DATEL ADS-B946, ADS-946MM, ADS-946MC, ADS-946GM, ADS-946GC Datasheet

Figure 1. ADS-946 Functional Block Diagram

FEATURES

• 14-bit resolution

• 8MHz guaranteed sampling rate

• No missing codes over full military temperature range

• Ideal for both time and frequency-domain applications

• Excellent THD (–75dB) and SNR (77dB)

• Edge-triggered; No pipeline delays

• Small, 24-pin, ceramic DDIP or SMT

• Requires only ±5V supplies

• Low-power, 2 Watts

• MIL-STD-883 screening optional

GENERAL DESCRIPTION

The low-cost ADS-946 is a 14-bit, 8MHz sampling A/D
converter. This device accurately samples full-scale input
signals up to Nyquist frequencies with no missing codes.
Excellent differential nonlinearity error (DNL), signal-to-noise
ratio (SNR), and total harmonic distortion (THD) make the
ADS-946 the ideal choice for both time-domain (CCD/FPA
imaging, scanners, process control) and frequency-domain
(radar, telecommunications, spectrum analysis) applications.

The functionally complete ADS-946 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. The
ADS-946 only requires the rising edge of a start convert
pulse to operate.

Requiring only ±5V supplies, the ADS-946 typically dissipates
just 2 Watts. The device is offered with a bipolar input range
of ±2V. Models are available for use in either commercial
(0 to +70°C) or military (–55 to +125°C) operating

®

®

INNOV A TION and EX CELLENCE

temperature ranges. A proprietary, auto-calibrating, error­correcting circuit allows the device to achieve specified
performance over the full military temperature range.

INPUT/OUTPUT CONNECTIONS

PIN FUNCTION PIN FUNCTION

1 BIT 1 (MSB) 24 ANALOG GROUND
2 BIT 2 23 OFFSET ADJUST
3 BIT 3 22 +5V ANALOG SUPPLY
4 BIT 4 21 ANALOG INPUT
5 BIT 5 20 –5V SUPPLY
6 BIT 6 19 ANALOG GROUND
7 BIT 7 18 START CONVERT
8 BIT 8 17 EOC

9 BIT 9 16 BIT 14 (LSB)
10 BIT 10 15 BIT 13
11 BIT 11 14 DIGITAL GROUND
12 BIT 12 13 +5V DIGITAL SUPPLY

ADS-946

14-Bit, 8MHz

Sampling A/D Converters

REF

DAC

REGISTERREGISTER

OUTPUT REGISTER

16 BIT 14 (LSB)
15 BIT 13
12 BIT 12
11 BIT 11
10 BIT 10
9 BIT 9
8 BIT 8
7 BIT 7
6 BIT 6
5 BIT 5
4 BIT 4
3 BIT 3
2 BIT 2
1 BIT 1 (MSB)

TIMING AND

CONTROL LOGIC

OFFSET ADJUST 23

ANALOG INPUT 21

START CONVERT 18

EOC 17

+5V ANALOG SUPPLY 22
+5V DIGITAL SUPPLY 13
–5V SUPPLY 20
ANALOG GROUND 19, 24
DIGITAL GROUND 14

–
+

S/H

BUFFER

DIGITAL CORRECTION LOGIC

FLASH

ADC

1

FLASH

ADC

2

POWER AND GROUNDING

Σ

AMP

DATEL, Inc., 11 Cabot Boulevard, Mansfield, MA 02048 (U.S.A.) • Tel: [phone] Fax: [phone] • For immediate assistance: [phone]

ADS-946

2

® ®

PARAMETERS MIN. TYP. MAX. UNITS

Operating Temp. Range, Case

ADS-946MC, GC 0 — +70 °C
ADS-946MM, GM, 883, G/883 –55 — +125 °C

Thermal Impedance

θjc — 6 — °C/Watt
θca — 23 — °C/Watt

Storage Temperature Range –65 — +150 °C
Package Type 24-pin, metal-sealed, ceramic DDIP or SMT

Weight 0.42 ounces (12 grams)

ABSOLUTE MAXIMUM RATINGS

PARAMETERS LIMITS UNITS

+5V Supply (Pins 13, 22) 0 to +6 Volts
–5V Supply (Pin 20) 0 to –6 Volts
Digital Input (Pin 18) –0.3 to +V

DD +0.3 Volts

Analog Input (Pin 21) ±5 Volts
Lead Temperature (10 seconds) +300 °C

PHYSICAL/ENVIRONMENTAL

+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 ➁ — ±2 — — ±2 — — ±2 — Volts
Input Resistance — 200 — — 200 — — 200 — Ω
Input Capacitance — 6 15 — 6 15 — 6 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 10 20 — 10 20 — 10 20 — ns

STATIC PERFORMANCE

Resolution — 14 — — 14 — — 14 — Bits
Integral Nonlinearity (f

in = 10kHz) — ±0.75 — — ±0.75 — — ±1 — LSB

Differential Nonlinearity (f

in = 10kHz) –0.95 ±0.5 +1.25 –0.95 ±0.5 +1.25 –0.95 ±0.75 +1.99 LSB

Full Scale Absolute Accuracy — ±0.15 ±0.4 — ±0.15 ±0.4 — ±0.4 ±0.8 %FSR
Bipolar Zero Error (Tech Note 2) — ±0.2 ±0.4 — ±0.2 ±0.4 — ±0.4 ±0.65 %FSR
Gain Error (Tech Note 2) — ±0.2 ±0.75 — ±0.2 ±0.75 — ±0.4 ±1.25 %
No Missing Codes (f

in = 10kHz) 14 — — 14 — — 14 — — Bits

DYNAMIC PERFORMANCE

Peak Harmonics (–0.5dB)

dc to 500kHz — –76 –72 — –76 –72 — –74 –70 dB
500kHz to 1MHz — –75 –72 — –75 –72 — –74 –68 dB
1MHz to 4MHz — –75 –71 — –75 –71 — –69 –65 dB

Total Harmonic Distortion (–0.5dB)

dc to 500kHz — –75 –71 — –75 –71 — –74 –70 dB
500kHz to 1MHz — –75 –70 — –75 –70 — –72 –68 dB
1MHz to 4MHz — –75 –70 — –75 –70 — –69 –64 dB

Signal-to-Noise Ratio

(w/o distortion, –0.5dB)
dc to 500kHz 73 77 — 73 77 — 72 76 — dB
500kHz to 1MHz 73 77 — 73 77 — 72 76 — dB
1MHz to 4MHz 73 77 — 73 77 — 72 76 — dB

Signal-to-Noise Ratio ➃

(& distortion, –0.5dB)
dc to 500kHz 70 74 — 70 74 — 68 73 — dB
500kHz to 1MHz 69 73 — 69 73 — 65 70 — dB
1MHz to 4MHz 69 73 — 69 73 — 65 70 — dB

Noise — 150 — — 150 — — 150 — µVrms
Two-Tone Intermodulation

Distortion (f

in = 2.45MHz,

1.975MHz, f

s = 8MHz, –0.5dB) — –82 — — –82 — — –82 — dB

Input Bandwidth (–3dB)

Small Signal (–20dB input) — 30 — — 30 — — 30 — MHz
Large Signal (–0.5dB input) — 10 — — 10 — — 10 — MHz

Feedthrough Rejection (f

in = 4MHz) — 85 — — 85 — — 85 — dB

Slew Rate — ±400 — — ±400 — — ±400 — V/µs
Aperture Delay Time — +5 — — +5 — — +5 — ns
Aperture Uncertainty — 2 — — 2 — — 2 — ps rms

FUNCTIONAL SPECIFICATIONS

(TA = +25°C, ±VDD = ±5V, 8MHz sampling rate, and a minimum 3 minute warmup ➀ unless otherwise specified.)

ADS-946

3

® ®

+25°C 0 to +70°C –55 to +125°C

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

S/H Acquisition Time

( to ±0.003%FSR, 4V step) — 55 60 — 55 60 — 55 60 ns

Overvoltage Recovery Time ➄ — 100 125 — 100 125 — 100 125 ns
A/D Conversion Rate 8 — — 8 — — 8 — — MHz

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

Offset Binary

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 — +250 +270 — +250 +270 — +250 +270 mA
–5V Supply — –150 –170 — –150 –170 — –150 –170 mA

Power Dissipation — 2 2.2 — 2 2.2 — 2 2.2 Watts
Power Supply Rejection — — ±0.05 — — ±0.05 — — ±0.05 %FSR/%V

Footnotes:

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 ±2.2V (S/H saturation voltage).

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

6.02

(SNR + Distortion) – 1.76 + 20 log

Full Scale Amplitude

Actual Input Amplitude

➀ All power supplies should be on before applying a start convert pulse. All

supplies and the clock (start convert pulses) must be present during warmup
periods. The device must be continuously converting during this time.

➁ Contact DATEL for other input voltage ranges.

➂ An 8MHz clock with a 20nsec positive pulse width is used for all production

testing. See Timing Diagram, Figure 4, for more details.

➃ 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.

4. A passive bandpass filter is used at the input of the A/D for
all production testing.

Figure 2. Optional ADS-946 Gain Adjust Calibration Circuit

TECHNICAL NOTES

1. Obtaining fully specified performance from the ADS-946
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 24) directly to a
large analog ground plane beneath the package.

Bypass all power supplies 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-946 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 Figures 2 and 3. When
using this circuitry, or any similar offset and gain calibration
hardware, make adjustments following warmup. To avoid
interaction, always adjust offset before gain.

To Pin 21
of ADS-946

–5V

SIGNAL

INPUT

GAIN

ADJUST

1.98k

Ω

50Ω

+5V

2k

Ω