DATEL ADS-944MM, ADS-944MC, ADS-944-883, ADS-B944 Datasheet

1 +5V ANALOG SUPPLY 32 START CONVERT
2 –5.2V DIGITAL SUPPLY 31 BIT 1 (MSB)
3 ANALOG INPUT 30 BIT 1 (MSB)
4 ANALOG GROUND 29 BIT 2
5 OFFSET ADJUST 28 BIT 3
6 ANALOG GROUND 27 BIT 4
7 GAIN ADJUST 26 BIT 5
8 COMP. BITS 25 BIT 6

9 OUTPUT ENABLE 24 BIT 7
10 +5V DIGITAL SUPPLY 23 BIT 8
11 ANALOG GROUND 22 BIT 9
12 +15V SUPPLY 21 BIT 10
13 –15V SUPPLY 20 BIT 11
14 –5.2V ANALOG SUPPLY 19 BIT 12
15 DIGITAL GROUND 18 BIT 13
16 EOC 17 BIT 14 (LSB)

FEATURES

• 14-bit resolution

• 5MHz minimum sampling rate

• No missing codes over full military temperature range

• Edge-triggered, no pipeline delay

• Low power, 2.95 Watts

• Small, 32-pin, ceramic TDIP package

• SMT package available

• Excellent dynamic performance

• MIL-STD-883 screening or DESC SMD available

® ®

ADS-944

14-Bit, 5MHz

Sampling A/D Converters

DATEL, Inc., 11 Cabot Boulevard, Mansfield, MA 02048-1151 (U.S.A.) • Tel: [phone] Fax: [phone] • For immediate assistance: [phone]

GENERAL DESCRIPTION

The low-cost ADS-944 is a high-performance, 14-bit, 5MHz
sampling A/D converter. This device accurately samples full­scale input signals up to Nyquist frequencies with no missing
codes. The dynamic performance of the ADS-944 has been
optimized to achieve a THD of –77dB and a SNR of 76dB.

Packaged in a small, 32-pin TDIP, the functionally complete
ADS-944 contains a fast-settling sample-hold amplifier, a
subranging (two-pass) A/D converter, an internal reference,
timing and control logic, three-state outputs, and error­correction circuitry. Digital input and output levels are TTL.

Requiring ±15V, +5V and –5.2V supplies, the ADS-944
typically dissipates 2.95 Watts. The unit is offered with a
bipolar input range of ±1.25V. Models are available for use in
either commercial (0 to +70°C) or military (–55 to +125°C)
operating temperature ranges. Typical applications include
radar signal analysis, medical/graphic imaging, and
FFT spectrum analysis.

INPUT/OUTPUT CONNECTIONS

PIN FUNCTION PIN FUNCTION

Figure 1. ADS-944 Functional Block Diagram

REF

DAC

3-STATE OUTPUT REGISTER

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

TIMING AND

CONTROL LOGIC

ANALOG INPUT 3

START CONVERT 32

EOC 16

–
+

S/H

BUFFER

DIGITAL CORRECTION LOGIC

FLASH

ADC

1

FLASH

ADC

2

Σ

AMP

GAIN

CIRCUIT

GAIN ADJUST 7

OFFSET
CIRCUIT

OFFSET ADJUST 5

1

+5V

ANALOG

SUPPLY

2

–5.2V

DIGITAL

SUPPLY

4, 6, 11

ANALOG

GROUND

10

+5V

DIGITAL

SUPPLY

12

+15V

SUPPLY

14

–5.2V

ANALOG

SUPPLY

15

DIGITAL

GROUND

8

COMP.

BITS

9

OUTPUT ENABLE

ADS-944

2

® ®

PARAMETERS LIMITS UNITS

+15V Supply (Pins 12) 0 to +16 Volts
–15V Supply (Pin 13) 0 to –16 Volts
+5V Supply (Pins 1, 10) 0 to +6 Volts
–5V Supply (Pin 2, 14) 0 to –6 Volts
Digital Input (Pin 8, 9, 32) –0.3 to +V

DD +0.3 Volts

Analog Input (Pin 3) –5 to +5 Volts
Lead Temperature (10 seconds) +300 °C

PARAMETERS MIN. TYP. MAX. UNITS

Operating Temp. Range, Case

ADS-944MC 0 — +70 °C
ADS-944MM/883 –55 — +125 °C

Thermal Impedance

θjc — 7 — °C/Watt
θca — 21 — °C/Watt

Storage Temperature Range –65 — +150 °C
Package Type 32-pin, metal-sealed, ceramic TDIP or SMT

Weight 0.46 ounces (13 grams)

ABSOLUTE MAXIMUM RATINGS

PHYSICAL/ENVIRONMENTAL

FUNCTIONAL SPECIFICATIONS

(TA = +25°C, ±VCC = ±15V, +VDD = +5V,Vdd = –5.2V, 5MHz sampling rate, and a minimum 3 minute warmup ➀ unless otherwise specified.)

+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 — ±1.25 — — ±1.25 — — ±1.25 — Volts
Input Resistance 500 550 — 500 550 — 500 550 — 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" ➁ — — –20 — — –20 — — –20 µA

Start Convert Positive Pulse Width ➂ 40 80 — 40 80 — 40 80 — ns

STATIC PERFORMANCE

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

in = 10kHz) — ±0.75 — — ±0.75 — — ±1.0 — LSB

Differential Nonlinearity (f

in = 10kHz) –0.95 ±0.5 +1.2 –0.95 ±0.5 +1.2 –0.95 ±0.5 +1.5 LSB

Full Scale Absolute Accuracy — ±0.15 ±0.4 — ±0.15 ±0.4 — ±0.4 ±0.8 %FSR
Bipolar Zero Error (Tech Note 2) — ±0.1 ±0.3 — ±0.1 ±0.3 — ±0.3 ±0.6 %FSR
Bipolar Offset Error (Tech Note 2) — ±0.2 ±0.4 — ±0.2 ±0.4 — ±0.3 ±0.9 %FSR
Gain Error (Tech Note 2) — ±0.2 ±0.4 — ±0.2 ±0.4 — ±0.4 ±1.5 %
No Missing Codes (f

in = 10kHz) 14 — — 14 — — 14 — — Bits

DYNAMIC PERFORMANCE

Peak Harmonics (–0.5dB)

dc to 100kHz — –85 –77 — –85 –75 — –81 –71 dB
100kHz to 1MHz — –78 –71 — –78 –70 — –75 –67 dB
1MHz to 2.5MHz — –75 –70 — –75 –68 — –71 –61 dB

Total Harmonic Distortion (–0.5dB)

dc to 100kHz — –82 –76 — –82 –74 — –78 –70 dB
100kHz to 1MHz — –77 –70 — –77 –70 — –73 –65 dB
1MHz to 2.5MHz — –73 –68 — –73 –65 — –70 –60 dB

Signal-to-Noise Ratio

(w/o distortion, –0.5dB)
dc to 100kHz 73 76 — 73 76 — 71 75 — dB
100kHz to 1MHz 73 76 — 73 76 — 71 75 — dB
1MHz to 2.5MHz 73 75 — 73 75 — 71 75 — dB

Signal-to-Noise Ratio ➃

(& distortion, –0.5dB)
dc to 100kHz 71 75 — 71 75 — 68 73 — dB
100kHz to 1MHz 70 73 — 69 73 — 65 71 — dB
1MHz to 2.5MHz 68 71 — 66 71 — 62 69 — dB

Noise — 135 — — 135 — — 135 — µVrms
Two-tone Intermodulation

Distortion (f

in = 2.45MHz,

1.975MHz, f

s = 5MHz, –0.5dB) — –82 — — –82 — — –82 — dB

Input Bandwidth (–3dB)

Small Signal (–20dB input) — 20 — — 20 — — 20 — MHz
Large Signal (–0.5dB input) — 13 — — 13 — — 13 — MHz

Feedthrough Rejection (f

in = 2.5MHz) — 90 — — 90 — — 90 — dB

Slew Rate — ±110 — — ±110 — — ±110 — V/µs
Aperture Delay Time — +10 — — +10 — — +10 — ns
Aperture Uncertainty — 3 — — 3 — — 3 — ps rms

ADS-944

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, 2.5V step) — 85 90 — 85 90 — 85 90 ns

Overvoltage Recovery Time ➄ — 200 — — 200 — — 200 — ns
A/D Conversion Rate 5 — — 5 — — 5 — — 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

Delay, Edge of ENABLE

to Output Data Valid/Invalid — — 10 — — 10 — — 10 ns

Output Coding

Offset Binary, Complementary Offset Binary, Two's Complement

POWER REQUIREMENTS

Power Supply Ranges ➅

+15V Supply +14.25 +15.0 +15.75 +14.25 +15.0 +15.75 +14.25 +15.0 +15.75 Volts
–15V Supply –14.25 –15.0 –15.75 –14.25 –15.0 –15.75 –14.25 –15.0 –15.75 Volts
+5V Supply +4.75 +5.0 +5.25 +4.75 +5.0 +5.25 +4.9 +5.0 +5.25 Volts
–5V Supply –4.95 –5.2 –5.45 –4.95 –5.2 –5.45 –5.1 –5.2 –5.45 Volts

Power Supply Currents ➆

+15V Supply — +36 +45 — +36 +45 — +36 +45 mA
–15V Supply — –55 –65 — –55 –65 — –55 –65 mA
+5V Supply — +155 +168 — +155 +168 — +155 +168 mA
–5.2V Supply — –167 –175 — –167 –175 — –167 –175 mA

Power Dissipation — 2.95 3.3 — 2.95 3.3 — 2.95 3.3 Watts
Power Supply Rejection — — ±0.05 — — ±0.05 — — ±0.05 %FSR/%V

TECHNICAL NOTES

1. Obtaining fully specified performance from the ADS-944
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 (4, 6, 11, and 15)
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. It is very important that the bypass capacitors be
located as close to the unit as possible. Inductors or
ferrite beads can also be used to improve the power supply
filtering. Refer to Figure 4, the ADS-944 Evaluation Board
Schematic, for more details.

2. The ADS-944 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 warmup. To avoid interaction,
always adjust offset before gain.

3. Pin 8 (COMP. BITS) selects the ADS-944's digital output
coding. When a logic "1" is applied to pin 8, the output
coding is complementary offset binary. When pin 8 has a
logic "0" applied, the output coding becomes offset binary.
The MSB output (pin 31) may be used under these condi­tions to achieve two's complement coding. Pin 8 is TTL­compatible and can be driven with digital logic for those who
want dynamic control of its function. There is an internal
pull-up resistor on this pin, allowing pin 8 to be either
connected to +5V or left open when a logic "1" is needed.

4. To enable the three-state outputs, apply a logic "0" (low) to
OUTPUT ENABLE (pin 9). To disable, apply a logic "1"
(high) to pin 9.

Footnotes:

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 When COMP. BITS (pin 8) is low, logic loading "0" will be –350µA for this pin.
➂ An 80ns wide start convert pulse is used for all production testing. The start

convert pulse should be between 40 – 80ns or 130 – 160ns to ensure proper
operations. The latter range could be used for those applications requiring less
than a 5MHz sampling rate.

6.02

(SNR + Distortion) – 1.76 + 20 log

Full Scale Amplitude

Actual Input Amplitude

➃ Effective bits is equal to:

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

back within its range.

➅ The minimum supply voltages of +4.9V and –5.1V for ±V

DD are required for

–55°C operations only. The minimum limits are +4.75V and –4.95V when
operating at +125°C.

➆ Typical +5V and –5.2V current drain breakdowns are as follows:

+5V

Analog = +85mA –5.2VAnalog = –114mA

+5V

Digital = +70mA –5.2VDigital = –53mA

+5VTotal = +155mA –5.2VTotal = –167mA