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參數(shù)資料
| 型號(hào)： | AD9022SZ |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | 12-Bit 20 MSPS Monolithic A/D Converter |
| 中文描述： | 1-CH 12-BIT PROPRIETARY METHOD ADC, PARALLEL ACCESS, CDSO28 |
| 封裝： | CERAMIC, LCC-28 |
| 文件頁數(shù)： | 9/12頁 |
| 文件大小： | 240K |
| 代理商： | AD9022SZ |
AD9022
REV. B
–9–
USING T HE AD9022
Layout Information
Preserving the accuracy and dynamic performance of the
AD9022 requires that designers pay special attention to the
layout of the printed circuit board.
Analog paths should be kept as short as possible and be properly
terminated to avoid reflections. T he analog input connection
should be kept away from digital signal paths; this reduces the
amount of digital switching noise, which is capacitively coupled
into the analog section. Digital signal paths should also be kept
short, and run lengths should be matched to avoid propagation
delay mismatch. T he AD9022 digital outputs should be buff-
ered or latched close to the device (<2 cm). T his prevents load
transients that may feed back into the device.
In high speed circuits, layout of the ground is critical. A single,
low impedance ground plane on the component side of the
board is recommended. Power supplies should be capacitively
coupled to the ground plane with high quality 0.1
μ
F chip ca-
pacitors to reduce noise in the circuit. All power pins of the
AD9022 should be bypassed individually. T he compensation
pin (COMP Pin 17) should be bypassed directly to the –V
S
supply (Pin 15) as close to the part as possible using a 0.1
μ
F
chip capacitor.
Multilayer boards allow designers to lay out signal traces with-
out interrupting the ground plane, and provide low impedance
ground planes. In systems with dedicated analog and digital
grounds, all grounds for the AD9022 should be connected to
the analog ground plane.
In systems using multilayer boards, dedicated power planes are
recommended to provide low impedance connections for device
power. Sockets limit dynamic performance and are not recom-
mended for use with the AD9022.
T iming
Conversion by the AD9022 is initiated by the rising edge of the
ENCODE clock (Pin 8). All required timing is generated inter-
nal to the ADC. Care should be taken to ensure that the encode
clock to the AD9022 is free from jitter that can degrade dy-
namic performance. T he clock driver should be compatible with
T T L LS logic series devices. Drivers with excessive slew rate or
overdrive will degrade the dynamic performance of the AD9022.
Pulsewidth of the ADC encode clock must be controlled to
ensure the best possible performance. Dynamic performance is
guaranteed with a clock pulse HIGH minimum of 25 ns. Opera-
tion with narrower pulses will degrade SNR and dynamic per-
formance. From a system perspective, this is generally not a
problem, because a simple inverter can be used to generate a
suitable clock if the system clock is less than 25 ns wide.
T he AD9022 provides latched data outputs. Data outputs are
available two pipeline delays and one propagation delay after the
rising edge of the encode clock (refer to the AD9022 T iming
Diagram). T he length of the output data lines and the loads
placed on them should be minimized to reduce transients within
the AD9022; these transients can detract from the converter’s
dynamic performance.
Operation at encode rates less than 4 MSPS is not recom-
mended. T he internal track-and-hold saturates, causing errone-
ous conversions. T his T /H saturation precludes clocking the
AD9022 in a burst mode.
T he duty cycle of the encode clock for the AD9022 is critical for
obtaining rated performance of the ADC. Internal pulsewidths
within the track-and-hold are established by the encode com-
mand pulsewidth; to ensure rated performance, minimum and
maximum pulsewidth restrictions should be observed. Operation at
20 MSPS is optimized when the duty cycle is held at 55%.
Analog Input
T he analog input (Pin 12) voltage range is nominally
±
1.024
volts. T he range is set with an internal voltage reference and
cannot be adjusted by the user. T he input resistance is 300
and the analog bandwidth is 110 MHz, making the AD9022
useful in undersampling applications.
T he AD9022 should be driven from a low impedance source.
T he noise and distortion of the amplifier should be considered
to preserve the dynamic range of the AD9022.
Power Supplies
T he power supplies of the AD9022 should be isolated from the
supplies used for noisy devices (digital logic especially) to re-
duce the amount of noise coupled into the ADC. For optimum
performance, linear supplies ensure that switching noise from
the supplies does not introduce distortion products during
the encoding process. If switching supplies must be used,
decoupling recommendations above are critically important.
T he PSRR of the AD9022 is a function of the ripple frequency
present on the supplies. Clearly, power supplies with the lowest
possible frequency should be selected.
AD9022 E VALUAT ION BOARD
T he evaluation board for the AD9022 (AD9022/PCB) provides
an easy and flexible method for evaluating the ADC’s perfor-
mance without (or prior to) developing a user-specific printed
circuit board. T he two-sided board includes a reconstruction
DAC and digital output interface, and uses the layout and appli-
cations suggestions outlined above. It is available at nominal
cost from Analog Devices, Inc.
Input/Output/Supply Information
Power supply, analog input, clock connections and recon-
structed output (RC OUT PUT ) are identified by labels on the
evaluation board.
Operation of the evaluation board will conform to the following
characteristics:
Parameter
T ypical
Units
Supply Current
+5 V
–5 V
A
IN
Impedance
Voltage Range
CLOCK
Impedance
Frequency
RC OUT PUT
Impedance
Voltage Range
150
300
mA
mA
51
±
1.024
V
51
20
MSPS
51
0 to –1
V
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD9023/PCB | 制造商:Analog Devices 功能描述: |
| AD9023AQ | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| AD9023AZ | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| ad9023bq | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Analog Devices 功能描述: |
| AD9023BZ | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
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