FEATURES

16-bit resolution

1MHz minimum sampling rate

No missing codes over full military temperature range

Very low power, 1.25 Watts

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

Edge-triggered

Excellent performance

Ideal for both time and frequency-domain applications

Low cost

military (55 to +125°C) operating temperature ranges. A
proprietary, auto-calibrating, error-correcting circuit enables
the device to achieve specified performance over the full
military temperature range.

ADS-937

16-Bit, 1MHz, Low-Power

Sampling A/D Converters

GENERAL DESCRIPTION

The low-cost ADS-937 is a 16-bit, 1MHz sampling A/D con-
verter. 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-937 the ideal
choice for both time-domain (CCD/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-937 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.
ADS-937 only requires the rising edge of the start convert
pulse to operate.

Requiring ±15V and ±5V supplies, the ADS-937 typically
dissipates 1.25 Watts. The device is offered with both bipolar
(±5V) and unipolar (0 to 10V) analog input ranges. Models
are available for use in either commercial (0 to +70°C) or

INPUT/OUTPUT CONNECTIONS

Figure 1. ADS-937 Functional Block Diagram

ANALOG INPUT

BIT 1 (MSB)

ANALOG GROUND

BIT 2

UNIPOLAR

BIT 3

OFFSET ADJUST

BIT 4

+5V REFERENCE OUT

BIT 5

GAIN ADJUST

BIT 6

COMPENSATION

BIT 7

15V SUPPLY

BIT 8

+15V SUPPLY

BIT 9

+5V ANALOG SUPPLY

BIT 10

5V ANALOG SUPPLY

BIT 11

ANALOG GROUND

BIT 12

DIGITAL GROUND

BIT 13

+5V DIGITAL SUPPLY

BIT 14

EOC

BIT 15

START CONVERT

BIT 16 (LSB)

PIN

FUNCTION

PIN

FUNCTION

REF

DAC

32 BIT 1 (MSB)

31 BIT 2

30 BIT 3

29 BIT 4

28 BIT 5

27 BIT 6

26 BIT 7

25 BIT 8

24 BIT 9

23 BIT 10

22 BIT 11

21 BIT 12

20 BIT 13

19 BIT 14

18 BIT 15

17 BIT 16 (LSB)

TIMING AND

CONTROL LOGIC

ANALOG INPUT 1

START CONVERT 16

EOC 15

S/H

BUFFER

I
G

I
T

I
O

I
C

FLASH

ADC

FLASH

ADC

AMP

GAIN

CIRCUIT

COMPENSATION 7

+5V REFERENCE OUT 5

+5V ANALOG

SUPPLY

5V ANALOG

SUPPLY

2, 12

ANALOG

GROUND

+5V DIGITAL

SUPPLY

+15V

SUPPLY

15V

SUPPLY

DIGITAL

GROUND

OFFSET ADJUST 4

UNIPOLAR 3

GAIN ADJUST 6

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

ADS-937

+25°C

0 to +70°C

55 to +125°C

ANALOG INPUTS

MIN.

TYP.

MAX.

MIN.

TYP.

MAX.

MIN.

TYP.

MAX.

UNITS

Input Voltage Ranges

Bipolar

±5

Volts

Unipolar

0 to 10

Volts

Input Resistance

Input Capacitance

DIGITAL INPUTS

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

±0.75

±1.5

±2

LSB

Differential Nonlinearity (f

= 10kHz)

0.95

±0.5

0.95

±0.5

0.95

±0.5

+1.5

LSB

Full Scale Absolute Accuracy

±0.1

±0.25

±0.2

±0.4

±0.25

±0.5

%FSR

Bipolar Zero Error (Tech Note 2)

±0.1

±0.15

±0.1

±0.25

±0.15

±0.5

%FSR

Bipolar Offset Error (Tech Note 2)

±0.1

±0.2

±0.15

±0.3

±0.2

±0.5

%FSR

Gain Error (Tech Note 2)

±0.1

±0.3

±0.25

±0.5

±0.4

±0.7

Unipolar Offset Error (Tech Note 2)

±0.1

±0.15

±0.1

±0.25

±0.15

±0.5

%FSR

No Missing Codes (f

= 10kHz)

Bits

DYNAMIC PERFORMANCE

Peak Harmonics (0.5dB)

dc to 100kHz

100kHz to 500kHz

Total Harmonic Distortion (0.5dB)

dc to 100kHz

100kHz to 500kHz

Signal-to-Noise Ratio

(w/o distortion, 0.5dB)
dc to 100kHz

100kHz to 500kHz

Signal-to-Noise Ratio

(& distortion, 0.5dB)
dc to 100kHz

100kHz to 500kHz

Noise

110

µVrms

Two-Tone Intermodulation
Distortion (f

= 100kHz,

240kHz, f

= 1MHz, 0.5dB)

Input Bandwidth (3dB)

Small Signal (20dB input)

4.5

MHz

Large Signal (0.5dB input)

MHz

Feedthrough Rejection (f

= 500kHz)

Slew Rate

±33

V/µs

Aperture Delay Time

+20

Aperture Uncertainty

ps rms

S/H Acquisition Time

( to ±0.003%FSR, 10V step)

260

300

260

300

260

300

Overvoltage Recovery Time

500

1000

500

1000

500

1000

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 1)

±15

Volts

Lead Temperature (10 seconds)

+300

°C

PARAMETERS

MIN.

TYP.

MAX.

UNITS

Operating Temp. Range, Case

ADS-937MC

+70

°C

ADS-937MM/883

+125

°C

Thermal Impedance

°C/Watt

Storage Temperature Range

+150

°C

Package Type

32-pin,side-brazed, metal-sealed, ceramic TDIP

Weight

0.56 ounces (16 grams)

ABSOLUTE MAXIMUM RATINGS

PHYSICAL/ENVIRONMENTAL

FUNCTIONAL SPECIFICATIONS

= +25°C, ±V

= ±15V, ±V

= ±5V, 1MHz sampling rate, and a minimum 1 minute warm-up unless otherwise specified.)

ADS-937

+25°C

0 to +70°C

55 to +125°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 Binary / 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

15V Supply

+5V Supply

+133

+145

+133

+145

+133

+145

5V Supply

Power Dissipation

1.25

1.35

1.25

1.35

1.25

1.35

Watts

Power Supply Rejection

±0.01

%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 55 to +125°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-937

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 (2, 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 4.7µF 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
(See figure 2.).

2. The ADS-937 achieves its specified accuracies without the

need for external calibration. If required, the device's small
initial offset and gain 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 warm-up. To avoid interaction,
always adjust offset before gain. Float pins 4 and 6 if not
using offset and 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 warm-up
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 less 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 inaccurate
conversion cycle. Data for the interrupted and subsequent
conversions will be invalid.

ADS-937

3. For a bipolar input - Adjust the offset potentiometer until the

output code flickers equally between 1000 0000 0000 0000
and 0111 1111 1111 1111.

For a unipolar input - Adjust the offset potentiometer until
all output bits are 0's and the LSB flickers between 0 and 1.

Gain Adjust Procedure

1. Apply 4.999771V to the ANALOG INPUT (pin 1) for

bipolar gain adjust or apply 9.999771V to pin 1 for
unipolar gain adjust.

2. For a unipolar input - Adjust the gain potentiometer until all

output bits are 1's and the LSB flickers between 1 and 0.

For a bipolar input - 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.

UNIPOLAR

INPUT VOLTAGE

INPUT RANGE

BIPOLAR

SCALE

0 to 10V

MSB

LSB

MSB

LSB

±5V

SCALE

FS +1 LSB

9.999847

1111 1111 1111 1111

0000 0000 0000 0000

+4.999847

+FS 1 LSB

7/8 FS

8.750000

1110 0000 0000 0000

0001 1111 1111 1111

+3.750000

+3/4 FS

3/4 FS

7.500000

1100 0000 0000 0000

0011 1111 1111 1111

+2.500000

+1/2 FS

1/2 FS

5.000000

1000 0000 0000 0000

0111 1111 1111 1111

+0.000000

1/4 FS

2.500000

0100 0000 0000 0000

1011 1111 1111 1111

2.500000

1/2 FS

1/8 FS

1.250000

0010 0000 0000 0000

1101 1111 1111 1111

3.750000

3/4 FS

1 LSB

0.000153

0000 0000 0000 0001

1111 1111 1111 1110

4.999847

FS +1 LSB

0.000000

0000 0000 0000 0000

1111 1111 1111 1111

5.000000

OUTPUT CODING

COMPLEMENTARY

BINARY

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-937'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-937, offset adjusting is normally accomplished
when the analog input is 0 minus ½LSB (76.3µV). See Table
2 for the proper bipolar and unipolar output coding.

Gain adjusting is accomplished when the analog input is at
nominal full scale minus 1½LSB's (9.999771V for unipolar
and 4.999771V for bipolar).

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 unipolar or bipolar zero/offset adjust, apply 76.3µV to

the ANALOG INPUT (pin 1).

INPUT VOLTAGE

INPUT

TIE

RANGE

PIN

TOGETHER

±5V

Pin 1

Pins 2 and 3

0 to 10V

Pin 1

Pins 3 and 5

Table 1. Input Connections

ADS-937

Figure 3. ADS-937 Timing Diagram

Figure 2. Typical ADS-937 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

Note: Scale is approximately 50ns per division. Sampling Rate = 1MHz.

ADS-937

20k

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 (LSB)

+5V ANALOG

ANALOG
GROUND

DIGITAL
GROUND

0.1µF

4.7µF

0.1µF

UNIPOLAR

4.7µF

+5V
REF. OUT

COMPENSATION

47µF

START CONVERT

+5V DIGITAL

15V

+15V

OFFSET

ADJUST

GAIN

ADJUST

0.1µF

4.7µF

0.1µF

4.7µF

0.1µF

4.7µF

0.1µF

4.7µF

EOC

5V ANALOG

+15V

15V

ANALOG INPUT

Pin 5 (ADS-937)

10k

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