®
®
ADS-112
12-Bit, 1MHz, Low-Power
Sampling A/D Converters
FEATURES
•
•
•
•
•
•
•
•
12-bit resolution
No missing codes
1MHz minimum sampling rate
Functionally complete
Small 24-pin DDIP
Low-power, 1.3 Watts
Three-state output buffers
Samples to Nyquist frequencies
GENERAL DESCRIPTION
DATEL’s ADS-112 is a 12-bit, functionally complete, sampling
A/D converter that is packaged in a space-saving 24-pin DDIP.
Requiring ±15V and +5V supplies, a minimum sampling rate of
1MHz is achieved while only dissipating 1.3 Watts. The
ADS-112 digitizes signals up to Nyquist frequencies. Models
are available for use in either commercial (0 to + 70°C) or
military (–55 to +125°C) operating temperature ranges.
Typical applications include spectrum, transient, vibration and
waveform analysis. This device is also ideally suited for radar,
sonar, video digitization, medical instrumentation and high-
speed data acquisition systems.
PIN
1
2
3
4
5
6
7
8
9
10
11
12
INPUT/OUTPUT CONNECTIONS
FUNCTION
BIT 12 (LSB)
BIT 11
BIT 10
BIT 9
BIT 8
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1 (MSB)
PIN
24
23
22
21
20
19
18
17
16
15
14
13
FUNCTION
–15V SUPPLY
ANALOG GROUND
+15V SUPPLY
+10V REFERENCE
BIPOLAR
ANALOG INPUT
COMP BIN
ENABLE (1-12)
START CONVERT
EOC
DIGITAL GROUND
+5V SUPPLY
17 ENABLE (1-12)
DAC
12 BIT 1 (MSB)
+10V REF. 21
S
2
S/H
S
1
BIPOLAR 20
REGISTER
BUFFER
FLASH
ADC
REF
DIGITAL CORRECTION LOGIC
3-STATE OUTPUT REGISTER
11 BIT 2
10 BIT 3
9
8
7
6
5
4
3
2
1
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
BIT 10
BIT 11
BIT 12 (LSB)
ANALOG INPUT 19
–
+
COMP BIN 18
START CONVERT 16
EOC 15
TIMING AND
CONTROL LOGIC
13
+5V SUPPLY
14
DIGITAL GROUND
22
+15V SUPPLY
REGISTER
23
ANALOG GROUND
24
–15V SUPPLY
Figure 1. ADS-112 Functional Block Diagram
DATEL, Inc., 11 Cabot Boulevard, Mansfield, MA 02048-1151 (U.S.A.)
•
Tel: (508) 339-3000 Fax: (508) 339-6356
•
For immediate assistance: (800) 233-2765
®
®
ADS-112
ABSOLUTE MAXIMUM RATINGS
PARAMETERS
+15V Supply
(Pin 22)
–15V Supply
(Pin 24)
+5V Supply
(Pin 13)
Digital Inputs
(Pin 16, 17, 18)
Analog Input
(Pin 19)
Lead Temp.
(10 seconds)
LIMITS
0 to +18
0 to –18
0 to +6
–0.3 to +V
DD
+0.3
–9 to +15
+300
UNITS
Volts
Volts
Volts
Volts
Volts
°C
DYNAMIC PERF. (cont)
Signal-to-Noise Ratio
(wo/distort., –0.5dB)
dc to 100kHz
100kHz to 500kHz
Signal-to-Noise Ratio
(& distort., –0.5dB)
dc to 100kHz
100kHz to 500kHz
Two-tone Intermodulation
Distortion
(f
in
= 75kHz,
105kHz, f
s
= 1MHz, –0.7dB)
Two-tone Intermodulation
Distortion
(f
in
= 480kHz,
490kHz, f
s
= 1MHz, –0.7dB)
Input Bandwith
(–3dB)
Small Signal (–20dB input)
Large Signal (–0.5dB input)
Slew Rate
Apperture Delay TIme
Effect. Aperture Delay Time
Apperture Uncertainity (Jitter)
RMS
Peak
Overvoltage Recovery Time
S/H Acquisition Time
Conversion Rate
(Changing Inputs)
+25°C
0°C to +70°C
–55°C to +125°C
DIGITAL OUTPUTS
Output Coding
Pin 18 High
Pin 18 Low
Logic Level
Logic "1"
Logic "0"
Logic Loading "1"
Logic Loading "0"
POWER REQUIREMENTS
Power Supply Ranges
+15V Supply
–15V Supply
+5V Supply
Power Supply Current
+15V Supply
–15V Supply
+5V Supply
Power Dissipation
Power Supply Rejection
PHYSICAL/ENVIRONMENTAL
—
—
+9.98
—
—
±0.1
±0.3
+10.0
±5
—
±0.38
±0.60
+10.02
±30
1.5
%
%
Volts
ppm/°C
mA
Operating Temp. Range, Case
ADS-112MC
ADS-112MM, 883
Storage Temperature Range
Package Type
Weight
See Table 3 also
Effective bits is equal to:
(SNR + Distortion) – 1.76 +
20 log
6.02
Full Scale Amplitude
Actual Input Amplitude
MIN.
TYP.
MAX.
UNITS
68
67
66
66
—
—
8
6
—
—
—
—
—
—
160
1
1
1
72
71
70
70
–88
–68
10
8
±150
—
—
—
—
—
250
—
—
—
—
—
—
—
–80
–65
—
—
—
20
16
15
±50
1000
280
—
—
—
dB
dB
dB
dB
dB
dB
MHz
MHz
V/µs
ns
ns
ps
ps
ns
ns
MHz
MHz
MHz
FUNCTIONAL SPECIFICATIONS
(T
A
= +25°C, ±V
CC
= ±15V, +V
DD
=+5V, 1MHz sampling rate, and a minimum 1 minute
warmup unless otherwise specified.)
ANALOG INPUTS
Input Voltage Range
Bipolar
Unipolar
Input Impedence
Input Capacitance
DIGITAL INPUTS
Logic Levels
Logic "1"
Logic "0"
Logic Loading "1"
Logic Loading "0"
PERFORMANCE
Resolution
No Missing Codes
(12 Bits; f
in
= 1MHz)
Integral Non-Linearity
+25°C
0°C to +70°C
–55°C to +125°C
Differential Non-Linearity
+25°C
0°C to +70°C
–55°C to +125°C
Full Scale Absolute Accuracy
+25°C
0°C to +70°C
–55°C to +125°C
Unipolar Zero Error
†
0°C to +70°C
–55°C to +125°C
Bipolar Zero Error †
0°C to +70°C
–55°C to +125°C
Bipolar Offset Error
†
0°C to +70°C
–55°C to +125°C
Gain Error
†
0°C to +70°C
–55°C to +125°C
Internal Reference Voltage,
+25°C
Drift
External Current
DYNAMIC PERFORMANCE
In-Band Harmonics
(–0.5dB)
dc to 100kHz
100kHz to 500kHz
Total Harm. Distort.
(–0.5dB)
dc to 100kHz
100kHz to 500kHz
† See Tech Note 1
—
—
—
—
–81
–75
–78
–73
–75
–70
–75
–68
dB
dB
dB
dB
12 Bits
Over the operating temperature range
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
±1/4
±1/4
±1/2
±1/4
±1/4
±1/2
±0.13
±0.15
±0.25
±0.074
±0.224
±0.074
±0.124
±0.1
±0.3
±3/4
±3/4
±1.5
±3/4
±3/4
±1
±0.25
±0.44
±0.78
±0.265
±0.43
±0.166
±0.210
±0.38
±0.60
LSB
LSB
LSB
LSB
LSB
LSB
%FSR
%FSR
%FSR
%FSR
%FSR
%FSR
%FSR
%FSR
%FSR
+2.0
—
—
—
—
—
—
—
—
+0.8
+10
–600
Volts
Volts
µA
µA
MIN.
—
—
4.5
—
TYP.
±5
0 to +10
5
6
MAX.
—
—
—
15
UNITS
Volts
Volts
kΩ
pF
Staight binary/Offset binary
Complementary binary
Complementary offset binary
+2.4
—
—
—
—
—
—
—
—
+0.4
–160
+6.4
Volts
Volts
µA
mA
+14.25
–14.25
+4.75
—
—
—
—
—
+15.0
–15.0
+5.0
+24
–40
+80
1.3
—
+15.75
–15.75
+5.25
+35
–48
+95
1.7
±0.07
Volts
Volts
Volts
mA
mA
mA
Watts
%FSR%V
0
—
+70
°C
–55
—
+125
°C
–65
—
+150
°C
24-pin, metal-sealed, ceramic DDIP
0.42 ounces (12 grams)
For ±12V, +5V operation, contact DATEL
2
®
®
ADS-112
TECHNICAL NOTES
1. Applications which are unaffected by endpoint errors or
remove them through software will use the typical connec-
tions shown in Figure 3. Remove system errors or adjust
the small initial errors of the ADS-112 to zero using the
optional external circuitry shown in Figure 4. The external
adjustment circuit has no effect on the throughput rate.
2. For best performance, always connect the analog and
digital ground pins to a ground plane beneath the converter.
The analog and digital grounds are not connected to each
other internally.
3. Bypass the analog and digital supplies and the +10V
reference (pin 21) to ground with 4.7µF, 25V tantalum
electrolytic capacitors in parallel with 0.1µF ceramic
capacitors. Bypass the +10V reference (pin 21) to analog
ground (pin 23).
4. Obtain straight binary/offset binary output coding by tying
COMP BIN (pin 18) to +5V or leaving it open. The device
has an internal pull-up resistor on this pin. To obtain
complementary binary or complementary offset binary
output coding, tie pin 18 to ground. The pin 18 signal is
compatible with CMOS/TTL logic levels for those users
desiring dynamic control of this function.
5. To enable the three-state outputs, connect ENABLE (pin 17)
to a logic "0" (low). To disable, connect pin 17 to a logic "1"
(high).
6. Do not change the status of pin 18 when EOC is high.
7. Re-initiating the START CONVERT (pin 16) while EOC is a
logic "1" (high) will result in a new conversion sequence.
TIMING
Figure 2 shows the relationship between the various input
signals. The timing shown applies over the operating
temperature range and over the operating power supply
range. These times are guaranteed by design.
N
START
CONVERT
150ns, ±25ns
N+1
10ns min.
20ns max.
INTERNAL S/H
Hold
Acquisition Time
250ns
20ns max.
EOC
Conversion Time
600ns max.
60ns max.
35ns max.
OUTPUT
DATA
DATA N-1 VALID
800ns min.
INVALID
DATA
200ns max.
DATA N VALID
INVALID
DATA
Note: Scale is approximately 50ns per division.
Figure 2. ADS-112 Timing Diagram
3
®
®
ADS-112
CALIBRATION PROCEDURE
1. Connect the converter per Figures 3 and 4 and Tables 1 and
3 for the appropriate input range. Apply a pulse of 150
nanoseconds to the START CONVERT input (pin 16) at a
rate of 250kHz. This rate is chosen to reduce the flicker if
LED’s are used on the outputs for calibration purposes.
2.
Zero Adjustments
Apply a precision voltage reference source between the
amplifier’s analog input and ground. Adjust the output of the
reference source per Table 2. For unipolar, adjust the zero
trimming potentiometer so that the output code flickers
equally between 0000 0000 0000 and 0000 0000 0001 with
COMP BIN (pin 18) tied high (straight binary) or between
1111 1111 1111 and 1111 1111 1110 with pin 18 tied low
(complementary binary).
For bipolar operation, adjust the potentiometer such that the
code flickers equally between 1000 0000 0000 and 1000
0000 0001 with pin 18 tied high (offset binary) or between
0111 1111 1111 and 0111 1111 1110 with pin 18 tied low
(complementary offset binary).
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 trimming potentiom-
eter so that the output code flickers equally between 1111
1111 1110 and 1111 1111 1111 for pin 18 tied high or between
0000 0000 0001 and 0000 0000 0000 for pin 18 tied low.
To confirm proper operation of the device, vary the precision
reference voltage source to obtain the output coding listed
in Table 4.
Table 1. Input Range Selection
R2
R1
SIGNAL
INPUT
+15V
5k
Ω
50
Ω
GAIN
ADJUST
5k
Ω
10k
Ω
ZERO/
OFFSET
ADJUST
–15V
To Pin19
of ADS-112
For values of R1 and R2 refer to Table 3.
Figure 4. Optional Calibration Circuit
Table 2. Zero and Gain Adjust
Input
Range
0 to +10V
±5V
Zero Adjust
+1/2 LSB
+1.22mV
+1.22mV
Gain Adjust
+FS – 1 1/2 LSB
+9.9963V
+4.9963V
Table 3. Input Range (using external calibration)
INPUT RANGE
0 to 10V, ±5
0 to 5V, ±2.5V
0 to +2.5V, ±1.25V
R1
2
2
2
R2
2
6
14
UNIT
kΩ
kΩ
kΩ
INPUT RANGE
±5v
0 to +10V
INPUT PIN
Pin 19
Pin 19
TIE TOGETHER
Pin 20 to Pin 21
Pin 20 to Ground
BIPOLAR
OPERATION
20
21
UNIPOLAR
OPERATION
20
21 +10V REF.
+
0.1µF
4.7µF
12 BIT 1 (MSB)
11 BIT 2
10 BIT 3
9 BIT 4
8 BIT 5
7 BIT 6
6
5
4
3
2
1
BIT 7
BIT 8
BIT 9
–15V
4.7µF
4.7µF
+15V
+5V
4.7µF
+
0.1µF
+
0.1µF
24
ADS-112
23
22
13
BIT 10
BIT 11
BIT 12 (LSB)
15 EOC
17 ENABLE (1-12)
16 START CONVERT
19 ANALOG INPUT
+
0.1µF
14
COMP BIN 18
Note: Always bypass pin 21 to ground
+5V
Figure 3. Typical ADS-112 Connection Diagram
4
®
®
ADS-112
Table 4. Output Coding
STRAIGHT BIN.
UNIPOLAR
SCALE
INPUT RANGE
0 to +10V
COMP. BINARY
LSB
INPUT RANGE
±5V
BIPOLAR
SCALE
OUTPUT CODING
MSB LSB
MSB
+FS – 1 LSB
+7/8 FS
+3/4 FS
+1/2 FS
+1/4 FS
+1/8 FS
+1 LSB
0
+9.9976
+8.7500
+7.5000
+5.0000
+2.5000
+1.2500
+0.0024
0.0000
1111
1110
1100
1000
0100
0010
0000
0000
1111
0000
0000
0000
0000
0000
0000
0000
1111
0000
0000
0000
0000
0000
0001
0000
0000
0001
0011
0111
1011
1101
1111
1111
0000
1111
1111
1111
1111
1111
1111
1111
0000
1111
1111
1111
1111
1111
1110
1111
+4.9976
+3.7500
+2.5000
0.0000
–2.5000
–3.7500
–4.9976
–5.0000
+FS –1 LSB
+3/4FS
+1/2FS
0
–1/2FS
–3/4FS
–FS+1LSB
–FS
OFF. BINARY
COMP. OFF. BIN.
0
–10
Amplitude Relative to Full Scale (dB)
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
–130
0
50
100
150
200
250
300
350
400
450
500
Frequency (kHz)
(fs = 1MHz, fin = 485kHz, Vin = –0.5dB, 4,096-point FFT)
Figure 5. FFT Analysis of ADS-112
5
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