DEM-ADS9XXE [ETC]
DEM-ADS9xxE - EVALUATION FIXTURE ; DEM - ADS9xxE - 评价灯具\n
| 型号： | DEM-ADS9XXE |
| 厂家： | 
ETC |
| 描述： | DEM-ADS9xxE - EVALUATION FIXTURE
|
| 文件： | 总10页 (文件大小：174K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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DEM-ADS9xxE
EVALUATION FIXTURE
DESCRIPTION
FEATURES
The DEM-ADS9xxE evaluation fixture is designed
for ease of use when evaluating the high speed analog-
to-digital converter of the ADS9xx family. It was
designed to be the common evalution platform for four
of the models within the ADS9xxE family. The board
will acommodate the ADS900 and ADS930, convert-
ers with internal references, as well as the ADS901
and ADS931, which require the external references.
Because of its flexible design, the user can evaluate
the converter in many different configurations; either
with DC-coupled or AC-coupled input, or single-
ended or differential inputs.
● PROVIDES FAST AND EASY PERFOR-
MANCE TESTING FOR ADS900/ADS901
AND ADS930/ADS931
● AC- AND DC-COUPLED INPUTS
● ON-BOARD REFERENCE
● ON-BOARD CLOCK
● ON-BOARD REGULATOR FOR +3V AND
+5V OPERATION
Furthermore, the board can be operated with the on-
board crystal clock or with an external clock. The on-
board reference circuit is adjustable, and the data
outputs from the ADS9xx converter are decoupled
from the connector via the TTL-buffer.
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
© 1997 Burr-Brown Corporation
LI-488A
Printed in U.S.A. January, 1997
INITIAL CONFIGURATION AND QUICK START
throughout a wide frequency range. The level shift should be
set to 0V at pin 5 of the OPA2650 by adjusting RV2, which
will produce a ground-centered signal swing at the output of
the op amp. In order to implement the correct common-
mode voltage for the A/D converter, resistor R30 must be
added. The value is not critical but should be between 1kΩ
and 5kΩ.
Through the use of the solder switches the demonstration
board, DEM-ADS9xxE, can be adjusted in a variety of
configurations to accommodate a specific model or function.
Before starting evalution, the user should decide on the
configuration and make the appropriate connections. The
following list is a guideline for an inital setup:
Alternatively, a single-ended-to-differential input interface
can be implemented using a RF transformer. Note that only
the ADS900 and ADS930 feature the differential inputs. For
setting it up, remove resistor R22 and add resistors R28 and
R29, which should have a value of 24.9Ω. Remove resistors
R27 and R30, if used, and close solder switch ‘MID’. To
establish symmetrical inputs, capacitor C26 should equal
capacitor C31, typically 22pF. The footprint of the trans-
former was selected to accommodate RF-transformer case
style KK81, similar to T1-6T by Mini-Circuits.
• The supply voltage should be +3V for the A/D converter;
close switch ‘ADC/REF’ at the +3V side. If the board is
equipped with HC541 buffers, select switch ‘U9/U10’ on
the +5V side. If LCX541s are used, select the +3V side.
Note that the LCX series will provide logic levels compat-
ible for 3V logic.
• The clock source is the on-board crystal. Close switch
‘CCLK’ and ‘DIV2’ to activate the clock and operate with
a divider ratio of ÷2.
• The DC-coupled input is activated through connecter J2,
‘–VIN BUF’.
CLOCK
• The external references are not applied to the converter;
solder switches ‘REFT’ and ‘REFB’ are open.
On-Board Clock
The ADS9xxE demonstration board is equipped with a
crystal oscillator and D-type Flip-Flops (U7), which allow
two different divider ratios (÷2 and ÷4) for the clock. The
selection of the divider ratio can be done using the solder
switched labeled ‘DIV2’ and ‘DIV4’. When using the on-
board clock make sure that solder switch ‘CCLK’ is closed
and ‘ECLK’ is open. The DEM-ADS9xxE comes with a
40MHz crystal which supports the full sampling speed of the
ADS900 and ADS901. To evaluate the ADS930 and ADS931
at its maximum sampling speed of 30MHz, the crystal must
be replaced with a 60MHz type. The replacement is easily
done since the crystal is socketed.
• The power-down function is disabled.
The evaluation board typically requies a ±5V supply unit.
The negative supply is necessary to appropriately power the
op amp used in the interface circuit. Reconfiguring the
demonstration board for AC-coupled input, in combination
with the crystal clock, makes it possible to operate the board
on a single +5V supply.
INPUTS
DC-Coupled
The standard configuration of the evaluation board uses the
dual high-speed op amp OPA2650, a voltage feedback type
op amp. In order to implement level shifting into the DC-
coupled circuit, op amp U3:B operates in an inverting mode,
with the level shifting voltage applied its noninverting input.
To offer a high impedance input to this interface circuit, the
second op amp, U3:A, buffers the inverting gain stage. This
provides a terminated 50Ω input to the demonstration board
through connector J2, ‘–VIN BUF’. Besides using op amp
U3:A as a buffer, it can be reconfigured for gain by changing
the resistor values for R9 and R3. If it is desired to evaluate
the circuit with only one op amp in the signal path, the
second input, J1, can be used which requires some additional
components to be soldered to the board. Note that in this
case, the input impedance to the board is also determined by
the input resistor value, R10, and an appropriate termination
resistor, R1, value must be selected. A desired common-
mode voltage can be set by adjusting potentiometer RV2.
External Clock
In addition to the on-board clock, the A/D converter can be
driven by an external clock. For this, a low-jitter sine wave
generator may be used. Apply the generator to SMA connec-
tor J3 (‘EXT CLK’). The ECL to TTL translator IC (U4) will
transform the sine wave into a logic signal with a 50% duty
cycle. When operating in this external clock mode, open
solder switch ‘CCLK’ and close ‘ECLK’. Note that the
external clock passes the divider as well.
EXTERNAL REFERENCE
While the ADS900 and ADS930 have references on-chip,
the ADS901 and ADS931 require two external reference
voltages; a top reference (REFT) and a bottom reference
(REFB). Both references are available by the on-board
reference circuit consisting of the micropower reference
IC, REF-1004, and a general purpose single-supply op
amp. This reference circuit is designed to operate on +5V
and +3V. This supply voltage can be selected via the
solder switches ‘ADC/REF’. The REF-1004 produces a
stable +1.2V. With potentiometer RV1 (REFT/B), this
voltage can be adjusted between approximately +1.24V
and +0.4V, and will affect both reference levels at the
AC-Coupled
The DC-coupled circuit previously discussed can also be
reconfigured for AC-coupling. To do so, resistor R17 (0Ω)
must be taken out and capacitors C20 and C22 assembled. The
purpose of using two capacitors, one ceramic and one
tantalum type, in parallel, is to assure a constant impedance
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DEM-ADS9xx
same time. The default configuration for the bottom refer-
ence driver (U5:B) is a unity gain stage, but can easily be
modified by changing resistors R12 and R18. The top
reference driver (U5:A) employs gain, which can be ad-
justed through potentiometer RV3. The gain range is from
approximately 1.3V/V to 3V/V. If the ADS901 or ADS931
are to be used on the demonstration board, solder switches
‘REFB’ and ‘REFT’ must be closed. The voltage set for
the references on these models determines the full-scale
input signal range of the converter. For example, with
REFT = +2V and REFB = +1V, the input range for an
ADS901 will be 1Vp-p.
PC BOARD LAYOUT
The DEM-ADS9xxE demonstration board is made as 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 para-
sitic capacitance and inductance. The A/D converter is
treated like an analog component therefore, the demonstra-
tion board has a consistent ground plane. Keep in mind that
this approach may not yield optimum performance results
when designing the ADS9xx into different individual appli-
cations. In any case, thoroughly bypassing the supply and
reference pins of the converter, as shown on the demonstra-
tion board, is strongly recommended.
Alternatively, a very simple way of setting up the refer-
ence voltages is by deriving them from the power supply.
Using resistors R25 and R26 will allow a current flow from
the supply through the A/D’s internal resistor ladder. In
this case, solder switches ‘+VS’ and ‘GND’ must be closed
and ‘REFT’ and ‘REFB’ open.
SUPPLY VOLTAGE SETTING
The ADS9xx converter family consists of models that oper-
ate on +3V or +5V supplies. To allow the evaluation of each
converter in its typical environment, a voltage regulator was
added to the demonstration board. The factory configuration
uses the REG1117-3, a fixed +3V voltage regulator. Through
a set of four solder switches, the two circuit blocks—the A/
D plus the reference, and the output buffer, can be tied
independently to either the +3V or +5V supply. The respec-
tive labels of the solder switches are ‘ADC/REF’ and ‘U9/
U10’. If desired, the REG1117-3 can be replaced with
models producing other output voltages, such as +2.85V or
+3.3V, or the adjustable output model. Refer to the REG1117
data sheet for details.
Depending on the model and its specified supply voltage, it
may be necessary to reconfigure the reference circuit to
obtain the recommended reference voltages (see the indi-
vidual data sheets for details). Resistors R23 and R24 are used
to establish the level shift voltage (common-mode voltage,
VCM) needed for the DC-coupled input circuit. This voltage
will track if adjustments are made to the reference voltages.
DATA OUTPUT
The data output is provided at CMOS logic levels. All
ADS9xx converters use straight offset binary coding. The
data output pins of the converter are buffered from the
connector, P3, by two CMOS octal buffers (HC541). As an
alternative, the HC type can be replaced with the new
LCX541 (available from Motorola or National Semiconduc-
tor). These devices are designed for +3V operation and offer
5V tolerant inputs.
ADS900/ADS930 SETTINGS
The ADS900 and ADS930 are 10- and 8-bit converters,
respectively, and operate with sampling frequencies up to
20MHz. Both models have internal references, therefore, the
solder switches ‘REFT’ and ‘REFB’ must be open. Resistor
R27 (0Ω) and R30 (3kΩ) should be installed. For the ADS900,
the supply voltage must be set to +3V, whereas the ADS930
can operate with either +3V or +5V.
ADS901/ADS931 SETTINGS
The ADS901 and ADS931 are 10-and 8-bit converters,
respectively, and operate with sampling frequencies up to
30MHz. These models do not have an internal reference and
the connection to the on-board reference circuit is required.
Also, resistor R27 must be removed.
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DEM-ADS9xx
R16
402Ω
(1)
R10
J1
–VIN
(1)
R1
(1)
C20
0.1µF
U3:A
OPA2650U
U3:B
J2
R11
402Ω
OPA2650U
–VIN
BUF
3
4
R22
R17
1
6
24.9Ω
0Ω
7
2
R2
49.9Ω
5
(1)
R9
8
(1)
C22
2.2µF
R5
C15
R3
+
24.9Ω
0.1µF
Open
(1)
C23
0.1µF
RV2
5kΩ
U3, 4
U3, 8
C5
–5V
–5V
+5V
+5V
+
C1
2.2µF
C3
0.1µF
C8
2.2µF
0.1µF
+
VCM
NOTE: (1) Part Not Assembled.
FIGURE 1. DEM-ADS9xxE Analog Input Circuit.
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DEM-ADS9xx
FIGURE 2. DEM-ADS9xxE Reference Circuit.
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DEM-ADS9xx
FIGURE 3. DEM-ADS9xxE DUT and Digital Outputs.
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DEM-ADS9xx
FIGURE 4. DEM-ADS9xxE Clock and Power Supply Circuit.
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DEM-ADS9xx
FIGURE 5. Top-Layer (component side) with Silkscreen; DEM-ADS9xxE.
FIGURE 6. Power Plane; DEM-ADS9xxE.
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DEM-ADS9xx
FIGURE 7. Bottom Layer with Silkscreen; DEM-ADS9xxE.
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DEM-ADS9xx
COMPONENT LIST
REFERENCE
U1
QTY
1
COMPONENT
ADS9xxE
DESCRIPTION
High-Speed ADC, 28-Pin SSOP
3V Fixed Regulator
MANUFACTURER
Burr-Brown
Burr-Brown
Burr-Brown
Motorola
Motorola
Fox
U2
1
REG1117-3
U3
1
OPA2650U
Dual VFA Op Amp, SO-8
U4
1
MC100ELT25D
MC34072D
ECL to TTL Translator, SO-8
Dual, Single-Supply Op Amp, SO-8
Crystal, 40MHz/60MHz
U5
1
U6
1
F3000
U7
1
74AC11074D
Dual D-Type Flip-Flop, SO-14
1.2V Reference, SO-8
Texas Instruments
Burr-Brown
Motorola
div.
U8
1
REF1004C-1.2
MC74LCX541DW
74HC541
U9, U10
2
3V Octal Buffer, 20-Pin SOIC
5V Octal Buffer, 20-Pin SOIC
0Ω, MF 1206 Chip Resistor, 1%
24.9Ω, MF 1206 Chip Resistor, 1%
49.9Ω, MF 1206 Chip Resistor, 1%
402Ω, MF 1206 Chip Resistor, 1%
1kΩ, MF 1206 Chip Resistor, 1%
3kΩ, MF 1206 Chip Resistor, 1%
10kΩ, MF 1206 Chip Resistor, 1%
5kΩ, 1/4" 10-Turn Pot
U9, U10
2
R15, R17, R18
R5, R19, R21, R22
R2, R4, R8
R11, R16
R20, R23, R24
R7, R13, R30
R6, R32, R33, R34
RV1, RV2, RV3
C6, C7, C9, C16
3
CRCW1206ZEROF
CRCW120624R9F
CRCW120649R9F
CRCW12064020F
CRCW12061001F
CRCW12063001F
CRCW12061002
RJ26FW-502
Dale
4
Dale
3
Dale
2
Dale
3
Dale
3
Dale
4
Dale
3
Bourns
4
ECE-V1CV100SR
TAJR225006
10µF/16V, Surface-Mount Polar, Alu Capacitor
2.2µF/10V, 3216 Tantalum Capacitor
Panasonic
AVX
C1, C8, C25, C32, C35
5
C2, C3, C4, C5, C10, C11, C12, C14,
C15, C17, C21, C24, C27, C28, C29
C30, C33, C34, C36, C37, C38
22
2
12065C104KAT
12065C220KAT
ED555/2DS
0.1µF/50V, X7R 1206 Ceramic Capacitor
22pF/50V, NP0 1206 Ceramic Capacitor
2-Pin Term Block
AVX
C26, C31
AVX
P1
1
On-Shore Technology
On-Shore Technology
Robinson-Nugent
EF Johnson
P2
1
ED555/3DS
3-Pin Term Block
P3
1
IDH-40LP-S3-TG
142-0701-201
#701C
20x2 Dual-Row Shrouded Header
Straight SMA PCB Connector
Flush Mount Pins
J2, J3
2
Sockets for U6
4
McKenzie Technology
Digi-Key
4
1-SJ5003-0-N
PCBA 2161
Rubber Feet, Black, 0.44x0.2
PC Board A2161, Rev. A
1
Burr-Brown
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DEM-ADS9xx
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