DEM-ADS8XXE/DEM-ADS8XXU [ETC]
DEM-ADS8xxE. DEM-ADS8xxU - EVALUATION FIXTURE ; DEM- ADS8xxE 。 DEM - ADS8xxU - 评价灯具
| 型号： | DEM-ADS8XXE/DEM-ADS8XXU |
| 厂家： | 
ETC |
| 描述： | DEM-ADS8xxE. DEM-ADS8xxU - EVALUATION FIXTURE
|
| 文件： | 总11页 (文件大小：232K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DEM-ADS8xxE
®
DEM-ADS8xxU
EVALUATION FIXTURE
DESCRIPTION
FEATURES
The DEM-ADS8xxU/E evaluation fixtures are de-
signed for ease of use when evaluating the high speed
analog-to-digital converter of the ADS8xx family. A
separate demonstration board is available for each of
the five different converter products (see ordering
information). However, all boards provide similar fea-
tures that allow the user to evaluate all functions of the
converter. For example, two options to apply the
analog input signal are available, one DC-coupled and
one AC-coupled path. The converter can be operated
with one out of the three clock modes; on-board
crystal clock, external clock, or external sine wave.
Furthermore, a reference circuit is provided to evalu-
ate the converter with reference voltages other than the
internal voltage levels. The data outputs from the
ADS8xx converter are decoupled from the connector
via TTL-buffer.
● PROVIDES FAST AND EASY PERFOR-
MANCE TESTING
● AC-COUPLED AND DC-COUPLED INPUTS
● ON-BOARD CLOCK
● EXTERNAL REFERENCES
● OPTIMIZED 4-LAYER PC BOARD LAYOUT
International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111
Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
© 1996 Burr-Brown Corporation
LI-476A
Printed in U.S.A. October, 1996
INITIAL CONFIGURATION
AND QUICK START
the transformer to the converter inputs. At the same time it
is recommended that resistors R38 and R39 are taken out.
The center tap of the secondary side of the transformer can
be connected to the mid-reference of the ADS8xx by closing
solder switch “CM”. If necessary the center tap can also be
driven by the buffer amplifier U10. To activate this buffer
open solder switch CM and close the one labeled T1-CT. In
addition, closing solder switch “X2” located at the primary
side of the RF-transformer will short out half of the primary
winding and change the turns ratio to 1:2. This function is
not available with the transformer type used on the board.
The demo board DEM-ADS8xx comes in a default configu-
ration that makes it easy for the user to start evaluation. The
factory settings are as follows:
• The clock source is the on-board crystal with the appropri-
ate divider ratio (÷2, ÷4, etc.) selected.
• The DC-coupled input is activated.
• The external reference is inactive; solder switches “REFT”
and “REFB” are open.
• The output data format is straight offset binary with the
solder switch “MSBI” open.
DC-Coupled
For evaluating input frequencies down to DC, the second
analog input should be used. It is available through connec-
tor J3, labeled “DC Coupled Input”. This input is also
terminated for a 50Ω system. The first stage consists of
amplifier U11, which is configured as a buffer amplifier.
Using appropriate values for R21 and R22 the amplifier can
be set for gain. The ADS8xx requires a differential input
signal with a common-mode voltage of +2.25V. This is
accomplished by amplifiers U8, U9, and U10 (refer to
Figure 1). The amplifier U8 is configured in a non-inverting
mode with a DC gain of +3V/V. The voltage divider formed
by R27 and R28 gives an overall gain of +2V/V. The
complementary input amplifier U9 is set for an inverting
gain of +2V/V. The common-mode voltage of +2.25V is
buffered from the ADS8xx by amplifier U10 and applied to
each of the driving amplifiers. The OPA642 was selected to
provide a low noise and low distortion front-end. To avoid
any additional distortion due to the required output swing of
+3.25V a level shifting stage was added. It consists of a
silicon diode in series with the output of each driving
amplifier and a resistor to the supply for biasing. Regardless
of the configuration of the driving amplifiers, a series
resistor (R38, R39) in combination with a small capacitor to
ground at the inputs of the ADS8xx can improve the AC-
performance. The capacitors (C34 and C35) will help to
reduce the current transients that are generated by the ADS8xx
during sampling. Note that when using the DC-coupled
input resistors R40 and R41 should be removed to avoid
unnecessary loading of the driving op amps.
• The data output is enabled with the solder switch
“OE\” open.
• The data read delay’s set to one delay, solder switch
“DLY1” closed.
• Note that the “PWRDWN” solder switch is without func-
tion and should stay open.
MODEL
ADS800
ADS801
ADS802
ADS820
ADS821
CRYSTAL ECLK DIV 2
DIV4 DIV 8
B11
X
DLY 1
80MHz
50MHz
80MHz
80MHz
80MHz
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
TABLE I. Factory configuration table of solder switches for
the five different converter products.
Evaluation in this configuration requires a ±5V supply. The
negative supply is necessary to power the op amp driving
circuit, therefore, power connectors P1 and P2 must be
connected appropriately to the supply unit. Re-configuring
the demo board for AC-coupled input in combination with
the crystal or external pulse clock, makes it possible to
operate the demo board on a single +5V supply.
INPUTS
Transformer Coupled
The demo board provides one analog input at connector J4,
which is labeled “AC Coupled Input.” This input is termi-
nated with 50Ω and ties to the RF-transformer T1. The
model used is the T1-1T (by Mini-Circuits), a 1:1 ratio
transformer with bandpass characteristic. The –3dB frequen-
cies are at 50kHz and 200MHz for the lower and upper
corners of the transformer. The –1dB insertion loss frequen-
cies are listed with 0.2MHz and 80MHz, which might be
used for choosing the input frequency without effecting the
signal too much. If the AC-coupled input is used the two
resistors, R40 and R41 (0Ω) have to be inserted to connect
CLOCK
On-Board Clock
The ADS8xx demo board is equipped with a crystal oscilla-
tor and D-Type Flip-Flops (U6 and U7), which allow differ-
ent discrete divider ratios for the clock. The selection of the
divider ratio can be done using the solder switches labeled
DIV2, DIV4, DIV8, and DIV16. For this mode of operation
make sure that solder switch “ECLK” is closed and “CCLK”
is open.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.
®
2
DEM-ADS8xx
External Clock
DATA OUTPUT
In addition to the on-board clock the demo board allows for
two other clock configurations using external clock sources.
The first alternative requires an external pulse generator,
preferably with fast rise and fall times (≤ 2ns) and low jitter.
This source can be directly connected to the board using the
SMA connector J2. The input is terminated for 50Ω systems.
Operation in this mode requires to close solder switch
“CCLK” and open “ECLK.”
The output data is provided at CMOS logic levels. The
standard output coding is straight offset binary where the
full scale input signal corresponds to all “1” for the data
output. This is with solder switch “MSBI” open. Closing this
solder switch will invert the MSB (see the individual data
sheet for details). To account for different data read timing
up to four propagation delay cycles can be selected using the
solder switches DLY1 through DLY4. The minimum propa-
gation delay for the used buffer is 1.5ns with a maximum of
8ns.
If a low jitter sine wave generator is the only signal source
available the second external clock input might be used. The
ECL to TTL translator IC (U5) will transform the sine wave
input into a logic signal with 50% duty cycle. Different
divider ratios can be selected. The solder switch “XCLK”
and “ECLK” should be closed in this mode and solder
switch “CCLK” should be open.
PC-BOARD LAYOUT
The ADS8xx demo board is a four layer pc-board. To
achieve the highest level of performance surface mount
components are used wherever possible. This reduces the
trace length and minimizes the effects of parasitic capaci-
tance and inductance. The analog-to-digital converter is
treated like a pure analog component. Therefore the demo
board has only one consistent ground plane. This approach
may or may not yield optimum performance results when
designing the ADS8xx into different individual applications.
In any case, thoroughly bypassing the supply pins of the
converter, like demonstrated on the demo board, is strongly
recommended.
EXTERNAL REFERENCE
Each of the converter inputs operates with a 2Vp-p input
signal swing set between +1.25V and +3.25V. The input
structure of the ADS8xx is differential making the comple-
mentary input of the ADS8xx 180° out of phase. This allows
for an effective full scale input range of 4Vp-p. The +1.25V
and the +3.25V are set by the internal reference voltages of
the converter. These reference voltages may be adjusted
with external references in order to reduce the full scale
range. The demo board provides a circuit for this mainly
consisting of the reference IC U13 and the op amps U12 and
U14. To activate this circuit the solder switches labeled
“REFT” and “REFB” should be closed. The top reference
voltage can be adjusted with potentiometer RV1 between
+3.25V and +2.25V. Potentiometer RV2 adjusts the bottom
reference between +1.25V and +2.25V. Note that those
reference voltages can vary slightly. Also, reducing the
references too much will degrade the signal-to-noise ratio.
ORDERING INFORMATION
A/D
RESOLUTION
12-Bit
fCONV
40MHz
25MHz
10MHz
20MHz
40MHz
—
ORDER NUMBER
DEM-ADS800U
DEM-ADS801U
DEM-ADS802U
DEM-ADS820U
DEM-ADS821U
DEM-ADS8xxE
ADS800
ADS801
ADS802
ADS820
ADS821
ADS8xx
12-Bit
12-Bit
10-Bit
10-Bit
10/12-Bit
Note: The demo board DEM-ADS8xxE is designed to fit the ADS8xx line of
converters in the 28-pin SSOP package. The board is offered as fully populated
except for the individual A/D converter (U1), which can be obtained through a
sample request.
®
3
DEM-ADS8xx
FIGURE 1a. DEM-ADS8xx Circuit Schematic.
®
4
DEM-ADS8xx
FIGURE 1b. DEM-ADS8xx Circuit Schematic.
®
5
DEM-ADS8xx
FIGURE 1c. DEM-ADS8xx Circuit Schematic.
®
6
DEM-ADS8xx
FIGURE 1d. DEM-ADS8xx Circuit Schematic.
®
7
DEM-ADS8xx
FIGURE 2. Top-Layer (component side) with Silk-Screen; DEM-ADS8xxU.
FIGURE 3. Power Plane; DEM-ADS8xxU.
®
8
DEM-ADS8xx
FIGURE 4. Ground Plane; DEM-ADS8xxU.
FIGURE 5. Bottom Layer with Silk-Screen; DEM-ADS8xxU.
®
9
DEM-ADS8xx
FIGURE 6. Top-Layer with Silk-Screen; DEM-ADS8xxE.
FIGURE 7. Bottom-Layer with Silk-Screen; DEM-ADS8xxE.
®
10
DEM-ADS8xx
COMPONENT LIST
REFERENCE
QTY
PART NUMBER
DESCRIPTION
MANUFACTURER
C1, C2, C3, C4, C7, C8, C11-13, C15,
C18, C22, C25-29, C31, C33, C38, C40,
C41, C44, C47, C48, C50, C56, C57
28
08055C104KAT
0.1µF 50V X7R 0805 Ceramic Capacitor
AVX
C14, C16, C17, C19-C21, C30,
14
TAJR225006
2.2µF 10V 3216 Tantalum Capacitor
AVX
C32, C37, C39, C45, C46, C49, C51
C34, C35
2
2
4
1
2
4
1
1
1
6
6
7
1
1
1
1
2
1
4
4
3
2
1
1
1
3
2
3
1
2
1
1
1
1
2
3
1
4
08055C220KAT
08055C100KAT
ECE-V1AA101P
ECE-V1CV100SR
BAS16
22pF 50V NPO 0805 Ceramic Capacitor
10pF 50V NPO 0805 Ceramic Capacitor
100µF 16V Surface-Mount Aluminum Capacitor
10µF 16V Surface-Mount Aluminum Capacitor
Signal Diode SOT-23
AVX
AVX
C6, C10
C5, C36, C42, C43
Panasonic
Panasonic
Philips
C9
D1, D2
J1-4
142-0701-201
ED555/3DS
Straight SMA PCB Connector
EF Johnson
On-Shore Technology
On-Shore Technology
Robinson-Nugent
Dale
P1
3-Pin Term Block
P2
ED555/2DS
2-Pin Term Block
P3
IDH-40LP-S3-TG
CRCW080549R9F
CRCW08053010F
CRCW08052491F
CRCW08056040F
CRCW08052001F
CRCW08056191F
CRCW08051372F
CRCW08051001F
CRCW080524R9F
CRCW12061000F
CRCW08056040F
CRCW0805ZEROF
CRCW08051003F
RJ26FW-202
20 x 2 Dual-Row Shrouded Header
49.9Ω 1/10W 1% MF 0805 Chip Resistor
301Ω 1/10W 1% MF 0805 Chip Resistor
2.49kΩ 1/10W 1% MF 0805 Chip Resistor
20kΩ 1/10W 5% MF 0805 Chip Resistor
2kΩ 1/10W 1% MF 0805 Chip Resistor
6.19kΩ 1/10W 1% MF 0805 Chip Resistor
13.7kΩ 1/10W 1% MF 0805 Chip Resistor
1kΩ 1/10W 1% MF 0805 Chip Resistor
24.9Ω 1/10W 1% MF 0805 Chip Resistor
100Ω 1/10W 1% MF 1206 Chip Resistor
604Ω 1/10W 1% MF 0805 Chip Resistor
0Ω 1/10W 1% MF 0805 Chip Resistor
100kΩ 1/10W 1% MF 0805 Chip Resistor
2kΩ 1/4" 10-Turn Pot
R1, R7, R9, R33, R38, R39
R26, R28, R30, R32, R36, R37
Dale
R11, R16, R18-20, R34, R35
Dale
R12
Dale
R13
Dale
R14
Dale
R15
Dale
R2, R6
Dale
R22
Dale
R23, R24, R42, R43
Dale
R25, R27, R29, R31
Dale
R3, R10, R17
R4, R5
Dale
Dale
RV1
Bourns
RV2
RJ26FW-502
5kΩ 1/4" 10-Turn Pot
Bourns
T1
T1-1T-KK81
RF Transformer
Mini-Circuits
Mouser
Concord
Motorola
Burr-Brown
IDT
REFB, REFT, CM
TP4, TP5
U10, U12, U14
U13
151-205
Test Point
10-216-2-01
Turret Terminal, Brass, Silver Plated
Single Op-Amp SO-8
MC34071D
REF1004C-2.5
IDT74FCT 541T
ADS8xxU
2.5V Voltage Reference SO-8
Octal Bi-directional Buffers SO-20
Monolithic High-Speed ADC SO-28
80MHz DIP Crystal Oscillator
U2, U3
U3
Burr-Brown
Fox
(1)
U4A
F3000 80.000MHz
F3000 50.000MHz
MC100ELT25
74AC11074
(2)
U4B
50MHz DIP Crystal Oscillator
Fox
U5
ECL to TTL Translator SO-8
Motorola
T.I.
U6, U7
U8, U9, U11
Dual D-Type Flip-Flop SO-14
OPA642U
Single High-Speed Op-Amp SO-8
PCB
Burr-Brown
A039A
SJ5003-0-N
Rubber Feet, Black, 0.44 x 0.2
Digi-Key
NOTES: (1) Used on the DEM-ADS800U, DEM-ADS802U, DEM-ADS820U, and DEM-ADS821U. (2) Used on the DEM-ADS801U.
®
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DEM-ADS8xx
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