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ADS-950
18-Bit, 500kHz, Low-Power Sampling A/D Converters
PRELIMINARY PRODUCT DATA
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
PIN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
INPUT/OUTPUT CONNECTIONS
FUNCTION BIT 2 BIT 1 (MSB) ANALOG GROUND ANALOG INPUT +5V REFERENCE OUT GAIN ADJUST COMPENSATION -15V SUPPLY +15V SUPPLY +5V ANALOG SUPPLY -5V ANALOG SUPPLY ANALOG GROUND DIGITAL GROUND +5V DIGITAL SUPPLY EOC START CONVERT PIN 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 FUNCTION BIT 3 BIT 4 BIT 5 BIT 6 BIT 7 BIT 8 BIT 9 BIT 10 BIT 11 BIT 12 BIT 13 BIT 14 BIT 15 BIT 16 BIT 17 BIT 18 (LSB)
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, telecommunications, spectrum analysis) applications. Packaged in a 32-pin, side-brazed, metal-sealed, ceramic TDIP, the functionally complete ADS-950 contains a fastsettling sample-hold amplifier, a subranging (two-pass) A/D converter, an internal reference, timing/control logic, and errorcorrection 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)
operating temperature ranges. A proprietary, auto-calibrating, error-correcting circuit enables the device to achieve specified performance over the full military temperature range.
2 1
BIT 1 (MSB) BIT 2
BUFFER
ANALOG INPUT 4
32 BIT 3
- S/H +
FLASH ADC 1
DIGITAL CORRECTION LOGIC
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)
GAIN ADJUST 6
GAIN CIRCUIT
REF
+5V REFERENCE OUT 5 COMPENSATION 7
5
DAC
AMP
FLASH ADC 2
START CONVERT 16 EOC 15
TIMING AND CONTROL LOGIC
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
Figure 1. ADS-950 Functional Block Diagram
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
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ADS-950
ABSOLUTE MAXIMUM RATINGS
PARAMETERS +15V Supply (Pin 9) -15V Supply (Pin 8) +5V Supply (Pins 10, 14) -5V Supply (Pin 11) Digital Input (Pin 16) Analog Input (Pin 4) Lead Temperature (10 seconds) LIMITS 0 to +16 0 to -16 0 to +6 0 to -6 -0.3 to +VDD +0.3 15 +300 UNITS Volts Volts Volts Volts Volts Volts C
PHYSICAL/ENVIRONMENTAL
PARAMETERS Operating Temp. Range, Case ADS-951MC ADS-951MM Thermal Impedance qjc qca Storage Temperature Range Package Type Weight MIN. 0 -55 TYP. -- -- MAX. +70 +125 UNITS C C
-- 5 -- C/Watt -- 22 -- C/Watt -65 -- +150 C 32-pin,side-brazed, metal-sealed, ceramic TDIP 0.46 ounces (13 grams)
FUNCTIONAL SPECIFICATIONS
(TA = +25C, VCC = 15V, VDD = 5V, 500kHz sampling rate, and a minimum 1 minute warmup unless otherwise specified.) +25C TYP. 5 500 7 0 to +70C TYP. 5 500 7 -55 to +125C TYP. MAX. 5 500 7 -- -- 15
ANALOG INPUT Input Voltage Range Input Resistance Input Capacitance DIGITAL INPUT Logic Levels Logic "1" Logic "0" Logic Loading "1" Logic Loading "0" Start Convert Positive Pulse Width STATIC PERFORMANCE Resolution Integral Nonlinearity (fin = 10kHz) Differential Nonlinearity (fin = 10kHz) Full Scale Absolute Accuracy Bipolar Zero Error (Tech Note 2) Bipolar Offset Error (Tech Note 2) Gain Error (Tech Note 2) No Missing Codes (fin = 10kHz) DYNAMIC PERFORMANCE Peak Harmonics (-0.5dB) dc to 100kHz Total Harmonics Distortion (-0.5dB) dc to 100kHz Signal-to-Noise Ratio (w/o distortion, -0.5dB) dc to 100kHz Signal-to-Noise Ratio (& distortion, -0.5dB) dc to 100kHz Noise Two-Tone Intermodulation Distortion (fin = 100kHz, 240kHz, fs = 1MHz, -0.5dB) Input Bandwidth (-3dB) Small Signal (-20dB input) Large Signal (-0.5dB input) Feedthrough Rejection (fin = 500kHz) Slew Rate Aperture Delay Time Aperture Uncertainty S/H Acquisition Time ( to 0.003%FSR, 10V step) Overvoltage Recovery Time A/D Conversion Rate
MIN. -- -- --
MAX. -- -- 15
MIN. -- -- --
MAX. -- -- 15
MIN. -- -- --
UNITS Volts W pF
+2.0 -- -- -- 20
-- -- -- -- 500
-- +0.8 +20 -20 --
+2.0 -- -- -- 20
-- -- -- -- 500
-- +0.8 +20 -20 --
+2.0 -- -- -- 20
-- -- -- -- 500
-- +0.8 +20 -20 --
Volts Volts A A ns
-- -- -0.95 -- -- -- -- 18
18 0.75 0.5 0.1 0.1 0.1 0.1 --
-- -- +1 0.25 0.15 0.2 0.25 --
-- -- -0.95 -- -- -- -- 18
18 1.5 0.5 0.25 0.15 0.2 0.25 --
-- -- +1 0.4 0.25 0.3 0.4 --
-- -- -0.95 -- -- -- -- 18
18 2 0.50 0.4 0.25 0.3 0.4 --
-- -- +1.25 0.8 0.5 0.6 0.9 --
Bits LSB LSB %FSR %FSR %FSR % Bits
-- -- 92 -- -- -- -- -- -- -- -- -- -- -- 500
-90 -89 94 86 38 -85 TBD TBD 84 TBD +20 5 260 1 --
-- -- -- -- 48 -- -- -- -- -- -- -- -- -- --
-- -- 92 -- -- -- -- -- -- -- -- -- -- -- 500
-90 -89 94 86 38 -85 TBD TBD 84 TBD +20 5 260 1 --
-- -- -- -- 48 -- -- -- -- -- -- -- -- -- --
-- -- -- -- -- -- -- -- -- -- -- -- -- -- 500
-86 -85 92 82 38 -85 TBD TBD 84 TBD +20 5 260 1 --
-- -- -- -- -- -- -- -- -- -- -- -- -- -- --
dB dB dB dB Vrms dB MHz MHz dB V/s ns ps rms ns s kHz
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ADS-950
+25C ANALOG OUTPUT Internal Reference Voltage Drift External Current DIGITAL OUTPUTS Logic Levels Logic "1" Logic "0" Logic Loading "1" Logic Loading "0" Output Coding POWER REQUIREMENTS Power Supply Ranges +15V Supply -15V Supply +5V Supply -5V Supply Power Supply Currents +15V Supply -15V Supply +5V Supply -5V Supply Power Dissipation Power Supply Rejection +14.5 -14.5 +4.75 -4.75 -- -- -- -- -- -- +15.0 -15.0 +5.0 -5.0 +29 -15 +104 -54 1.45 -- +15.5 -15.5 +5.25 -5.25 -- -- -- -- 1.65 0.05 +14.5 -14.5 +4.75 -4.75 -- -- -- -- -- -- +2.4 -- -- -- -- -- -- -- -- +0.4 -4 +4 +2.4 -- -- -- MIN. +4.95 -- -- TYP. +5.0 30 1 MAX. +5.05 -- -- MIN. +4.95 -- --
0 to +70C TYP. +5.0 30 1 MAX. +5.05 -- -- MIN. +4.95 -- --
-55 to +125C TYP. +5.0 30 1 MAX. +5.05 -- -- UNITS Volts ppm/C mA
-- -- -- +0.4 -- -4 -- +4 Complementary Offset Binary
+2.4 -- -- --
-- -- -- --
-- +0.4 -4 +4
Volts Volts mA mA
+15.0 -15.0 +5.0 -5.0 +29 -15 +104 -54 1.45 --
+15.5 -15.5 +5.25 -5.25 -- -- -- -- 1.65 0.05
+14.5 -14.5 +4.75 -4.75 -- -- -- -- -- --
+15.0 -15.0 +5.0 -5.0 +29 -15 +104 -54 1.45 --
+15.5 -15.5 +5.25 -5.25 -- -- -- -- 1.65 0.05
Volts Volts Volts Volts mA mA mA mA Watts %FSR/%V
Footnotes:
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:
(SNR + Distortion) - 1.76 + 20 log 6.02 Full Scale Amplitude Actual Input Amplitude
This is the time required before the A/D output data is valid once the analog input is back within the specified range.
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 adjustments following warmup. To avoid interaction, always adjust offset before gain. Float pin 6 if not using gain adjust circuits. 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.
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 (TA = +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.
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ADS-950
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 1/2LSB (-19V). See Table 2 for the proper bipolar output coding. Gain adjusting is accomplished when the analog input is at nominal full scale minus 11/2LSB's (-4.999943V). 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.
Table 1. Input Connections
INPUT VOLTAGE RANGE 5V
ZERO ADJUST (-1/2 LSB) -19V
GAIN ADJUST (-FS +11/2 LSB) -4.999943
Table 2. Output Coding COMPLEMENTARY OFFSET BINARY
BIPLOAR SCALE +FS -1 LSB +3/4 FS +1/2 FS 0 -1/2 FS -3/4 FS -FS +1 LSB -FS
INPUT VOLTAGE 5V +4.999962 +3.750000 +2.500000 +0.000000 -2.500000 -3.750000 -4.999962 -5.000000
OUTPUT CODING MSB 00 00 00 01 10 11 11 11 LSB
0000 0000 0000 0000 0111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 0111 1111 1111 1111 1111 1111 1111 1110 1111 1111 1111 1111
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ADS-950
P in 5 ( A D S - 9 5 1 )
10k9 6
15 EOC 2 1 32 31 30 B IT 1 (M S B ) B IT 2 B IT 3 B IT 4 B IT 5 B IT 6 B IT 7 B IT 8 B IT 9 B IT 1 0 B IT 1 1 B IT 1 2 B IT B IT B IT B IT B IT B IT 13 14 15 16 17 1 8 (L S B )
G A IN A D JU S T + 5 V D IG IT A L 10F 0 .1 F 14
13
D IG IT A L GROUND 8
29 28 27 26 25 24
15V 10F 0 .1 F
12
AN ALO G GROUND
+
+15V
10F
0 .1 F 9
A D S -9 5 0
23 22 21 20 19 18
+
+5V AN ALO G + 10F + 5V AN ALO G 10F
10 0 .1 F 3 AN ALO G GROUND START CONVERT C O M P E N S A T IO N 5 +5V R EF.O U T AN ALO G 0 .1 F 10F IN P U T 4 16 7
17
0 .1 F
11
47F +
Figure 2. Typical ADS-950 Connection Diagram
N START CONVERT 1 0 0 0 n s ty p .
N+1
5 n s ty p . IN T E R N A L S /H 8 1 0 n s ty p . H o ld
A c q u is itio n T im e
6 5 n s ty p . EOC 8 0 0 n s ty p . C o n v e r s io n T im e 8 0 0 n s ty p .
2 0 n s ty p . OUTPUT DATA D a ta N - 2 V a lid D a ta N - 1 V a lid 1 9 8 0 n s ty p . S c a le is a p p r o x im a te ly 1 0 0 n s p e r d iv is io n .
20ns N N
Figure 3. ADS-950 Timing Diagram
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ADS-950
MECHANICAL DIMENSIONS INCHES (mm)
1.62 MAX. (41.15)
Dimension Tolerances (unless otherwise indicated): 2 place decimal (.XX) 0.010 (0.254) 3 place decimal (.XXX) 0.005 (0.127)
0.92 MAX. (23.37)
Lead Material: Kovar Alloy Lead Finish: 50 microinches (minimum) gold plating over 100 microinches (nominal) nickel plating
1.50 TYP (38.10) SEATING PLANE 0.05 TYP. (1.27) PIN 1 INDEX
0.220 TYP. (6.86)
0.010 TYP. (0.254) 0.05 TYP. (1.27) 0.018 TYP. (0.46) 0.100 TYP. (2.54) 0.175 TYP (4.45) 0.05 TYP. (1.27) 0.90 TYP. (22.86)
ORDERING INFORMATION
OPERATING TEMP. RANGE 0 to +70C -55 to +125C 32-PIN PACKAGE TDIP TDIP
MODEL NUMBER ADS-950MC ADS-950MM
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.
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ISO 9001
REGISTERED
DS-0????
07/2000
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 Munchen, Germany Tel: 89-544334-0 DATEL KK Tokyo, Japan Tel: 3-3779-1031, Osaka Tel: 6-6354-2025
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.

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