This will cause the
sampling interval to vary, causing excessive output noise
and a reduction in SNR and SINAD performance.
A
www.national.com
19
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| ADC12040_06 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:12-Bit, 40 MSPS, 340mW A/D Converter with Internal Sample-and-Hold |
| ADC12040CIVY | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 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 |
| ADC12040CIVY/NOPB | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 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 |
| ADC12040CIVYX | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 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 |
| ADC12040CIVYX/NOPB | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 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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