FEATURES
18-bit resolution
500kHz minimum sampling rate
No missing codes over full military temperature range
Very low power, 1.45 Watts
Small, 32-pin, side-brazed, ceramic TDIP
Edge-triggered
Excellent performance
Ideal for both time and frequency-domain applications
Low cost
operating temperature ranges. A proprietary, auto-calibrating,
error-correcting circuit enables the device to achieve specified
performance over the full military temperature range.
PRELIMINARY PRODUCT DATA
ADS-950
18-Bit, 500kHz, Low-Power
Sampling A/D Converters
GENERAL DESCRIPTION
The low-cost ADS-950 is an 18-bit, 500kHz sampling A/D
converter. This device accurately samples full-scale input
signals up to Nyquist frequencies with no missing codes. This
feature, combined with excellent signal-to-noise ratio (SNR)
and total harmonic distortion (THD), makes the ADS-950 the
ideal choice for both time-domain (medical imaging, scanners,
process control) and frequency-domain (radar, telecommunica-
tions, spectrum analysis) applications.
Packaged in a 32-pin, side-brazed, metal-sealed, ceramic
TDIP, the functionally complete ADS-950 contains a fast-
settling sample-hold amplifier, a subranging (two-pass) A/D
converter, an internal reference, timing/control logic, and error-
correction circuitry. Digital input and output levels are TTL, and
the ADS-950 only requires the rising edge of the start convert
pulse to operate.
Requiring 15V and 5V supplies, the ADS-950 typically
dissipates 1.45 Watts. The device is offered with a bipolar
(5V) analog input range. Models are available for use in
either commercial (0 to +70C) or military (55 to +125C)
INPUT/OUTPUT CONNECTIONS
Figure 1. ADS-950 Functional Block Diagram
1
BIT 2
32
BIT 3
2
BIT 1 (MSB)
31
BIT 4
3
ANALOG GROUND
30
BIT 5
4
ANALOG INPUT
29
BIT 6
5
+5V REFERENCE OUT
28
BIT 7
6
GAIN ADJUST
27
BIT 8
7
COMPENSATION
26
BIT 9
8
15V SUPPLY
25
BIT 10
9
+15V SUPPLY
24
BIT 11
10
+5V ANALOG SUPPLY
23
BIT 12
11
5V ANALOG SUPPLY
22
BIT 13
12
ANALOG GROUND
21
BIT 14
13
DIGITAL GROUND
20
BIT 15
14
+5V DIGITAL SUPPLY
19
BIT 16
15
EOC
18
BIT 17
16
START CONVERT
17
BIT 18 (LSB)
PIN
FUNCTION
PIN
FUNCTION
DATEL, Inc., Mansfield, MA 02048 (USA)
Tel: (508) 339-3000, (800) 233-2765 Fax: (508) 339-6356
Email: sales@datel.com
Internet: www.datel.com
REF
DAC
2 BIT
1
(MSB)
1 BIT 2
32 BIT 3
31 BIT 4
30 BIT 5
29
BIT 6
28 BIT 7
27 BIT 8
26 BIT 9
25 BIT 10
24 BIT 11
23 BIT
12
22 BIT
13
21 BIT 14
20 BIT
15
19 BIT
16
18 BIT 17
17 BIT 18 (LSB)
TIMING AND
CONTROL LOGIC
ANALOG INPUT 4
START CONVERT 16
EOC 15
+
S/H
BUFFER
DI
GI
TAL
CORRECTI
O
N L
OGI
C
FLASH
ADC
1
FLASH
ADC
2
5
AMP
GAIN
CIRCUIT
COMPENSATION 7
+5V REFERENCE OUT 5
10
+5V ANALOG
SUPPLY
11
5V ANALOG
SUPPLY
3, 12
ANALOG
GROUND
14
+5V DIGITAL
SUPPLY
9
+15V
SUPPLY
8
15V
SUPPLY
13
DIGITAL
GROUND
GAIN ADJUST 6
ADS-950
2
+25C
0 to +70C
55 to +125C
ANALOG INPUT
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
UNITS
Input Voltage Range
--
5
--
--
5
--
--
5
--
Volts
Input Resistance
--
500
--
--
500
--
--
500
--
W
Input Capacitance
--
7
15
--
7
15
--
7
15
pF
DIGITAL INPUT
Logic Levels
Logic "1"
+2.0
--
--
+2.0
--
--
+2.0
--
--
Volts
Logic "0"
--
--
+0.8
--
--
+0.8
--
--
+0.8
Volts
Logic Loading "1"
--
--
+20
--
--
+20
--
--
+20
A
Logic Loading "0"
--
--
20
--
--
20
--
--
20
A
Start Convert Positive Pulse Width
20
500
--
20
500
--
20
500
--
ns
STATIC PERFORMANCE
Resolution
--
18
--
--
18
--
--
18
--
Bits
Integral Nonlinearity (f
in
= 10kHz)
--
0.75
--
--
1.5
--
--
2
--
LSB
Differential Nonlinearity (f
in
= 10kHz)
0.95
0.5
+1
0.95
0.5
+1
0.95
0.50
+1.25
LSB
Full Scale Absolute Accuracy
--
0.1
0.25
--
0.25
0.4
--
0.4
0.8
%FSR
Bipolar Zero Error (Tech Note 2)
--
0.1
0.15
--
0.15
0.25
--
0.25
0.5
%FSR
Bipolar Offset Error (Tech Note 2)
--
0.1
0.2
--
0.2
0.3
--
0.3
0.6
%FSR
Gain Error (Tech Note 2)
--
0.1
0.25
--
0.25
0.4
--
0.4
0.9
%
No Missing Codes (f
in
= 10kHz)
18
--
--
18
--
--
18
--
--
Bits
DYNAMIC PERFORMANCE
Peak Harmonics (0.5dB)
dc to 100kHz
--
90
--
--
90
--
--
86
--
dB
Total Harmonics Distortion (0.5dB)
dc to 100kHz
--
89
--
--
89
--
--
85
--
dB
Signal-to-Noise Ratio
(w/o distortion, 0.5dB)
dc to 100kHz
92
94
--
92
94
--
--
92
--
dB
Signal-to-Noise Ratio
(& distortion, 0.5dB)
dc to 100kHz
--
86
--
--
86
--
--
82
--
dB
Noise
--
38
48
--
38
48
--
38
--
Vrms
Two-Tone Intermodulation
Distortion (f
in
= 100kHz,
240kHz, f
s
= 1MHz, 0.5dB)
--
85
--
--
85
--
--
85
--
dB
Input Bandwidth (3dB)
Small Signal (20dB input)
--
TBD
--
--
TBD
--
--
TBD
--
MHz
Large Signal (0.5dB input)
--
TBD
--
--
TBD
--
--
TBD
--
MHz
Feedthrough Rejection (f
in
= 500kHz)
--
84
--
--
84
--
--
84
--
dB
Slew Rate
--
TBD
--
--
TBD
--
--
TBD
--
V/s
Aperture Delay Time
--
+20
--
--
+20
--
--
+20
--
ns
Aperture Uncertainty
--
5
--
--
5
--
--
5
--
ps rms
S/H Acquisition Time
( to 0.003%FSR, 10V step)
--
260
--
--
260
--
--
260
--
ns
Overvoltage Recovery Time
--
1
--
--
1
--
--
1
--
s
A/D Conversion Rate
500
--
--
500
--
--
500
--
--
kHz
PARAMETERS
LIMITS
UNITS
+15V Supply (Pin 9)
0 to +16
Volts
15V Supply (Pin 8)
0 to 16
Volts
+5V Supply (Pins 10, 14)
0 to +6
Volts
5V Supply (Pin 11)
0 to 6
Volts
Digital Input (Pin 16)
0.3 to +V
DD
+0.3
Volts
Analog Input (Pin 4)
15
Volts
Lead Temperature (10 seconds)
+300
C
PARAMETERS
MIN.
TYP.
MAX.
UNITS
Operating Temp. Range, Case
ADS-951MC
0
--
+70
C
ADS-951MM
55
--
+125
C
Thermal Impedance
qjc
--
5
--
C/Watt
qca
--
22
--
C/Watt
Storage Temperature Range
65
--
+150
C
Package Type
32-pin,side-brazed, metal-sealed, ceramic TDIP
Weight
0.46 ounces (13 grams)
ABSOLUTE MAXIMUM RATINGS
PHYSICAL/ENVIRONMENTAL
FUNCTIONAL SPECIFICATIONS
(T
A
= +25C, V
CC
= 15V, V
DD
= 5V, 500kHz sampling rate, and a minimum 1 minute warmup unless otherwise specified.)
ADS-950
3
+25C
0 to +70C
55 to +125C
ANALOG OUTPUT
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
UNITS
Internal Reference
Voltage
+4.95
+5.0
+5.05
+4.95
+5.0
+5.05
+4.95
+5.0
+5.05
Volts
Drift
--
30
--
--
30
--
--
30
--
ppm/C
External Current
--
1
--
--
1
--
--
1
--
mA
DIGITAL OUTPUTS
Logic Levels
Logic "1"
+2.4
--
--
+2.4
--
--
+2.4
--
--
Volts
Logic "0"
--
--
+0.4
--
--
+0.4
--
--
+0.4
Volts
Logic Loading "1"
--
--
4
--
--
4
--
--
4
mA
Logic Loading "0"
--
--
+4
--
--
+4
--
--
+4
mA
Output Coding
Complementary Offset Binary
POWER REQUIREMENTS
Power Supply Ranges
+15V Supply
+14.5
+15.0
+15.5
+14.5
+15.0
+15.5
+14.5
+15.0
+15.5
Volts
15V Supply
14.5
15.0
15.5
14.5
15.0
15.5
14.5
15.0
15.5
Volts
+5V Supply
+4.75
+5.0
+5.25
+4.75
+5.0
+5.25
+4.75
+5.0
+5.25
Volts
5V Supply
4.75
5.0
5.25
4.75
5.0
5.25
4.75
5.0
5.25
Volts
Power Supply Currents
+15V Supply
--
+29
--
--
+29
--
--
+29
--
mA
15V Supply
--
15
--
--
15
--
--
15
--
mA
+5V Supply
--
+104
--
--
+104
--
--
+104
--
mA
5V Supply
--
54
--
--
54
--
--
54
--
mA
Power Dissipation
--
1.45
1.65
--
1.45
1.65
--
1.45
1.65
Watts
Power Supply Rejection
--
--
0.05
--
--
0.05
--
--
0.05
%FSR/%V
THERMAL REQUIREMENTS
All DATEL sampling A/D converters are fully characterized and
specified over operating temperature (case) ranges of 0 to
+70C and 55 to +125C. All room-temperature (T
A
= +25C)
production testing is performed without the use of 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. 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.
TECHNICAL NOTES
1. Obtaining fully specified performance from the ADS-950
requires careful attention to pc-card layout and power
supply decoupling. The device's analog and digital ground
systems are not connected to each other internally. For
optimal performance, tie all ground pins (3, 12 and 13)
directly to a large analog ground plane beneath the
package.
Bypass all power supplies and the +5V REFERENCE
OUTPUT (pin 5) to ground with 10F tantalum capacitors in
parallel with 0.1F ceramic capacitors. Locate the bypass
capacitors as close to the unit as possible. Tie a 47F
capacitor between COMPENSATION (pin 7) and ground.
2. The ADS-950 achieves its specified accuracies without the
need for external calibration. If required, the device's small
initial errors can be reduced to zero using the adjustment
circuitry shown in Figure 2. When using this circuitry, or any
similar offset and gain calibration hardware, make adjust-
ments following warmup. To avoid interaction, always adjust
offset before gain. Float pin 6 if not using gain adjust
circuits.
Footnotes:
This is the time required before the A/D output data is valid once the analog input
is back within the specified range.
6.02
(SNR + Distortion) 1.76 + 20 log
Full Scale Amplitude
Actual Input Amplitude
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.
Contact DATEL for other input voltage ranges.
A 500kHz clock with a 1sec positive pulse width (50% duty cycle) is
used for all production testing. Any duty cycle may be used as long as a
minimum positive pulse width of 20nsec is maintained. For applications
requiring lower sampling rates, clock frequencies lower than 1MHz
may be used.
Effective bits is equal to:
3. Applying a start convert pulse while a conversion is in
progress (EOC = logic "1") will initiate a new and probably
inaccurate conversion cycle. Data for the interrupted and
subsequent conversions will be invalid.
ADS-950
4
Zero/Offset Adjust Procedure
1. Apply a train of pulses to the START CONVERT input
(pin 16) so that the converter is continuously converting.
2. For bipolar zero/offset adjust, apply 19V to the ANALOG
INPUT (pin 4).
3. Adjust the offset potentiometer until the output code flickers
equally between 01 1111 1111 1111 1111 and 10 0000
0000 0000 0000.
Gain Adjust Procedure
1. Apply 4.999943V to the ANALOG INPUT (pin 4).
2. Adjust the gain potentiometer until all output bits are 1's
and the LSB flickers between 1 and 0.
3. To confirm proper operation of the device, vary the applied
input voltage to obtain the output coding listed in Table 2.
BIPLOAR
INPUT VOLTAGE
SCALE
5V
MSB
LSB
+FS 1 LSB
+4.999962
00 0000 0000 0000 0000
+3/4 FS
+3.750000
00 0111 1111 1111 1111
+1/2 FS
+2.500000
00 1111 1111 1111 1111
0
+0.000000
01 1111 1111 1111 1111
1/2 FS
2.500000
10 1111 1111 1111 1111
3/4 FS
3.750000
11 0111 1111 1111 1111
FS +1 LSB
4.999962
11 1111 1111 1111 1110
FS
5.000000
11 1111 1111 1111 1111
OUTPUT CODING
COMPLEMENTARY
OFFSET BINARY
Table 2. Output Coding
CALIBRATION PROCEDURE
Connect the converter per Table 1 for the appropriate input
voltage range. Any offset/gain calibration procedures should
not be implemented until the device is fully warmed up. To
avoid interaction, adjust offset before gain. The ranges of
adjustment for the circuits in Figure 2 are guaranteed to
compensate for the ADS-950's initial accuracy errors and may
not be able to compensate for additional system errors.
A/D converters are calibrated by positioning their digital outputs
exactly on the transition point between two adjacent digital
output codes. This is accomplished by connecting LED's to the
digital outputs and performing adjustments 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-950, offset adjusting is normally accomplished
when the analog input is 0 minus LSB (19V). See Table 2
for the proper bipolar output coding.
Gain adjusting is accomplished when the analog input is at
nominal full scale minus 1LSB's (4.999943V).
INPUT VOLTAGE
ZERO ADJUST
GAIN ADJUST
RANGE
( LSB)
(FS +1 LSB)
5V
19V
4.999943
Table 1. Input Connections
ADS-950
5
Figure 3. ADS-950 Timing Diagram
Figure 2. Typical ADS-950 Connection Diagram
S c a l e i s a p p r o x i m a t e l y 1 0 0 n s p e r d i v i s i o n .
S T A R T
C O N V E R T
I N T E R N A L S / H
N
N + 1
1 0 0 0 n s t y p .
A c q u i s i t i o n T i m e
5 n s t y p .
E O C
O U T P U T
D A T A
D a t a N - 2 V a l i d
1 9 8 0 n s t y p .
H o l d
2 0 n s t y p .
2 0 n s
N
N
8 0 0 n s t y p .
8 1 0 n s t y p .
6 5 n s t y p .
C o n v e r s i o n T i m e
8 0 0 n s t y p .
D a t a N - 1 V a l i d
3
1 1
A D S - 9 5 0
1 0
2
1
3 2
3 1
3 0
2 9
2 8
2 7
2 6
2 5
2 4
2 3
2 2
2 1
2 0
1 9
1 8
1 7
B I T 1 ( M S B )
B I T 2
B I T 3
B I T 4
B I T 5
B I T 6
B I T 7
B I T 8
B I T 9
B I T 1 0
B I T 1 1
B I T 1 2
B I T 1 3
B I T 1 4
B I T 1 5
B I T 1 6
B I T 1 7
B I T 1 8 ( L S B )
+ 5 V A N A L O G
1 5
A N A L O G
G R O U N D
A N A L O G
G R O U N D
D I G I T A L
G R O U N D
0 . 1 F
1 0 F
0 . 1 F
+
1 0 F
+ 5 V
R E F . O U T
C O M P E N S A T I O N
4 7 F
1 4
1 3
5
7
S T A R T C O N V E R T
+ 5 V D I G I T A L
G A I N
A D J U S T
6
1 6
0 . 1 F
1 0 F
1 2
9
0 . 1 F
1 0 F
8
++
0 . 1 F
1 0 F
0 . 1 F
1 0 F
+
+
E O C
5 V A N A L O G
+ 1 5 V
1 5 V
A N A L O G I N P U T
4
P i n 5 ( A D S - 9 5 1 )
1 0 k
9
ADS-950
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.
DS-0????
07/2000
MECHANICAL DIMENSIONS INCHES (mm)
ORDERING INFORMATION
OPERATING
32-PIN
MODEL NUMBER TEMP. RANGE
PACKAGE
ADS-950MC
0 to +70C
TDIP
ADS-950MM
55 to +125C
TDIP
ACCESSORIES
ADS-B950
Evaluation Board (without ADS-950)
Receptacles for PC board mounting can be ordered through AMP, Inc., Part # 3-331272-8
(Component Lead Socket), 32 required. For availability of MIL-STD-883 product, contact DATEL.
ISO 9001
ISO 9001
R
E
G
I
S
T
E
R
E
D
DATEL, Inc. 11 Cabot Boulevard, Mansfield, MA 02048-1151
Tel: (508) 339-3000 (800) 233-2765 Fax: (508) 339-6356
Email: sales@datel.com Internet: www.datel.com
DATEL (UK) LTD. Tadley, England Tel: (01256)-880444
DATEL S.A.R.L. Montigny Le Bretonneux, France Tel: 01-34-60-01-01
DATEL GmbH Mnchen, Germany Tel: 89-544334-0
DATEL KK Tokyo, Japan Tel: 3-3779-1031, Osaka Tel: 6-6354-2025
1.62 MAX.
(41.15)
0.92 MAX.
(23.37)
0.018 TYP.
(0.46)
1.50 TYP
(38.10)
0.100 TYP.
(2.54)
0.05 TYP.
(1.27)
0.175 TYP
(4.45)
0.05 TYP.
(1.27)
0.220 TYP.
(6.86)
0.90 TYP.
(22.86)
0.010 TYP.
(0.254)
Dimension Tolerances
(unless otherwise indicated):
2 place decimal (.XX) 0.010 (0.254)
3 place decimal (.XXX) 0.005 (0.127)
Lead Material: Kovar Alloy
Lead Finish: 50 microinches (minimum)
gold plating over 100 microinches
(nominal) nickel plating
PIN 1 INDEX
0.05 TYP.
(1.27)
SEATING PLANE
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