DATEL ADS-943MM, ADS-943MC, ADS-943GM, ADS-943GC, ADS-943G-883 Datasheet

® ®

ADS-943

14-Bit, 3MHz, Low-Distortion

Sampling A/D Converters

edge-triggered, requiring only the rising edge of a start convert
pulse to initiate a conversion.

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

Figure 1. ADS-943 Functional Block Diagram

INPUT/OUTPUT CONNECTIONS

PIN FUNCTION PIN FUNCTION

1 BIT1 (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

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

FEATURES

• 14-bit resolution

• 3MHz minimum sampling rate

• Ideal for both frequency and time-domain applications

• Excellent peak harmonics, –83dB

• Excellent signal-to-noise ratio, 79dB

• No missing codes over full military temperature range

• ±5V supplies, 1.7 Watts

• Small, 24-pin ceramic DDIP or SMT

• Low cost

GENERAL DESCRIPTION

The low-cost ADS-943 is a 14-bit, 3MHz sampling A/D
converter optimized to meet the demanding dynamic-range
and sampling-rate requirements of contemporary digital
telecommunications applications. The ADS-943's outstanding
dynamic performance is evidenced by a peak harmonic
specification of –83dB and a signal-to-noise ratio (SNR) of
79dB. Additionally, the ADS-943 easily achieves the 2.2MHz
minimum sampling rate required by digital receivers in certain
ADSL, HDSL and ATM applications. The ADS-943 also
addresses size and power constraints normally associated with
these types of applications. This device requires just ±5V
supplies, dissipates 1.7 Watts, and is packaged in a very small
24-pin DDIP.

Although optimized for frequency-domain applications, the
ADS-943's DNL and noise specifications are also outstanding,
thereby making it an equally impressive device for time-domain
applications (graphic and medical imaging, process control,
etc.). In fact, the ADS-943 guarantees no missing codes to the
14-bit level over the full military operating temperature range.

The functionally complete ADS-943 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 unit is

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

–
+

S/H

BUFFER

DIGITAL CORRECTION LOGIC

FLASH

ADC

1

FLASH

ADC

2

POWER AND GROUNDING

Σ

AMP

® ®

ADS-943

2

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 to +5 Volts
Lead Temperature (10 seconds) +300 °C

PHYSICAL/ENVIRONMENTAL

PARAMETERS MIN. TYP. MAX. UNITS

Operating Temp. Range, Case

ADS-943MC, GC 0 — +70 °C
ADS-943MM, 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)

+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 — 280 — — 280 — — 280 — 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 +1.5 LSB

Full Scale Absolute Accuracy — ±0.15 ±0.4 — ±0.15 ±0.4 — ±0.4 ±0.6 %FSR
Bipolar Zero Error (Tech Note 2) — ±0.1 ±0.3 — ±0.1 ±0.3 — ±0.3 ±0.6 %FSR
Gain Error (Tech Note 2) — ±0.2 ±0.5 — ±0.2 ±0.5 — ±0.4 ±1.25 %
No Missing Codes (f

in = 10kHz) 14 — — 14 — — 14 — — Bits

DYNAMIC PERFORMANCE

Peak Harmonics (–0.5dB)

dc to 500kHz — –83 –77 — –83 –77 — –81 –75 dB
500kHz to 1MHz — –83 –77 — –83 –77 — –81 –75 dB
1MHz to 1.5MHz — –83 –77 — –83 –77 — –81 –75 dB

Total Harmonic Distortion (–0.5dB)

dc to 500kHz — –80 –76 — –80 –76 — –78 –74 dB
500kHz to 1MHz — –80 –76 — –80 –76 — –77 –73 dB
1MHz to 1.5MHz — –80 –76 — –80 –76 — –77 –73 dB

Signal-to-Noise Ratio

(w/o distortion, –0.5dB)
dc to 500kHz 76 79 — 76 79 — 75 78 — dB
500kHz to 1MHz 76 79 — 76 79 — 74 77 — dB
1MHz to 1.5MHz 75 78 — 75 78 — 74 77 — dB

Signal-to-Noise Ratio ➃

(& distortion, –0.5dB)
dc to 500kHz 73 77 — 73 77 — 71 75 — dB
500kHz to 1MHz 73 77 — 73 77 — 71 75 — dB
1MHz to 1.5MHz 73 77 — 73 77 — 71 74 — dB

Noise — 125 — — 125 — — 125 — µVrms
Two-Tone Intermodulation

Distortion (f

in = 975kHz,

1.2MHz, f

s = 3MHz, –0.5dB) — –82 — — –82 — — –82 — dB

Input Bandwidth (–3dB)

Small Signal (–20dB input) — 30 — — 30 — — 30 — MHz
Large Signal (–0dB input) — 10 — — 10 — — 10 — MHz

Feedthrough Rejection (f

in = 1.5MHz) — 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, 3MHz sampling rate, and a minimum 3 minute warmup ➀ unless otherwise specified.)

® ®

ADS-943

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) — 208 215 — 208 215 — 208 215 ns

Overvoltage Recovery Time ➄ — 100 333 — 100 333 — 100 333 ns
A/D Conversion Rate 3 — — 3 — — 3 — — 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 — +210 +230 — +210 +230 — +210 +230 mA
–5V Supply — –125 –145 — –125 –145 — –125 –145 mA

Power Dissipation — 1.7 1.9 — 1.7 1.9 — 1.7 1.9 Watts
Power Supply Rejection — — ±0.05 — — ±0.05 — — ±0.05 %FSR/%V

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 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 minumum limits are +4.75V and –4.75V when
operating at +125°C.

TECHNICAL NOTES

1. Obtaining fully specified performance from the ADS-943
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-943 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 gain­calibration hardware, make adjustments following warmup.
To avoid interaction, always adjust offset before gain.

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.

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 Contact DATEL for other input voltage ranges.

➂ A 3MHz clock with a 20nsec positive pulse width is used for all production testing.

When sampling at 3MHz, the start convert pulse must be between 10 and
110nsec wide or between 160 and 300nsec wide. The falling edge must not occur
between 110 and 160nsec. For lower sampling rates, wider start pulses may be
used.

Figure 2. Optional ADS-943 Gain Adjust Calibration Circuit

To Pin21
of ADS-943

–5V

SIGNAL

INPUT

GAIN

ADJUST

1.98k

Ω

50

Ω

+5V

2k

Ω