®
®
ADS-947
14-Bit, 10MHz Sampling A/D Converters
PRODUCT OVERVIEW
The ADS-947 is a 14-bit, 10MHz 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-947
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-947 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-
947 only requires the rising edge of a start convert
pulse to operate.
Requiring only +5V and –5.2V supplies, the
ADS-947 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 extended (–40 to +100°C) operating
temperature ranges. A proprietary, auto-calibrating,
error-correcting circuit allows the device to achieve
specified performance over the extended tempera-
ture range.
FEATURES
■
■
■
■
14-bit resolution
10MHz minimum sampling rate
No missing codes
Ideal for both time and frequency-domain
applications
Excellent THD (–81dB) and SNR (76dB)
Edge-triggered
Small, 24-pin, ceramic DDIP or SMT
Requires only +5V and –5.2V supplies
Low-power, 2 Watts
■
■
■
■
■
PIN
1
2
3
4
5
6
7
8
9
10
11
12
INPUT/OUTPUT CONNECTIONS
FUNCTION
PIN
FUNCTION
BIT 1 (MSB)
24
ANALOG GROUND
BIT 2
23
OFFSET ADJUST
BIT 3
22
+5V ANALOG SUPPLY
BIT 4
21
ANALOG INPUT
BIT 5
20
–5.2V SUPPLY
BIT 6
19
ANALOG GROUND
BIT 7
18
START CONVERT
BIT 8
17
DATA VALID
BIT 9
16
BIT 14 (LSB)
BIT 10
15
BIT 13
BIT 11
14
DIGITAL GROUND
BIT 12
13
+5V DIGITAL SUPPLY
BLOCK DIAGRAM
OFFSET ADJUST 23
BUFFER
REGISTER
ANALOG INPUT 21
–
S/H
+
FLASH
ADC
1
16 BIT 14 (LSB)
15 BIT 13
12 BIT 12
DIGITAL CORRECTION LOGIC
11 BIT 11
OUTPUT REGISTER
10 BIT 10
9
8
7
6
5
4
3
2
1
BIT 9
BIT 8
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1 (MSB)
POWER AND GROUNDING
REF
+5V ANALOG SUPPLY
+5V DIGITAL SUPPLY
–5.2V SUPPLY
ANALOG GROUND
DIGITAL GROUND
22
13
20
19, 24
14
AMP
FLASH
ADC
2
REGISTER
DAC
START CONVERT 18
DATA VALID 17
TIMING AND
CONTROL LOGIC
Figure 1. ADS-947 Functional Block Diagram
DATEL, Inc., 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 Fax: (508) 339-6356 • www.datel.com • data.acquisition@datel.com
03 Jun 2010
MDA_ADS-947.B01
Page 1 of 9
®
®
ADS-947
14-Bit, 10MHz Sampling A/D Converters
UNITS
Volts
Volts
Volts
Volts
°C
PARAMETERS
Operating Temp. Range, Case
ADS-947MC, GC
ADS-947ME, GE, QL
Thermal Impedance
Tjc
Tca
Storage Temperature Range
Package Type
Weight
PHYSICAL/ENVIRONMENTAL
MIN.
TYP.
0
–40
—
—
MAX.
+70
+100
UNITS
°C
°C
ABSOLUTE MAXIMUM RATINGS
PARAMETERS
LIMITS
+5V Supply (Pins 13, 22)
0 to +6
–5.2V Supply (Pin 20)
0 to –5.5V
Digital Input (Pin 18)
–0.3 to +VDD +0.3
Analog Input (Pin 21)
±5
Lead Temperature (10 seconds)
+300
—
6
—
°C/Watt
—
23
—
°C/Watt
–65
—
+150
°C
24-pin, metal-sealed, ceramic DDIP or SMT
0.46 ounces (13 grams)
FUNCTIONAL SPECIFICATIONS
(T
A
= +25°C, +V
DD
= +5V, –V
DD
= –5.2V, 10MHz sampling rate,and a minimum 3 minute warmup
➀
unless otherwise specified.)
ANALOG INPUT
Input Voltage Range
d
Input Resistance
Input Capacitance
DIGITAL INPUT
Logic Levels
Logic "1"
Logic "0"
Logic Loading "1"
Logic Loading "0"
Start Convert Positive Pulse Width
➂
STATIC PERFORMANCE
Resolution
Integral Nonlinearity (fin = 10kHz)
Differential Nonlinearity (fin = 10kHz)
Full Scale Absolute Accuracy
Bipolar Zero Error (Tech Note 2)
Gain Error (Tech Note 2)
No Missing Codes (fin = 10kHz)
DYNAMIC PERFORMANCE
Peak Harmonics (–0.5dB)
dc to 1MHz
1MHz to 2.5MHz
2.5MHz to 5MHz
Total Harmonic Distortion (–0.5dB)
dc to 1MHz
1MHz to 2.5MHz
2.5MHz to 5MHz
Signal-to-Noise Ratio (w/o distortion, –0.5dB)
dc to 1MHz
1MHz to 2.5MHz
2.5MHz to 5MHz
Signal-to-Noise Ratio
f
(& distortion, –0.5dB)
dc to 1MHz
1MHz to 2.5MHz
2.5MHz to 5MHz
Noise
Two-Tone Intermodulation Distortion
(fin = 2.45MHz, 1.975MHz, fs = 10MHz, –0.5dB)
Input Bandwidth (–3dB)
Small Signal (–20dB input)
Large Signal (–0.5dB input)
Feedthrough Rejection (fin = 5MHz)
Slew Rate
Aperture Delay Time
Aperture Uncertainty
S/H Acquisition Time (to ±0.003%FSR, 4V step)
Overvoltage Recovery Time
➄
A/D Conversion Rate
MIN.
—
—
—
+25°C
TYP.
±2
250
6
MAX.
—
—
15
MIN.
—
—
—
0 TO +70°C
TYP.
±2
250
6
MAX.
—
—
15
MIN.
—
—
—
–55 TO +125°C
TYP.
±2
250
6
MAX.
—
—
15
UNITS
Volts
:
pF
+2.0
—
—
—
10
—
—
–0.95
—
—
—
14
—
—
—
—
20
14
±0.75
±0.5
±0.15
±0.1
±0.2
—
—
+0.8
+20
–20
—
—
—
+1.25
±0.4
±0.3
±0.4
—
+2.0
—
—
—
10
—
—
–0.95
—
—
—
14
—
—
—
—
20
14
±0.75
±0.5
±0.15
±0.1
±0.2
—
—
+0.8
+20
–20
—
—
—
+1.25
±0.4
±0.3
±0.4
—
+2.0
—
—
—
10
—
—
–0.95
—
—
—
14
—
—
—
—
20
14
±1
±0.75
±0.4
±0.3
±0.4
—
—
+0.8
+20
–20
—
—
—
+1.5
±0.8
±0.6
±1.5
—
Volts
Volts
μA
μA
ns
Bits
LSB
LSB
%FSR
%FSR
%
Bits
—
—
—
—
—
—
72
72
71
70
70
68
—
—
—
—
—
—
—
—
—
—
10
–83
–78
–76
–81
–76
–74
76
76
75
74
74
73
150
–82
30
10
85
±400
+5
2
40
—
—
–76
–72
–71
–74
–71
–69
—
—
—
—
—
—
—
—
—
—
—
—
—
—
45
100
—
—
—
—
—
—
—
72
72
71
70
70
68
—
—
—
—
—
—
—
—
—
—
10
–83
–78
–76
–81
–76
–74
76
76
75
74
74
73
150
–82
30
10
85
±400
+5
2
40
—
—
–75
–72
–71
–74
–71
–69
—
—
—
—
—
—
—
—
—
—
—
—
—
—
45
100
—
—
—
—
—
—
—
70
70
70
68
66
65
—
—
—
—
—
—
—
—
—
—
10
–79
–73
–71
–77
–72
–69
75
75
75
73
71
70
150
–82
30
10
85
±400
+5
2
40
—
—
–71
–68
–65
–70
–66
–63
—
—
—
—
—
—
—
—
—
—
—
—
—
—
45
100
—
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
μVrms
dB
MHz
MHz
dB
V/μs
ns
ps rms
ns
ns
MHz
DATEL, Inc., 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 Fax: (508) 339-6356 • www.datel.com • data.acquisition@datel.com
03 Jun 2010
MDA_ADS-947.B01
Page 2 of 9
®
®
ADS-947
14-Bit, 10MHz Sampling A/D Converters
+25°C
TYP.
—
—
—
—
MAX.
—
+0.4
–4
+4
MIN.
+2.4
—
—
—
0 TO +70°C
TYP.
MAX.
MIN.
+2.4
—
—
—
–55 TO +125°C
TYP.
—
—
—
—
MAX.
—
+0.4
–4
+4
UNITS
Volts
Volts
mA
mA
DIGITAL OUTPUTS
Logic Levels
Logic "1"
Logic "0"
Logic Loading "1"
Logic Loading "0"
Output Coding
POWER REQUIREMENTS
Power Supply Ranges
➅
+5V Supply
–5.2V Supply
Power Supply Currents
+5V Supply
–5.2V Supply
Power Dissipation
Power Supply Rejection
MIN.
+2.4
—
—
—
—
—
—
+0.4
—
–4
—
+4
Offset Binary
+4.75
–4.75
—
—
—
—
+5.0
–5.2
+250
–200
2.0
—
+5.25
–5.45
+260
–210
2.25
±0.1
+4.75
–4.75
—
—
—
—
+5.0
–5.2
+250
–200
2.0
—
+5.25
–5.45
+260
–210
2.25
±0.1
+4.9
–4.9
—
—
—
—
+5.0
–5.2
+250
–200
2.0
—
+5.25
–5.45
+260
–210
2.25
±0.1
Volts
Volts
mA
mA
Watts
%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
Contact DATEL for other input voltage ranges; the range for ADS-947MC-31122 is
±0.5 Volts.
➂
A 10MHz clock with a 20ns positive pulse width is used for all production testing.
See Timing Diagram, figure 4, for more details.
➃
Effective bits is equal to:
Full Scale Amplitude
(SNR + Distortion) – 1.76 +
20 log
Actual Input Amplitude
6.02
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 –5.1V for ±VDD are required for
–40°C operation only. The minimum limits are +4.75V and –4.95V when operating
at +125°C.
TECHNICAL NOTES
1. Obtaining fully specified performance from the ADS-947 requires care-
ful 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-947 achieves its specified accuracies without the need for exter-
nal 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 calibra-
tion 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.
2k
:
GAIN
ADJUST
1.98k
:
50
:
To Pin 21
of ADS-946
+5V
SIGNAL
INPUT
–5V
Figure 2. Optional ADS-947 Gain Adjust Calibration Circuit
DATEL, Inc., 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 Fax: (508) 339-6356 • www.datel.com • data.acquisition@datel.com
03 Jun 2010
MDA_ADS-947.B01
Page 3 of 9
®
®
ADS-947
14-Bit, 10MHz Sampling A/D Converters
Gain Adjust Procedure
1. Apply +1.99963V to the ANALOG INPUT (pin 21).
2. Adjust the gain potentiometer until all output bits are 1’s and the LSB flick-
ers between 1 and 0.
3. To confirm proper operation of the device, vary the input signal to obtain
the output coding listed in Table 2.
CALIBRATION PROCEDURE
Any offset and/or gain calibration procedures should not be implemented
until devices are fully warmed up. To avoid interaction, offset must be
adjusted before gain. The ranges of adjustment for the circuits in Figures
2 and 3 are guaranteed to compensate for the ADS-947’s initial accuracy
errors and may not be able to compensate for additional system errors.
A/D converters are calibrated by positioning their digital outputs exactly
on the transition point between two adjacent digital output codes. This can
be accomplished by connecting LED’s to the digital outputs and adjusting
until certain LED’s “flicker” equally between on and off. Other approaches
employ digital comparators or microcontrollers to detect when the outputs
change from one code to the next.
Offset adjusting for the ADS-947 is normally accomplished at the point
where the MSB is a 1 and all other output bits are 0’s and the LSB just
changes from a 0 to a 1. This digital output transition ideally occurs when
the applied analog input is +½ LSB (+122μV).
Gain adjusting is accomplished when all bits are 1’s and the LSB just
changes from a 1 to a 0. This transition ideally occurs when the analog
input is at +full scale minus 1½ LSB's (+1.99963V).
INPUT VOLTAGE
RANGE
±2V
ZERO ADJUST
+½ LSB
+122μV
GAIN ADJUST
+FS –1½ LSB
+1.99963V
Table 1. Gain and Zero Adjust
Zero/Offset Adjust Procedure
1. Apply a train of pulses to the START CONVERT input (pin 18) so the con-
verter is continuously converting.
2. Apply +122μV to the ANALOG INPUT (pin 21).
3. Adjust the offset potentiometer until the output bits are 10 0000 0000 0000
and the LSB flickers between 0 and 1.
–5.2V
+5V
BIPOLAR
SCALE
+FS –1 LSB
+3/4 FS
+1/2 FS
0
–1/2 FS
–3/4 FS
–FS +1 LSB
–FS
INPUT RANGE
(±2V RANGE)
+1.99976
+1.50000
+1.00000
0.00000
–1.00000
–1.50000
–1.99976
–2.00000
OFFSET BINARY
MSB
LSB
11 1111 1111 1111
11 1000 0000 0000
11 0000 0000 0000
10 0000 0000 0000
01 0000 0000 0000
00 1000 0000 0000
00 0000 0000 0001
00 0000 0000 0000
Table 2. Output Coding for Bipolar Operation
4.7μF
+
4.7μF 4.7μF
+ +
0.1μF
0.1μF
0.1μF
19
ANALOG
INPUT
+5V
ZERO/
OFFSET
ADJUST
–5V
START
CONVERT
18
20
24
22, 13
14
21
23
20k
ADS-947
1 BIT 1 (MSB)
2 BIT 2
3 BIT 3
4 BIT 4
5 BIT 5
6 BIT 6
7 BIT 7
8 BIT 8
9 BIT 9
10 BIT 10
11 BIT 11
12 BIT 12
15 BIT 13
16 BIT 14 (LSB)
17 DATA VALID
A single +5V supply should be used for both the +5V analog and +5V digital.
If separate supplies are used, the difference between the two cannot exceed 100mV.
Figure 3. Typical ADS-947 Connection Diagram
DATEL, Inc., 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 Fax: (508) 339-6356 • www.datel.com • data.acquisition@datel.com
03 Jun 2010
MDA_ADS-947.B01
Page 4 of 9
®
®
ADS-947
14-Bit, 10MHz Sampling A/D Converters
the device, should be as heavy as possible to help conduct heat away from the
package.
Electrically-insulating, thermally-conductive "pads" may be installed under-
neath the package. Devices should be soldered to boards rather than socketed,
and of course, minimal air flow over the surface can greatly help reduce the
package temperature.
THERMAL REQUIREMENTS
All DATEL sampling A/D converters are fully characterized and specified over
operating temperature (case) ranges of 0 to +70°C and –40 to +100°C. All
room temperature (TA = +25°C) production testing is performed without the
use of heat sinks or forced air cooling. Thermal impedance figures for each
device are listed in their respective specification tables. These devices do not
normally require heat sinks, however, standard precautionary 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
N
START
CONVERT
20ns
typ.
N+1
10ns typ.
INTERNAL S/H
Acquisition Time
35ns
typ.
Hold
65ns typ.
(61ns min., 68ns max.)
25ns typ. (22ns min., 28ns max.)
INTERNAL EOC
15ns
DATA N-1 VALID
DATA
VALID
40ns typ.
(±5ns)
DATA N VALID
40ns typ.
(±5ns)
Conversion Time
70ns typ.
40ns max.
OUTPUT
DATA
DATA N-1 VALID
50ns typ.
(±5ns)
50ns typ.
DATA N VALID
INVALID DATA
Notes:
1. Scale is approximately 5ns per division. Sampling rate = 10MHz.
2. The start convert pulse must be between 20 and 50ns wide or between 80 and 100ns wide (when sampling at 10MHz)
to ensure proper operation. For sampling rates less than 10MHz, the start pulse can be wider than 85nsec, however a minimum
pulse width low of 15nsec should be maintained. A 10MHz clock with a 20nsec positive pulse width is used for all production testing.
3. For no latency delay and an input range of ±0.5 Volts, order ADS-947MC-31122.
Figure 4. ADS-947 Timing Diagram
DATEL, Inc., 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 Fax: (508) 339-6356 • www.datel.com • data.acquisition@datel.com
03 Jun 2010
MDA_ADS-947.B01
Page 5 of 9
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