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ADS-946
14-Bit, 8MHz Sampling A/D Converters
INNOVATION and EXCELLENCE
FEATURES
* * * * * * * * * * 14-bit resolution 8MHz guaranteed sampling rate No missing codes over full military temperature range Ideal for both time and frequency-domain applications Excellent THD (-75dB) and SNR (77dB) Edge-triggered; No pipeline delays Small, 24-pin, ceramic DDIP or SMT Requires only 5V supplies Low-power, 2 Watts MIL-STD-883 screening optional
GENERAL DESCRIPTION
The low-cost ADS-946 is a 14-bit, 8MHz 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-946 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-946 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-946 only requires the rising edge of a start convert pulse to operate. Requiring only 5V supplies, the ADS-946 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 +70C) or military (-55 to +125C) operating
PIN 1 2 3 4 5 6 7 8 9 10 11 12
INPUT/OUTPUT CONNECTIONS
FUNCTION BIT BIT BIT BIT BIT BIT BIT BIT BIT BIT BIT BIT 1 (MSB) 2 3 4 5 6 7 8 9 10 11 12 PIN 24 23 22 21 20 19 18 17 16 15 14 13 FUNCTION ANALOG GROUND OFFSET ADJUST +5V ANALOG SUPPLY ANALOG INPUT -5V SUPPLY ANALOG GROUND START CONVERT EOC BIT 14 (LSB) BIT 13 DIGITAL GROUND +5V DIGITAL SUPPLY
temperature ranges. A proprietary, auto-calibrating, errorcorrecting circuit allows the device to achieve specified performance over the full military temperature range.
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 -5V SUPPLY ANALOG GROUND DIGITAL GROUND 22 13 20 19, 24 14 AMP FLASH ADC 2 REGISTER DAC
START CONVERT 18 EOC 17
TIMING AND CONTROL LOGIC
Figure 1. ADS-946 Functional Block Diagram
DATEL, Inc., 11 Cabot Boulevard, Mansfield, MA 02048 (U.S.A.) * Tel: (508)339-3000 Fax: (508)339-6356 * For immediate assistance: (800) 233-2765
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ADS-946
ABSOLUTE MAXIMUM RATINGS
PARAMETERS +5V Supply (Pins 13, 22) -5V Supply (Pin 20) Digital Input (Pin 18) Analog Input (Pin 21) Lead Temperature (10 seconds) LIMITS 0 to +6 0 to -6 -0.3 to +VDD +0.3 5 +300 UNITS Volts Volts Volts Volts C
PHYSICAL/ENVIRONMENTAL
PARAMETERS Operating Temp. Range, Case ADS-946MC, GC ADS-946MM, GM, 883, G/883 Thermal Impedance jc ca Storage Temperature Range Package Type Weight MIN. 0 -55 -- -- -65 TYP. -- -- 6 23 -- MAX. +70 +125 -- -- +150 UNITS C C C/Watt C/Watt C
24-pin, metal-sealed, ceramic DDIP or SMT 0.42 ounces (12 grams)
FUNCTIONAL SPECIFICATIONS
(TA = +25C, VDD = 5V, 8MHz sampling rate, and a minimum 3 minute warmup unless otherwise specified.) +25C 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 (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 500kHz 500kHz to 1MHz 1MHz to 4MHz Total Harmonic Distortion (-0.5dB) dc to 500kHz 500kHz to 1MHz 1MHz to 4MHz Signal-to-Noise Ratio (w/o distortion, -0.5dB) dc to 500kHz 500kHz to 1MHz 1MHz to 4MHz Signal-to-Noise Ratio (& distortion, -0.5dB) dc to 500kHz 500kHz to 1MHz 1MHz to 4MHz Noise Two-Tone Intermodulation Distortion (fin = 2.45MHz, 1.975MHz, fs = 8MHz, -0.5dB) Input Bandwidth (-3dB) Small Signal (-20dB input) Large Signal (-0.5dB input) Feedthrough Rejection (fin = 4MHz) Slew Rate Aperture Delay Time Aperture Uncertainty -- -- -- -- -- -- 73 73 73 70 69 69 -- -- -- -- -- -- -- -- -76 -75 -75 -75 -75 -75 77 77 77 74 73 73 150 -82 30 10 85 400 +5 2 -72 -72 -71 -71 -70 -70 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 73 73 73 70 69 69 -- -- -- -- -- -- -- -- -76 -75 -75 -75 -75 -75 77 77 77 74 73 73 150 -82 30 10 85 400 +5 2 -72 -72 -71 -71 -70 -70 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 72 72 72 68 65 65 -- -- -- -- -- -- -- -- -74 -74 -69 -74 -72 -69 76 76 76 73 70 70 150 -82 30 10 85 400 +5 2 -70 -68 -65 -70 -68 -64 -- -- -- -- -- -- -- -- -- -- -- -- -- -- dB dB dB dB dB dB dB dB dB dB dB dB Vrms dB MHz MHz dB V/s ns ps rms -- -- -0.95 -- -- -- 14 14 0.75 0.5 0.15 0.2 0.2 -- -- -- +1.25 0.4 0.4 0.75 -- -- -- -0.95 -- -- -- 14 14 0.75 0.5 0.15 0.2 0.2 -- -- -- +1.25 0.4 0.4 0.75 -- -- -- -0.95 -- -- -- 14 14 1 0.75 0.4 0.4 0.4 -- -- -- +1.99 0.8 0.65 1.25 -- 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 A A ns MIN. -- -- -- TYP. 2 200 6 MAX. -- -- 15 MIN. -- -- -- 0 to +70C TYP. 2 200 6 MAX. -- -- 15 MIN. -- -- -- -55 to +125C TYP. 2 200 6 MAX. -- -- 15 UNITS Volts pF
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+25C 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 -5V Supply Power Supply Currents +5V Supply -5V Supply Power Dissipation Power Supply Rejection +4.75 -4.75 -- -- -- -- +5.0 -5.0 +250 -150 2 -- +5.25 -5.25 +270 -170 2.2 0.05 +4.75 -4.75 -- -- -- -- +2.4 -- -- -- -- -- -- -- -- +0.4 -4 +4 +2.4 -- -- -- MIN. -- -- 8 TYP. 55 100 -- MAX. 60 125 -- MIN. -- -- 8
0 to +70C TYP. 55 100 -- MAX. 60 125 -- MIN. -- -- 8
-55 to +125C TYP. 55 100 -- MAX. 60 125 -- UNITS ns ns MHz
-- -- -- +0.4 -- -4 -- +4 Offset Binary
+2.4 -- -- --
-- -- -- --
-- +0.4 -4 +4
Volts Volts mA mA
+5.0 -5.0 +250 -150 2 --
+5.25 -5.25 +270 -170 2.2 0.05
+4.9 -4.9 -- -- -- --
+5.0 -5.0 +250 -150 2 --
+5.25 -5.25 +270 -170 2.2 0.05
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. An 8MHz clock with a 20nsec 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 -4.9V for VDD are required for -55C operation only. The minimum limits are +4.75V and -4.75V when operating at +125C
TECHNICAL NOTES
1. Obtaining fully specified performance from the ADS-946 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 4.7F tantalum capacitors in parallel with 0.1F ceramic capacitors. Locate the bypass capacitors as close to the unit as possible. 2. The ADS-946 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. 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 +5V SIGNAL INPUT 1.98k 50 To Pin 21 of ADS-946
-5V
Figure 2. Optional ADS-946 Gain Adjust Calibration Circuit
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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-946'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-946 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 +1/2 LSB (+122V). 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 11/2 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 +122V 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 +1/2 LSB +122V
GAIN ADJUST +FS -11/2 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
-5V
+5V
4.7F +
4.7F 4.7F ++
0.1F
0.1F 0.1F
19 ANALOG INPUT +5V ZERO/ OFFSET ADJUST -5V START CONVERT 18
20
24
22, 13
14
21
23 20k
ADS-946
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) EOC
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-946 Connection Diagram
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ADS-946
THERMAL REQUIREMENTS
All DATEL sampling A/D converters are fully characterized and specified over operating temperature (case) ranges of 0 to +70C and -55 to +125C. All room-temperature (TA = +25C) 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 AN-8, "Heat Sinks for DIP Data Converters," or contact DATEL directly, for additional information.
N START CONVERT 20ns typ. 10ns typ. INTERNAL S/H 70ns typ. Hold Acquisition Time 55ns typ. 60ns max.
N+1
20ns typ. EOC Conversion Time 78ns min., 85ns typ., 90ns max.
25ns typ.
10ns typ. OUTPUT DATA Data N-1 Valid 95ns typ. 30ns typ. Invalid Data Data N Valid
Notes: 1. Scale is approximately 5ns per division. Sampling rate = 8MHz. 2. The start convert positive pulse width must be between 10 and 50ns or between 80 and 110ns (when sampling at 8MHz) to ensure proper operation. For sampling rates less than 8MHz, the start pulse can be wider than 110nsec, however a minimum pulse width low of 15nsec should be maintained. An 8MHz clock with a 20nsec positive pulse width is used for all production testing.
Figure 4. ADS-946 Timing Diagram
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0 -10 Amplitude Relative to Full Scale (dB) -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 -140 -150 0 400 kHz 800 kHz 1.2 MHz 1.6 MHz 2.0 MHz 2.4 MHz 2.8 MHz 3.2 MHz 3.6 MHz 4.0 MHz
Frequency (fs = 8MHz, fin = 3.85MHz, Vin = -0.5dB, 16,384-point FFT) Figure 5. FFT Analysis of ADS-946
+0.81
Number of Occurrences
-0.57 0 Codes 16,384
DNL (LSB's)
0
Digital Output Code
16,384
Figure 6. ADS-946 Histogram and Differential Nonlinearity
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OPTION +15V +5VA
SG5
SG6
C18 R2 (Optional) 4 - 5 U4 +5VF (Optional) C19 SG7 +5VF 14 -5VA -15V X1 8 1 R3 1 2 74HCT86 SG4 -5V -5V ANA. IN +5VA U1 OFFSET ADJUST +15V R1 2 -15V 20k C3 C10 0.01F 2.2F C22 2.2F 0.01F +5V START CONVERT U5 3 3.2k + 2.2F 23 0.1F C21 C25 15pF HCT7474 C26 C27 2.2F 7 4 2 3 1 JPR1 C17 PR 5 D U6 Q 6 CK Q CLR 7 SG8 0.1F (Optional) SG9 14 2.2F +5VF 8MHz CRYSTAL +5VF 0.1F C24 + C23 10 P3 CLC402 HI2541 11 START CONV. 0.1F (Optional)
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P4
ANA. IN 6
+
ANA. IN
L1
20H 2.2F 0.01F 0.1F
+
C1
L2
+
C8
74HCT573
20H C2 C9
L3
+
2 3 4 5 6 7 8 9 11 + 2.2F C16 0.1F
20H
+
20 Q1 19 1D 18 2D Q2 Q3 17 3D 16 4D Q4 15 5D U3 Q5 6D Q6 14 13 Q7 7D Q8 12 8D OE 1 CE 10 +5VF
L4 C20 C4 -5VA 0.1F 2.2F 0.01F ADS-946 C11
+
+
20H C6 C13 +5VF 2.2F 0.01F +5VA U6 12 13 7 GND 74HCT86 4 5 U5 6 U5 11 Q 9 8 C7 0.01F HCT7474 C14 14 0.1F +5VF C15
+
+
7
+5V C5 -15V 2.2F 0.01F +15V SPARE GATES 9 U5 10 C12 2.2F 10 12 11 13 PR D CK CLR
20H
24 23 22 21 20 19 18 17 16 15 14 13 AGND BIT1 1 OFFSET BIT2 2 +5VA BIT3 3 AIN BIT4 4 -5V BIT5 5 AGND BIT6 6 TRIG BIT7 7 EOC BIT8 8 BIT14 BIT9 9 BIT13 BIT10 10 DGND BIT11 11 +5VD BIT12 12
B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 TRIG JPR2 1 23 CE
34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 P1
L5
33 31 29 27 25 23 21 19 17 15 13 11 9 7 5 3 1
20H
2 3 4 5 6 7 8 9 11
20 Q1 1D 2D Q2 Q3 3D 4D Q4 U2 Q5 5D 6D Q6 Q7 7D Q8 8D OE CE 10 8 74HCT86
19 18 17 16 15 14 13 12 1 74HCT573
26 24 22 20 18 16 14 12 10 8 6 4 2
25 23 21 19 17 15 13 11 9 7 5 3 1
L6
P2
SG1
L7
SG2
20H
NOTES:
SG3
SG10
1. UNLESS OTHERWISE SPECIFIED ALL CAPACITORS ARE 50V. C1 - C7 ARE 20V. ALL RESISTORS ARE IN OHMS. 2. CLOSE SG1-SG3, SG9, SG10. 3. SEE DATEL DWG A-24546 FOR ADDITIONAL INFORMATION ON ADS-B946 EVALUATION BOARD.
ADS-946
Figure 7. ADS-946 Evaluation Board Schematic (ADS-B946)
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ADS-946
MECHANICAL DIMENSIONS INCHES (mm)
24-Pin DDIP Versions
24 1.31 MAX. (33.27) Dimension Tolerances (unless otherwise indicated): 2 place decimal (.XX) 0.010 (0.254) 3 place decimal (.XXX) 0.005 (0.127) 0.80 MAX. (20.32) 1 12 Lead Material: Kovar alloy Lead Finish: 50 microinches (minimum) gold plating over 100 microinches (nominal) nickel plating
ADS-946MC ADS-946MM ADS-946/883
13
0.100 TYP. (2.540) 1.100 (27.940) 0.235 MAX. (5.969) 0.200 MAX. (5.080)
0.010 -0.001 (0.254) 0.190 MAX. (4.826) 0.018 0.002 (0.457) 0.100 (2.540) 0.040 (1.016)
+0.002
SEATING PLANE 0.025 (0.635)
0.600 0.010 (15.240)
0.100 (2.540)
1.31 MAX. (33.02)
24-Pin Surface Mount Versions ADS-946GC ADS-946GM ADS-946G/883
24
13
Dimension Tolerances (unless otherwise indicated): 2 place decimal (.XX) 0.010 (0.254) 3 place decimal (.XXX) 0.005 (0.127) 0.80 MAX. (20.32) Lead Material: Kovar alloy Lead Finish: 50 microinches (minimum) gold plating over 100 microinches (nominal) nickel plating
1
12
0.190 MAX. (4.826)
0.020 TYP. (0.508) PIN 1 INDEX
0.060 TYP. (1.524) 0.130 TYP. (3.302)
0.015 (0.381) MAX. radius for any pin
0.100 (2.540) 0.100 TYP. (2.540) 0.040 (1.016)
0.020 (0.508)
0.010 TYP. (0.254)
ORDERING INFORMATION
MODEL ADS-946MC ADS-946MM ADS-946/883 ADS-946GC ADS-946GM ADS-946G/883 OPERATING TEMP. RANGE 0 to +70C -55 to +125C -55 to +125C 0 to +70C -55 to +125C -55 to +125C 24-PIN PACKAGE DDIP DDIP DDIP SMT SMT SMT ACCESSORIES ADS-B946 HS-24 Evaluation Board (without ADS-946) Heat Sink for all ADS-946 DDIP models
Receptacles for pc board mounting can be ordered through AMP, Inc., Part # 3-331272-8 (Component Lead Socket), 24 required. For MIL-STD-883 product specifcation, contact DATEL.
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ISO 9001
E G I S T E R E D
DS-0314 03/97
DATEL, Inc. 11 Cabot Boulevard, Mansfield, MA 02048-1151 Tel: (508) 339-3000 (800) 233-2765 Fax: (508) 339-6356 Internet: www.datel.com E-mail:sales@datel.com Data Sheet Fax Back: (508) 261-2857
DATEL (UK) LTD. Tadley, England Tel: (01256)-880444 DATEL S.A.R.L. Montigny Le Bretonneux, France Tel: 1-34-60-01-01 DATEL GmbH Munchen, Germany Tel: 89-544334-0 DATEL KK Tokyo, Japan Tel: 3-3779-1031, Osaka Tel: 6-354-2025
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.

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