FEATURES

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18-bit resolution

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1MHz minimum sampling rate

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No missing codes over extended temperature range

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Very low power, 1.45 Watts

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Small, 32-pin, side-brazed, ceramic TDIP

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Edge-triggered

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Excellent performance

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Ideal for both time and frequency-domain applications

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Low cost

operating temperature ranges. A proprietary, auto-calibrating,

error-correcting circuit enables the device to achieve speci-
fied performance over the full military temperature range.

PRELIMINARY PRODUCT DATA

ADS-951

18-Bit, 1MHz, Low-Power

Sampling A/D Converters

GENERAL DESCRIPTION

The ADS-951 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 total

harmonic distortion (THD), makes the ADS-951 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-951 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-951 only requires the rising edge of the start convert

pulse to operate.

Requiring ±15V and ±5V supplies, the ADS-951 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 +70°C) or extended (40 to +110°C)

INPUT/OUTPUT CONNECTIONS

Figure 1. ADS-951 Functional Block Diagram

BIT 2

BIT 3

BIT 1 (MSB)

BIT 4

ANALOG GROUND

BIT 5

ANALOG INPUT

BIT 6

+5V REFERENCE OUT

BIT 7

GAIN ADJUST

BIT 8

COMPENSATION

BIT 9

15V SUPPLY

BIT 10

+15V SUPPLY

BIT 11

+5V ANALOG SUPPLY

BIT 12

5V ANALOG SUPPLY

BIT 13

ANALOG GROUND

BIT 14

DIGITAL GROUND

BIT 15

+5V DIGITAL SUPPLY

BIT 16

EOC

BIT 17

START CONVERT

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

(MSB)

1 BIT 2

32 BIT 3

31 BIT 4

30 BIT 5

BIT 6

28 BIT 7

27 BIT 8

26 BIT 9

25 BIT 10

24 BIT 11

23 BIT

22 BIT

21 BIT 14

20 BIT

19 BIT

18 BIT 17

17 BIT 18 (LSB)

TIMING AND

CONTROL LOGIC

ANALOG INPUT 4

START CONVERT 16

EOC 15

S/H

BUFFER

TAL

CORRECTI

N L

OGI

FLASH

ADC

FLASH

ADC

AMP

GAIN

CIRCUIT

COMPENSATION 7

+5V REFERENCE OUT 5

+5V ANALOG

SUPPLY

5V ANALOG

SUPPLY

3, 12

ANALOG

GROUND

+5V DIGITAL

SUPPLY

+15V

SUPPLY

15V

SUPPLY

DIGITAL

GROUND

GAIN ADJUST 6

ADS-951

+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

±5

Volts

Input Resistance

500

Input Capacitance

DIGITAL INPUT

Logic Levels

Logic "1"

+2.0

Volts

Logic "0"

+0.8

Volts

Logic Loading "1"

+20

µA

Logic Loading "0"

µA

Start Convert Positive Pulse Width

500

STATIC PERFORMANCE

Resolution

Bits

Integral Nonlinearity (f

= 10kHz)

±10

±15

LSB

Differential Nonlinearity (f

= 10kHz)

0.95

±0.5

0.95

±0.5

0.95

±0.50

+1.25

LSB

Full Scale Absolute Accuracy

±0.1

±0.25

±0.4

±0.8

%FSR

Bipolar Zero Error (Tech Note 2)

±0.1

±0.15

±0.25

±0.5

%FSR

Bipolar Offset Error (Tech Note 2)

±0.1

±0.2

±0.3

±0.6

%FSR

Gain Error (Tech Note 2)

±0.1

±0.25

±0.4

±0.9

No Missing Codes (f

= 10kHz)

Bits

DYNAMIC PERFORMANCE (500kHz Sampling Rate)

Peak Harmonics (0.5dB)

dc to 100kHz

Total Harmonic 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

DC Noise

µVrms

Two-Tone Intermodulation

Distortion (f

= 100kHz,

240kHz, f

= 500kHz, 0.5dB)

Input Bandwidth (3dB)

Small Signal (20dB input)

TBD

MHz

Large Signal (0.5dB input)

TBD

MHz

Feedthrough Rejection (f

= 500kHz)

Slew Rate

TBD

V/µs

Aperture Delay Time

+20

Aperture Uncertainty

ps rms

S/H Acquisition Time

( to ±0.003%FSR, 10V step)

260

Overvoltage Recovery Time

500

A/D Conversion Rate

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 +V

+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

+70

°C

ADS-951ME

+110

° C

Thermal Impedance

°C/Watt

Storage Temperature Range

+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

= +25°C, ±V

= ±15V, ±V

= ±5V, 1MHz sampling rate, and a minimum 1 minute warmup

unless otherwise specified.)

ADS-951

+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

ppm/°C

External Current

DIGITAL OUTPUTS

Logic Levels

Logic "1"

+2.4

Volts

Logic "0"

+0.4

Volts

Logic Loading "1"

Logic Loading "0"

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

15V Supply

+5V Supply

+104

5V Supply

Power Dissipation

1.45

1.65

1.45

1.65

1.45

1.65

Watts

Power Supply Rejection

±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
+70°C and 40 to +110°C. All room-temperature (T

= +25°C)

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-951

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 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.

2. The ADS-951 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 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.

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-951

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 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

+0.000000

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

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-951'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-951, 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

ADS-951

Figure 3. ADS-951 Timing Diagram

Figure 2. Typical ADS-951 Connection Diagram

Scale is approximately 50ns per division.

START

CONVERT

INTERNAL S/H

N+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

ADS-951

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

ANALOG
GROUND

DIGITAL
GROUND

0.1µF

10µF

0.1µF

10µF

+5V
REF. OUT

COMPENSATION

47µF

START CONVERT

+5V DIGITAL

GAIN

ADJUST

0.1µF

10µF

0.1µF

10µF

0.1µF

10µF

0.1µF

10µF

EOC

5V ANALOG

+15V

15V

ANALOG INPUT

Pin 5 (ADS-951)

10k

ADS-951

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-0366Preliminary

01/02

MECHANICAL DIMENSIONS INCHES (mm)

ORDERING INFORMATION

OPERATING

32-PIN

MODEL NUMBER TEMP. RANGE

PACKAGE

ADS-951MC

0 to +70°C

TDIP

ADS-951ME

40 to +110°C

TDIP

ACCESSORIES
ADS-B951

Evaluation Board (without ADS-951)

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

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 München, 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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