AD9200JRSRL [ADI]
Complete 10-Bit, 20 MSPS, 80 mW CMOS A/D Converter; 完整的10位, 20 MSPS , 80毫瓦的CMOS A / D转换器型号: | AD9200JRSRL |
厂家: | ADI |
描述: | Complete 10-Bit, 20 MSPS, 80 mW CMOS A/D Converter |
文件: | 总24页 (文件大小:341K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
Complete 10-Bit, 20 MSPS, 80 mW
CMOS A/D Converter
a
AD9200
FEATURES
A single clock input is used to control all internal conversion
cycles. The digital output data is presented in straight binary
output format. An out-of-range signal (OTR) indicates an over-
flow condition which can be used with the most significant bit
to determine low or high overflow.
CMOS 10-Bit, 20 MSPS Sampling A/D Converter
Pin-Compatible with AD876
Power Dissipation: 80 mW (3 V Supply)
Operation Between 2.7 V and 5.5 V Supply
Differential Nonlinearity: 0.5 LSB
Power-Down (Sleep) Mode
Three-State Outputs
Out-of-Range Indicator
Built-In Clamp Function (DC Restore)
Adjustable On-Chip Voltage Reference
IF Undersampling to 135 MHz
The AD9200 can operate with supply range from 2.7 V to
5.5 V, ideally suiting it for low power operation in high speed
portable applications.
The AD9200 is specified over the industrial (–40°C to +85°C)
and commercial (0°C to +70°C) temperature ranges.
PRODUCT HIGHLIGHTS
Low Power
PRODUCT DESCRIPTION
The AD9200 is a monolithic, single supply, 10-bit, 20 MSPS
analog-to-digital converter with an on-chip sample-and-hold
amplifier and voltage reference. The AD9200 uses a multistage
differential pipeline architecture at 20 MSPS data rates and
guarantees no missing codes over the full operating temperature
range.
The AD9200 consumes 80 mW on a 3 V supply (excluding the
reference power). In sleep mode, power is reduced to below
5 mW.
Very Small Package
The AD9200 is available in both a 28-lead SSOP and 48-lead
LQFP packages.
The input of the AD9200 has been designed to ease the devel-
opment of both imaging and communications systems. The user
can select a variety of input ranges and offsets and can drive the
input either single-ended or differentially.
Pin Compatible with AD876
The AD9200 is pin compatible with the AD876, allowing older
designs to migrate to lower supply voltages.
300 MHz On-Board Sample-and-Hold
The versatile SHA input can be configured for either single-
ended or differential inputs.
The sample-and-hold (SHA) amplifier is equally suited for both
multiplexed systems that switch full-scale voltage levels in suc-
cessive channels and sampling single-channel inputs at frequen-
cies up to and beyond the Nyquist rate. AC coupled input
signals can be shifted to a predetermined level, with an onboard
clamp circuit (AD9200ARS, AD9200KST). The dynamic per-
formance is excellent.
Out-of-Range Indicator
The OTR output bit indicates when the input signal is beyond
the AD9200’s input range.
Built-In Clamp Function
Allows dc restoration of video signals with AD9200ARS and
AD9200KST.
The AD9200 has an onboard programmable reference. An
external reference can also be chosen to suit the dc accuracy and
temperature drift requirements of the application.
FUNCTIONAL BLOCK DIAGRAM
CLAMP
IN
CLK
AVDD
DRVDD
CLAMP
STBY
SHA
GAIN
SHA
GAIN
SHA
GAIN
SHA
GAIN
SHA
MODE
AIN
REFTS
REFBS
A/D
THREE-
STATE
D/A
D/A
D/A
A/D
A/D
D/A
A/D
A/D
REFTF
REFBF
CORRECTION LOGIC
OUTPUT BUFFERS
OTR
VREF
D9
(MSB)
AD9200
1V
REFSENSE
D0
(LSB)
DRVSS
AVSS
REV. E
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
World Wide Web Site: http://www.analog.com
© Analog Devices, Inc., 1999
(AVDD = +3 V, DRVDD = +3 V, FS = 20 MHz (50% Duty Cycle), MODE = AVDD, 2 V Input
AD9200–SPECIFICATIONS Span from 0.5 V to 2.5 V, External Reference, TMIN to TMAX unless otherwise noted)
Parameter
Symbol Min
Typ Max
Units
Bits
Condition
RESOLUTION
CONVERSION RATE
10
FS
20
MHz
DC ACCURACY
Differential Nonlinearity
Integral Nonlinearity
Offset Error
DNL
INL
EZS
±0.5 ±1
±0.75 ±2
LSB
LSB
% FSR
% FSR
REFTS = 2.5 V, REFBS = 0.5 V
0.4
1.4
1.2
3.5
Gain Error
EFS
REFERENCE VOLTAGES
Top Reference Voltage
REFTS
1
AVDD
V
Bottom Reference Voltage
Differential Reference Voltage
Reference Input Resistance1
REFBS GND
AVDD – 1
V
2
10
4.2
V p-p
kΩ
kΩ
REFTS, REFBS: MODE = AVDD
Between REFTF and REFBF: MODE = AVSS
ANALOG INPUT
Input Voltage Range
Input Capacitance
Aperture Delay
Aperture Uncertainty (Jitter)
Input Bandwidth (–3 dB)
Full Power (0 dB)
AIN
CIN
tAP
tAJ
BW
REFBS
REFTS
V
REFBS Min = GND: REFTS Max = AVDD
Switched
1
4
2
pF
ns
ps
300
23
MHz
µA
DC Leakage Current
Input = ±FS
INTERNAL REFERENCE
Output Voltage (1 V Mode)
Output Voltage Tolerance (1 V Mode)
Output Voltage (2 V Mode)
Load Regulation (1 V Mode)
VREF
VREF
1
V
mV
V
REFSENSE = VREF
±10 ±25
2
0.5
REFSENSE = GND
1 mA Load Current
2
mV
POWER SUPPLY
Operating Voltage
AVDD
2.7
3
3
5.5
5.5
V
V
mA
mW
mW
DRVDD 2.7
IAVDD
PD
Supply Current
Power Consumption
Power-Down
26.6 33.3
80
4
AVDD = 3 V, MODE = AVSS
AVDD = DRVDD = 3 V, MODE = AVSS
STBY = AVDD, MODE and CLOCK =
AVSS
100
Gain Error Power Supply Rejection
PSRR
1
% FS
DYNAMIC PERFORMANCE (AIN = 0.5 dBFS)
Signal-to-Noise and Distortion
f = 3.58 MHz
f = 10 MHz
SINAD
54.5
57
54
dB
dB
Effective Bits
f = 3.58 MHz
f = 10 MHz
9.1
8.6
Bits
Bits
Signal-to-Noise
f = 3.58 MHz
f = 10 MHz
SNR
55
57
56
dB
dB
Total Harmonic Distortion
f = 3.58 MHz
f = 10 MHz
Spurious Free Dynamic Range
f = 3.58 MHz
f = 10 MHz
THD
SFDR
–59
–61
–66
–58
dB
dB
–69
–61
dB
dB
Two-Tone Intermodulation
Distortion
Differential Phase
Differential Gain
IMD
DP
DG
68
0.1
0.05
dB
f = 44.49 MHz and 45.52 MHz
Degree NTSC 40 IRE Mod Ramp
%
REV. E
–2–
AD9200
Parameter
Symbol
Min
Typ
Max
Units
Condition
DIGITAL INPUTS
High Input Voltage
Low Input Voltage
VIH
VIL
2.4
V
V
0.3
DIGITAL OUTPUTS
High-Z Leakage
Data Valid Delay
Data Enable Delay
Data High-Z Delay
IOZ
tOD
tDEN
tDHZ
–10
+10
µA
ns
ns
ns
Output = GND to VDD
CL = 20 pF
25
25
13
LOGIC OUTPUT (with DRVDD = 3 V)
High Level Output Voltage (IOH = 50 µA)
High Level Output Voltage (IOH = 0.5 mA)
Low Level Output Voltage (IOL = 1.6 mA)
Low Level Output Voltage (IOL = 50 µA)
VOH
VOH
VOL
VOL
+2.95
+2.80
V
V
V
V
+0.4
+0.05
LOGIC OUTPUT (with DRVDD = 5 V)
High Level Output Voltage (IOH = 50 µA)
High Level Output Voltage (IOH = 0.5 mA)
Low Level Output Voltage (IOL = 1.6 mA)
Low Level Output Voltage (IOL = 50 µA)
VOH
VOH
VOL
VOL
+4.5
+2.4
V
V
V
V
+0.4
+0.1
CLOCKING
Clock Pulsewidth High
Clock Pulsewidth Low
Pipeline Latency
tCH
tCL
22.5
22.5
ns
ns
Cycles
3
CLAMP2
Clamp Error Voltage
Clamp Pulsewidth
EOC
tCPW
±20
2
±40
mV
µs
CLAMPIN = 0.5 V–2.7 V, RIN = 10 Ω
CIN = 1 µF (Period = 63.5 µs)
NOTES
1See Figures 1a and 1b.
2Available only in AD9200ARS and AD9200KST.
Specifications subject to change without notice.
REFTS
10k⍀
10k⍀
REFTS
AD9200
AD9200
REFTF
REFBF
4.2k⍀
REFBS
MODE
0.4
؋
V DD
REFBS
MODE
AV
DD
Figure 1a.
Figure 1b.
REV. E
–3–
AD9200
ABSOLUTE MAXIMUM RATINGS*
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those indicated in the operational
sections of this specification is not implied. Exposure to absolute maximum
ratings for extended periods may effect device reliability.
With
Respect
to
Parameter
Min
Max
Units
ORDERING GUIDE
AVDD
DRVDD
AVSS
AVDD
MODE
CLK
Digital Outputs
AIN
VREF
REFSENSE
REFTF, REFTB
REFTS, REFBS
Junction Temperature
Storage Temperature
Lead Temperature
10 sec
AVSS
DRVSS
DRVSS
DRVDD –6.5
AVSS
AVSS
DRVSS
AVSS
AVSS
AVSS
AVSS
AVSS
–0.3
–0.3
–0.3
+6.5
+6.5
+0.3
+6.5
AVDD + 0.3
AVDD + 0.3
DRVDD + 0.3 V
AVDD + 0.3
AVDD + 0.3
AVDD + 0.3
AVDD + 0.3
AVDD + 0.3
+150
V
V
V
V
V
V
Temperature Package
Package
Options*
Model
Range
Description
–0.3
–0.3
–0.3
–0.3
–0.3
–0.3
–0.3
–0.3
AD9200JRS
AD9200ARS
AD9200JST
AD9200KST
0°C to +70°C
28-Lead SSOP
RS-28
RS-28
ST-48
ST-48
–40°C to +85°C 28-Lead SSOP
0°C to +70°C
0°C to +70°C
48-Lead LQFP
48-Lead LQFP
V
V
V
V
V
°C
°C
AD9200JRSRL 0°C to +70°C
28-Lead SSOP (Reel) RS-28
AD9200ARSRL –40°C to +85°C 28-Lead SSOP (Reel) RS-28
AD9200JSTRL 0°C to +70°C
AD9200KSTRL 0°C to +70°C
AD9200 SSOP-EVAL
48-Lead LQFP (Reel) ST-48
48-Lead LQFP (Reel) ST-48
Evaluation Board
–65
+150
AD9200 LQFP-EVAL
Evaluation Board
*RS = Shrink Small Outline; ST = Thin Quad Flatpack.
+300
°C
AVDD
DRVDD
AVDD
AVDD
AVDD
AVDD
AVSS
DRVSS
DRVSS
AVSS
AVSS
AVSS
AVSS
a. D0–D9, OTR
b. Three-State, Standby, Clamp
c. CLK
AVDD
AVDD
REFTF
REFBS
AVDD
AVSS
AVSS
AVSS
AVDD
AVDD
REFTS
REFBF
AVSS
AVSS
d. AIN
e. Reference
AVDD
AVDD
AVDD
AVDD
AVSS
AVSS
AVSS
AVSS
f. CLAMPIN
g. MODE
h. REFSENSE
i. VREF
Figure 2. Equivalent Circuits
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the AD9200 features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
REV. E
–4–
AD9200
PIN CONFIGURATIONS
28-Lead Shrink Small Outline (SSOP)
48-Lead Plastic Thin Quad Flatpack (LQFP)
AVDD
AIN
AVSS
DRVDD
D0
1
2
28
27
48 47 46 45 44 43 42 41 40 39 38 37
3
26 VREF
1
2
D0
D1
D2
D3
D4
NC
NC
D5
D6
D7
D8
D9
36
35
34
33
32
31
30
29
28
27
26
25
NC
D1
REFBS
25
4
PIN 1
IDENTIFIER
REFBS
REFBF
NC
D2
REFBF
24
5
3
AD9200
TOP VIEW
(Not to Scale)
D3
6
23
22
21
20
19
18
17
16
15
MODE
REFTF
REFTS
4
5
D4
7
MODE
NC
AD9200
TOP VIEW
(Not to Scale)
6
8
D5
D6
D7
7
REFTF
REFTS
CLAMPIN
CLAMP
REFSENSE
NC
9
CLAMPIN
CLAMP
8
10
11
12
13
14
9
D8
D9
REFSENSE
STBY
10
11
12
OTR
THREE-STATE
CLK
DRVSS
13 14 15 16 17 18 19 20 21 22 23 24
NC = NO CONNECT
PIN FUNCTION DESCRIPTIONS
SSOP
Pin No.
LQFP
Pin No.
Name
Description
1
2
3
44
45
1
AVSS
DRVDD
D0
Analog Ground
Digital Driver Supply
Bit 0, Least Significant Bit
4
2
D1
Bit 1
5
3
D2
Bit 2
6
7
4
5
D3
D4
Bit 3
Bit 4
8
8
D5
Bit 5
9
9
D6
D7
D8
D9
OTR
DRVSS
CLK
THREE-STATE
STBY
REFSENSE
CLAMP
CLAMPIN
REFTS
REFTF
MODE
REFBF
REFBS
VREF
AIN
Bit 6
Bit 7
Bit 8
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
10
11
12
16
17
22
23
24
26
27
28
29
30
32
34
35
38
39
42
Bit 9, Most Significant Bit
Out-of-Range Indicator
Digital Ground
Clock Input
HI: High Impedance State. LO: Normal Operation
HI: Power-Down Mode. LO: Normal Operation
Reference Select
HI: Enable Clamp Mode. LO: No Clamp
Clamp Reference Input
Top Reference
Top Reference Decoupling
Mode Select
Bottom Reference Decoupling
Bottom Reference
Internal Reference Output
Analog Input
AVDD
Analog Supply
REV. E
–5–
AD9200
DEFINITIONS OF SPECIFICATIONS
Offset Error
Integral Nonlinearity (INL)
The first transition should occur at a level 1 LSB above “zero.”
Offset is defined as the deviation of the actual first code transi-
tion from that point.
Integral nonlinearity refers to the deviation of each individual
code from a line drawn from “zero” through “full scale”. The
point used as “zero” occurs 1/2 LSB before the first code transi-
tion. “Full scale” is defined as a level 1 1/2 LSB beyond the last
code transition. The deviation is measured from the center of
each particular code to the true straight line.
Gain Error
The first code transition should occur for an analog value 1 LSB
above nominal negative full scale. The last transition should
occur for an analog value 1 LSB below the nominal positive full
scale. Gain error is the deviation of the actual difference be-
tween first and last code transitions and the ideal difference
between the first and last code transitions.
Differential Nonlinearity (DNL, No Missing Codes)
An ideal ADC exhibits code transitions that are exactly 1 LSB
apart. DNL is the deviation from this ideal value. It is often
specified in terms of the resolution for which no missing codes
(NMC) are guaranteed.
Pipeline Delay (Latency)
The number of clock cycles between conversion initiation and
the associated output data being made available. New output
data is provided every rising edge.
(AVDD = +3 V, DRVDD = +3 V, FS = 20 MHz (50% Duty Cycle), MODE = AVDD, 2 V Input
Span from 0.5 V to 2.5 V, External Reference, unless otherwise noted)
Typical Characterization Curves
60
1.0
–0.5 AMPLITUDE
55
–6.0 AMPLITUDE
50
45
0.5
0
–20.0 AMPLITUDE
40
35
30
25
–0.5
–1.0
20
1.00E+05
1.00E+06
1.00E+07
1.00E+08
0
128
256
384
512
640
768
896 1024
INPUT FREQUENCY – Hz
CODE OFFSET
Figure 5. SNR vs. Input Frequency
Figure 3. Typical DNL
60
55
50
45
40
35
30
1.0
0.5
–0.5 AMPLITUDE
–6.0 AMPLITUDE
0
–20.0 AMPLITUDE
–0.5
–1.0
25
20
1.00E+05
1.00E+06
1.00E+07
1.00E+08
0
128
256
384
512
640
768
896 1024
INPUT FREQUENCY – Hz
CODE OFFSET
Figure 6. SINAD vs. Input Frequency
Figure 4. Typical INL
REV. E
–6–
AD9200
–30
–35
–40
80.5
80.0
79.5
79.0
78.5
78.0
77.5
77.0
CLOCK = 20MHz
–20.0 AMPLITUDE
–6.0 AMPLITUDE
–45
–50
–55
–60
–65
–70
–0.5 AMPLITUDE
1.00E+06
–75
–80
1.00E+05
1.00E+07
1.00E+08
100E+06
100
0
2
4
6
8
10
12
14
16
18
20
INPUT FREQUENCY – Hz
CLOCK FREQUENCY – MHz
Figure 7. THD vs. Input Frequency
Figure 10. Power Consumption vs. Clock Frequency
(MODE = AVSS)
–70
–60
–50
–40
–30
–20
–10
1M
900k
800k
700k
600k
F
= 1MHz
IN
499856
500k
400k
300k
200k
100k
0
54383
N–1
54160
N+1
0
100E+03
1E+06
10E+06
N
CLOCK FREQUENCY – Hz
CODE
Figure 8. THD vs. Clock Frequency
Figure 11. Grounded Input Histogram
20
0
1.005
1.004
1.003
1.002
1.001
1.000
0.999
0.998
CLOCK = 20MHz
–20
–40
–60
–80
–100
–120
–140
–40
–20
0
20
40
60
80
0E+0 1E+6 2E+6 3E+6 4E+6 5E+6 6E+6 7E+6 8E+6 9E+6 10E+6
SINGLE TONE FREQUENCY DOMAIN
TEMPERATURE – °C
Figure 9. Voltage Reference Error vs. Temperature
Figure 12. Single-Tone Frequency Domain
REV. E
–7–
AD9200
0
–3
–6
–9
APPLYING THE AD9200
THEORY OF OPERATION
The AD9200 implements a pipelined multistage architecture to
achieve high sample rate with low power. The AD9200 distrib-
utes the conversion over several smaller A/D subblocks, refining
the conversion with progressively higher accuracy as it passes
the results from stage to stage. As a consequence of the distrib-
uted conversion, the AD9200 requires a small fraction of the
1023 comparators used in a traditional flash type A/D. A
sample-and-hold function within each of the stages permits the
first stage to operate on a new input sample while the second,
third and fourth stages operate on the three preceding samples.
–12
–15
–18
–21
–24
–27
1.0E+6
10.0E+6
100.0E+6
1.0E+9
OPERATIONAL MODES
FREQUENCY – Hz
The AD9200 is designed to allow optimal performance in a
wide variety of imaging, communications and instrumentation
applications, including pin compatibility with the AD876 A/D.
To realize this flexibility, internal switches on the AD9200 are
used to reconfigure the circuit into different modes. These modes
are selected by appropriate pin strapping. There are three parts
of the circuit affected by this modality: the voltage reference, the
reference buffer, and the analog input. The nature of the appli-
cation will determine which mode is appropriate: the descrip-
tions in the following sections, as well as the Table I should
assist in picking the desired mode.
Figure 13. Full Power Bandwidth
25
20
15
10
REFBS = 0.5V
REFTS = 2.5V
CLOCK = 20MHz
5
0
–5
–10
–15
–20
–25
0
0.5
1.0
1.5
2.0
2.5
3.0
INPUT VOLTAGE – V
Figure 14. Input Bias Current vs. Input Voltage
Table I. Mode Selection
Input
Connect
Input
Span
MODE
Pin
REFSENSE
Pin
Modes
REF
REFTS
REFBS
Figure
TOP/BOTTOM AIN
AIN
1 V
2 V
AVDD
AVDD
Short REFSENSE, REFTS and VREF Together
AGND Short REFTS and VREF Together
AGND
AGND
18
19
CENTER SPAN AIN
AIN
1 V
2 V
AVDD/2 Short VREF and REFSENSE Together
AVDD/2 AGND No Connect
AVDD/2 Short VREF and REFSENSE Together
AVDD/2
AVDD/2
AVDD/2 20
AVDD/2
Differential
AIN Is Input 1
1 V
AVDD/2
AVDD/2 29
REFTS and
REFBS Are
Shorted Together
for Input 2
2 V
AVDD/2 AGND
No Connect
No Connect
AVDD/2
AVDD/2
External Ref
AD876
AIN
2 V max AVDD
AVDD
Span = REFTS
21, 22
23
– REFBS (2 V max)
AGND
Short to
Short to
VREFTF
VREFBF
AIN
2 V
Float or AVDD
AVSS
No Connect
Short to
Short to
30
VREFTF
VREFBF
REV. E
–8–
AD9200
SUMMARY OF MODES
VOLTAGE REFERENCE
1 V Mode the internal reference may be set to 1 V by connect-
ing REFSENSE and VREF together.
AIN
A/D
CORE
SHA
REFTS
2 V Mode the internal reference my be set to 2 V by connecting
REFSENSE to analog ground
AD9200
External Divider Mode the internal reference may be set to a
point between 1 V and 2 V by adding external resistors. See
Figure 16f.
REFBS
Figure 15. AD9200 Equivalent Functional Input Circuit
In single-ended operation, the input spans the range,
REFBS ≤ AIN ≤ REFTS
External Reference Mode enables the user to apply an exter-
nal reference to REFTS, REFBS and VREF pins. This mode
is attained by tying REFSENSE to VDD.
where REFBS can be connected to GND and REFTS con-
nected to VREF. If the user requires a different reference range,
REFBS and REFTS can be driven to any voltage within the
power supply rails, so long as the difference between the two is
between 1 V and 2 V.
REFERENCE BUFFER
Center Span Mode midscale is set by shorting REFTS and
REFBS together and applying the midscale voltage to that point
The MODE pin is set to AVDD/2. The analog input will swing
about that midscale point.
In differential operation, REFTS and REFBS are shorted to-
gether, and the input span is set by VREF,
Top/Bottom Mode sets the input range between two points.
The two points are between 1 V and 2 V apart. The Top/Bottom
Mode is enabled by tying the MODE pin to AVDD.
(REFTS – VREF/2) ≤ AIN ≤ (REFTS + VREF/2)
where VREF is determined by the internal reference or brought
in externally by the user.
ANALOG INPUT
Differential Mode is attained by driving the AIN pin as one
differential input and shorting REFTS and REFBS together and
driving them as the second differential input. The MODE pin
is tied to AVDD/2. Preferred mode for optimal distortion
performance.
The best noise performance may be obtained by operating the
AD9200 with a 2 V input range. The best distortion perfor-
mance may be obtained by operating the AD9200 with a 1 V
input range.
Single-Ended is attained by driving the AIN pin while the
REFTS and REFBS pins are held at dc points. The MODE pin is
tied to AVDD.
REFERENCE OPERATION
The AD9200 can be configured in a variety of reference topolo-
gies. The simplest configuration is to use the AD9200’s onboard
bandgap reference, which provides a pin-strappable option to
generate either a 1 V or 2 V output. If the user desires a refer-
ence voltage other than those two, an external resistor divider
can be connected between VREF, REFSENSE and analog
ground to generate a potential anywhere between 1 V and 2 V.
Another alternative is to use an external reference for designs
requiring enhanced accuracy and/or drift performance. A
third alternative is to bring in top and bottom references,
bypassing VREF altogether.
Single-Ended/Clamped (AC Coupled) the input may be
clamped to some dc level by ac coupling the input. This is done
by tying the CLAMPIN to some dc point and applying a pulse
to the CLAMP pin. MODE pin is tied to AVDD.
SPECIAL
AD876 Mode enables users of the AD876 to drop the AD9200
into their socket. This mode is attained by floating or grounding
the MODE pin.
Figures 16d, 16e and 16f illustrate the reference and input ar-
chitecture of the AD9200. In tailoring a desired arrangement,
the user can select an input configuration to match drive circuit.
Then, moving to the reference modes at the bottom of the
figure, select a reference circuit to accommodate the offset and
amplitude of a full-scale signal.
INPUT AND REFERENCE OVERVIEW
Figure 16, a simplified model of the AD9200, highlights the
relationship between the analog input, AIN, and the reference
voltages, REFTS, REFBS and VREF. Like the voltages applied
to the resistor ladder in a flash A/D converter, REFTS and
REFBS define the maximum and minimum input voltages to
the A/D.
Table I outlines pin configurations to match user requirements.
The input stage is normally configured for single-ended opera-
tion, but allows for differential operation by shorting REFTS
and REFBS together to be used as the second input.
REV. E
–9–
AD9200
V*
+FS
–FS
MIDSCALE
AD9200
MODE
REFTF
AIN
AVDD/2
AD9200
SHA
AIN
MODE
(AVDD)
SHA
+F/S RANGE OBTAINED
FROM VREF PIN OR
EXTERNAL REF
0.1F
10k⍀
0.1F
10k⍀
REFTF
10k⍀
10k⍀
REFTS
REFBS
10k⍀
10k⍀
REFTS
REFBS
A2
0.1F
A/D
CORE
4.2k⍀
TOTAL
10F
A2
0.1F
A/D
CORE
4.2k⍀
TOTAL
10F
INTERNAL
REF
0.1F
10k⍀
–F/S RANGE OBTAINED
FROM VREF PIN OR
EXTERNAL REF
0.1F
10k⍀
REFBF
REFBF
MIDSCALE OFFSET
VOLTAGE IS DERIVED
FROM INTERNAL OR
EXTERNAL REF
* MAXIMUM MAGNITUDE OF V IS DETERMINED
BY INTERNAL REFERENCE
a. Top/Bottom Mode
b. Center Span Mode
MAXIMUM MAGNITUDE OF V
IS DETERMINED BY INTERNAL
REFERENCE AND TURNS RATIO
V
AD9200
MODE
REFTF
AIN
AVDD/2
SHA
AVDD/2
0.1F
10k⍀
10k⍀
10k⍀
REFTS
REFBS
A2
0.1F
A/D
CORE
4.2k⍀
TOTAL
10F
INTERNAL
REF
0.1F
10k⍀
REFBF
c. Differential Mode
VREF
(2V)
VREF
(1V)
A1
A1
1V
0.01F
1.0F
1V
10k⍀
10k⍀
REFSENSE
AVSS
0.1F
1.0F
REFSENSE
AVSS
AD9200
AD9200
d. 1 V Reference
e. 2 V Reference
VREF
(= 1 + R /R
)
A
B
A1
1V
0.1F
1.0F
R
A
A1
VREF
1V
REFSENSE
REFSENSE
AVDD
R
B
AD9200
AVSS
AD9200
INTERNAL 10K REF RESISTORS ARE
SWITCHED OPEN BY THE PRESENSE
OF R AND R
.
A
B
f. Variable Reference
(Between 1 V and 2 V)
g. Internal Reference Disable
(Power Reduction)
Figure 16.
–10–
REV. E
AD9200
The actual reference voltages used by the internal circuitry of
the AD9200 appear on REFTF and REFBF. For proper opera-
tion, it is necessary to add a capacitor network to decouple these
pins. The REFTF and REFBF should be decoupled for all
internal and external configurations as shown in Figure 17.
Figure 19 shows the single-ended configuration for 2 V p-p
operation. REFSENSE is connected to GND, resulting in a 2 V
reference output.
2V
AIN
AD9200
MODE
SHA
AVDD
0V
0.1F
REFTF
10k⍀
REFTF
10F
0.1F
AD9200
10k⍀
10k⍀
REFTS
REFBS
REFBF
A2
0.1F
A/D
CORE
4.2k⍀
TOTAL
10F
0.1F
0.1F
0.1F
10k⍀
Figure 17. Reference Decoupling Network
REFBF
VREF
Note: REFTF = reference top, force
REFBF = reference bottom, force
REFTS = reference top, sense
A1
1V
1.0F
0.1F
REF
SENSE
REFBS = reference bottom, sense
INTERNAL REFERENCE OPERATION
Figure 19. Internal Reference, 2 V p-p Input Span
(Top/Bottom Mode)
Figures 18, 19 and 20 show example hookups of the AD9200
internal reference in its most common configurations. (Figures
18 and 19 illustrate top/bottom mode while Figure 20 illustrates
center span mode). Figure 29 shows how to connect the AD9200
for 1 V p-p differential operation. Shorting the VREF pin
directly to the REFSENSE pin places the internal reference
amplifier, A1, in unity-gain mode and the resultant reference
output is 1 V. In Figure 18 REFBS is grounded to give an input
range from 0 V to 1 V. These modes can be chosen when the
supply is either +3 V or +5 V. The VREF pin must be bypassed to
AVSS (analog ground) with a 1.0 µF tantalum capacitor in
parallel with a low inductance, low ESR, 0.1 µF ceramic capacitor.
Figure 20 shows the single-ended configuration that gives the
good high frequency dynamic performance (SINAD, SFDR).
To optimize dynamic performance, center the common-mode
voltage of the analog input at approximately 1.5 V. Connect the
shorted REFTS and REFBS inputs to a low impedance 1.5V
source. In this configuration, the MODE pin is driven to a volt-
age at midsupply (AVDD/2).
Maximum reference drive is 1 mA. An external buffer is re-
quired for heavier loads.
1V
AIN
AD9200
2V
MODE
AIN
AD9200
SHA
AVDD
MODE
0V
AVDD/2
SHA
1V
0.1F
10k⍀
REFTF
0.1F
REFTF
10k⍀
10k⍀
10k⍀
REFTS
REFBS
10k⍀
10k⍀
REFTS
REFBS
A2
0.1F
A/D
CORE
4.2k⍀
TOTAL
10F
A2
+1.5V
0.1F
A/D
CORE
4.2k⍀
TOTAL
10F
0.1F
10k⍀
0.1F
10k⍀
REFBF
REFBF
VREF
A1
VREF
1V
A1
REF
SENSE
1V
1.0F
0.1F
REF
SENSE
0.1F
1.0F
Figure 18. Internal Reference 1 V p-p Input Span
(Top/Bottom Mode)
Figure 20. Internal Reference 1 V p-p Input Span,
(Center Span Mode)
REV. E
–11–
AD9200
EXTERNAL REFERENCE OPERATION
4V
2V
VIN
Using an external reference may provide more flexibility and
improve drift and accuracy. Figures 21 through 23 show ex-
amples of how to use an external reference with the AD9200.
To use an external reference, the user must disable the internal
reference amplifier by connecting the REFSENSE pin to VDD.
The user then has the option of driving the VREF pin, or driv-
ing the REFTS and REFBS pins.
REFTS
REFTF
4V
2V
AD9200
1
F
0
0
F
F
REFBF
0
F
REFBS
VREF
The AD9200 contains an internal reference buffer (A2), that
simplifies the drive requirements of an external reference. The
external reference must simply be able to drive a 10 kΩ load.
REFSENSE
MODE
AVDD
Figure 21 shows an example of the user driving the top and bottom
references. REFTS is connected to a low impedance 2 V source
and REFBS is connected to a low impedance 1 V source. REFTS
and REFBS may be driven to any voltage within the supply as
long as the difference between them is between 1 V and 2 V.
Figure 23a. External Reference—2 V p-p Input Span
REFTS
+5V
C4
0
F
6
5
2V
8
AIN
7
AD9200
REFTF
SHA
1V
C3
0
REFT
C6
0
F
C2
1
AD9200
F
F
0.1F
10k⍀
REFTF
REFBS
10k⍀
10k⍀
REFTS
REFBS
C5
0
2V
1V
2
3
F
A2
0.1F
6
A/D
CORE
4.2k⍀
TOTAL
10F
REFBF
REFB
C1
0
4
F
REF
SENSE
0.1F
10k⍀
AVDD
MODE
REFBF
Figure 23b. Kelvin Connected Reference Using the AD9200
Figure 21. External Reference Mode—1 V p-p Input Span
STANDBY OPERATION
The ADC may be placed into a powered down (sleep) mode by
driving the STBY (standby) pin to logic high potential and
holding the clock at logic low. In this mode the typical power
drain is approximately 4 mW. If there is no connection to the
STBY pin, an internal pull-down circuit will keep the ADC in a
“wake-up” mode of operation.
Figure 22 shows an example of an external reference generating
2.5 V at the shorted REFTS and REFBS inputs. In this in-
stance, a REF43 2.5 V reference drives REFTS and REFBS. A
resistive divider generates a 1 V VREF signal that is buffered by
A3. A3 must be able to drive a 10 kΩ, capacitive load. Choose
this op amp based on noise and accuracy requirements.
The ADC will “wake up” in 400 ns (typ) after the standby pulse
goes low.
AD9200
3.0V
2.5V
2.0V
AIN
CLAMP OPERATION
AVDD
AVDD
The AD9200ARS and AD9200KST parts feature an optional
clamp circuit for dc restoration of video or ac coupled signals.
Figure 24 shows the internal clamp circuitry and the external
control signals needed for clamp operation. To enable the
clamp, apply a logic high to the CLAMP pin. This will close
the switch SW1. The clamp amplifier will then servo the volt-
age at the AIN pin to be equal to the clamp voltage applied at
the CLAMPIN pin. After the desired clamp level is attained,
SW1 is opened by taking CLAMP back to a logic low. Ignoring
the droop caused by the input bias current, the input capacitor
CIN will hold the dc voltage at AIN constant until the next
clamp interval. The input resistor RIN has a minimum recom-
mended value of 10 Ω, to maintain the closed-loop stability of
the clamp amplifier.
REFTS
REFBS
0.1F
0.1F
0.1F
REFTF
10F
1.5k⍀
A3
0.1F
10F
VREF
MODE
1.0F
0.1F
REFBF
0.1F
1k⍀
+5V
AVDD
REFSENSE
REF43
0.1F
AVDD/2
Figure 22. External Reference Mode—1 V p-p Input
Span 2.5 VCM
Figure 23a shows an example of the external references driving
the REFTF and REFBF pins that is compatible with the
AD876. REFTS is shorted to REFTF and driven by an external
4 V low impedance source. REFBS is shorted to REFBF and
driven by a 2 V source. The MODE pin is connected to GND
in this configuration.
The allowable voltage range that can be applied to CLAMPIN
depends on the operational limits of the internal clamp ampli-
fier. When operating off of 3 volt supplies, the recommended
clamp range is between 0.5 volts and 2.0 volts.
REV. E
–12–
AD9200
The input capacitor should be sized to allow sufficient acquisi-
tion time of the clamp voltage at AIN within the CLAMP inter-
val, but also be sized to minimize droop between clamping
intervals. Specifically, the acquisition time when the switch is
closed will equal:
back porch to truncate the SYNC below the AD9200’s mini-
mum input voltage. With a CIN = 1 µF, and RIN = 20 Ω, the
acquisition time needed to set the input dc level to one volt
with 1 mV accuracy is about 140 µs, assuming a full 1 volt VC.
With a 1 µF input coupling capacitor, the droop across one
horizontal can be calculated:
VC
TACQ = RINCIN ln
VE
I
BIAS = 10 µA, and t = 63.5 µs, so dV = 0.635 mV, which is less
than one LSB.
where VC is the voltage change required across CIN, and VE is
the error voltage. VC is calculated by taking the difference be-
tween the initial input dc level at the start of the clamp interval
and the clamp voltage supplied at CLAMPIN. VE is a system-
dependent parameter, and equals the maximum tolerable devia-
tion from VC. For example, if a 2-volt input level needs to be
clamped to 1 volt at the AD9200’s input within 10 millivolts,
then VC equals 2 – 1 or 1 volt, and VE equals 10 mV. Note that
once the proper clamp level is attained at the input, only a very
small voltage change will be required to correct for droop.
After the input capacitor is initially charged, the clamp pulse-
width only needs to be wide enough to correct small voltage
errors such as the droop. The fine scale settling characteristics
of the clamp circuitry are shown in Table II.
Depending on the required accuracy, a CLAMP pulsewidth of
1 µs–3 µs should work in most applications. The OFFSET val-
ues ignore the contribution of offset from the clamp amplifier;
they simply compare the output code with a “final value” mea-
sured with a much longer CLAMP pulse duration.
The voltage droop is calculated with the following equation:
Table II.
IBIAS
CIN
dV =
t
( )
CLAMP
OFFSET
10 µs
5 µs
4 µs
3 µs
2 µs
1 µs
<1 LSB
5 LSBs
7 LSBs
11 LSBs
19 LSBs
42 LSBs
where t = time between clamping intervals.
The bias current of the AD9200 will depend on the sampling
rate, FS. The switched capacitor input AIN appears resistive
over time, with an input resistance equal to 1/CSFS. Given a
sampling rate of 20 MSPS and an input capacitance of 1 pF, the
input resistance is 50 kΩ. This input resistance is equivalently
terminated at the midscale voltage of the input range. The worst
case bias current will thus result when the input signal is at the
extremes of the input range, that is, the furthest distance from
the midscale voltage level. For a 1-volt input range, the maxi-
mum bias current will be ±0.5 volts divided by 50 kΩ, which is
±10 µA.
AD9200
CLAMP IN
CLAMP
SW1
If droop is a critical parameter, then the minimum value of CIN
should be calculated first based on the droop requirement.
Acquisition time—the width of the CLAMP pulse—can be
adjusted accordingly once the minimum capacitor value is cho-
sen. A tradeoff will often need to be made between droop and
acquisition time, or error voltage VE.
CIN
RIN
AIN
TO
SHA
Figure 24a. Clamp Operation
Clamp Circuit Example
A single supply video amplifier outputs a level-shifted video
signal between 2 and 3 volts with the following parameters:
AIN
0
0
F
F
REFTF
REFTS
horizontal period = 63.56 µs,
horizontal sync interval = 10.9 µs,
horizontal sync pulse = 4.7 µs,
sync amplitude = 0.3 volts,
1
F
0F
AD9200
REFBF
REFBS
video amplitude of 0.7 volts,
reference black level = 2.3 volts
AVDD
2
MODE
CLAMP
The video signal must be dc restored from a 2- to 3-volt range
down to a 1- to 2-volt range. Configuring the AD9200 for a
one volt input span with an input range from 1 to 2 volts (see
Figure 24), the CLAMPIN voltage can be set to 1 volt with an
external voltage or by direct connection to REFBS. The CLAMP
pulse may be applied during the SYNC pulse, or during the
SHORT TO REFBS
OR EXTERNAL DC
CLAMPIN
Figure 24b. Video Clamp Circuit
REV. E
–13–
AD9200
DRIVING THE ANALOG INPUT
In many cases, particularly in single-supply operation, ac cou-
pling offers a convenient way of biasing the analog input signal
at the proper signal range. Figure 25 shows a typical configura-
tion for ac-coupling the analog input signal to the AD9200.
Maintaining the specifications outlined in the data sheet
requires careful selection of the component values. The most
important is the f–3 dB high-pass corner frequency. It is a function of
R2 and the parallel combination of C1 and C2. The f–3 dB point
can be approximated by the equation:
Figure 25 shows the equivalent analog input of the AD9200, a
sample-and-hold amplifier (switched capacitor input SHA).
Bringing CLK to a logic low level closes Switches 1 and 2 and
opens Switch 3. The input source connected to AIN must
charge capacitor CH during this time. When CLK transitions
from logic “low” to logic “high,” Switches 1 and 2 open, placing
the SHA in hold mode. Switch 3 then closes, forcing the output
of the op amp to equal the voltage stored on CH. When CLK
transitions from logic “high” to logic “low,” Switch 3 opens
first. Switches 1 and 2 close, placing the SHA in track mode.
f
–3 dB = 1/(2 × pi × [R2] CEQ)
where CEQ is the parallel combination of C1 and C2. Note that
C1 is typically a large electrolytic or tantalum capacitor that
becomes inductive at high frequencies. Adding a small ceramic
or polystyrene capacitor (on the order of 0.01 µF) that does not
become inductive until negligibly higher frequencies, maintains
a low impedance over a wide frequency range.
The structure of the input SHA places certain requirements on
the input drive source. The combination of the pin capacitance,
CP, and the hold capacitance, CH, is typically less than 5 pF.
The input source must be able to charge or discharge this ca-
pacitance to 10-bit accuracy in one half of a clock cycle. When
the SHA goes into track mode, the input source must charge or
discharge capacitor CH from the voltage already stored on CH
to the new voltage. In the worst case, a full-scale voltage step on
the input, the input source must provide the charging current
through the RON (50 Ω) of Switch 1 and quickly (within 1/2 CLK
period) settle. This situation corresponds to driving a low input
impedance. On the other hand, when the source voltage equals
the value previously stored on CH, the hold capacitor requires
no input current and the equivalent input impedance is ex-
tremely high.
NOTE: AC coupled input signals may also be shifted to a desired
level with the AD9200’s internal clamp. See Clamp Operation.
C1
R1
V
AIN
IN
R2
I
B
AD9200
C2
V
BIAS
Adding series resistance between the output of the source and
the AIN pin reduces the drive requirements placed on the
source. Figure 26 shows this configuration. The bandwidth of
the particular application limits the size of this resistor. To
maintain the performance outlined in the data sheet specifica-
tions, the resistor should be limited to 20 Ω or less. For applica-
tions with signal bandwidths less than 10 MHz, the user may
proportionally increase the size of the series resistor. Alterna-
tively, adding a shunt capacitance between the AIN pin and
analog ground can lower the ac load impedance. The value of
this capacitance will depend on the source resistance and the
required signal bandwidth.
Figure 27. AC Coupled Input
There are additional considerations when choosing the resistor
values. The ac-coupling capacitors integrate the switching tran-
sients present at the input of the AD9200 and cause a net dc
bias current, IB, to flow into the input. The magnitude of the
bias current increases as the signal magnitude deviates from
V midscale and the clock frequency increases; i.e., minimum
bias current flow when AIN = V midscale. This bias current
will result in an offset error of (R1 + R2) × IB. If it is necessary
to compensate this error, consider making R2 negligibly small or
modifying VBIAS to account for the resultant offset.
The input span of the AD9200 is a function of the reference
voltages. For more information regarding the input range, see
the Internal and External Reference sections of the data sheet.
In systems that must use dc coupling, use an op amp to level-
shift a ground-referenced signal to comply with the input re-
quirements of the AD9200. Figure 28 shows an AD8041 config-
ured in noninverting mode.
CH
+V
CC
AIN
0
F
S1
CP
SHA
S3
NC
AD9200
S2
7
0V
DC
1V p-p
(REFTS
REFBS)
CH
2
3
1
5
2
CP
AD8041
6
AIN
AD9200
4
MIDSCALE
OFFSET
NC
VOLTAGE
Figure 25. AD9200 Equivalent Input Structure
Figure 28. Bipolar Level Shift
<
20⍀
AIN
AD9200
V
S
Figure 26. Simple AD9200 Drive Configuration
REV. E
–14–
AD9200
DIFFERENTIAL INPUT OPERATION
The pipelined architecture of the AD9200 operates on both
rising and falling edges of the input clock. To minimize duty
cycle variations the recommended logic family to drive the clock
input is high speed or advanced CMOS (HC/HCT, AC/ACT)
logic. CMOS logic provides both symmetrical voltage threshold
levels and sufficient rise and fall times to support 20 MSPS
operation. The AD9200 is designed to support a conversion rate
of 20 MSPS; running the part at slightly faster clock rates may
be possible, although at reduced performance levels. Conversely,
some slight performance improvements might be realized by
clocking the AD9200 at slower clock rates.
The AD9200 will accept differential input signals. This function
may be used by shorting REFTS and REFBS and driving them
as one leg of the differential signal (the top leg is driven into
AIN). In the configuration below, the AD9200 is accepting a
1 V p-p signal. See Figure 29.
AD9200
2V
AIN
0.1F
1V
AVDD/2
REFTF
REFTS
0.1F
10F
0.1F
REFBS
VREF
S1
S2
ANALOG
INPUT
S4
REFBF
tC
S3
1.0F
0.1F
tCH
tCL
REFSENSE
MODE
INPUT
CLOCK
AVDD/2
25ns
DATA
OUTPUT
Figure 29. Differential Input
AD876 MODE OF OPERATION
The AD9200 may be dropped into the AD876 socket. This will
allow AD876 users to take advantage of the reduced power
consumption realized when running the AD9200 on a 3.0 V
analog supply.
DATA 1
Figure 31. Timing Diagram
The power dissipated by the output buffers is largely propor-
tional to the clock frequency; running at reduced clock rates
provides a reduction in power consumption.
Figure 30 shows the pin functions of the AD876 and AD9200.
The grounded REFSENSE pin and floating MODE pin effec-
tively put the AD9200 in the external reference mode. The
external reference input for the AD876 will now be placed on
the reference pins of the AD9200.
DIGITAL INPUTS AND OUTPUTS
Each of the AD9200 digital control inputs, THREE-STATE
and STBY are reference to analog ground. The clock is also
referenced to analog ground.
The format of the digital output is straight binary (see Figure
32). A low power mode feature is provided such that for STBY
= HIGH and the clock disabled, the static power of the AD9200
will drop below 5 mW.
The clamp controls will be grounded by the AD876 socket. The
AD9200 has a 3 clock cycle delay compared to a 3.5 cycle delay
of the AD876.
4V
OTR
AIN
AD9200
2V
REFTS
4V
2V
REFTF
0.1F
0.1F
10F
REFBF
0.1F
REFBS
NC
MODE
REFSENSE
AVDD
CLAMP
CLAMPIN
–FS+1LSB
+FS
OTR
VREF
0.1F
–FS
+FS–1LSB
Figure 32. Output Data Format
Figure 30. AD876 Mode
THREE-
STATE
tDHZ
tDEN
CLOCK INPUT
DATA
The AD9200 clock input is buffered internally with an inverter
powered from the AVDD pin. This feature allows the AD9200
to accommodate either +5 V or +3.3 V CMOS logic input sig-
nal swings with the input threshold for the CLK pin nominally
at AVDD/2.
(D0–D9)
HIGH
IMPEDANCE
Figure 33. Three-State Timing Diagram
REV. E
–15–
AD9200
APPLICATIONS
Figure 34 shows a simplified schematic of the AD9200 config-
ured in an IF sampling application. To reduce the complexity of
the digital demodulator in many quadrature demodulation ap-
plications, the IF frequency and/or sample rate are selected such
that the bandlimited IF signal aliases back into the center of the
ADC’s baseband region (i.e., FS/4). For example, if an IF sig-
nal centered at 45 MHz is sampled at 20 MSPS, an image of
this IF signal will be aliased back to 5.0 MHz which corre-
sponds to one quarter of the sample rate (i.e., FS/4). This
demodulation technique typically reduces the complexity of the
post digital demodulator ASIC which follows the ADC.
DIRECT IF DOWN CONVERSION USING THE AD9200
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 ben-
efits in using the ADC to alias (i.e., or mix) down a narrowband
or wideband 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.
To maximize its distortion performance, the AD9200 is config-
ured in the differential mode with a 1 V span using a transformer.
The center tap of the transformer is biased at midsupply via a
resistor divider. Preceding the AD9200 is a bandpass filter as
well as a 32 dB gain stage. A large gain stage may be required
to compensate for the high insertion losses of a SAW filter used
for image rejection. The gain stage will also provide adequate
isolation for the SAW filter from the charge “kick back” currents
associated with AD9200’s input stage.
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 similar manner that a mixer will down-
convert 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 tradeoff exists between the complexity of this image rejection
filter and the sample rate as well as dynamic range of the ADC.
The gain stage can be realized using one or two cascaded
AD8009 op amps amplifiers. The AD8009 is a low cost, 1 GHz,
current-feedback op amp having a 3rd order intercept character-
ized up to 250 MHz. A passive bandpass filter following the
AD8009 attenuates its dominant 2nd order distortion products
which would otherwise be aliased back into the AD9200’s
baseband region. Also, it reduces any out-of-band noise which
would also be aliased back due to the AD9200’s noise band-
width of 220+ MHz. Note, the bandpass filters specifications
are application dependent and will affect both the total distor-
tion and noise performance of this circuit.
The AD9200 is well suited for various narrowband IF sampling
applications. The AD9200’s low distortion input SHA has a
full-power bandwidth extending to 300 MHz thus encompassing
many popular IF frequencies. A DNL of ±0.5 LSB (typ) com-
bined with low thermal input referred noise allows the AD9200 in
the 2 V span to provide 60 dB of SNR for a baseband input sine
wave. Also, its low aperture jitter of 2 ps rms ensures minimum
SNR degradation at higher IF frequencies. In fact, the AD9200
is capable of still maintaining 56 dB of SNR at an IF of 135 MHz
with a 1 V (i.e., 4 dBm) input span. Note, although the AD9200
will typically yield a 3 to 4 dB improvement in SNR when con-
figured for the 2 V span, the 1 V span provides the optimum
full-scale distortion performance. Furthermore, the 1 V span
reduces the performance requirements of the input driver cir-
cuitry and thus may be more practical for system implementa-
tion purposes.
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 an assessing an
ADC’s noise performance and noise contribution due to aper-
ture 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.
G
= 20dB
G
= 12dB
L-C
1
2
SAW
FILTER
OUTPUT
MINI CIRCUITS
T4 - 6T
BANDPASS
FILTER
AD9200
50⍀
50⍀
1:4
AIN
50⍀
200⍀
200⍀
REFTS
REFBS
280⍀
22.1⍀
93.1⍀
VREF
REFSENSE
1.0F 0.1F
0.1F
1k⍀
1k⍀
AVDD
Figure 34. Simplified AD9200 IF Sampling Circuit
REV. E
–16–
AD9200
Figures 35–38 combine the dual-tone SFDR as well as single
tone SFDR and SNR performance at IF frequencies of 45 MHz,
70 MHz, 85 MHz and 135 MHz. Note, the SFDR vs. ampli-
tude 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 AD9200 without the AD8009.
The AD9200 was operated in the differential mode (via trans-
former) with a 1 V span at 20 MSPS. The analog supply
(AVDD) and the digital supply (DRVDD) were set to +5 V and
3.3 V, respectively.
Although not presented, data was also taken with the insertion
of an AD8009 gain stage of 32 dB in the signal path. No
degradation in two-tone SFDR vs. amplitude was noted at an
IF of 45 MHz, 70 MHz and 85 MHz. However, at 135 MHz,
the AD8009 became the limiting factor in the distortion perfor-
mance until the two input tones were decreased to –15 dBFS
from their full-scale level of –6.5 dBFS. Note: the SNR perfor-
mance in each case degraded by approximately 0.5 dB due to
the AD8009’s in-band noise contribution.
90
90
SINGLE TONE SFDR
80
80
DUAL TONE SFDR
70
70
SINGLE TONE SFDR
DUAL TONE SFDR
60
60
50
40
50
40
30
30
SNR
SNR
CLK = 20MSPS
SINGLE TONE – 45.52MHz
DUAL TONE– F = 44.49MHz
1
20
10
0
20
10
0
CLK = 20MSPS
SINGLE TONE – 85.52MHz
DUAL TONE– F = 84.49MHz
1
– F = 45.52MHz
2
– F = 85.52MHz
2
–60
–50
–40
–30
–20
–10
0
–60
–50
–40
–30
–20
–10
0
INPUT POWER LEVEL – dBFS
INPUT POWER LEVEL – dBFS
Figure 35. SNR/SFDR for IF @ 45 MHz
Figure 37. SNR/SFDR for IF @ 85 MHz
90
90
SINGLE TONE SFDR
80
80
70
60
DUAL TONE SFDR
SINGLE TONE SFDR
70
DUAL TONE SFDR
60
50
40
50
40
30
30
20
10
SNR
SNR
20
10
0
CLK = 20MSPS
SINGLE TONE – 135.52MHz
DUAL TONE – F = 134.44MHz
CLK = 21.538MSPS
SINGLE TONE – 70.55MHz
1
DUAL TONE– F = 69.50MHz
1
– F = 135.52MHz
2
– F = 70.55MHz
2
0
–60
–50
–40
–30
–20
–10
0
–60
–50
–40
–30
–20
–10
0
INPUT POWER LEVEL – dBFS
INPUT POWER LEVEL – dBFS
Figure 36. SNR/SFDR for IF @ 70 MHz
Figure 38. SNR/SFDR for IF @ 135 MHz
REV. E
–17–
AD9200
R11
15k⍀
R10
5k⍀
+3–5A
R17
316⍀
+3–5A
TP14
5
6
R15
0.626V TO 4.8V
R7
1k⍀
7
2
3
AD822
U2
Q1
2N3906
TP16
5.49k⍀
4
XXXX
ADJ.
R8
10k⍀
1
AD822
U2
C7
0.1F
EXTT
8
D1
C11
0.1F
CW
C8
10/10V
C13
10/10V
C12
0.1F
AD1580
R19
178⍀
R9
1.5k⍀
+3–5A
CM
R13
11k⍀
R20
178⍀
TP17
R12
C29
10k⍀
0.1F
2
3
XXXX
4
ADJ.
EXTB
6
1
AD822
U3
C14
0.1F
C15
10/10V
7
R14
10k⍀
AD822
U3
Q2
2N3904
8
5
C10
0.1F
CW
R16
1k⍀
C9
10/10V
R18
316k⍀
+3–5A
TP11
J7
JP5
CLAMP
R37
1k⍀
DRVDD
R53
49.9⍀
B
JP17
JP18
1
S3
2
2
THREE-STATE
STBY
R38
1k⍀
3
1
A
S4
B
GND
3
A
R39
1k⍀
7
5
10
13
11
9
J8
J8
J8
J8
J8
RN1
22⍀
DRVDD
AVDD
27
25
J8
J8
C16
0.1F
C19
0.1F
6
11
RN1
22⍀
3
2
J8
J8
C18
10/10V
C17
12
10/10V
4
J8
RN1
22⍀
6
8
J8
J8
28
AVDD
2
16
15
21
8
4
13
B
OTR
TP19
WHITE
U4
A
DRVDD
7
9
3
4
5
6
7
10
1
2
B
B
B
B
B
U4
U4
U4
U4
U4
U4
U4
VCCA
T/R
A
A
A
A
A
RN1
22⍀
U1
10
12
D5
J8
J8
D6
D7
D8
D9
20
19
18
17
14
24
23
22
13
AD9200
13
2
15
OTR
5
14
J8
RN1
22⍀
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
15
16
17
18
19
20
21
22
23
24
3
4
5
6
7
8
9
10
11
12
B
B
A
A
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
16
18
DUTCLK
THREE-STATE
STBY
REFSENSE
CLAMP
CLK
THREE-STATE
J8
J8
B 1
S2
2
+3–5D
DRVDD
C40
0.1F
VCCB
NC1
OE
1
16
STBY
3
1
J8
20
22
C20
0.1F
J8
J8
REFSENSE
11
12
RN1
22⍀
A
GD2
GD3
CLAMP
GD1
CLAMPIN
REFTS
REFTF
MODE
REFBF
REFBS
VREF
AIN
CLAMPIN
REFTS
REFTF
MODE
REFBF
U4
GND
24
26
J8
J8
GND GND
GND
CLK
74LVXC4245WM
JP21
1
WHITE
3
+3–5D
6
11
2
19
5
NC
39
J8
25
26
27
CLK
B
B
B
B
B
B
B
B
33
U5
U5
U5
U5
U5
U5
U5
U5
VCCA
A
A
A
A
A
A
A
A
J8
REFBS
20
21
18
17
4
3
6
7
C42
0.1F
RN2
22⍀
28
29
J8
J8
VREF
AIN
CLK_OUT
5
12
D0
D1
D2
D3
J8
23
AVSS
1
DRVSS
14
+
RN2
22⍀
C33
10/10V
30
31
J8
J8
16
15
14
24
23
22
13
8
9
10
1
2
11
12
D4
13
4
32
34
J8
21
J8
+3–5D
VCCB
NC1
OE
RN2
22⍀
J8
J8
T/R
GD2
GD3
C21
DRVDD
0.1F
NC 35
3
14
C41
GD1
U5
19 J8
36
0.1F
J8
J8
GND
RN2
22⍀
74LVXC4245WM
3
NC 37
GND
GND
38
40
J8
J8
2
15
2
1
17
15
J8
J8
RN2
22⍀
JP20
C43
0.1F
GND
16
1
GND
RN2
22⍀
Figure 39a. Evaluation Board Schematic
REV. E
–18–
AD9200
JP14
REFSENSE
EXTB
AVDD
JP1
JP2
JP10
R5
10
AVDD
MODE
TP3
TP4
C3
0
F
TP1
JP15
JP16
REFBF
REFTF
C4
0
C5
10/10V
+
R6
10
F
JP3
JP4
JP9
C6
0
F
VREF
AVDDCLK
JP22
TP5
B
1
GND
AVDD
EXTT
S5
GND
R35
4.99
2
CLAMPIN
EXTT
3
JP11
TP6
A
R34
2
JP6
CW
REFTS
GND
JP12
R36
4.99
C36
0
C37
0
C38
0
C35
10/10V
U6
U6
B
F
F
F
1
2
TP7
5
6
REFBS
EXTB
GND
JP7
JP13
TP12
2
C30
B
A
T1–1T
4
1
1
0
F
AIN
S7
S6
2
3
2
J1
A
3
3
3
2
J5
A
R51
49
S8
ADC_CLK
B
1
R1
TP8
49
R4
49
6
P
S
CLK
1
JP8
REFBS
CM
TP13
T1
R52
49
TP9
R2
10
U6
JP26
3
4
C1
0
DUTCLK
F
TP10
DCIN
A
3
R3
10
2
S1
C2
47/10V
1
B
TP29
TP20
TP21
TP22
L4
U6 DECOUPLING
AVDDCLK
+3–5D
J9
C31
10/10V
C32
0
F
F
F
14
U6
L1
L2
L3
74AHC14
PWR
U6
8
9
C28
0
J2
J3
J4
DRVDD
AVDD
F
C22
0
C23
10/10V
GND
U6
U6
11
13
10
7
12
C24
0
C25
33/16V
+3–5A
C26
0
C27
10/10V
F
TP23 TP24 TP25 TP26 TP27 TP28
GND J6
GND J10
Figure 39b. Evaluation Board Schematic
REV. E
–19–
AD9200
Figure 40a. Evaluation Board, Component Signal (Not to Scale)
Figure 40b. Evaluation Board, Solder Signal (Not to Scale)
–20–
REV. E
AD9200
Figure 40c. Evaluation Board Power Plane (Not to Scale)
Figure 40d. Evaluation Board Ground Plane (Not to Scale)
–21–
REV. E
AD9200
Figure 40e. Evaluation Board Component Silk (Not to Scale)
Figure 40f. Evaluation Board Solder Silk (Not to Scale)
–22–
REV. E
AD9200
GROUNDING AND LAYOUT RULES
DIGITAL OUTPUTS
As is the case for any high performance device, proper ground-
ing and layout techniques are essential in achieving optimal
performance. The analog and digital grounds on the AD9200
have been separated to optimize the management of return
currents in a system. Grounds should be connected near the
ADC. It is recommended that a printed circuit board (PCB) of
at least four layers, employing a ground plane and power planes,
be used with the AD9200. The use of ground and power planes
offers distinct advantages:
Each of the on-chip buffers for the AD9200 output bits
(D0–D9) is powered from the DRVDD supply pins, separate
from AVDD. The output drivers are sized to handle a variety
of logic families while minimizing the amount of glitch energy
generated. In all cases, a fan-out of one is recommended to keep
the capacitive load on the output data bits below the specified
20 pF level.
For DRVDD = 5 V, the AD9200 output signal swing is compat-
ible with both high speed CMOS and TTL logic families. For
TTL, the AD9200 on-chip, output drivers were designed to
support several of the high speed TTL families (F, AS, S). For
applications where the clock rate is below 20 MSPS, other TTL
families may be appropriate. For interfacing with lower voltage
CMOS logic, the AD9200 sustains 20 MSPS operation with
DRVDD = 3 V. In all cases, check your logic family data sheets
for compatibility with the AD9200 Digital Specification table.
1. The minimization of the loop area encompassed by a signal
and its return path.
2. The minimization of the impedance associated with ground
and power paths.
3. The inherent distributed capacitor formed by the power plane,
PCB insulation and ground plane.
These characteristics result in both a reduction of electro-
magnetic interference (EMI) and an overall improvement in
performance.
THREE-STATE OUTPUTS
The digital outputs of the AD9200 can be placed in a high
impedance state by setting the THREE-STATE pin to HIGH.
This feature is provided to facilitate in-circuit testing or evaluation.
It is important to design a layout that prevents noise from cou-
pling onto the input signal. Digital signals should not be run in
parallel with the input signal traces and should be routed away
from the input circuitry. Separate analog and digital grounds
should be joined together directly under the AD9200 in a solid
ground plane. The power and ground return currents must be
carefully managed. A general rule of thumb for mixed signal
layouts dictates that the return currents from digital circuitry
should not pass through critical analog circuitry.
REV. E
–23–
AD9200
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
48-Lead Plastic Thin Quad Flatpack (LQFP)
(ST-48)
0.063 (1.60) MAX
0.354 (9.00) BSC
30 0 7
0.057 (1.45)
0.276 (7.0) BSC
0.030 (0.75)
0.018 (0.45)
0.053 (1.35)
37
36
48
1
SEATING
PLANE
TOP VIEW
(PINS DOWN)
0.006 (0.15)
12
13
25
24
0.002 (0.05)
0° MIN
0° – 7°
0.007 (0.18)
0.004 (0.09)
0.011 (0.27)
0.006 (0.17)
0.019 (0.5)
BSC
28-Lead Shrink Small Outline Package (SSOP)
(RS-28)
0.407 (10.34)
0.397 (10.08)
28
15
14
1
0.07 (1.79)
0.078 (1.98)
PIN 1
0.066 (1.67)
0.068 (1.73)
0.03 (0.762)
8°
0°
0.0256
(0.65)
BSC
0.015 (0.38)
0.010 (0.25)
0.022 (0.558)
0.008 (0.203)
0.002 (0.050)
SEATING
PLANE
0.009 (0.229)
0.005 (0.127)
REV. E
–24–
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