The ADS-917 is a high-performance, 14-bit, 1MHz sampling
A/D converter. This device samples input signals up to Nyquist
frequencies with no missing codes. The ADS-917 features
outstanding dynamic performance including a THD of –80dB.
Housed in a small 24-pin DDIP or SMT (gull-wing) package,
the functionally complete ADS-917 contains a fast-settling
sample-hold amplifier, a subranging (two-pass) A/D converter,
a precise voltage reference, timing/control logic, and errorcorrection circuitry. Digital input and output levels are TTL.
Requiring ±15V (or ±12V) and +5V supplies, the ADS-917
dissipates 1.9W (1.6W for ±12V) maximum. The unit is offered
with a unipolar input (0 to +10V). Models are available for use
in either commercial (0 to +70°C) or military (–55 to +125°C)
operating temperature ranges. Applications include radar,
sonar, spectrum analysis, and graphic/medical imaging.
+12V/+15V Supply (Pin 22)0 to +16Volts
–12V/–15V Supply (Pin 24)0 to –16Volts
+5V Supply (Pin 13)0 to +6Volts
Digital Input (Pin 16)–0.3 to +V
Analog Input (Pin 20)–4 to +17Volts
Lead Temperature (10 seconds)+300°C
Power Dissipation—1.41.6—1.41.6—1.41.6Watts
Power Supply Rejection——±0.01——±0.01——±0.01%FSR/%V
Footnotes:
➀ All power supplies must be on before applying a start convert pulse. All supplies
and the clock (START CONVERT) must be present during warmup periods. The
device must be continuously converting during this time. There is a slight
degradation in performance when using ±12V supplies.
➁ See Ordering Information for availability of ±5V input range. Contact DATEL for
availability of other input voltage ranges.
➂ A 1MHz clock with a 200ns wide start convert pulse is used for all production
testing. See Timing Diagram for more details.
TECHNICAL NOTES
1. Obtaining fully specified performance from the ADS-917
requires careful attention to pc-card layout and power
supply decoupling. The device's analog and digital ground
systems are connected to each other internally. For optimal
performance, tie all ground pins (14, 19 and 23) directly to a
large analog ground plane beneath the package.
Bypass all power supplies, as well as the REFERENCE
OUTPUT (pin 21), to ground with 4.7µF tantalum capacitors
in parallel with 0.1µF ceramic capacitors. Locate the
bypass capacitors as close to the unit as possible. If the
user-installed offset and gain adjusting circuit shown in
Figure 2 is used, also locate it as close to the ADS-917 as
possible.
2. The ADS-917 achieves its specified accuracies without the
➃ Effective bits is equal to:
(SNR + Distortion) – 1.76 + 20 log
6.02
➄ This is the time required before the A/D output data is valid after the analog input
is back within the specified range.
Full Scale Amplitude
Actual Input Amplitude
need for external calibration. If required, the device's small
initial offset and gain errors can be reduced to zero using
the input circuit of Figure 2. When using this circuit, or any
similar offset and gain-calibration hardware, make adjustments following warmup. To avoid interaction, always
adjust offset before gain.
3. When operating the ADS-917 from ±12V supplies, do not
drive external circuitry with the REFERENCE OUTPUT. The
reference's accuracy and drift specifications may not be
met, and loading the circuit may cause accuracy errors
within the converter.
4. Applying a start convert pulse while a conversion is in
progress (EOC = logic "1") initiates a new and inaccurate
conversion cycle. Data from the interrupted and subsequent
conversions will be invalid.
3
Page 4
ADS-917
–12V/–15V
–15V
®®
CALIBRATION PROCEDURE
(Refer to Figures 2 and 3)
Any offset and/or gain calibration procedures should not be
implemented until devices are fully warmed up. To avoid
interaction, offset must be adjusted before gain. The ranges of
adjustment for the circuit of Figure 2 are guaranteed to
compensate for the ADS-917's initial accuracy errors and may
not be able to compensate for additional system errors.
All fixed resistors in Figure 2 should be metal-film types, and
multiturn potentiometers should have TCR’s of 100ppm/°C or
less to minimize drift with temperature.
A/D converters are calibrated by positioning their digital
outputs exactly on the transition point between two adjacent
digital output codes. This can be accomplished by connecting
LED's to the digital outputs and adjusting until certain LED's
"flicker" equally between on and off. Other approaches
employ digital comparators or microcontrollers to detect when
the outputs change from one code to the next.
For the ADS-919, offset adjusting is normally accomplished at
the point where the output bits are 0's and the LSB just
changes from a 0 to a 1. This digital output transition ideally
occurs when the applied analog input is +½ LSB (+305µV).
Gain adjusting is accomplished when all bits are 1's and the
LSB just changes from a 1 to a 0. This transition ideally
occurs when the analog input is at +full scale minus 1½ LSB's
(+9.999085V) .
+15V
2k
+15V
Ω200kΩ20kΩ
To Pin 20
of ADS-917
ZERO/
OFFSET
ADJUST
SIGNAL
INPUT
–15V
GAIN
ADJUST
Ω
1.98k
50
Ω
Zero/Offset Adjust Procedure
1. Apply a train of pulses to the START CONVERT input
(pin 16) so the converter is continuously converting. If
using LED's on the outputs, a 200kHz conversion rate will
reduce flicker.
2. Apply +305µV to the ANALOG INPUT (pin 20).
3. Adjust the offset potentiometer until the output bits are
all 0's and the LSB flickers between 0 and 1.
Gain Adjust Procedure
1. Apply +9.999085V to the ANALOG INPUT (pin 20).
2. Adjust the gain potentiometer until the output bits are all 1's
and the LSB flickers between 1 and 0.
All DATEL sampling A/D converters are fully characterized and
specified over operating temperature (case) ranges of
0 to +70°C and –55 to + 125°C. All room-temperature
A = +25°C) production testing is performed without the use of
(T
heat sinks or forced-air cooling. Thermal impedance figures
for each device are listed in their respective specification
tables.
These devices do not normally require heat sinks, however,
standard precautionary design and layout procedures should
be used to ensure devices do not overheat. The ground and
power planes beneath the package, as well as all pcb signal
runs to and from the device, should be as heavy as possible to
help conduct heat away from the package.
N
START
CONVERT
INTERNAL S/H
200ns
typ.
10ns typ.
Hold
430ns typ.
Electrically-insulating, thermally-conductive "pads" may be
installed underneath the package. Devices should be soldered
to boards rather than "socketed", and of course, minimal air
flow over the surface can greatly help reduce the package
temperature.
In more severe ambient conditions, the package/junction
temperature of a given device can be reduced dramatically
(typically 35%) by using one of DATEL's HS Series heat sinks.
See Ordering Information for the assigned part number. See
page 1-183 of the DATEL Data Acquisition Components
Catalog for more information on the HS Series. Request
DATEL Application Note AN-8, "Heat Sinks for DIP Data
Converters", or contact DATEL directly, for additional
information.
N+1
Acquisition Time
570ns ±40ns
EOC
OUTPUT
DATA
70ns ±10ns
90ns typ.
Conversion Time
420ns ±20ns
35ns max.
74ns max.
Data (N – 1) Valid
926ns min.
Notes: 1. f
s = 500kHz.
2. The ADS-917 is an edge-triggered device. All internal operations
are triggered by the rising edge of the start convert pulse, which
may be as narrow as 20nsec. All production testing is performed
at a 1MHz sampling rate with 200nsec wide start pulses. For
lower sampling rates, wider start pulses may be used, however, a
minimum pulse width low of 20nsec must be maintained.
Figure 7. ADS-917 Histogram and Differential Nonlinearity
7
Page 8
ADS-917
(2.540)
(1.016)
(unless otherwise indicated):
ISO 9001
REGISTERED
24-Pin DDIP
Versions
ADS-917MC
ADS-917MM
ADS-927MC
ADS-927MM
ADS-927/883
MECHANICAL DIMENSIONS INCHES (mm)
1.31 MAX.
(33.27)
0.235 MAX.
0.190 MAX.
(4.826)
24
112
(5.969)
PIN 1 INDEX
0.018 ±0.002
(0.457)
1.100
(27.940)
0.100 TYP.
(2.540)
0.100
(2.540)
0.040
(1.016)
13
0.80 MAX.
(20.32)
0.200 MAX.
(5.080)
SEATING
PLANE
0.025
(0.635)
Dimension Tolerances
2 place decimal (.XX) ±0.010 (±0.254)
3 place decimal (.XXX) ±0.005 (±0.127)
Lead Material:
Lead Finish:
over 100 microinches (nominal) nickel plating
(unless otherwise indicated):
Kovar alloy
50 microinches (minimum) gold plating
+0.002
0.010
–0.001
(0.254)
0.100
0.600 ±0.010
(15.240)
(2.540)
®®
24-Pin
Surface Mount
Versions
24
1.31 MAX.
(33.02)
ADS-917GC
ADS-917GM
ADS-927GC
ADS-927GM
0.190 MAX.
(4.826)
PIN 1
INDEX
0.100 TYP.
ORDERING INFORMATION
MODELOPERATINGANALOG
NUMBERTEMP. RANGEINPUT
ADS-917MC0 to +70°CUnipolar (0 to +10V)
ADS-917MM–55 to +125°CUnipolar (0 to +10V)
ADS-917GC0 to +70°CUnipolar (0 to +10V)
ADS-917GM–55 to +125°CUnipolar (0 to +10V)
ADS-927MC0 to +70°CBipolar (±5V)*
ADS-927MM–55 to +125°CBipolar (±5V)*
ADS-927GC0 to +70°CBipolar (±5V)*
ADS-927GM–55 to +125°CBipolar (±5V)*
ADS-927/883–55 to +125°CBipolar (±5V)*
0.020 TYP.
(0.508)
0.040
Dimension Tolerances
0.100
(2.540)
2 place decimal (.XX) ±0.010 (±0.254)
3 place decimal (.XXX) ±0.005 (±0.127)
Lead Material:
Lead Finish: 50 microinches (minimum) gold plating
over 100 microinches (nominal) nickel plating
0.020
(0.508)
Kovar alloy
0.060 TYP.
(1.524)
0.130 TYP.
(3.302)
MAX. radius
0.010 TYP.
0.015
(0.381)
for any pin
(0.254)
13
0.80 MAX.
(20.32)
121
ACCESSORIES
ADS-B916/917Evaluation Board (without ADS-917)
HS-24Heat Sinks for all ADS-917/927 DDIP models
Receptacles for PC board mounting can be ordered through
AMP Inc. Part #3-331272-8 (Component Lead Socket), 24 required.
For MIL-STD-883 product specifications, contact DATEL.
* For information, see ADS-927 data sheet.
®®
DATEL, Inc. 11 Cabot Boulevard, Mansfield, MA 02048-1151
Tel: (508) 339-3000 (800) 233-2765 Fax: (508) 339-6356
Internet: www.datel.com E-mail:sales@datel.com
Data Sheet Fax Back: (508) 261-2857
DATEL makes no representation that the use of its products in the circuits described herein, or the use of other technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein
do not imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without notice. The DATEL logo is a registered DATEL, Inc. trademark.
ISO 9001
DS-0293B 11/96
DATEL (UK) LTD. Tadley, England Tel: (01256)-880444
DATEL S.A.R.L. Montigny Le Bretonneux, France Tel: 1-34-60-01-01
DATEL GmbH München, Germany Tel: 89-544334-0
DATEL KK Tokyo, Japan Tel: 3-3779-1031, Osaka Tel: 6-354-2025
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