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參數(shù)資料
| 型號： | AD9020KZ |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | 10-Bit 60 MSPS A/D Converter |
| 中文描述： | 1-CH 10-BIT FLASH METHOD ADC, PARALLEL ACCESS, CQFP68 |
| 封裝： | CERAMIC, LCC-68 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大小： | 204K |
| 代理商： | AD9020KZ |
AD9020
–6–
REV. A
T HE ORY OF OPE RAT ION
Refer to the AD9020 block diagram. As shown, the AD9020
uses a modified “flash,” or parallel, A/D architecture. T he ana-
log input range is determined by an external voltage reference
(+V
REF
and –V
REF
), nominally
±
1.75 V. An internal resistor lad-
der divides this reference into 512 steps, each representing two
quantization levels. T aps along the resistor ladder (1/4
REF
,
1/2
REF
and 3/4
REF
) are provided to optimize linearity. Rated per-
formance is achieved by driving these points at 1/4, 1/2 and 3/4,
respectively, of the voltage reference range.
T he A/D conversion for the nine most significant bits (MSBs) is
performed by 512 comparators. T he value of the least signifi-
cant bit (LSB) is determined by a unique interpolation scheme
between adjacent comparators. T he decoding logic processes
the comparator outputs and provides a 10-bit code to the output
stage of the converter.
Flash architecture has an advantage over other A/D architec-
tures because conversion occurs in one step. T his means the
performance of the converter is primarily limited by the speed
and matching of the individual comparators. In the AD9020, an
innovative interpolation scheme takes advantage of flash archi-
tecture but minimizes the input capacitance, power and device
count usually associated with that method of conversion.
T hese advantages occur by using only half the normal number
of input comparator cells to accomplish the conversion. In addi-
tion, a proprietary decoding scheme minimizes error codes. In-
put control pins allow the user to select from among Binary,
Inverted Binary, T wos Complement and Inverted T wos
Complement coding (see AD9020 T ruth T able).
APPLIC AT IONS
Many of the specifications used to describe analog/digital con-
verters have evolved from system performance requirements in
these applications. Different systems emphasize particular speci-
fications, depending on how the part is used. T he following ap-
plications highlight some of the specifications and features that
make the AD9020 attractive in these systems.
Wideband Receivers
Radar and communication receivers (baseband and direct IF
digitization), ultrasound medical imaging, signal intelligence
and spectral analysis all place stringent ac performance require-
ments on analog-to-digital converters (ADCs). Frequency do-
main characterization of the AD9020 provides signal-to-noise
ratio (SNR) and harmonic distortion data to simplify selection
of the ADC.
Receiver sensitivity is limited by the Signal-to-Noise Ratio
of the
system. T he SNR for an ADC is measured in the frequency do-
main and calculated with a Fast Fourier T ransform (FFT ). T he
SNR equals the ratio of the fundamental component of the sig-
nal (rms amplitude) to the rms value of the noise. T he noise is
the sum of all other spectral components, including harmonic
distortion, but excluding dc.
Good receiver design minimizes the level of spurious signals in
the system. Spurious signals developed in the ADC are the re-
sult of imperfections in the device transfer function (non-
linearities, delay mismatch, varying input impedance, etc.). In
the ADC, these spurious signals appear as Harmonic Distortion.
Harmonic Distortion is also measured with an FFT and is speci-
fied as the ratio of the fundamental component of the signal
(rms amplitude) to the rms value of the worst case harmonic
(usually the 2nd or 3rd).
Two-Tone Intermodulation Distortion (IMD)
is
a frequently cited
specification in receiver design. In narrow-band receivers, third-
order IMD products result in spurious signals in the pass band
of the receiver. Like mixers and amplifiers, the ADC is charac-
terized with two, equal-amplitude, pure input frequencies. T he
IMD equals the ratio of the power of either of the two input sig-
nals to the power of the strongest third-order IMD signal. Un-
like mixers and amplifiers, the IMD does not always behave as it
does in linear devices (reduced input levels do not result in pre-
dictable reductions in IMD).
Performance graphs provide typical harmonic and SNR data for
the AD9020 for increasing analog input frequencies. In choos-
ing an A/D converter, always look at the dynamic range for the
analog input frequency of interest. T he AD9020 specifications
provide guaranteed minimum limits at three analog test
frequencies.
Aperture Delay
is
the delay between the rising edge of the EN-
CODE command and the instant at which the analog input is
sampled. Many systems require simultaneous sampling of more
than one analog input signal with multiple ADCs. In these situ-
ations, timing is critical and the absolute value of the aperture
delay is not as critical as the matching between devices.
Aperture Uncertainty,
or jitter, is the sample-to-sample variation
in aperture delay. T his is especially important when sampling
high slew rate signals in wide bandwidth systems. Aperture un-
certainty is one of the factors that degrade dynamic performance
as the analog input frequency is increased.
相關(guān)PDF資料 |
PDF描述 |
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| AD9020PCB | 10-Bit 60 MSPS A/D Converter |
| AD9034 | 12-Bit 20 MSPS A/D Converter(20MSPS 12位A/D轉(zhuǎn)換器) |
| AD9040 | 10-Bit 40 MSPS A/D Converter |
| AD9040APWB | 10-Bit 40 MSPS A/D Converter |
| AD9040AJN | 10-Bit 40 MSPS A/D Converter |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD9020PCB | 制造商:AD 制造商全稱:Analog Devices 功能描述:10-Bit 60 MSPS A/D Converter |
| AD9020SE/883 | 制造商:AD 制造商全稱:Analog Devices 功能描述:10-Bit 60 MSPS A/D Converter |
| AD9020SZ/883 | 制造商:AD 制造商全稱:Analog Devices 功能描述:10-Bit 60 MSPS A/D Converter |
| AD9020TE/883 | 制造商:AD 制造商全稱:Analog Devices 功能描述:10-Bit 60 MSPS A/D Converter |
| AD9020TZ/883 | 制造商:AD 制造商全稱:Analog Devices 功能描述:10-Bit 60 MSPS A/D Converter |
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