DATEL ADS-B931, ADS-931MM, ADS-931MC Datasheet

PIN FUNCTION PIN FUNCTION

1 +3.2V REF. OUT 40 NO CONNECTION
2 UNIPOLAR 39 NO CONNECTION
3 ANALOG INPUT 38 +5V ANALOG SUPPLY
4 ANALOG GROUND 37 –5V SUPPLY
5 OFFSET ADJUST 36 ANALOG GROUND
6 GAIN ADJUST 35 COMP. BITS
7 DIGITAL GROUND 34 OUTPUT ENABLE
8 FIFO/DIR 33 OVERFLOW

9 FIFO READ 32 EOC
10 FSTAT1 31 +5V DIGITAL SUPPLY
11 FSTAT2 30 DIGITAL GROUND
12 START CONVERT 29 BIT 1 (MSB)
13 BIT 16 (LSB) 28 BIT 1 (MSB)
14 BIT 15 27 BIT 2
15 BIT 14 26 BIT 3
16 BIT 13 25 BIT 4
17 BIT 12 24 BIT 5
18 BIT 11 23 BIT 6
19 BIT 10 22 BIT 7
20 BIT 9 21 BIT 8

FEATURES

• 16-bit resolution

• 1MHz sampling rate

• Functionally complete

• No missing codes over full military temperature range

• Edge-triggered

• ±5V supplies, 1.85 Watts

• Small, 40-pin, ceramic TDIP

• 87dB SNR, –89dB THD

• Ideal for both time and frequency-domain applications

16-Bit, 1MHz

Sampling A/D Converters

®

®

INNOV A TION and EX CELLENCE

GENERAL DESCRIPTION

The low-cost ADS-931 is a 16-bit, 1MHz sampling A/D
converter. This device accurately samples full-scale input
signals up to Nyquist frequencies with no missing codes. The
dynamic performance of the ADS-931 has been optimized to
achieve a signal-to-noise ratio (SNR) of 87dB and a total
harmonic distortion (THD) of –89dB.

Packaged in a 40-pin TDIP, the functionally complete ADS-931
contains a fast-settling sample-hold amplifier, a subranging (two­pass) A/D converter, an internal reference, timing/control logic,
and error-correction circuitry. Digital input and output levels are
TTL. The ADS-931 only requires the rising edge of the start
convert pulse to operate.

Requiring only ±5V supplies, the ADS-931 dissipates 1.85
Watts. The device is offered with a bipolar (±2.75V) analog
input range or a unipolar (0 to –5.5V) input range. Models are
available for use in either commercial (0 to +70°C) or 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. Typical applications include medical
imaging, radar, sonar, communications and instrumentation.

INPUT/OUTPUT CONNECTIONS

ADS-931

DATEL, Inc., Mansfield, MA 02048 (USA) • Tel: [phone] Fax: [phone] • E-mail:[e-mail] • Internet: www.datel.com

Figure 1. ADS-931 Functional Block Diagram

3-STATE

OUTPUT REGISTER

29 BIT 1 (MSB)
28 BIT 1 (MSB)
27 BIT 2
26 BIT 3
25 BIT 4
24 BIT 5
23 BIT 6
22 BIT 7
21 BIT 8
20 BIT 9
19 BIT 10
18 BIT 11
17 BIT 12
16 BIT 13
15 BIT 14
14 BIT 15
13 BIT 16 (LSB)

TIMING AND

CONTROL LOGIC

GAIN ADJUST 6

+3.2V REF. OUT 1

OFFSET ADJUST 5

EOC 32

ANALOG GROUND 4, 36
DIGITAL GROUND 7, 30
+5V DIGITAL SUPPLY 31
–5V SUPPLY 37
+5V ANALOG SUPPLY 38
NO CONNECTION 39, 40

CUSTOM GATE ARRAY

POWER and GROUNDING

2-PASS ANALOG-TO-DIGITAL CONVERTER

S/H

GAIN

ADJUST

CKT.

OFFSET
ADJUST

CKT.

PRECISION

+3.2V REFERENCE

ANALOG INPUT 3

START CONVERT 12

COMP. BITS 35

10 FSTAT1
11 FSTAT2

8 FIFO/DIR
9 FIFO/READ

34 OUTPUT ENABLE

33 OVERFLOW

UNIPOLAR 2

OFFSET ADJUST 5

ADS-931

® ®

2

+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

Unipolar — 0 to –5.5 — — 0 to –5.5 — — 0 to –5.5 — Volts
Bipolar — ±2.75 — — ±2.75 — — ±2.75 — Volts

Input Resistance (pin 3) — 685 — — 685 — — 685 — Ω
Input Resistance (pin 2) — 400 — — 426 — — 426 — Ω
Input Capacitance — 10 15 — 10 15 — 10 15 pF

DIGITAL INPUTS

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" ➁ — — –20 — — –20 — — –20 µA

Start Convert Positive Pulse Width ➂ 40 100 — 40 100 — 40 100 — ns

STATIC PERFORMANCE

Resolution — 16 — — 16 — — 16 — Bits
Integral Nonlinearity — ±1 — — ±1.5 — — ±2 — LSB
Differential Nonlinearity (f

in = 10kHz) –0.95 ±0.5 +1.0 –0.95 ±0.5 +1.0 –0.95 ±0.5 +1.5 LSB

Full Scale Absolute Accuracy — ±0.1 ±0.3 — ±0.15 ±0.5 — ±0.5 ±0.8 %FSR
Bipolar Zero Error (Tech Note 2) — ±0.1 ±0.2 — ±0.2 ±0.4 — ±0.5 ±0.9 %FSR
Bipolar Offset Error (Tech Note 2) — ±0.1 ±0.3 — ±0.2 ±0.5 — ±0.4 ±0.9 %FSR
Gain Error (Tech Note 2) — ±0.1 ±0.3 — ±0.15 ±0.5 — ±0.5 ±0.9 %
No Missing Codes (f

in = 10kHz) 16 — — 16 — — 16 — — Bits

DYNAMIC PERFORMANCE

Peak Harmonics (–0.5dB)

dc to 250kHz — –91 –85 — –91 –85 — –90 –83 dB
250kHz to 500kHz — –91 –85 — –91 –85 — –90 –83 dB

Total Harmonic Distortion (–0.5dB)

dc to 250kHz — –89 –83 — –89 –83 — –87 –81 dB
250kHz to 500kHz — –87 –80 — –87 –80 — –85 –79 dB

Signal-to-Noise Ratio

(w/o distortion, –0.5dB)
dc to 250kHz 84 87 — 84 87 — 82 86 — dB
250kHz to 500kHz 83 86 — 83 86 — 80 84 — dB

Signal-to-Noise Ratio ➃

(& distortion, –0.5dB)
dc to 250kHz 80 85 — 80 85 — 77 83 — dB
250kHz to 500MHz 79 84 — 79 84 — 76 82 — dB

Noise — 82 — — 82 — — 82 — µVrms
Two-Tone Intermodulation

Distortion (f

in = 98kHz,

240kHz, f

s = 1MHz, –0.5dB) — –89 — — –89 — — –89 — dB

Input Bandwidth (–3dB)

Small Signal (–20dB input) — 4.8 — — 4.8 — — 4.8 — MHz
Large Signal (–0.5dB input) — 4.1 — — 4.1 — — 4.1 — MHz

Feedthrough Rejection

(f

in = 480kHz) — 90 — — 90 — — 90 — dB

Slew Rate — ±51 — — ±51 — — ±51 — V/µs
Aperture Delay Time — +8 — — +8 — — +8 — ns
Aperture Uncertainty — 5 — — 5 — — 5 — ps rms
S/H Acquisition Time

( to ±0.001%FSR, 5.5V step) 700 725 — 700 725 — 700 725 — ns

PARAMETERS MIN. TYP. MAX. UNITS

Operating Temp. Range, Case

ADS-931MC 0 — +70 °C
ADS-931MM –55 — +125 °C

Thermal Impedance

θjc — 4 — °C/Watt
θca — 18 — °C/Watt

Storage Temperature Range –65 — +150 °C
Package Type 40-pin, metal-sealed, ceramic TDIP

Weight 0.56 ounces (16 grams)

ABSOLUTE MAXIMUM RATINGS

PARAMETERS LIMITS UNITS

+5V Supply (Pins 31, 38) 0 to +6 Volts
–5V Supply (Pin 37) 0 to –6 Volts
Digital Inputs (Pins 8, 9, 12, 34, 35) –0.3 to +V

DD +0.3 Volts

Analog Input (Pin 3) Volts

Bipolar ±5 Volts
Unipolar –10 to +5 Volts

Lead Temperature (10 seconds) +300 °C

PHYSICAL/ENVIRONMENTAL

FUNCTIONAL SPECIFICATIONS

(TA = +25°C, ±VCC = ±5V, +VDD = +5V, 1MHz sampling rate, and a minimum 3 minute warm-up ➀ unless otherwise specified.)

ADS-931

® ®

3

+25°C 0 TO +70°C –55 TO +125°C

DYNAMIC PERFORMANCE (Cont.) MIN. TYP. MAX. MIN. TYP. MAX. MIN. TYP. MAX. UNITS

Overvoltage Recovery Time ➄ — — 1000 — — 1000 — — 1000 ns
A/D Conversion Rate 1 — — 1 — — 1 — — MHz

Footnotes:

➃ Effective bits is equal to:

➀ 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. There is a slight
degradation in performance when operating the device in the unipolar mode.

➁ When COMP. BITS (pin 35) is low, logic loading "0" will be –350µA.
➂ A 1MHz clock with a positive pulse width is used for all production testing. See

Timing Diagram for more details.
40ns < Start Pulse < 175ns or 280ns < Start Pulse < 460ns

6.02

(SNR + Distortion) – 1.76 + 20 log

Full Scale Amplitude

Actual Input Amplitude

➄ This is the time required before the A/D output data is valid once the analog input

is back within the specified range. This time is only guaranteed if the input does not

exceed ±4.75V (bipolar) or +2 to –7.5V (unipolar).

➅ The minimum supply voltages of +4.9V and –4.9V for ±V

DD are required for

–55°C operation only. The minimum limits are +4.75V and –4.75V when

operating at +125°C.

TECHNICAL NOTES

1. Obtaining fully specified performance from the ADS-931
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 (4, 7, 30 and 36) directly to a large
analog ground plane beneath the package.

Bypass all power supplies and the +3.2V reference output 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.

2. The ADS-931 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. Tie pins 5 and 6 to
ANALOG GROUND (pin 4) if not using offset and gain
adjust circuits.

3. Pin 35 (COMP. BITS) is used to select the digital output
coding format of the ADS-931 (see Tables 2a and 2b). When
this pin has a TTL logic "0" applied, it complements the ADS­931’s B1-B16 & B1 outputs.

Pin 35 is TTL compatible and can be directly driven with digital
logic in applications requiring dynamic control over its function.
There is an internal pull-up resistor on pin 35 allowing it to be
either connected to +5V or left open when a logic "1" is
required.

4. To enable the three-state outputs, connect OUTPUT
ENABLE (pin 34) to a logic "0" (low). To disable, connect
pin 34 to a logic "1" (high).

5. Applying a start convert pulse while a conversion is in
progress (EOC = logic "1") will initiate a new and probably
inaccurate conversion cycle. Data from both the interrupted
and subsequent conversions will be invalid.

ANALOG OUTPUT

Internal Reference

Voltage 3.15 +3.2 3.25 3.15 +3.2 3.25 3.15 +3.2 3.25 Volts
Drift — ±30 — — ±30 — — ±30 — ppm/°C

External Current — 5 — — 5 — — 5 — 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

Delay, Falling Edge of Enable to
Output Data Valid — — 20 — — 20 — — 20 ns

Output Coding

Straight Binary, Complementary Binary, Complementary Offset Binary,
Complementary Two's Complement, Offset Binary, Two's Complement

POWER REQUIREMENTS

Power Supply Ranges ➅

+5V Supply +4.75 +5.0 +5.25 +4.75 +5.0 +5.25 +4.9 +5.0 +5.25 Volts
–5V Supply –4.75 –5.0 –5.25 –4.75 –5.0 –5.25 –4.9 –5.0 –5.25 Volts

Power Supply Currents

+5V Supply — +225 260 — +225 260 — +225 260 mA
–5V Supply –140 –135 — –140 –135 — –140 –135 — mA

Power Dissipation — 1.85 2.0 — 1.85 2.0 — 1.85 2.0 Watts
Power Supply Rejection — — ±0.07 — — ±0.07 — — ±0.07 %FSR/%V