AD9203ARU Analog Devices Inc, AD9203ARU Datasheet - Page 18

• Manufacturer Part Number: AD9203ARU
• Description: ADC Single Pipelined 40MSPS 10-Bit Parallel 28-Pin TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD9203ARU

• Package: 28TSSOP
• Resolution: 10 Bit
• Sampling Rate: 40 MSPS
• Architecture: Pipelined
• Number Of Analog Inputs: 1
• Digital Interface Type: Parallel
• Input Type: Voltage
• Signal To Noise Ratio: 60(Typ) dB
• Rohs Status: RoHS non-compliant
• Number Of Bits: 10
• Sampling Rate (per Second): 40M
• Data Interface: Parallel
• Number Of Converters: 5
• Power Dissipation (max): 108mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-TSSOP (0.173", 4.40mm Width)

AD9203
APPLICATIONS
DIRECT IF DOWN CONVERSION
Sampling IF signals above an ADC’s baseband region (i.e., dc to
FS/2) is becoming increasingly popular in communication
applications. This process is often referred to as direct IF down
conversion or undersampling. There are several potential
benefits in using the ADC to alias (or mix) down a narrow band
or wide band IF signal. First and foremost is the elimination of a
complete mixer stage with its associated amplifiers and filters,
reducing cost and power dissipation. Second is the ability to
apply various DSP techniques to perform such functions as
filtering, channel selection, quadrature demodulation, data
reduction, detection, etc. A detailed discussion on using this
technique in digital receivers can be found in Analog Devices
Application Notes AN-301 and AN-302.
In direct IF down conversion applications, one exploits the
inherent sampling process of an ADC in which an IF signal
lying outside the baseband region can be aliased back into the
baseband region in a manner similar to a mixer downconverting
an IF signal. Similar to the mixer topology, an image rejection
filter is required to limit other potential interfering signals from
also aliasing back into the ADC’s baseband region.
A trade-off exists between the complexity of this image
rejection filter and the ADC’s sample rate and dynamic range.
The AD9203 is well suited for various IF sampling applications.
Its low distortion input SHA has a full-power bandwidth
extending to 130 MHz, thus encompassing many popular IF
frequencies. Only the 2 V span should be used for
undersampling beyond 20 MHz. A DNL of ±0.25 LSB
combined with low thermal input referred noise allows the
AD9203 in the 2 V span to provide >59 dB of SNR for a
baseband input sine wave. Also, its low aperture jitter of 1.2 ps
rms ensures minimum SNR degradation at higher IF
frequencies. In fact, the AD9203 is capable of still maintaining
58 dB of SNR at an IF of 70 MHz with a 2 V input span.
To maximize its distortion performance, the AD9203 should be
configured in the differential mode with a 2 V span using a
transformer. The center-tap of the transformer is biased to the
reference output of the AD9203. Preceding the AD9203 and
transformer is an optional bandpass filter as well as a gain stage.
A low Q passive bandpass filter can be inserted to reduce out of
band distortion and noise that lies within the AD9203’s 390
MHz bandwidth. A large gain stage(s) is often required to
compensate for the high insertion losses of a SAW filter used for
channel selection and image rejection. The gain stage will also
provide adequate isolation for the SAW filter from the charge
kick back currents associated with the AD9203’s switched
capacitor input stage.
Rev. B | Page 18 of 28
The distortion and noise performance of an ADC at the given
IF frequency is of particular concern when evaluating an ADC
for a narrowband IF sampling application. Both single tone and
dual tone SFDR vs. amplitude are very useful in assessing an
ADC’s dynamic and static nonlinearities. SNR vs. amplitude
performance at the given IF is useful in assessing the ADC’s
noise performance and noise contribution due to aperture jitter.
In any application, one is advised to test several units of the
same device under the same conditions to evaluate the given
applications sensitivity to that particular device. Figure 34 and
Figure 35 combine the dual tone SFDR as well as single tone
SFDR and SNR performances at IF frequencies of 70 MHz, and
130 MHz. Note, the SFDR vs. amplitude data is referenced to
dBFS while the single tone SNR data is referenced to dBc. The
performance characteristics in these figures are representative
of the AD9203 without any preceding gain stage. The AD9203
was operated in the differential mode (via transformer) with a
2 V span and a sample rate of 40 MSPS. The analog supply
(AVDD) and the digital supply (DRVDD) were set to 3.0 V.
90
80
70
60
50
40
30
20
10
80
70
60
50
40
30
20
10
0
0
Figure 35. SNR/SFDR for IF @ 130 MHz (Clock = 40 MSPS)
Figure 34. SNR/SFDR for IF @ 70 MHz (Clock = 40 MSPS)
0
0
5
5
INPUT POWER LEVEL (dB FULL SCALE)
INPUT POWER LEVEL (dB FULL SCALE)
SFDR 1 TONE
SFDR 2 TONE
10
10
SNR
15
15
SFDR 1 TONE
20
SNR
20
SFDR 2 TONE
25
25
30
3
3
0
5