ETC ADS

®
®
ADS-951
18-Bit, 1MHz, Low-Power
Sampling A/D Converters
PRELIMINARY PRODUCT DATA
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
Ideal for both time and frequency-domain applications
Low cost
INPUT/OUTPUT CONNECTIONS
GENERAL DESCRIPTION
The ADS-951 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 total
harmonic distortion (THD), makes the ADS-951 the ideal
choice for both time-domain (medical imaging, scanners,
process control) and frequency-domain (radar, telecommunications, spectrum analysis) applications.
Packaged in a 32-pin, side-brazed, metal-sealed, ceramic
TDIP, the functionally complete ADS-951 contains a fastsettling sample-hold amplifier, a subranging (two-pass) A/D
converter, an internal reference, timing/control logic, and errorcorrection circuitry. Digital input and output levels are TTL, and
the ADS-951 only requires the rising edge of the start convert
pulse to operate.
Requiring ±15V and ±5V supplies, the ADS-951 typically
dissipates 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)
PIN
FUNCTION
PIN
FUNCTION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
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
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
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)
operating temperature ranges. A proprietary, auto-calibrating,
error-correcting circuit enables the device to achieve specified performance over the full military temperature range.
–
30 BIT 5
29 BIT 6
REF
DAC
5
+5V REFERENCE OUT 5
COMPENSATION 7
FLASH
ADC
2
AMP
28 BIT 7
DIGITAL CORRECTION LOGIC
GAIN
CIRCUIT
BIT 2
31 BIT 4
FLASH
ADC
1
S/H
+
GAIN ADJUST 6
BIT 1 (MSB)
1
32 BIT 3
BUFFER
ANALOG INPUT 4
2
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)
START CONVERT 16
TIMING AND
CONTROL LOGIC
EOC 15
10
11
3, 12
14
9
8
13
+5V ANALOG
SUPPLY
–5V ANALOG
SUPPLY
ANALOG
GROUND
+5V DIGITAL
SUPPLY
+15V
SUPPLY
–15V
SUPPLY
DIGITAL
GROUND
Figure 1. ADS-951 Functional Block Diagram
DATEL, Inc., Mansfield, MA 02048 (USA) • Tel: (508) 339-3000, (800) 233-2765 Fax: (508) 339-6356 • Email: [email protected] • Internet: www.datel.com
®
®
ADS-951
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)
PHYSICAL/ENVIRONMENTAL
LIMITS
UNITS
0 to +16
0 to –16
0 to +6
0 to –6
–0.3 to +VDD +0.3
±15
+300
Volts
Volts
Volts
Volts
Volts
Volts
°C
PARAMETERS
MIN.
TYP.
MAX.
UNITS
Operating Temp. Range, Case
ADS-951MC
0
—
+70
°C
ADS-951ME
–40
—
+110
°C
Thermal Impedance
θjc
—
5
—
°C/Watt
θca
—
22
—
°C/Watt
Storage Temperature Range
–65
—
+150
°C
Package Type
32-pin,side-brazed, metal-sealed, ceramic TDIP
Weight
0.46 ounces (13 grams)
FUNCTIONAL SPECIFICATIONS
(TA = +25°C, ±VCC = ±15V, ±VDD = ±5V, 1MHz sampling rate, and a minimum 1 minute warmup ➀ unless otherwise specified.)
ANALOG INPUT
Input Voltage Range ➁
Input Resistance
Input Capacitance
MIN.
+25°C
TYP.
MAX.
MIN.
0 to +70°C
TYP.
MAX.
—
—
—
±5
500
7
—
—
15
—
—
—
±5
500
7
—
—
15
—
—
—
±5
500
7
—
—
15
Volts
Ω
pF
+2.0
—
—
—
20
—
—
—
—
500
—
+0.8
+20
–20
—
+2.0
—
—
—
20
—
—
—
—
500
—
+0.8
+20
–20
—
+2.0
—
—
—
20
—
—
—
—
500
—
+0.8
+20
–20
—
Volts
Volts
µA
µA
ns
—
—
–0.95
—
—
—
—
18
18
±10
±0.5
±0.1
±0.1
±0.1
±0.1
—
—
—
+1
±0.25
±0.15
±0.2
±0.25
—
—
—
–0.95
—
—
—
—
18
18
±10
±0.5
±0.25
±0.15
±0.2
±0.25
—
—
—
+1
±0.4
±0.25
±0.3
±0.4
—
—
—
–0.95
—
—
—
—
18
18
±15
±0.50
±0.4
±0.25
±0.3
±0.4
—
—
—
+1.25
±0.8
±0.5
±0.6
±0.9
—
Bits
LSB
LSB
%FSR
%FSR
%FSR
%
Bits
MIN.
–40 to +110°C
TYP.
MAX.
UNITS
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)
Bipolar Offset Error (Tech Note 2)
Gain Error (Tech Note 2)
No Missing Codes (fin = 10kHz)
DYNAMIC PERFORMANCE (500kHz Sampling Rate)
Peak Harmonics (–0.5dB)
dc to 100kHz
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 (fin = 100kHz,
240kHz, fs = 500kHz, –0.5dB)
Input Bandwidth (–3dB)
Small Signal (–20dB input)
Large Signal (–0.5dB input)
Feedthrough Rejection (fin = 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
—
–87
–80
—
–87
–80
—
–82
—
dB
—
–85
–80
—
–85
–80
—
–81
—
dB
91
93
—
91
93
—
—
92
—
dB
76
—
84
76
—
—
76
—
84
76
—
—
—
—
80
76
—
—
dB
µVrms
—
–85
—
—
–85
—
—
–81
—
dB
—
—
—
—
—
—
TBD
TBD
84
TBD
+20
5
—
—
—
—
—
—
—
—
—
—
—
—
TBD
TBD
84
TBD
+20
5
—
—
—
—
—
—
—
—
—
—
—
—
TBD
TBD
84
TBD
+20
5
—
—
—
—
—
—
MHz
MHz
dB
V/µs
ns
ps rms
—
—
1
260
500
—
—
—
—
—
—
1
260
500
—
—
—
—
—
—
1
260
500
—
—
—
—
ns
ns
MHz
2
®
®
ADS-951
+25°C
0 to +70°C
–40 to +110°C
ANALOG OUTPUT
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
UNITS
Internal Reference
Voltage
Drift
External Current
+4.95
—
—
+5.0
±30
1
+5.05
—
—
+4.95
—
—
+5.0
±30
1
+5.05
—
—
+4.95
—
—
+5.0
±30
1
+5.05
—
—
Volts
ppm/°C
mA
+2.4
—
—
—
—
—
—
—
—
+0.4
–4
+4
+2.4
—
—
—
+2.4
—
—
—
—
—
—
—
—
+0.4
–4
+4
Volts
Volts
mA
mA
+14.5
–14.5
+4.75
–4.75
+15.0
–15.0
+5.0
–5.0
+15.5
–15.5
+5.25
–5.25
+14.5
–14.5
+4.75
–4.75
+15.0
–15.0
+5.0
–5.0
+15.5
–15.5
+5.25
–5.25
+14.5
–14.5
+4.75
–4.75
+15.0
–15.0
+5.0
–5.0
+15.5
–15.5
+5.25
–5.25
Volts
Volts
Volts
Volts
—
—
—
—
—
—
+29
–15
+104
–54
1.45
—
—
—
—
—
1.65
±0.05
—
—
—
—
—
—
+29
–15
+104
–54
1.45
—
—
—
—
—
1.65
±0.05
—
—
—
—
—
—
+29
–15
+104
–54
1.45
—
—
—
—
—
1.65
±0.05
mA
mA
mA
mA
Watts
%FSR/%V
DIGITAL OUTPUTS
Logic Levels
Logic "1"
Logic "0"
Logic Loading "1"
Logic Loading "0"
Output Coding
—
—
—
+0.4
—
–4
—
+4
Complementary Offset Binary
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
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.
➃ Effective bits is equal to:
(SNR + Distortion) – 1.76 +
➁ Contact DATEL for other input voltage ranges.
20 log
Full Scale Amplitude
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.
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.
TECHNICAL NOTES
1. Obtaining fully specified performance from the ADS-951
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
package.
3. Applying a start convert pulse while a conversion is in
progress (EOC = logic "1") will initiate a new and probably
inaccurate conversion cycle. Data for the interrupted and
subsequent conversions will be invalid.
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 (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.
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-951 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 adjustments following warmup. To avoid interaction, always adjust
offset before gain. Float pin 6 if not using gain adjust
circuits.
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.
3
®
®
ADS-951
CALIBRATION PROCEDURE
Connect the converter per Table 1 for the appropriate input
voltage 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-951's initial accuracy errors and may
not be able to compensate for additional system errors.
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.
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.
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.
For the ADS-951, offset adjusting is normally accomplished
when the analog input is 0 minus ½LSB (–19µV). See Table 2
for the proper bipolar output coding.
3. To confirm proper operation of the device, vary the applied
input voltage to obtain the output coding listed in Table 2.
Gain adjusting is accomplished when the analog input is at
nominal full scale minus 1½LSB's (–4.999943V).
Table 1. Input Connections
INPUT VOLTAGE
RANGE
±5V
ZERO ADJUST
(–½ LSB)
GAIN ADJUST
(–FS +1½ LSB)
–19µV
–4.999943
Table 2. Output Coding
COMPLEMENTARY
OFFSET BINARY
BIPLOAR
SCALE
INPUT VOLTAGE
±5V
+FS –1 LSB
+3/4 FS
+1/2 FS
0
–1/2 FS
–3/4 FS
–FS +1 LSB
–FS
+4.999962
+3.750000
+2.500000
+0.000000
–2.500000
–3.750000
–4.999962
–5.000000
4
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
®
®
ADS-951
Pin 5 (ADS-951)
10k9
15
6
GAIN
ADJUST
10µF
0.1µF
32 BIT 3
31 BIT 4
30 BIT 5
13 DIGITAL
GROUND
8
10µF
+
10µF
0.1µF
+
–15V
0.1µF
12 ANALOG
GROUND
ADS-951
9
+
10µF
3 ANALOG
GROUND
0.1µF
+
10µF
0.1µF
START CONVERT
11
COMPENSATION
BIT 6
BIT 7
BIT 8
BIT 9
BIT 10
24
23
22
21
BIT 11
BIT 12
BIT 13
BIT 14
16
7
47µF
+
5 +5V
REF. OUT
ANALOG INPUT
0.1µF
29
28
27
26
25
20 BIT 15
19 BIT 16
18 BIT 17
17 BIT 18 (LSB)
10
+5V ANALOG
–5V ANALOG
2 BIT 1 (MSB)
1 BIT 2
14
+5V DIGITAL
+15V
EOC
4
10µF
Figure 2. Typical ADS-951 Connection Diagram
N
START
CONVERT
N+1
500ns typ.
5ns typ.
INTERNAL S/H
Acquisition Time
740ns typ.
260ns typ.
Hold
65ns typ.
EOC
Conversion Time
730ns typ.
20ns typ.
OUTPUT
DATA
Invalid Data
20ns
Data N-1 Valid
Data N-2 Valid
980ns typ.
Scale is approximately 50ns per division.
Figure 3. ADS-951 Timing Diagram
5
N
®
®
ADS-951
MECHANICAL DIMENSIONS INCHES (mm)
1.62 MAX.
(41.15)
Dimension Tolerances
(unless otherwise indicated):
2 place decimal (.XX) ±0.010 (±0.254)
3 place decimal (.XXX) ±0.005 (±0.127)
0.92 MAX.
(23.37)
Lead Material: Kovar Alloy
Lead Finish: 50 microinches (minimum)
gold plating over 100 microinches
(nominal) nickel plating
1.50 TYP
(38.10)
SEATING PLANE
0.05 TYP.
(1.27)
0.220 TYP.
(6.86)
PIN 1 INDEX
0.010 TYP.
(0.254)
0.05 TYP.
(1.27)
0.018 TYP.
(0.46)
0.100 TYP.
(2.54)
0.90 TYP.
(22.86)
0.175 TYP
(4.45)
0.05 TYP.
(1.27)
ORDERING INFORMATION
MODEL NUMBER
OPERATING
TEMP. RANGE
32-PIN
PACKAGE
ADS-951MC
ADS-951ME
0 to +70°C
–40 to +110°C
TDIP
TDIP
ACCESSORIES
ADS-B951
Evaluation Board (without ADS-951)
Receptacles for PC board mounting can be ordered through AMP, Inc., Part # 3-331272-8
(Component Lead Socket), 32 required. For availability of MIL-STD-883 product, contact DATEL.
®
®
ISO 9001
R E G I S T E R E D
DS-0366Preliminary
DATEL, Inc. 11 Cabot Boulevard, Mansfield, MA 02048-1151
Tel: (508) 339-3000 (800) 233-2765
Fax: (508) 339-6356
Email: [email protected] Internet: www.datel.com
01/02
DATEL (UK) LTD. Tadley, England Tel: (01256)-880444
DATEL S.A.R.L. Montigny Le Bretonneux, France Tel: 01-34-60-01-01
DATEL GmbH München, Germany Tel: 89-544334-0
DATEL KK Tokyo, Japan Tel: 3-3779-1031, Osaka Tel: 6-6354-2025
DATEL 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. Specifications are subject to change without notice. The DATEL logo is a registered DATEL, Inc. trademark.