®
®
ADS-953
18-Bit, 1MHz, Low-Distortion
Sampling A/D Converters
A SUBSIDIARY OF C&D TECHNOLOGIES
FEATURES
•
•
•
•
•
•
•
•
•
18-bit resolution
1MHz minimum sampling rate
No missing codes over extended temperature range
Very low power, 1.45 Watts
Small, 32-pin, side-brazed, ceramic TDIP
Edge-triggered
Excellent performance, –95dB peak harmonics
Ideal for both time and frequency-domain applications
Low cost
PIN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
INPUT/OUTPUT CONNECTIONS
FUNCTION
BIT 2
BIT 1 (MSB)
ANALOG GROUND
ANALOG INPUT
+5V REFERENCE OUT
GAIN ADJUST
COMPENSATION
–15V SUPPLY
+15V SUPPLY
+5V ANALOG SUPPLY
–5V ANALOG SUPPLY
ANALOG GROUND
DIGITAL GROUND
+5V DIGITAL SUPPLY
EOC
START CONVERT
PIN
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
FUNCTION
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
BIT 10
BIT 11
BIT 12
BIT 13
BIT 14
BIT 15
BIT 16
BIT 17
BIT 18 (LSB)
GENERAL DESCRIPTION
The ADS-953 is an 18-bit, 1MHz sampling A/D converter. This
device accurately samples full-scale input signals up to Nyquist
frequencies with no missing codes. This feature, combined with
excellent signal-to-noise ratio (SNR) and –95dB peak harmonic
distortion (THD), makes the ADS-953 the ideal choice for both
time-domain (medical imaging, scanners, process control) and
frequency-domain (radar, telecommunications, spectrum analy-
sis) applications.
Packaged in a 32-pin, side-brazed, metal-sealed, ceramic TDIP,
the functionally complete ADS-953 contains a fast-settling sam-
ple-hold amplifier, a subranging (two-pass) A/D converter, an
internal reference, timing/control logic, and error-correction cir-
cuitry. Digital input and output levels are TTL, and the ADS-953
only requires the rising edge of the start convert pulse to
operate.
Requiring ±15V and ±5V supplies, the ADS-953 typically dis-
sipates 1.45 Watts. The device is offered with a bipolar (±5V)
analog input range. Models are available for use in either
commercial (0 to +70°C) or extended (–40 to +110°C) operat-
ing temperature ranges. A proprietary, auto-calibrating, error-
correcting circuit enables the device to achieve specified per-
formance over the full military temperature range.
2
1
BIT 1 (MSB)
BIT 2
BUFFER
ANALOG INPUT 4
32 BIT 3
–
+
S/H
FLASH
ADC
1
DIGITAL CORRECTION LOGIC
31 BIT 4
30 BIT 5
29 BIT 6
28 BIT 7
27 BIT 8
26 BIT 9
25 BIT 10
24 BIT 11
23 BIT 12
22 BIT 13
21 BIT 14
20 BIT 15
19 BIT 16
18 BIT 17
17 BIT 18 (LSB)
GAIN ADJUST 6
GAIN
CIRCUIT
REF
+5V REFERENCE OUT 5
COMPENSATION 7
Σ
DAC
AMP
FLASH
ADC
2
START CONVERT 16
EOC 15
TIMING AND
CONTROL LOGIC
10
+5V ANALOG
SUPPLY
11
–5V ANALOG
SUPPLY
3, 12
ANALOG
GROUND
14
+5V DIGITAL
SUPPLY
9
+15V
SUPPLY
8
–15V
SUPPLY
13
DIGITAL
GROUND
Figure 1. ADS-953 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
®
®
ADS-953
ABSOLUTE MAXIMUM RATINGS
PARAMETERS
+15V Supply
(Pin 9)
–15V Supply
(Pin 8)
+5V Supply
(Pins 10, 14)
–5V Supply
(Pin 11)
Digital Input
(Pin 16)
Analog Input
(Pin 4)
Lead Temperature
(10 seconds)
LIMITS
0 to +16
0 to –16
0 to +6
0 to –6
–0.3 to +V
DD
+0.3
±15
+300
UNITS
Volts
Volts
Volts
Volts
Volts
Volts
°C
PHYSICAL/ENVIRONMENTAL
PARAMETERS
Operating Temp. Range, Case
ADS-953MC
ADS-953ME
Thermal Impedance
θjc
θca
Storage Temperature Range
Package Type
Weight
MIN.
0
–40
TYP.
—
—
MAX.
+70
+110
UNITS
°C
°C
—
5
—
°C/Watt
—
22
—
°C/Watt
–65
—
+150
°C
32-pin,side-brazed, metal-sealed, ceramic TDIP
0.46 ounces (13 grams)
FUNCTIONAL SPECIFICATIONS
(T
A
= +25°C, ±V
CC
= ±15V, ±V
DD
= ±5V, 1MHz sampling rate, and a minimum 1 minute warmup
➀
unless otherwise specified.)
+25°C
TYP.
±5
500
7
0 to +70°C
TYP.
±5
500
7
–40 to +110°C
MIN.
TYP.
MAX.
—
—
—
±5
500
7
—
—
15
ANALOG INPUT
Input Voltage Range
➁
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
(f
in
= 10kHz)
Differential Nonlinearity
(f
in
= 10kHz)
Full Scale Absolute Accuracy
Bipolar Zero Error
(Tech Note 2)
Bipolar Offset Error
(Tech Note 2)
Gain Error
(Tech Note 2)
No Missing Codes
(f
in
= 10kHz)
Peak Harmonics
(–0.5dB)
dc to 1kHz
Total Harmonic Distortion
(–0.5dB)
dc to 100kHz
Signal-to-Noise Ratio
(w/o distortion, –0.5dB)
dc to 100kHz
Signal-to-Noise Ratio
➃
(& distortion, –0.5dB)
dc to 100kHz
DC Noise
Two-Tone Intermodulation
Distortion
(f
in
= 100kHz,
240kHz, f
s
= 500kHz, –0.5dB)
Input Bandwidth
(–3dB)
Small Signal (–20dB input)
Large Signal (–0.5dB input)
Feedthrough Rejection
(f
in
= 500kHz)
Slew Rate
Aperture Delay Time
Aperture Uncertainty
S/H Acquisition Time
( to ±0.003%FSR, 10V step)
Overvoltage Recovery Time
➄
A/D Conversion Rate
MIN.
—
—
—
MAX.
—
—
15
MIN.
—
—
—
MAX.
—
—
15
UNITS
Volts
Ω
pF
+2.0
—
—
—
20
—
—
–0.95
—
—
—
—
18
—
—
—
—
500
18
±10
±0.5
±0.1
±0.1
±0.1
±0.1
—
—
+0.8
+20
–20
—
—
—
+1
±0.25
±0.15
±0.2
±0.25
—
+2.0
—
—
—
20
—
—
–0.95
—
—
—
—
18
—
—
—
—
500
18
±10
±0.5
±0.25
±0.15
±0.2
±0.25
—
—
+0.8
+20
–20
—
—
—
+1
±0.4
±0.25
±0.3
±0.4
—
+2.0
—
—
—
20
—
—
–0.95
—
—
—
—
18
—
—
—
—
500
18
±15
±0.50
±0.4
±0.25
±0.3
±0.4
—
—
+0.8
+20
–20
—
—
—
+1.25
±0.8
±0.5
±0.6
±0.9
—
Volts
Volts
µA
µA
ns
Bits
LSB
LSB
%FSR
%FSR
%FSR
%
Bits
DYNAMIC PERFORMANCE
(500kHz Sampling Rate)
—
—
91
76
—
—
—
—
—
—
—
—
—
—
1
–95
–85
93
84
76
–85
TBD
TBD
84
TBD
+20
5
260
500
—
–93
–80
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
91
76
—
—
—
—
—
—
—
—
—
—
1
–95
–85
93
84
76
–85
TBD
TBD
84
TBD
+20
5
260
500
—
–93
–80
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
1
–82
–81
92
80
76
–81
TBD
TBD
84
TBD
+20
5
260
500
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
dB
dB
dB
dB
µVrms
dB
MHz
MHz
dB
V/µs
ns
ps rms
ns
ns
MHz
2
®
®
ADS-953
+25°C
ANALOG OUTPUT
Internal Reference
Voltage
Drift
External Current
DIGITAL OUTPUTS
Logic Levels
Logic "1"
Logic "0"
Logic Loading "1"
Logic Loading "0"
Output Coding
POWER REQUIREMENTS
Power Supply Ranges
+15V Supply
–15V Supply
+5V Supply
–5V Supply
Power Supply Currents
+15V Supply
–15V Supply
+5V Supply
–5V Supply
Power Dissipation
Power Supply Rejection
+14.5
–14.5
+4.75
–4.75
—
—
—
—
—
—
+15.0
–15.0
+5.0
–5.0
+29
–15
+104
–54
1.45
—
+15.5
–15.5
+5.25
–5.25
—
—
—
—
1.65
±0.05
+14.5
–14.5
+4.75
–4.75
—
—
—
—
—
—
+15.0
–15.0
+5.0
–5.0
+29
–15
+104
–54
1.45
—
+15.5
–15.5
+5.25
–5.25
—
—
—
—
1.65
±0.05
+14.5
–14.5
+4.75
–4.75
—
—
—
—
—
—
+15.0
–15.0
+5.0
–5.0
+29
–15
+104
–54
1.45
—
+15.5
–15.5
+5.25
–5.25
—
—
—
—
1.65
±0.05
Volts
Volts
Volts
Volts
mA
mA
mA
mA
Watts
%FSR/%V
+2.4
—
—
—
—
—
—
—
—
+0.4
–4
+4
+2.4
—
—
—
—
+0.4
—
—
–4
—
—
+4
Complementary Offset Binary
+2.4
—
—
—
—
—
—
—
—
+0.4
–4
+4
Volts
Volts
mA
mA
MIN.
+4.95
—
—
TYP.
+5.0
±30
1
MAX.
+5.05
—
—
MIN.
+4.95
—
—
0 to +70°C
TYP.
+5.0
±30
1
MAX.
+5.05
—
—
MIN.
+4.95
—
—
–40 to +110°C
TYP.
+5.0
±30
1
MAX.
+5.05
—
—
UNITS
Volts
ppm/°C
mA
Footnotes:
➀
All power supplies must be on before applying a start convert pulse. All supplies
and the clock (START CONVERT) 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 1MHz clock with a 500nsec positive pulse width (50% duty cycle) is used for
all production testing. Any duty cycle may be used as long as a minimum
positive pulse width of 20nsec is maintained. For applications requiring lower
sampling rates, clock frequencies lower than 1MHz may be used.
➃
Effective bits is equal to:
(SNR + Distortion) – 1.76 +
20 log
6.02
Full Scale Amplitude
Actual Input Amplitude
➄
This is the time required before the A/D output data is valid once the analog input
is back within the specified range.
TECHNICAL NOTES
1. Obtaining fully specified performance from the ADS-953
requires careful attention to pc-card layout and power
supply decoupling. The device's analog and digital ground
systems are not connected to each other internally. For
optimal performance, tie all ground pins (3, 12 and 13)
directly to a large
analog
ground plane beneath the pack-
age.
Bypass all power supplies and the +5V REFERENCE
OUTPUT (pin 5) to ground with 10µF tantalum capacitors in
parallel with 0.1µF ceramic capacitors. Locate the bypass
capacitors as close to the unit as possible. Tie a 47µF
capacitor between COMPENSATION (pin 7) and ground.
2. The ADS-953 achieves its specified accuracies without the
need for external calibration. If required, the device's small
initial errors can be reduced to zero using the adjustment
circuitry shown in Figure 2. When using this circuitry, or any
similar offset and gain calibration hardware, make adjust-
ments following warmup. To avoid interaction, always adjust
offset before gain. Float pin 6 if not using gain adjust
circuits.
3. Applying a start convert pulse while a conversion is in prog-
ress (EOC = logic "1") will initiate a new and probably
inaccurate conversion cycle. Data for the interrupted and
subsequent conversions will be invalid.
3
®
®
ADS-953
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 +110°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 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.
Zero/Offset Adjust Procedure
1. Apply a train of pulses to the START CONVERT input
(pin 16) so that the converter is continuously converting.
2. For bipolar zero/offset adjust, apply –19µV to the ANALOG
INPUT (pin 4).
3. Adjust the offset potentiometer until the output code flickers
equally between 01 1111 1111 1111 1111 and 10 0000
0000 0000 0000.
Gain Adjust Procedure
1. Apply –4.999943V to the ANALOG INPUT (pin 4).
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 applied
input voltage to obtain the output coding listed in Table 2.
Table 1. Input Connections
CALIBRATION PROCEDURE
Connect the converter per Table 1 for the appropriate input volt-
age range. Any offset/gain calibration procedures should not
be implemented until the device is fully warmed up. To avoid
interaction, adjust offset before gain. The ranges of adjustment
for the circuits in Figure 2 are guaranteed to compensate for
the ADS-953'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 is accomplished by connecting LED's to
the digital outputs and performing adjustments 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.
For the ADS-953, offset adjusting is normally accomplished
when the analog input is 0 minus ½LSB (–19µV). See Table 2
for the proper bipolar output coding.
Gain adjusting is accomplished when the analog input is at
nominal full scale minus 1½LSB's (–4.999943V).
INPUT VOLTAGE
RANGE
±5V
ZERO ADJUST
(–½ LSB)
–19µV
GAIN ADJUST
(–FS +1½ LSB)
–4.999943
Table 2. Output Coding
COMPLEMENTARY
OFFSET BINARY
BIPLOAR
SCALE
+FS –1 LSB
+3/4 FS
+1/2 FS
0
–1/2 FS
–3/4 FS
–FS +1 LSB
–FS
INPUT
VOLTAGE ±5V
+4.999962
+3.750000
+2.500000
+0.000000
–2.500000
–3.750000
–4.999962
–5.000000
OUTPUT CODING
MSB
00
00
00
01
10
11
11
11
LSB
0000 0000 0000 0000
0111 1111 1111 1111
1111 1111 1111 1111
1111 1111 1111 1111
1111 1111 1111 1111
0111 1111 1111 1111
1111 1111 1111 1110
1111 1111 1111 1111
4
®
®
ADS-953
Pin 5 (ADS-953)
10kΩ
6
GAIN
ADJUST
15
EOC
2 BIT 1 (MSB)
1 BIT 2
32 BIT 3
31 BIT 4
30 BIT 5
29 BIT 6
28 BIT 7
27 BIT 8
26 BIT 9
25 BIT 10
24 BIT 11
+5V DIGITAL
10µF
0.1µF
14
13 DIGITAL
GROUND
8
10µF
10µF
0.1µF
0.1µF
12 ANALOG
GROUND
9
–15V
+
+15V
+
ADS-953
23 BIT 12
22 BIT 13
21 BIT 14
20 BIT 15
19 BIT 16
18 BIT 17
17 BIT 18 (LSB)
START CONVERT
COMPENSATION
16
7
4
47µF
+
+5V ANALOG
10µF
10
+
0.1µF
+
0.1µF
3 ANALOG
GROUND
11
5 +5V
REF. OUT
0.1µF
10µF
–5V ANALOG
10µF
ANALOG INPUT
Figure 2. Typical ADS-953 Connection Diagram
N
START
CONVERT
500ns typ.
N+1
5ns typ.
INTERNAL S/H
740ns typ.
Hold
Acquisition Time
260ns typ.
65ns typ.
EOC
Conversion Time
730ns typ.
20ns typ.
OUTPUT
DATA
Data N-2 Valid
Scale is approximately 50ns per division.
Invalid Data
Data N-1 Valid
980ns typ.
20ns
N
Figure 3. ADS-953 Timing Diagram
5
Microcontroller MCU
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