®
®
ADS-947
14-Bit, 10MHz
Sampling A/D Converters
PRELIMINARY PRODUCT DATA
FEATURES
•
•
•
•
•
•
•
•
•
•
14-bit resolution
10MHz minimum sampling rate
No missing codes over full military temperature range
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
Low cost
GENERAL DESCRIPTION
The low-cost 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 military (–55 to +125°C) operating
PIN
1
2
3
4
5
6
7
8
9
10
11
12
INPUT/OUTPUT CONNECTIONS
FUNCTION
BIT 1 (MSB)
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
BIT 10
BIT 11
BIT 12
PIN
24
23
22
21
20
19
18
17
16
15
14
13
FUNCTION
ANALOG GROUND
OFFSET ADJUST
+5V ANALOG SUPPLY
ANALOG INPUT
–5.2V SUPPLY
ANALOG GROUND
START CONVERT
DATA VALID
BIT 14 (LSB)
BIT 13
DIGITAL GROUND
+5V DIGITAL SUPPLY
temperature ranges. A proprietary, auto-calibrating, error-
correcting circuit allows the device to achieve specified
performance over the full military temperature range.
OFFSET ADJUST 23
BUFFER
ANALOG INPUT 21
–
S/H
+
FLASH
ADC
1
16 BIT 14 (LSB)
REGISTER
15 BIT 13
12 BIT 12
DIGITAL CORRECTION LOGIC
11 BIT 11
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
DAC
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)
S
START CONVERT 18
DATA VALID 17
TIMING AND
CONTROL LOGIC
Figure 1. ADS-947 Functional Block Diagram
DATEL, Inc., Mansfield, MA 02048 (USA)
•
Tel: (508) 339-3000, (800) 233-2765 Fax: (508) 339-6356
•
Email: sales@datel.com
•
Internet: www.datel.com
REGISTER
®
®
ADS-947
ABSOLUTE MAXIMUM RATINGS
PARAMETERS
+5V Supply
(Pins 13, 22)
–5.2V Supply
(Pin 20)
Digital Input
(Pin 18)
Analog Input
(Pin 21)
Lead Temperature
(10 seconds)
LIMITS
0 to +6
0 to –5.5V
–0.3 to +V
DD
+0.3
±5
+300
UNITS
Volts
Volts
Volts
Volts
°C
PHYSICAL/ENVIRONMENTAL
PARAMETERS
Operating Temp. Range, Case
ADS-947MC, GC
ADS-947MM, GM, 883
Thermal Impedance
θjc
θca
Storage Temperature Range
Package Type
Weight
MIN.
0
–55
TYP.
—
—
MAX.
+70
+125
UNITS
°C
°C
—
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
unless otherwise specified.)
+25°C
ANALOG INPUT
Input Voltage Range
Input Resistance
Input Capacitance
DIGITAL INPUT
Logic Levels
Logic "1"
Logic "0"
Logic Loading "1"
Logic Loading "0"
Start Convert Positive Pulse Width
STATIC PERFORMANCE
Resolution
Integral Nonlinearity
(f
in
= 10kHz)
Differential Nonlinearity
(f
in
= 10kHz)
Full Scale Absolute Accuracy
Bipolar Zero Error
(Tech Note 2)
Gain Error
(Tech Note 2)
No Missing Codes
(f
in
= 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
(& distortion, –0.5dB)
dc to 1MHz
1MHz to 2.5MHz
2.5MHz to 5MHz
Noise
Two-tone Intermodulation
Distortion
(f
in
= 2.45MHz,
1.975MHz, f
s
= 10MHz, –0.5dB)
Input Bandwidth
(–3dB)
Small Signal (–20dB input)
Large Signal (–0.5dB input)
Feedthrough Rejection
(f
in
= 5MHz)
Slew Rate
Aperture Delay Time
Aperture Uncertainty
—
—
—
—
—
—
72
72
71
70
70
68
—
—
—
—
—
—
—
—
–83
–78
–76
–81
–76
–74
76
76
75
74
74
73
150
–82
30
10
85
±400
+5
2
–76
–72
–71
–74
–71
–69
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
72
72
71
70
70
68
—
—
—
—
—
—
—
—
–83
–78
–76
–81
–76
–74
76
76
75
74
74
73
150
–82
30
10
85
±400
+5
2
–75
–72
–71
–74
–71
–69
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
70
70
70
68
66
65
—
—
—
—
—
—
—
—
–79
–73
–71
–77
–72
–69
75
75
75
73
71
70
150
–82
30
10
85
±400
+5
2
–71
–68
–65
–70
–66
–63
—
—
—
—
—
—
—
—
—
—
—
—
—
—
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
µVrms
dB
MHz
MHz
dB
V/µs
ns
ps rms
—
—
–0.95
—
—
—
14
14
±0.75
±0.5
±0.15
±0.1
±0.2
—
—
—
+1.25
±0.4
±0.3
±0.4
—
—
—
–0.95
—
—
—
14
14
±0.75
±0.5
±0.15
±0.1
±0.2
—
—
—
+1.25
±0.4
±0.3
±0.4
—
—
—
–0.95
—
—
—
14
14
±1
±0.5
±0.4
±0.3
±0.4
—
—
—
+1.5
±0.8
±0.6
±1.5
—
Bits
LSB
LSB
%FSR
%FSR
%
Bits
+2.0
—
—
—
10
—
—
—
—
20
—
+0.8
+20
–20
—
+2.0
—
—
—
10
—
—
—
—
20
—
+0.8
+20
–20
—
+2.0
—
—
—
10
—
—
—
—
20
—
+0.8
+20
–20
—
Volts
Volts
µA
µA
ns
MIN.
—
—
—
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
Ω
pF
2
®
®
ADS-947
+25°C
DYNAMIC PERFORMANCE
(Cont.)
S/H Acquisition Time
( to ±0.003%FSR, 4V step)
Overvoltage Recovery Time
A/D Conversion Rate
DIGITAL OUTPUTS
Logic Levels
Logic "1"
Logic "0"
Logic Loading "1"
Logic Loading "0"
Output Coding
POWER REQUIREMENTS
Power Supply Ranges
+5V Supply
–5.2V Supply
Power Supply Currents
+5V Supply
–5.2V Supply
Power Dissipation
Power Supply Rejection
+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
—
—
—
—
+2.4
—
—
—
—
—
—
—
—
+0.4
–4
+4
+2.4
—
—
—
MIN.
—
—
10
TYP.
40
—
—
MAX.
45
100
—
MIN.
—
—
10
0 to +70°C
TYP.
40
—
—
MAX.
45
100
—
MIN.
—
—
10
–55 to +125°C
TYP.
40
—
—
MAX.
45
100
—
UNITS
ns
ns
MHz
—
—
—
+0.4
—
–4
—
+4
Offset Binary
+2.4
—
—
—
—
—
—
—
—
+0.4
–4
+4
Volts
Volts
mA
mA
+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:
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.
Contact DATEL for other input voltage ranges.
A 10MHz clock with a 20ns positive pulse width is used for all production
testing. See Timing Diagram, figure 4, for more details.
Effective bits is equal to:
(SNR + Distortion) – 1.76 +
20 log
6.02
Full Scale Amplitude
Actual Input Amplitude
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).
The minimum supply voltages of +4.9V and –5.1V for ±V
DD
are required for
–55°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 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-947 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 gain
calibration hardware, make adjustments following warmup.
To avoid interaction, always adjust offset before gain.
SIGNAL
INPUT
50Ω
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.
2kΩ
GAIN
ADJUST
+5V
1.98kΩ
To Pin 21
of ADS-947
–5V
Figure 2. Optional ADS-947 Gain Adjust Calibration Circuit
3
®
®
ADS-947
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).
Zero/Offset Adjust Procedure
1. Apply a train of pulses to the START CONVERT input (pin
18) so the converter 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.
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 flickers 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.
Table 1. Gain and Zero Adjust
INPUT VOLTAGE
RANGE
±2V
ZERO ADJUST
+½ LSB
+122µV
GAIN ADJUST
+FS –1½ LSB
+1.99963V
Table 2. Output Coding for Bipolar Operation
BIPOLAR
SCALE
+FS –1 LSB
+3/4 FS
+1/2 FS
0
–1/2 FS
–3/4 FS
–FS +1 LSB
–FS
INPUT VOLTAGE
(±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
–5.2V
+5V
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
1
2
3
4
5
6
7
8
9
10
11
12
15
16
17
BIT 1 (MSB)
BIT 2
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)
DATA VALID
23
20kW
ADS-947
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
4
®
®
ADS-947
THERMAL REQUIREMENTS
All DATEL sampling A/D converters are fully characterized
and specified over operating temperature (case) ranges of
0 to +70°C and –55 to +125°C. All room temperature
(T
A
= +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 the device, should be as heavy as possible
to help conduct heat away from the package.
Electrically-insulating, thermally-conductive "pads" may be
installed underneath 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.
In more severe ambient conditions, the package/junction
temperature of a given device can be reduced dramatically
(typically 35%) by using one of DATEL's HS Series heat sinks.
See Ordering Information for the assigned part number. See
page 1-183 of the DATEL Data Acquisition Components Catalog
for more information on the HS Series. Request DATEL
Application Note AN8, "Heat Sinks for DIP Data Converters",
or contact DATEL directly, for additional information.
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.
Figure 4. ADS-947 Timing Diagram
5
Talking
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