FEATURES
8-Bit, 50, 80 and 100 MSPS ADC
Low Power: 90 mW at 100 MSPS
On-Chip Reference and Track/Hold
475 MHz Analog Bandwidth
SNR = 46.5 dB @ 41 MHz at 100 MSPS
1 V p-p Analog Input Range
Single +3.0 V Supply Operation (2.7 V–3.6 V)
Power-Down Mode: 4.2 mW
APPLICATIONS
Battery Powered Instruments
Hand-Held Scopemeters
Low Cost Digital Oscilloscopes
GENERAL DESCRIPTION
The AD9283 is an 8-bit monolithic sampling analog-to-digital
converter with an on-chip track-and-hold circuit and is optimized for low cost, low power, small size and ease of use. The
product operates at a 100 MSPS conversion rate, with outstanding dynamic performance over its full operating range.
The ADC requires only a single 3.0 V (2.7 V to 3.6 V) power
supply and an encode clock for full performance operation. No
external reference or driver components are required for many
applications. The digital outputs are TTL/CMOS compatible
and a separate output power supply pin supports interfacing
with 3.3 V or 2.5 V logic.
3 V A/D Converter
AD9283
FUNCTIONAL BLOCK DIAGRAM
The encoder input is TTL/CMOS compatible. A power-down
function may be exercised to bring total consumption to
4.2 mW. In power-down mode, the digital outputs are driven
to a high impedance state.
Fabricated on an advanced CMOS process, the AD9283 is
available in a 20-lead surface mount plastic package (SSOP)
specified over the industrial temperature range (–40°C to +85°C).
REV. B
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.
Gain error and gain temperature coefficient are based on the ADC only (with a fixed 1.25 V external reference).
2
tV and tPD are measured from the 1.5 V level of the ENCODE input to the 50%/50% levels of the digital outputs swing. The digital output load during test is not to
exceed an ac load of 10 pF or a dc current of ± 40 µA.
3
Power dissipation measured with encode at rated speed and a dc analog input.
4
Typical thermal impedance for the RS style (SSOP) 20-lead package: θJC = 46°C/W, θCA = 80°C/W, θJA = 126°C/W.
5
SNR/harmonics based on an analog input voltage of –0.7 dBFS referenced to a 1.024 V full-scale input range.
Maximum Junction Temperature . . . . . . . . . . . . . . . +175°C
Maximum Case Temperature . . . . . . . . . . . . . . . . . . +150°C
*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 outside of those indicated in the operation
sections of this specification is not implied. Exposure to absolute maximum
ratings for extended periods may affect device reliability.
ORDERING GUIDE
TemperaturePackagePackage
ModelRangesDescriptionsOptions
AD9283BRS
-50, -80, -100 –40°C to +85°C 20-Lead SSOPRS-20
AD9283/PCB+25°CEvaluation Board
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 AD9283 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.
–3–REV. B
AD9283
EXPLANATION OF TEST LEVELS
Test Level
I100% production tested.
II100% production tested at +25°C and sample tested at
specified temperatures.
III Sample tested only.
IV Parameter is guaranteed by design and characterization
testing.
VParameter is a typical value only.
VI 100% production tested at +25°C; guaranteed by design
and characterization testing for industrial temperature
range; 100% production tested at temperature extremes for
military devices.
PIN CONFIGURATION
VREF IN
GND
A
A
GND
1
2
3
4
5
V
D
6
IN
7
IN
8
V
D
9
10
PWRDWN
VREF OUT
ENCODE
Table I. Output Coding (VREF = +1.25 V)
StepAIN–A
IN
2550.5121111 1111
• ••
• ••
1280.0021000 0000
127–0.0020111 1111
• ••
• ••
0–0.5120000 0000
20
D0 (LSB)
19
D1
18
D2
17
D3
16
15
14
13
12
11
GND
V
DD
D4
D5
D6
D7 (MSB)
AD9283
TOP VIEW
(Not to Scale)
Digital Output
PIN FUNCTION DESCRIPTIONS
Pin NumberNameFunction
1PWRDWNPower-down function select; Logic HIGH for power-down mode (digital outputs go to
high impedance state).
2VREF OUTInternal Reference Output (+1.25 V typ); Bypass with 0.1 µF to Ground.
3VREF INReference Input for ADC (+1.25 V typ).
4, 9, 16GNDGround.
5, 8V
6A
D
IN
Analog +3 V Power Supply.
Analog Input for ADC (Can be left open if operating in single-ended mode, but recom-
mend connection to a 0.1 µF capacitor and a 25 Ω resistor in series to ground for better
input matching).
7A
IN
Analog Input for ADC
10ENCODEEncode Clock for ADC (ADC samples on rising edge of ENCODE).
11–14, 17–20D7–D4, D3–D0Digital Outputs of ADC.
15V
DD
Digital output power supply. Nominally +2.5 V to +3.6 V.
Figure 16. Analog Power Dissipation vs. Encode Rate
20
10
0
6.564.54
75.553.53
ENCODE PULSEWIDTH HIGH – ns
Figure 14. SINAD/SNR vs. Encode Pulsewidth High
0.5
0.0
–0.5
–1.0
–1.5
–2.0
–2.5
dB
–3.0
–3.5
–4.0
–4.5
–5.0
–5.5
0
100200300400500
Figure 15. ADC Frequency Response: fS = 100 MSPS
BANDWIDTH – MHz
Figure 17. SINAD/SNR vs. Temperature
600
Figure 18. Differential Nonlinearity
–7–REV. B
AD9283
2.0
1.5
1.0
0.5
0.0
LSB
–0.5
–1.0
–1.5
–2.0
CODE
Figure 19. Integral Nonlinearity
APPLICATIONS
Theory of Operation
The analog signal is applied differentially or single-endedly to
the inputs of the AD9283. The signal is buffered and fed forward to an on-chip sample-and-hold circuit. The ADC core
architecture is a bit-per-stage pipeline type converter utilizing
switch capacitor techniques. The bit-per-stage blocks determine
the 5 MSBs and drive a FLASH converter to encode the 3 LSBs.
Each of the 5 MSB stages provides sufficient overlap and error
correction to allow optimization of performance with respect to
comparator accuracy. The output staging block aligns the data,
carries out the error correction and feeds the data to the eight
output buffers. The AD9283 includes an on-chip reference
(nominally 1.25 V) and generates all clocking signals from one
externally applied encode command. This makes the ADC easy
to interface with and requires very few external components for
operation.
ENCODE Input
The ENCODE input is fully TTL/CMOS compatible with a
nominal threshold of 1.5 V. Care was taken on the chip to
match clock line delays and maintain sharp clock logic transitions. Any high speed A/D converter is extremely sensitive to
the quality of the sampling clock provided by the user. This
ADC uses an on-chip sample-and-hold circuit which is essentially a mixer. Any timing jitter on the ENCODE will be combined with the desired signal and degrade the high frequency
performance of the ADC. The user is advised to give commensurate thought to the clock source.
Analog Input
The analog input to the ADC is fully differential and both inputs are internally biased. This allows the most flexible use of ac
or dc and differential or single-ended input modes. For peak
performance the inputs are biased at 0.3 × V
. See the specifi-
D
cation table for allowable common-mode range when dc coupling the input. The inputs are also buffered to reduce the load
the user needs to drive. For best dynamic performance, the
impedances at A
and AIN should be matched. The importance
IN
of this increases with sampling rate and analog input frequency.
The nominal input range is 1.024 V p-p.
Digital Outputs
The digital outputs are TTL/CMOS compatible. The output
buffers are powered from a separate supply, allowing adjustment
of the output voltage swing to ease interfacing with 2.5 V or
3.3 V logic. The AD9283 goes into a low power state within two
clock cycles following the assertion of the PWRDWN input.
PWRDWN is asserted with a logic high. During power-down
the outputs transition to a high impedance state. The time it
takes to achieve optimal performance after disabling the powerdown mode is approximately 15 clock cycles. Care should be
taken when loading the digital outputs of any high speed ADC.
Large output loads create current transients on the chip that can
degrade the converter’s performance.
Voltage Reference
A stable and accurate 1.25 V voltage reference is built into the
AD9283 (VREF OUT). In normal operation, the internal reference is used by strapping Pins 2 and 3 of the AD9283 together.
The input range can be adjusted by varying the reference voltage applied to the AD9283. No degradation in performance
occurs when the reference is adjusted ±5%. The full-scale range
of the ADC tracks reference voltage changes linearly. Whether
used or not, the internal reference (Pin 2) should be bypassed
with a 0.1 µF capacitor to ground.
Timing
The AD9283 provides latched data outputs with four pipeline
delays. Data outputs are available one propagation delay (t
PD
)
after the rising edge of the encode command (Figure 1. Timing
Diagram). The minimum guaranteed conversion rate to the
ADC is 1 MSPS. The dynamic performance of the converter
will degrade at encode rates below this sample rate.
Evaluation Board
The AD9283 evaluation board offers an easy way to test the
AD9283. It only requires a 3 V supply, an analog input and
encode clock to test the AD9283. The board is shipped with the
100 MSPS grade ADC.
The analog input to the board accepts a 1 V p-p signal centered
at ground. J1 should be used (Jump E3–E4, E18–E19) to drive
the ADC through Transformer T1. J2 should be used for singleended input drive (Jump E19–E21).
Both J1 and J2 are terminated to 50 Ω on the PCB. Each analog
path is ac-coupled to an on-chip resistor divider which provides
the required dc bias.
A (TTL/CMOS Level) sample clock is applied to connector
J3 which is terminated through 50 Ω on the PCB. This clock is
buffered by U5 which also provides the clocks for the 574
latches, DAC, and the off-card latch clock CLKCON. (Timing
can be modified at E17.)
There is a reconstruction DAC (AD9760) on the PCB. The
DAC is on the board to assist in debug only—the outputs
should not be used to measure performance of the ADC.
–8–REV. B
AD9283
Figure 20. Printed Circuit Board Top Side Silkscreen
Figure 21. Printed Circuit Board Bottom Side Silkscreen
Figure 22. Printed Circuit Board Top Side Copper
Figure 23. Printed Circuit Board “Split” Power Layer