Figure 1. ADS-941 Functional Block Diagram
REF
REGISTERREGISTER
31 BIT 1 OUT (MSB)
30 BIT 1 OUT (MSB)
29 BIT 2 OUT
28 BIT 3 OUT
27 BIT 4 OUT
26 BIT 5 OUT
25 BIT 6 OUT
24 BIT 7 OUT
23 BIT 8 OUT
22 BIT 9 OUT
21 BIT 10 OUT
20 BIT 11 OUT
19 BIT 12 OUT
18 BIT 13 OUT
17 BIT 14 OUT (LSB)
TIMING AND
CONTROL LOGIC
+10V REF. OUT 1
START CONVERT 32
EOC 16
DIGITAL CORRECTION LOGIC
DAC
FLASH
ADC
BUFFER
ANALOG INPUT 3
S2
S1
4
SIGNAL
GROUND
11
DIGITAL
GROUND
12
+15V
SUPPLY
3-STATE OUTPUT REGISTER
S/H
OFFSET
CIRCUIT
BIPOLAR 2
OFFSET ADJUST 5
10
+5V
SUPPLY
6, 14, 15
ANALOG
GROUND
8
CODING
SELECT
13
–5V
SUPPLY
9 ENABLE
7 OVERFLOW
BLOCK DIAGRAM
DATEL's ADS-941 is a functionally complete,
14-bit, 1MHz, sampling A/D converter. Its standard,
32-pin, triple-wide ceramic DIP contains a fast-
settling sample/hold amplifi er, a 14-bit subranging
(two-pass) A/D converter, a precision reference, a
three-state output register, and all the timing and
control logic necessary to operate from a single
start convert pulse.
The ADS-941 is optimized for wideband
frequency-domain applications and is fully FFT
tested. Total harmonic distortion (THD) and signal-
to-noise ratio (including distortion) typically run
at –85dB and 80dB, respectively, with full-scale
inputs up to 100kHz.
The ADS-941 requires ±15V and +5V supplies
and typically consumes 2.8 Watts.
PRODUCT OVERVIEW
FEATURES
■ 14-bit resolution
■ 1MHz minimum sampling rate
■ Functionally complete
■ Internal reference and sample/hold
■ No missing codes
■ Excellent performance
■ Full Nyquist-rate sampling
■ Small 32–pin DIP
■ Low power, 2.8 Watts
INPUT/OUTPUT CONNECTIONS
PIN FUNCTION PIN FUNCTION
1 +10V REF. OUT 32 START CONVERT
2 BIPOLAR 31 BIT 1 OUT (MSB)
3 ANALOG INPUT 30 BIT 1 OUT (MSB)
4 SIGNAL GROUND 29 BIT 2 OUT
5 OFFSET ADJUST 28 BIT 3 OUT
6 ANALOG GROUND 27 BIT 4 OUT
7 OVERFLOW 26 BIT 5 OUT
8 CODING SELECT 25 BIT 6 OUT
9 ENABLE 24 BIT 7 OUT
10 +5V SUPPLY 23 BIT 8 OUT
11 DIGITAL GROUND 22 BIT 9 OUT
12 +15V SUPPLY 21 BIT 10 OUT
13 –15V SUPPLY 20 BIT 11 OUT
14 ANALOG GROUND 19 BIT 12 OUT
15 ANALOG GROUND 18 BIT 13 OUT
16 EOC 17 BIT 14 OUT (LSB)
ADS-941
14-Bit, 1MHz Sampling A/D Converters
®®
DATEL • 11 Cabot Boulevard, Mansfi eld, MA 02048-1151 USA • Tel: (508) 339-3000 • www.datel.com • e-mail: help@datel.com
01 Apr 2011 MDA_ADS-941.B02 Page 1 of 5
FUNCTIONAL SPECIFICATIONS
(TA = +25°C, ±VCC = ±15V ±VDD = +5V, 1MHz sampling rate, and a minimum 7 minute
warmup ➀ unless otherwise specifi ed.)
ABSOLUTE MAXIMUM RATINGS
PARAMETERS LIMITS UNITS
+15V Supply (Pin 12) 0 to +16 Volts
–15V Supply (Pin 13) 0 to –16 Volts
+5V Supply (Pin 10) 0 to +6.0 Volts
Digital Inputs (Pin 8,9, 32) –0.3 to +VDD +0.3 Volts
Analog Input (Pin 3) ±15 Volts
Lead Temp. (10 seconds) 300 °C
ANALOG INPUTS MIN. TYP. MAX. UNITS
Input Voltage Range
Unipolar — 0 to +10 — Volts
Bipolar — ±5 — Volts
Input Impedence 2.2 2.5 — kW
Input Capacitance — 7 15 pF
DIGITAL INPUTS
Logic Levels
Logic "1" +2.0 — — Volts
Logic "0" — — +0.8 Volts
Logic Loading "1" — — +10 μA
Logic Loading "0" — — –600 μA
PERFORMANCE
Integral Non-Linearity (fi n = 10KHz)
+25°C — ±1 ±2 LSB
0 to +70°C — ±1.5 ±2 LSB
–40 to +85°C — ±2 ±3 LSB
Differential Non-Linearity (fi n = 10KHz)
+25°C –0.75 ±0.5 ±0.75 LSB
0 to +70°C –0.95 ±0.75 ±0.95 LSB
–40 to +85°C –1 ±0.95 +2.5 LSB
Full Scale Absolute Accuracy
+25°C — ±0.1 ±0.122 %FSR
0 to +70°C — ±0.12 ±0.36 %FSR
–40 to +85°C — ±0.45 ±0.85 %FSR
Unipolar Zero Error
+25°C (see Figure 3) — ±0.05 ±0.122 %FSR
0 to +70°C — ±0.1 ±0.2 %FSR
–40 to +85°C — ±0.2 ±0.3 %FSR
Bipolar Zero Error
+25°C (see Figure 3) — ±0.05 ±0.122 %FSR
0 to +70°C — ±0.1 ±0.2 %FSR
–40 to +85°C — ±0.2 ±0.3 %FSR
Bipolar Offset Error
+25°C (see Figure 3) — ±0.1 ±0.12 %FSR
0 to +70°C — ±0.12 ±0.3 %FSR
–40 to +85°C — ±0.5 ±0.8 %FSR
Gain Error
+25°C (see Figure 3) — ±0.018 ±0.122 %FSR
0 to +70°C — ±0.12 ±0.3 %FSR
–40 to +85°C — ±0.6 ±0.8 %FSR
No Missing Codes (fi n = 500kHz)
14 Bits 0 to +70°C
Resolution 14 Bits
OUTPUTS MIN. TYP. MAX. UNITS
Output Coding Staight Bin./Offset Bin./Two's Comp.
Comp. Bin./Comp. Offset Bin./C2C
Logic Level
Logic "1" +2.4 — — Volts
Logic "0" — — +0.4 Volts
Logic Loading "1" — — –160 μA
Logic Loading "0" — — +6.4 mA
Internal Reference
Voltage, +25°C +9.98 +10.0 +10.02 Volts
Drift — ±13 ±30 ppm/°C
External Current — — 5 mA
DYNAMIC PERFORMANCE
Slew Rate — ±250 — V/μs
Aperature Delay Time — — 10 ns
Aperature Uncertainty — — ±10 ps
S/H Aquisition Time (to ±0.003%FS, 10V step) — 250 350 ns
Total Harm. Distort. (–0.5dB)
dc to 100kHz –78 –85 — dB
100kHz to 500kHz –77 –80 — dB
Signal-to-Noise Ratio (w/o distortion, –0.5dB )
dc to 100kHz 75 80 — dB
100kHz to 500kHz 74 77 — dB
Signal-to-Noise Ratio (and distortion, –0.5dB)
dc to 100kHz 74 80 — dB
100kHz to 500kHz 73 78 — dB
Spurious Free Dyn. Range c
dc to 100kHz78 78 86 — dB
100 to 500kHz 77 83 — dB
Two-tone IMD Distortion (fi n = 100kHz,
240kHz, fs = 2.0Mhz, –0.5dB) — –85 — dB
Input Bandwidth (–3dB)
Small Signal (–20dB input) — 6 — MHz
Large Signal (–0dB input) — 1.75 — MHz
Feedthrough Rejection (fi n = 500KHz) — 87 — dB
Overvoltage Recovery, ±12V — 1000 2000 ns
A/D Conversion Rate 1 — — MHz
Noise — 250 — μVrms
POWER REQUIREMENTS
Power Supply Ranges
+15V Supply +14.25 +15.0 +15.75 Volts
–15V Supply –14.25 –15.0 –15.75 Volts
+5V Supply +4.75 +5.0 +5.25 Volts
Power Supply Currents
+15V Supply — +62 +85 mA
–15V Supply — –80 –105 mA
+5V Supply — +140 +185 mA
Power Dissipation — 2.8 3.5 Watts
Power Supply Rejection — — ±0.02 %FSR%V
PHYSICAL/ENVIRONMENTAL
Operating Temp. Range, Case
ADS-941MC 0 — +70 °C
ADS-941ME –40 — +85 °C
Storage Temperature Range –65 — +150 °C
Package Type 32-pin, metal-sealed, ceramic TDIP
Weight 0.46 ounces (13 grams)
Footnote:
c Same specifi cation as In-Band Harmonics and Peak Harmonics.
ADS-941
14-Bit, 1MHz Sampling A/D Converters
®®
DATEL • 11 Cabot Boulevard, Mansfi eld, MA 02048-1151 USA • Tel: (508) 339-3000 • www.datel.com • e-mail: help@datel.com
01 Apr 2011 MDA_ADS-941.B02 Page 2 of 5
TECHNICAL NOTES
1. Rated performance requires using good high-frequency circuit board layout
techniques. The analog and digital grounds are not connected to each other
internally. Avoid ground-related problems by connecting the digital and
analog grounds to one point, the ground plane beneath the converter. Due
to the inductance and resistance of the power supply return paths, return
the analog and digital ground separately to the power supplies.
2. Bypass the analog and digital supplies and the +10V REF. OUT (pin 1) to
ground with a 4.7μF, 25V tantalum electrolytic capacitor in parallel with a
0.1μF ceramic capacitor.
3. CODING SELECT (pin 8) is compatible with CMOS/TTL logic levels for those
users desiring logic control of this function. The device has an internal pull-
up resistor on this pin, allowing pin 8 to be connected to +5V or left open
when a logic 1 is needed. See the Calibration Procedure for selecting an
output coding.
4. To enable the three-state outputs, connect ENABLE (pin 9) to a logic "0"
(low). To disable, connect pin 9 to a logic "1" (high).
CALIBRATION PROCEDURE
1. Connect the converter per Figure 3 and Table 1 for the appropriate input
range. Apply a pulse of 50 nanoseconds minimum to START CONVERT (pin
32) at a rate of 200kHz. This rate is chosen to reduce fl icker if LED's are
used on the outputs for calibration purposes.
2. Zero Adjustments
Apply a precision voltage reference source between ANALOG INPUT (pin 3)
and SIGNAL GROUND (pin 4), then adjust the reference source output per
Table 2. For unipolar operation, adjust the zero trimpot so that the output
code fl ickers equally between 00 0000 0000 0000 and 00 0000 0000 0001
with CODING SELECT (pin 8) tied low (straight binary) or between 11 1111
1111 1111 and 11 1111 1111 1110 with pin 8 tied high (complementary
binary). For bipolar operation, adjust the trimpot until the code fl ickers
equally between 10 0000 0000 0000 and 10 0000 0000 0001 with pin 8
tied low (offset binary) or between 01 1111 1111 1111 and 01 1111 1111
1110 with pin 8 tied high (complementary offset binary). Two's complement
coding requires using BIT 1 OUT (MSB) (pin 31). With pin 8 tied low, adjust
the trimpot until the code fl ickers between 00 0000 0000 0000 and 00
0000 0000 0001.
3. Full-Scale Adjustment
Set the output of the voltage reference used in step 2 to the value shown
in Table 2. Adjust the gain trimpot until the output code fl ickers equally be-
tween 11 1111 1111 1110 and 11 1111 1111 1111 with pin 8 tied low for
straight binary/offset binary or between 00 0000 0000 0000 and 00 0000
0000 0001 with pin 8 tied high for complementary binary/complementary
offset binary. Two's complement coding requires using pin 31. With pin
8 tied low, adjust the gain trimpot until the output code fl ickers equally
between 01 1111 1111 1110 and 01 1111 1111 1111.
4. To confi rm proper operation of the device, vary the precision reference volt-
age source to obtain the output coding listed in Table 3.
THERMAL REQUIREMENTS
All DATEL sampling A/D converters are fully characterized and speci-
fi ed over operating temperature (case) ranges of 0 to +70°C and –55
to +125°C. All room-temperature (TA = +25°C) production testing is
performed without the use of heat sinks or forced-air cooling. Thermal
impedance fi gures for each device are listed in their respective specifi ca-
tion tables.
These devices do not normally require heat sinks, however, standard pre-
cautionary design and layout procedures should be used to ensure devices
do not overheat. The ground and power planes beneath the package, as
well as all pcb signal runs to and from the device, should be as heavy as
possible to help conduct heat away from the package. Electricallyinsulating,
thermally-conductive "pads" may be installed underneath the package. De-
vices should be soldered to boards rather than "socketed", and of course,
minimal air fl ow over the surface can greatly help reduce the package
temperature.
Removing System Errors
Use external potentiometers to remove system errors or to reduce the small
initial errors to zero. Use a 100W trimpot in series with the analog input for
gain adjustment. Use a fi xed 50W resistor instead of the trimpot for opera-
tion without adjustment. Use a 20kW trimpot with the wiper tied to OFFSET
ADJUST (pin 5) for zero/offset adjustment. Connect pin 5 to ANALOG
GROUND (pin 6) for operation without zero/offset adjustment.
Table 2. Zero and Gain Adjustments
INPUT RANGE ZERO ADJUST
+½ LSB
GAIN ADJUST
FS –1½ LSB
0 to +10V +305μV +9.999085V
±5V +305μV +4.999085V
Table 1. Input Connections
INPUT RANGE INPUT PIN TIE TOGETHER
0 +10V Pin 3 Pins 2 and 4
±5V Pin 3 Pins 1 and 2
Scale is approximatel
y
50ns per division.
START
CONVERT
INTERNAL S/H
NN+1
35ns max.
EOC
10ns typ.
Conversion Time
600ns typ.
OUTPUT
DATA DATA N VALID
Hold
DATA N-1 VALID
30ns max.
50ns min., 100ns max
350ns max.
Aquisition Time
INVALID DATA
600ns min.
400ns max.
Figure 2. ADS-941 Timing Diagram
ADS-941
14-Bit, 1MHz Sampling A/D Converters
®®
DATEL • 11 Cabot Boulevard, Mansfi eld, MA 02048-1151 USA • Tel: (508) 339-3000 • www.datel.com • e-mail: help@datel.com
01 Apr 2011 MDA_ADS-941.B02 Page 3 of 5
ADS-941
20k:
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
7
16
BIT 1 (MSB)
BIT 1 (MSB)
BIT2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
BIT 10
BIT 11
BIT 12
BIT 13
BIT 14 (LSB
)
OVERFLOW
EOC
ANALOG
GROUND
DIGITAL
GROUND
0.1F
4.7F
0.1F
ENABLE
4.7F
+10V
REF. OUT
CODING SELECT
10
11
9
1
8
+5V
–5V+5V
OFFSET
ADJUST
5
3
0.1F
4.7F
6, 14, 15
13
0.1F
4.7F
12
++
–15V
+15V
32
START CONVERT
ANALOG INPUT
100:
2
BIPOLAR
4SIGNAL GROUND
ZERO/OFFSET
ADJUST
0 to +10V
GAIN ADJUST
Figure 3. Typical ADS-941 Connection Diagram
Figure 4. ADS-941 FFT Analysis
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
–130
–140
–150
Frequency (kHz)
(fs = 1MHz, fin = 480kHz, Vin = –0.5dB, 16,384-point FFT)
Amplitude Relative to Full Scale (dB)
0 50 100 150 200 250 300 350 400 450 500
ADS-941
14-Bit, 1MHz Sampling A/D Converters
®®
DATEL • 11 Cabot Boulevard, Mansfi eld, MA 02048-1151 USA • Tel: (508) 339-3000 • www.datel.com • e-mail: help@datel.com
01 Apr 2011 MDA_ADS-941.B02 Page 4 of 5
STRAIGHT BINARY COMP. BINARY
UNIPOLAR
SCALE
INPUT RANGE
0 to +10V
OUTPUT CODING INPUT RANGE
±5V
BIPOLAR
SCALE
MSB LSB MSB LSB MSB LSB
+FS – 1 LSB +9.999390 11 1111 1111 1111 00 0000 0000 0000 01 1111 1111 1111 +4.999390 +FS – 1LSB
+7/8 FS +8.750000 11 1000 0000 0000 00 0111 1111 1111 01 1000 0000 0000 +3.750000 +3/4FS
+3/4 FS +7.500000 11 0000 0000 0000 00 1111 1111 1111 01 0000 0000 0000 +2.500000 +1/2FS
+1/2 FS +5.000000 10 0000 0000 0000 01 1111 1111 1111 00 0000 0000 0000 0.000000 0
+1/4 FS +2.500000 01 0000 0000 0000 10 1111 1111 1111 11 0000 0000 0000 –2.500000 –1/2FS
+1/8 FS +1.250000 00 1000 0000 0000 11 0111 1111 1111 10 1000 0000 0000 –3.750000 –3/4FS
+1 LSB +0.000610 00 0000 0000 0001 11 1111 1111 1110 10 0000 0000 0001 –4.999390 –FS+1LSB
0 0.000000 00 0000 0000 0000 11 1111 1111 1111 10 0000 0000 0000 –5.000000 –FS
OFFSET BINARY COMP. OFF. BIN. TWO'S COMP.
Table 3. Output Coding
MECHANICAL DIMENSIONS INCHES (mm)
ORDERING INFORMATION
MODEL
NUMBER
OPERATING
TEMP. RANGE ACCESSORIES
ADS-941MC 0 to +70°C ADS-B916/917 Evaluation Board (without ADS-942)
ADS-941ME –40 to +85°C HS-24 Heat Sink for all ADS-942 models
Receptacles for PC mounting can be ordered through AMP Inc., Part # 3-331272-8 (Component Lead
Socket), 32 required.
0.040
(1.016)
SEATING
PLANE
0.025
(0.635)
0.200 MAX.
(5.080)
0.235 MAX.
(5.969)
0.190 MAX.
(4.826) 0.900 ±0.010
(22.860)
1.11 MAX.
(28.19)
0.100 TYP.
(2.540)
1.72 MAX.
(43.69)
116
1732
1.500
(38.100)
0.100
(2.540)
0.100
(2.540)
0.018 ±0.002
(0.457)
0.010
(0.254)
Dimension Tolerances (unless otherwise indicated):
2 place decimal (.XX) ±0.010 (±0.254)
3 place decimal (.XXX) ±0.005 (±0.127)
Lead Material: Kovar alloy
Lead Finish: 50 microinches (minimum) gold plating
over 100 microinches (nominal) nickel plating
+0.002
–0.001
ADS-941
14-Bit, 1MHz Sampling A/D Converters
. makes no representation that the use of its products in the circuits described herein, or the use of other
technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not
imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifi cations are subject to change
without notice.
www.datel.com • e-mail: help@datel.com
®®
DATEL
11 Cabot Boulevard, Mansfi eld, MA 02048-1151 USA
ITAR and ISO 9001/14001 REGISTERED
01 Apr 2011 MDA_ADS-941.B02 Page 5 of 5