ADS-916

14-Bit, 500kHz, Low-Power

Sampling A/D Converters

Figure 1. ADS-916 Functional Block Diagram

DATEL, Inc., 11 Cabot Boulevard, Mansfield, MA 02048-1151 (U.S.A.)

Tel: (508) 339-3000 Fax: (508) 339-6356

For immediate assistance: (800) 233-2765

FEATURES

14-bit resolution

500kHz sampling rate

Functionally complete; No missing codes

Edge-triggered; No pipeline delays

Small 24-pin DDIP or SMT package

Low power, 1.8 Watts maximum

Operates from ±15V or ±12V supplies

Unipolar 0 to +10V input range

GENERAL DESCRIPTION

The ADS-916 is a high-performance, 14-bit, 500kHz sampling
A/D converter. This device samples input signals up to Nyquist
frequencies with no missing codes. The ADS-916 features
outstanding dynamic performance including a THD of 90dB.

Housed in a small 24-pin DDIP or SMT (gull-wing) package,
the functionally complete ADS-916 contains a fast-settling
sample-hold amplifier, a subranging (two-pass) A/D converter,
a precise voltage reference, timing/control logic, and error-
correction circuitry. Digital input and output levels are TTL.

Requiring ±15V (or ±12V) and +5V supplies, the ADS-916
dissipates 1.8W (1.6W for ±12V) maximum. The unit is offered
with a unipolar input (0 to +10V). Models are available for use
in either commercial (0 to +70°C) or military (55 to +125°C)
operating temperature ranges. Applications include radar,
sonar, spectrum analysis, and graphic/medical imaging.

INPUT/OUTPUT CONNECTIONS

PIN

FUNCTION

PIN

FUNCTION

BIT 14 (LSB)

12V/15V SUPPLY

BIT 13

ANALOG GROUND

BIT 12

+12V/+15V SUPPLY

BIT 11

+10V REFERENCE OUT

BIT 10

ANALOG INPUT

BIT 9

ANALOG GROUND

BIT 8

BIT 1 (MSB)

BIT 7

BIT 2

BIT 6

START CONVERT

BIT 5

EOC

BIT 4

DIGITAL GROUND

BIT 3

+5V SUPPLY

REF

I
S

18 BIT 1 (MSB)

17 BIT 2

12 BIT 3

11 BIT 4

10 BIT 5

9 BIT 6

8 BIT 7

7 BIT 8

6 BIT 9

5 BIT 10

4 BIT 11

3 BIT 12

2 BIT 13

1 BIT 14 (LSB)

TIMING AND

CONTROL LOGIC

+10V REF. OUT 21

START CONVERT 16

EOC 15

I
G

I
T

I
O

I
C

DAC

FLASH

ADC

BUFFER

S/H

ANALOG INPUT 20

+5V SUPPLY

+12V/+15V SUPPLY

19, 23

ANALOG GROUND

DIGITAL GROUND

12V/15V SUPPLY

ADS-916

ABSOLUTE MAXIMUM RATINGS

PARAMETERS

LIMITS

UNITS

+12V/+15V Supply (Pin 22)

0 to +16

Volts

12V/15V Supply (Pin 24)

0 to 16

Volts

+5V Supply (Pin 13)

0 to +6

Volts

Digital Input (Pin 16)

0.3 to +V

+0.3

Volts

Analog Input (Pin 20)

4 to +17

Volts

Lead Temperature (10 seconds)

+300

°C

PHYSICAL/ENVIRONMENTAL

PARAMETERS

MIN.

TYP.

MAX.

UNITS

Operating Temp. Range, Case

ADS-916MC, GC

+70

°C

ADS-916MM, GM

+125

°C

Thermal Impedance

°C/Watt

Storage Temperature

+150

°C

Package Type

24-pin, metal-sealed, ceramic DDIP or SMT

Weight

0.42 ounces (12 grams)

+25°C

0 to +70°C

55 to +125°C

ANALOG INPUT

MIN.

TYP.

MAX.

MIN.

TYP.

MAX.

MIN.

TYP.

MAX.

UNITS

Input Voltage Range

0 to +10

Volts

Input Resistance

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

200

STATIC PERFORMANCE

Resolution

Bits

Integral Nonlinearity (f

= 10kHz)

±0.5

±0.75

±1.5

LSB

Differential Nonlinearity (f

= 10kHz)

±0.5

±0.95

±0.5

±0.95

0.95

±0.75

+1.25

LSB

Full Scale Absolute Accuracy

±0.05

±0.1

±0.2

±0.15

±0.4

%FSR

Unipolar Offset Error (Tech Note 2)

±0.1

±0.2

±0.1

±0.2

±0.15

±0.4

%FSR

Gain Error (Tech Note 2)

±0.1

±0.25

±0.1

±0.25

±0.4

No Missing Codes (f

= 10kHz)

Bits

DYNAMIC PERFORMANCE

Peak Harmonics (0.5dB)

dc to 100kHz

100kHz to 250kHz

Total Harmonic Distortion (0.5dB)

dc to 100kHz

100kHz to 250kHz

Signal-to-Noise Ratio

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

100kHz to 250kHz

Signal-to-Noise Ratio

(& distortion, 0.5dB)
dc to 100kHz

100kHz to 250kHz

Two-Tone Intermodulation

Distortion (f

= 100kHz,

240kHz, f

= 500kHz 0.5dB)

Noise

310

360

µVrms

Input Bandwidth (3dB)

Small Signal (20dB input)

MHz

Large Signal (0.5dB input)

MHz

Feedthrough Rejection (f

= 250kHz)

Slew Rate

±40

V/µs

Aperture Delay Time

±20

Aperture Uncertainty

ps rms

S/H Acquisition Time

(to ±0.003%FSR, 10V step)

1530

1570

1610

1530

1570

1610

1530

1570

1610

Overvoltage Recovery Time

1400

2000

1400

2000

1400

2000

A/D Conversion Rate

500

kHz

FUNCTIONAL SPECIFICATIONS

= +25°C, ±V

= ±15V (or ±12V), +V

= +5V, 500kHz sampling rate, and a minimum 1 minute warmup unless otherwise specified.)

ADS-916

+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

+9.95

+10.0

+10.05

+9.95

+10.0

+10.05

+9.95

+10.0

+10.05

Volts

Drift

±5

ppm/°C

External Current

1.5

DIGITAL OUTPUTS

Logic Levels

Logic "1"

+2.4

Volts

Logic "0"

+0.4

Volts

Logic Loading "1"

Logic Loading "0"

Delay, Falling Edge of EOC

to Output Data Valid

Output Coding

Straight Binary

POWER REQUIREMENTS, ±15V

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

Power Supply Currents

+15V Supply

+50

+65

+50

+65

+50

+65

15V Supply

+5V Supply

+70

+85

+70

+85

+70

+85

Power Dissipation

1.6

1.8

1.6

1.8

1.6

1.8

Watts

Power Supply Rejection

±0.01

%FSR/%V

POWER REQUIREMENTS, ±12V

Power Supply Ranges

+12V Supply

+11.5

+12.0

+12.5

+11.5

+12.0

+12.5

+11.5

+12.0

+12.5

Volts

12V Supply

11.5

12.0

12.5

11.5

12.0

12.5

11.5

12.0

12.5

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

+12V Supply

+50

+65

+50

+65

+50

+65

12V Supply

+5V Supply

+70

+80

+70

+80

+70

+80

Power Dissipation

1.4

1.6

1.4

1.6

1.4

1.6

Watts

Power Supply Rejection

±0.01

%FSR/%V

6.02

(SNR + Distortion) 1.76 + 20 log

Full Scale Amplitude

Actual Input Amplitude

Effective bits is equal to:

This is the time required before the A/D output data is valid after the analog input
is back within the specified range.

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. There is a slight
degradation in performance when using ±12V supplies.

See Ordering Information for availability of ±5V input range. Contact DATEL for
availability of other input voltage ranges.

A 500 kHz clock with a 200ns wide start convert pulse is used for all production
testing. Only the rising edge of the start convert pulse is required for the device
to operate (edge-triggered). See Timing Diagram for more details.

TECHNICAL NOTES

1. Obtaining fully specified performance from the ADS-916

requires careful attention to pc-card layout and power
supply decoupling. The device's analog and digital ground
systems are connected to each other internally. For optimal
performance, tie all ground pins (14, 19 and 23) directly to a
large analog ground plane beneath the package.

Bypass all power supplies and the REFERENCE OUTPUT
(pin 21) to ground with 4.7µF tantalum capacitors in parallel
with 0.1µF ceramic capacitors. Locate the bypass capaci-
tors as close to the unit as possible. If the user-installed
offset and gain adjusting circuit shown in Figure 2 is used,
also locate it as close to the ADS-916 as possible.

2. The ADS-916 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 input circuit of Figure 2. When using this circuit, or any
similar offset and gain-calibration hardware, make adjust-
ments following warmup. To avoid interaction, always adjust
offset before gain.

3. When operating the ADS-916 from ±12V supplies, do not

drive external circuitry with the REFERENCE OUTPUT. The
reference's accuracy and drift specifications may not be
met, and loading the circuit may cause accuracy errors
within the converter.

4. Applying a start convert pulse while a conversion is in

progress (EOC = logic "1") initiates a new and inaccurate
conversion cycle. Data for the interrupted and subsequent
conversions will be invalid.

ADS-916

Zero/Offset Adjust Procedure

1. Apply a train of pulses to the START CONVERT input

(pin 16) so the converter is continuously converting. If using
LED's on the outputs, a 200kHz conversion rate will reduce
flicker.

2. Apply +305µV to the ANALOG INPUT (pin 20).

3. Adjust the offset potentiometer until the output bits are

all 0's and the LSB flickers between 0 and 1.

Gain Adjust Procedure

1. Apply +9.999085V to the ANALOG INPUT (pin 20).

2. Adjust the gain potentiometer until the output bits are all 1's

and the LSB flickers between 1 and 0.

INPUT VOLTAGE

ZERO ADJUST

GAIN ADJUST

RANGE

+½ LSB

+FS 1½ LSB

0 to +10V

+305µV

+9.999085V

Table 1. Zero and Gain Adjust

INPUT VOLTAGE

UNIPOLAR

DIGITAL OUTPUT

(0 to +10V)

SCALE

MSB

LSB

+9.999390

+FS 1LSB

11 1111 1111 1111

+7.500000

+3/4 FS

11 0000 0000 0000

+5.000000

+1/2 FS

10 0000 0000 0000

+2.500000

+1/4 FS

01 0000 0000 0000

+0.000610

+1LSB

00 0000 0000 0001

0.000000

00 0000 0000 0000

Table 2. Output Coding

Figure 3. Typical ADS-916 Connection Diagram

Coding is straight binary; 1LSB = 610µV.

CALIBRATION PROCEDURE

(Refer to Figures 2 and 3)

Any offset and/or gain calibration procedures should not be
implemented until devices are fully warmed up. To avoid
interaction, offset must be adjusted before gain. The ranges of
adjustment for the circuit of Figure 2 are guaranteed to
compensate for the ADS-916's initial accuracy errors and may
not be able to compensate for additional system errors.

All fixed resistors in Figure 2 should be metal-film types, and
multiturn potentiometers should have TCR's of 100ppm/°C or
less to minimize drift with temperature.

A/D converters are calibrated by positioning their digital outputs
exactly on the transition point between two adjacent digital
output codes. This can be accomplished by connecting LED's
to the digital outputs and adjusting 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-916, offset adjusting is normally accomplished at
the point where the output bits are 0's and the LSB just
changes from a 0 to a 1. This digital output transition ideally
occurs when the applied analog input is +½LSB (+305µV).

Gain adjusting is accomplished when all bits are 1's and the
LSB just changes from a 1 to a 0. This transition ideally occurs
when the analog input is at +full scale minus 1½ LSB's
(+9.999085V).

Figure 2. ADS-916 Calibration Circuit

ADS-916

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 (LSB)

EOC

ANALOG
INPUT

START

CONVERT

19, 23

0.1µF

4.7µF

+5V

0.1µF

4.7µF

0.1µF

4.7µF

12V/15V

+12V/+15V

0.1µF

4.7µF

21 +10V REF. OUT

DIGITAL
GROUND

0 to +10V

ANALOG
GROUND

To Pin 20
of ADS-916

15V

SIGNAL

INPUT

GAIN

ADJUST

1.98k

+15V

200k

20k

15V

+15V

ZERO/

OFFSET
ADJUST

ADS-916

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.

In more severe ambient conditions, the package/junction
temperature of a given device can be reduced dramatically
(typically 35%) by using one of DATEL's HS Series heat sinks.
See Ordering Information for the assigned part number. See
page 1-183 of the DATEL Data Acquisition Components
Catalog for more information on the HS Series. Request
DATEL Application Note AN-8, "Heat Sinks for DIP Data
Converters", or contact DATEL directly, for additional
information.

Figure 4. ADS-916 Timing Diagram

Notes: 1. f

= 500kHz.

2. The ADS-916 is an edge-triggered device. All internal operations

are triggered by the rising edge of the start convert pulse, which
may be as narrow as 50nsec. All production testing is performed
at a 500kHz sampling rate with 200nsec wide start pulses. For
lower sampling rates, wider start pulses may be used, however, a
minimum pulse width low of 50nsec must be maintained.

START

CONVERT

OUTPUT

DATA

INTERNAL S/H

Data (N 1) Valid

200ns

typ.

Acquisition Time

10ns typ.

Data N Valid (1926ns min.)

EOC

90ns typ.

Conversion Time

420ns ±20ns

Invalid

Data

74ns max.

70ns ±10ns

1570ns ±40ns

430ns typ.

35ns max.

Hold

N + 1

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