DATEL ADS-945EX, ADS-945 Datasheet

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3-STATE OUTPUT REGISTER

DIGITAL CORRECTION LOGIC

SUPPLY

SUPPLY

SUPPLY

GROUND

CONNECT

SUPPLY

FEATURES

• 14-bit resolution

• 10MHz minimum throughput

• Functionally complete

• No missing codes

• Low power, 4.2W

• Excellent dynamic performance

• Internally clamped input

• Edge triggered

• TTL compatible

• 2" x 4" module

• Very low profile

GENERAL DESCRIPTION

The low-cost ADS-945 is a high-performance, 14-bit, 10MHz
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-945
has been optimized to achieve a THD of –82dB and a
SNR of 79dB.

Packaged in a 2" x 4" module, the functionally complete
ADS-945 contains a fast-settling sample/hold amplifier, a
subranging (two-pass) A/D converter, a precise voltage
reference, timing/control logic, three-state outputs, and
error-correction circuitry. Digital inputs and outputs are TTL
compatible (except for pins 29 and 30 which are ECL).

Requiring ±15V, +5V and –5.2V supplies, the ADS-945
typically dissipates 4.2W. 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.

ADS-945

14-Bit, 10MHz

Sampling A/D Converters

INPUT/OUTPUT CONNECTIONS

PIN FUNCTION PIN FUNCTION

1 ANALOG GROUND 70-76 ANALOG GROUND
4 ANALOG INPUT 69 +5V ANALOG SUPPLY

5-6 ANALOG GROUND 64-68 ANALOG GROUND

7 +10V REFERENCE OUT 63 –5.2V ANALOG SUPPLY
8 ANALOG GROUND 62 ANALOG GROUND
9 GAIN ADJUST 61 NO CONNECT

10-11 DO NOT CONNECT 58-60 DIGITAL GROUND

12 –15V SUPPLY 57 –5.2V DIGITAL SUPPLY
13 ANALOG GROUND 56 DO NOT CONNECT
14 +15V SUPPLY 55 +5V DIGITAL SUPPLY

15-17 ANALOG GROUND 54 DIGITAL GROUND

18 OFFSET ADJUST 53 BIT 1 (MSB)

19-25 ANALOG GROUND 52 BIT 2

26 MISSING PIN 51 BIT 3
27 DIGITAL GROUND 50 BIT 4
28 DIGITAL GROUND 49 BIT 5
29 T/H STATUS 48 BIT 6
30 T/H STATUS 47 BIT 7
31 DIGITAL GROUND 46 BIT 8
32 START CONVERT 45 BIT 9
33 OVERFLOW 44 BIT 10
34 OUTPUT ENABLE (OE) 43 BIT 11
35 DIGITAL GROUND 42 BIT 12
36 O.S. 3 * 41 BIT 13
37 DIGITAL GROUND 40 BIT 14 (LSB)
38 DIGITAL GROUND 39 DIGITAL GROUND

* Refer to Timing Diagram notes

33 OVERFLOW

53

BIT 1 (MSB)

52

BIT 2

51

BIT 3

50

BIT 4

49

BIT 5

48

BIT 6

47

BIT 7

46

BIT 8

45

BIT 9

44

BIT 10

43

BIT 11

42

BIT 12

41

BIT 13

40

BIT 14 (LSB)

34 OUTPUT ENABLE
26 MISSING PIN

10,11,56 DO NOT CONNECT

57

ANALOG INPUT 4

GAIN ADJUST 9

+10 REF. OUT 7

1,2,3,5,6,8,13,15,17,

19-25,62,64-68,70-76

ANALOG GROUND

OFFSET ADJUST 18

START CONVERT 32

T/H STATUS 29
T/H STATUS 30

CASE

AGND

12

–15V

+1

T/H

GAIN

CIRCUIT

DGND

OFFSET
CIRCUIT

TIMING AND

CONTROL LOGIC

36

+15V

O.S. 3

Σ

AMP

14

27,28,31,35,37-39,54,58-60

BUFFER

REF

DIGITAL

FLASH

ADC

1

DAC

FLASH

ADC

2

61

NO

55

+5V DIGITAL

–5.2V DIGITAL

Figure 1. ADS-945 Functional Block Diagram

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

ADS-945

® ®

ABSOLUTE MAXIMUM RATINGS

PARAMETERS LIMITS UNITS

+15V Supply (Pins 14) 0 to +17 Volts
–15V Supply (Pin 12) 0 to –17 Volts
+5V Supply (Pins 55, 69) 0 to +6 Volts
–5V Supply (Pin 57, 63) 0 to –6 Volts
Digital Input (Pin 32, 34) –0.3 to +V
Analog Input (Pin 4) –5 to +5 Volts
Lead Temperature (10 seconds) +300 °C

DD +0.3 Volts

PHYSICAL/ENVIRONMENTAL

PARAMETERS MIN. TYP. MAX. UNITS

Operating Temp. Range, Case

ADS-945 0 — +70 °C
ADS-945EX –55 — +125 °C

Thermal Impedance

θjc — 10 — °C/Watt
θca — 8 — °C/Watt

Storage Temperature Range –65 — +150 °C
Package Type 2" x 4" module

Weight 2.1 oz. (60 grams)

FUNCTIONAL SPECIFICATIONS

(TA = +25°C, ±VCC = ±15V, +VDD = +5V, VDD = –5.2V, 10MHz sampling rate, and a minimum 10 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 ➁ — ±1.25 — — ±1.25 — — ±1.25 — Volts
Input Resistance 300 500 — 300 550 — 300 500 — kΩ
Input Capacitance — 10 15 — 10 15 — 10 15 pF
Input Bias Current — ±3 — — ±3 — — ±3 — µA

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 50 — 10 50 — 10 50 — ns

STATIC PERFORMANCE

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

in = 10kHz) — ±0.5 — — ±0.75 — — ±0.75 — LSB

in = 10kHz) — ±0.5 ±0.75 — ±0.5 ±0.75 –0.95 ±0.75 +1.5 LSB

Full Scale Absolute Accuracy — ±0.2 ±0.4 — ±0.3 ±0.5 — ±0.3 ±0.7 %FSR
Bipolar Offset Error (Tech Note 2) — ±0.15 ±0.25 — ±0.25 ±0.5 — ±0.3 ±0.7 %FSR
Gain Error (Tech Note 2) — ±0.1 ±0.2 — ±0.2 ±0.4 — ±0.3 ±0.7 %
No Missing Codes (f

in = 10kHz) 14 — — 14 — — 14 — — Bits

DYNAMIC PERFORMANCE

Peak Harmonics (–0.5dB)

dc to 1mHz — –86 –78 — –86 –78 — –80 –72 dB
1MHz to 2.5MHz — –82 –75 — –82 –75 — –79 –70 dB

2.5MHz to 5MHz — –79 –74 — –79 –74 — –78 –70 dB

Total Harmonic Distortion (–0.5dB)

dc to 1MHz — –82 –76 — –82 –76 — –78 –70 dB
1MHz to 2.5MHz — –80 –74 — –80 –74 — –76 –68 dB

2.5MHz to 5MHz — –78 –73 — –78 –73 — –76 –68 dB

Signal-to-Noise Ratio

(w/o distortion, –0.5dB)
dc to 1MHz 76 79 — 76 79 — 70 78 — dB
100kHz to 2.5MHz 76 78 — 76 78 — 70 77 — dB

2.5MHz to 5MHz 75 77 — 75 77 — 70 75 — dB

Signal-to-Noise Ratio ➃

(& distortion, –0.5dB)
dc to 100kHz 73 77 — 73 77 — 67 74 — dB
1MHz to 2.5MHz 72 76 — 72 76 — 67 74 — dB

2.5MHz to 5MHz 71 74 — 71 74 — 66 72 — dB

Noise — 110 — — 110 — — 110 — µVrms
Two-tone Intermodulation

Distortion (f

2.45MHz, f

in = 1.975MHz,

s = 10MHz, –0.5dB) — –84 — — –84 — — –84 — dB

Input Bandwidth (–3dB)

Small Signal (–20dB input) — 100 — — 100 — — 100 — MHz
Large Signal (–0.dB input) — 50 — — 50 — — 50 — MHz

Feedthrough Rejection (f

in = 4.85MHz) — 90 — — 90 — — 90 — dB

Slew Rate — ±850 — — ±850 — — ±850 — V/µs
Aperture Delay Time — +8 — — +8 — — +8 — ns
Aperture Uncertainty — 2 — — 2 — — 2 — ps rms

2

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ADS-945

+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) — 40 — — 40 — — 40 — ns

Overvoltage Recovery Time ➄ — 30 100 — 30 100 — 30 100 ns
A/D Conversion Rate 10 — — 10 — — 10 — — MHz

ANALOG OUTPUT

Reference Output +9.99 +10 +10.01 +9.99 +10 +10.01 +9.99 +10 +10.01 Volts
Reference Temperature Drift — ±40 — — ±40 — — ±40 — ppm/°C
Reference Load Curent — — 2.0 — — 2.0 — — 2.0 mA

DIGITAL OUTPUTS

Logic Levels

Logic "1" +2.7 — — +2.7 — — +2.7 — — Volts
Logic "0" — — +0.5 — — +0.5 — — +0.5 Volts
Logic Loading "1" — — –0.4 — — –0.4 — — –0.4 mA
Logic Loading "0" — — +8 — — +8 — — +8 mA

Delay, Falling Edge of T/H

to Output Data Valid — 55 — — 55 — — 55 — ns

Delay, Edge of ENABLE

to Output Data Valid/Invalid — — 18 — — 18 — — 18 ns

Output Coding

POWER REQUIREMENTS

Complementary Offset Binary

Power Supply Ranges

+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 +4.75 +5.0 +5.25 Volts
–5.2V Supply –4.95 –5.2 –5.45 –4.95 –5.2 –5.45 –4.95 –5.2 –5.45 Volts

Power Supply Currents ➅

+15V Supply — +35 +45 — +35 +45 — +35 +45 mA
–15V Supply — –55 –65 — –55 –65 — –55 –65 mA
+5V Supply — +140 +160 — +140 +160 — +140 +160 mA
–5.2V Supply — –430 –460 — –430 –460 — –430 –460 mA

Power Dissipation — 4.2 4.5 — 4.2 4.5 — 4.2 4.5 Watts
Power Supply Rejection — — ±0.04 — — ±0.04 — — ±0.04 %FSR/%V

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 The input to the ADS-945 is internally clamped at ±2.3V.
➂ An 50ns wide start convert pulse is used for all production testing. For

applications requiring less than a 10MHz sampling rate, a wider start convert
can be used.

TECHNICAL NOTES

1. Obtaining fully specified performance from the ADS-945
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 directly to a large analog
ground plane beneath the package.

Bypass all power supplies to ground with 10µF tantalum
capacitors in parallel with 0.1µF ceramic capacitors. The

bypass capacitors should be located as close to the
unit as possible.

2. The ADS-945 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

➃ Effective bits is equal to:

(SNR + Distortion) – 1.76 + 20 log

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

back within its range.

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

Analog = +100mA –5.2VAnalog= –210mA

+5V

Digital = +40mA –5.2VDigital = –220mA

+5V
+5VTotal = +140mA –5.2VTotal = –430mA

Full Scale Amplitude

Actual Input Amplitude

6.02

the adjustment circuitry shown in Figure 2. The typical
adjustment range is ±0.2%FSR for this circuitry.

When using this circuitry, or any similar offset and gain­calibration hardware, make adjustments following warmup.
To avoid interaction, always adjust offset before gain.

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

4. A passive bandpass filter (Allen Avionics F4202 Series) is
used at the input of the A/D for all production testing.

5. The ADS-945's digital outputs should not be directly
connected to a noisy data bus. Drive the bus with 573 or
574 type latches and use "low-noise" logic, such as the
74LS series.

3