®®
FEATURES
• 18-bit resolution
• 1MHz minimum sampling rate
• No missing codes over extended temperature range
• Very low power, 1.45 Watts
• Small, 32-pin, side-brazed, ceramic TDIP
• Edge-triggered
• Excellent performance, –95dB peak harmonics
• Ideal for both time and frequency-domain applications
• Low cost
ing temperature ranges. A proprietary, auto-calibrating, error-
correcting circuit enables the device to achieve specifi ed per-
formance over the full military temperature range.
ADS-953
18-Bit, 1MHz, Low-Distortion
Sampling A/D Converters
GENERAL DESCRIPTION
The ADS-953 is an 18-bit, 1MHz 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 –95dB peak harmonic
distortion (THD), makes the ADS-953 the ideal choice for both
time-domain (medical imaging, scanners, process control) and
frequency-domain (radar, telecommunications, spectrum analy-
sis) applications.
Packaged in a 32-pin, side-brazed, metal-sealed, ceramic TDIP,
the functionally complete ADS-953 contains a fast-settling sam-
ple-hold amplifi er, a subranging (two-pass) A/D converter, an
internal reference, timing/control logic, and error-correction cir-
cuitry. Digital input and output levels are TTL, and the ADS-953
only requires the rising edge of the start convert pulse to
operate.
Requiring ±15V and ±5V supplies, the ADS-953 typically dis-
sipates 1.45 Watts. The device is offered with a bipolar (±5V)
analog input range. Models are available for use in either
commercial (0 to +70°C) or extended (–40 to +110°C) operat-
INPUT/OUTPUT CONNECTIONS
Figure 1. ADS-953 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., Mansfi eld, 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
DIGITAL CORRECTION LOGIC
FLASH
ADC
1
FLASH
ADC
2
Σ
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-953
2
®®
+25°C 0 to +70°C –40 to +110°C
ANALOG INPUT MIN. TYP. MAX. MIN. TYP. MAX. MIN. TYP. MAX. UNITS
Input Voltage Range ➁ — ±5 — — ±5 — — ±5 — Volts
Input Resistance — 500 — — 500 — — 500 — Ω
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 µA
Logic Loading "0" — — –20 — — –20 — — –20 µA
Start Convert Positive Pulse Width ➂ 20 500 — 20 500 — 20 500 — ns
STATIC PERFORMANCE
Resolution — 18 — — 18 — — 18 — Bits
Integral Nonlinearity (fin = 10kHz) — ±10 — — ±10 — — ±15 — LSB
Differential Nonlinearity (fin = 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 (fin = 10kHz) 18 — — 18 — — 18 — — Bits
DYNAMIC PERFORMANCE (500kHz Sampling Rate)
Peak Harmonics (–0.5dB)
dc to 1kHz — –95 –93 — –95 –93 — –82 — dB
Total Harmonic Distortion (–0.5dB)
dc to 100kHz — –85 –80 — –85 –80 — –81 — dB
Signal-to-Noise Ratio
(w/o distortion, –0.5dB)
dc to 100kHz 91 93 — 91 93 — — 92 — dB
Signal-to-Noise Ratio ➃
(& distortion, –0.5dB)
dc to 100kHz 76 84 — 76 84 — — 80 — dB
DC Noise — 76 — — 76 — — 76 — µVrms
Two-Tone Intermodulation
Distortion (fin = 100kHz,
240kHz, fs = 500kHz, –0.5dB) — –85 — — –85 — — –81 — dB
Input Bandwidth (–3dB)
Small Signal (–20dB input) — TBD — — TBD — — TBD — MHz
Large Signal (–0.5dB input) — TBD — — TBD — — TBD — MHz
Feedthrough Rejection (fin = 500kHz) — 84 — — 84 — — 84 — dB
Slew Rate — TBD — — TBD — — TBD — V/µs
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 ➄ — 500 — — 500 — — 500 — ns
A/D Conversion Rate 1 — — 1 — — 1 — — MHz
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 +VDD +0.3 Volts
Analog Input (Pin 4) ±15 Volts
Lead Temperature (10 seconds) +300 °C
ABSOLUTE MAXIMUM RATINGS PHYSICAL/ENVIRONMENTAL
FUNCTIONAL SPECIFICATIONS
(TA = +25°C, ±VCC = ±15V, ±VDD = ±5V, 1MHz sampling rate, and a minimum 1 minute warmup ➀ unless otherwise specifi ed.)
PARAMETERS MIN. TYP. MAX. UNITS
Operating Temp. Range, Case
ADS-953MC 0 — +70 °C
ADS-953ME –40 — +110 °C
Thermal Impedance
θjc — 5 — °C/Watt
θca — 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)
ADS-953
3
®®
+25°C 0 to +70°C –40 to +110°C
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
TECHNICAL NOTES
1. Obtaining fully specifi ed performance from the ADS-953
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 pack-
age.
Bypass all power supplies and the +5V REFERENCE
OUTPUT (pin 5) to ground with 10µF tantalum capacitors in
parallel with 0.1µF ceramic capacitors. Locate the bypass
capacitors as close to the unit as possible. Tie a 47µF
capacitor between COMPENSATION (pin 7) and ground.
Footnotes:
➄ This is the time required before the A/D output data is valid once the analog input
is back within the specifi ed range.
6.02
(SNR + Distortion) – 1.76 + 20 log Full Scale Amplitude
Actual Input Amplitude
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.
➁ Contact DATEL for other input voltage ranges.
➂ A 1MHz clock with a 500nsec 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.
➃ Effective bits is equal to:
2. The ADS-953 achieves its specifi ed 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.
3. Applying a start convert pulse while a conversion is in prog-
ress (EOC = logic "1") will initiate a new and probably
inaccurate conversion cycle. Data for the interrupted and
subsequent conversions will be invalid.
ADS-953
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 –19µV to the ANALOG
INPUT (pin 4).
3. Adjust the offset potentiometer until the output code fl ickers
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 fl ickers between 1 and 0.
3. To confi rm proper operation of the device, vary the applied
input voltage to obtain the output coding listed in Table 2.
BIPLOAR INPUT
SCALE VOLTAGE ±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 volt-
age 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-953'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 "fl icker" 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-953, offset adjusting is normally accomplished
when the analog input is 0 minus ½LSB (–19µV). See Table 2
for the proper bipolar output coding.
Gain adjusting is accomplished when the analog input is at
nominal full scale minus 1½LSB's (–4.999943V).
INPUT VOLTAGE ZERO ADJUST GAIN ADJUST
RANGE (–½ LSB) (–FS +1½ LSB)
±5V –19µV –4.999943
Table 1. Input Connections
THERMAL REQUIREMENTS
All DATEL sampling A/D converters are fully characterized and
specifi ed over operating temperature (case) ranges of 0 to
+70°C and –40 to +110°C. All room-temperature (TA = +25°C)
production testing is performed without the use of heat sinks or
forced-air cooling. Thermal impedance fi gures for each device
are listed in their respective specifi cation 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 under-
neath the package. Devices should be soldered to boards
rather than "socketed", and of course, minimal air fl ow over the
surface can greatly help reduce the package temperature.
ADS-953
5
®®
Figure 3. ADS-953 Timing Diagram
Figure 2. Typical ADS-953 Connection Diagram
Scale is approximately 50ns per division.
START
CONVERT
INTERNAL S/H
NN+1
500ns typ.
Acquisition Time
260ns typ.
740ns typ.
5ns typ.
EOC
65ns typ.
Conversion Time
730ns typ.
OUTPUT
DATA Data N-2 Valid
980ns typ.
Hold
Data N-1 Valid
20ns typ. 20ns
Invalid Data
N
3
11
ADS-953
10
2
1
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
BIT 1 (MSB)
BIT 2
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)
+5V ANALOG
15
ANALOG
GROUND
ANALOG
GROUND
DIGITAL
GROUND
0.1µF
10µF
0.1µF
+
10µF
+5V
REF. OUT
COMPENSATION
47µF
14
13
5
7
START CONVERT
+5V DIGITAL
GAIN
ADJUST
6
16
0.1µF
10µF
12
9
0.1µF
10µF
8
++
0.1µF
10µF 0.1µF
10µF
+
+
EOC
–5V ANALOG
+15V
–15V
ANALOG INPUT 4
Pin 5 (ADS-953)
10kΩ
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
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. Specifi cations are subject to change without notice. The DATEL logo is a registered DATEL, Inc. trademark.
®® DATEL (UK) LTD. Tadley, England Tel: (01256)-880444
Internet: www.datel-europe.com E-mail: datel.ltd@datel.com
DATEL S.A.R.L. Montigny Le Bretonneux, France Tel: 01-34-60-01-01
Internet: www.datel-europe.com E-mail: datel.sarl@datel.com
DATEL GmbH München, Germany Tel: 89-544334-0
Internet: www.datel-europe.com E-mail: datel.gmbh@datel.com
DATEL KK Tokyo, Japan Tel: 3-3779-1031, Osaka Tel: 6-6354-2025
Internet: www.datel-co.jp E-mail: salestko@datel.co.jp, salesosa@datel.co.jp
DATEL China Shanghai, China Tel: 011-86-51317131
E-mail: davidx@datel.com
ISO 9001 REGISTERED
®®
ADS-953
DS-0541 4/04
MECHANICAL DIMENSIONS INCHES (mm)
ORDERING INFORMATION
OPERATING 32-PIN
MODEL NUMBER TEMP. RANGE PACKAGE
ADS-953MC 0 to +70°C TDIP
ADS-953ME –40 to +110°C TDIP
ACCESSORIES
ADS-B953 Evaluation Board (without ADS-953)
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.
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
