® ® 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 INPUT/OUTPUT CONNECTIONS 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. PIN 1 2 3 4 5 6 7 8 9 10 11 12 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 +70°C) or military (–55 to +125°C) operating FUNCTION PIN FUNCTION BIT BIT BIT BIT BIT BIT BIT BIT BIT BIT BIT BIT 24 23 22 21 20 19 18 17 16 15 14 13 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 1 (MSB) 2 3 4 5 6 7 8 9 10 11 12 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 16 BIT 14 (LSB) FLASH ADC 1 + POWER AND GROUNDING REF 22 +5V DIGITAL SUPPLY 13 –5V SUPPLY 20 ANALOG GROUND 19, 24 DIGITAL GROUND 14 DAC Σ AMP START CONVERT 18 EOC 17 FLASH ADC 2 REGISTER +5V ANALOG SUPPLY 15 BIT 13 12 BIT 12 11 BIT 11 OUTPUT REGISTER S/H DIGITAL CORRECTION LOGIC – REGISTER ANALOG INPUT 21 10 BIT 10 9 BIT 9 8 BIT 8 7 BIT 7 6 BIT 6 5 BIT 5 4 BIT 4 3 BIT 3 2 BIT 2 1 BIT 1 (MSB) 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 ® ® 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) PHYSICAL/ENVIRONMENTAL LIMITS UNITS 0 to +6 0 to –6 –0.3 to +VDD +0.3 ±5 +300 Volts Volts Volts Volts °C PARAMETERS MIN. TYP. MAX. UNITS Operating Temp. Range, Case ADS-946MC, GC ADS-946MM, GM, 883, G/883 Thermal Impedance θjc θca Storage Temperature Range 0 –55 — — +70 +125 °C °C — — –65 6 23 — — — +150 °C/Watt °C/Watt °C Package Type Weight 24-pin, metal-sealed, ceramic DDIP or SMT 0.42 ounces (12 grams) FUNCTIONAL SPECIFICATIONS (TA = +25°C, ±VDD = ±5V, 8MHz sampling rate, and a minimum 3 minute warmup ➀ unless otherwise specified.) +25°C ANALOG INPUT Input Voltage Range ➁ Input Resistance Input Capacitance 0 to +70°C MIN. TYP. MAX. — — — ±2 200 6 — — 15 +2.0 — — — 10 — — — — 20 — — –0.95 — — — 14 MIN. –55 to +125°C TYP. MAX. — — — ±2 200 6 — — 15 — +0.8 +20 –20 — +2.0 — — — 10 — — — — 20 14 ±0.75 ±0.5 ±0.15 ±0.2 ±0.2 — — — +1.25 ±0.4 ±0.4 ±0.75 — — — –0.95 — — — 14 — — — –76 –75 –75 –72 –72 –71 — — — –75 –75 –75 73 73 73 MIN. TYP. MAX. UNITS — — — ±2 200 6 — — 15 Volts Ω pF — +0.8 +20 –20 — +2.0 — — — 10 — — — — 20 — +0.8 +20 –20 — Volts Volts µA µA ns 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 — — — –76 –75 –75 –72 –72 –71 — — — –74 –74 –69 –70 –68 –65 dB dB dB –71 –70 –70 — — — –75 –75 –75 –71 –70 –70 — — — –74 –72 –69 –70 –68 –64 dB dB dB 77 77 77 — — — 73 73 73 77 77 77 — — — 72 72 72 76 76 76 — — — dB dB dB 70 69 69 — 74 73 73 150 — — — — 70 69 69 — 74 73 73 150 — — — — 68 65 65 — 73 70 70 150 — — — — dB dB dB µVrms — –82 — — –82 — — –82 — dB — — — — — — 30 10 85 ±400 +5 2 — — — — — — — — — — — — 30 10 85 ±400 +5 2 — — — — — — — — — — — — 30 10 85 ±400 +5 2 — — — — — — MHz MHz dB V/µs ns ps rms 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) 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 ➃ (& 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 2 ® ® ADS-946 +25°C DYNAMIC PERFORMANCE (Cont.) MIN. 0 to +70°C TYP. MAX. — — 8 55 100 — 60 125 — — — 8 +2.4 — — — — — — — — +0.4 –4 +4 +2.4 — — — +4.75 –4.75 +5.0 –5.0 +5.25 –5.25 +4.75 –4.75 +5.0 –5.0 — — — — +250 –150 2 — +270 –170 2.2 ±0.05 — — — — +250 –150 2 — S/H Acquisition Time ( to ±0.003%FSR, 4V step) Overvoltage Recovery Time ➄ A/D Conversion Rate MIN. –55 to +125°C TYP. MAX. 55 100 — 60 125 — MIN. TYP. MAX. UNITS — — 8 55 100 — 60 125 — ns ns MHz +2.4 — — — — — — — — +0.4 –4 +4 Volts Volts mA mA +5.25 –5.25 +4.9 –4.9 +5.0 –5.0 +5.25 –5.25 Volts Volts +270 –170 2.2 ±0.05 — — — — +250 –150 2 — +270 –170 2.2 ±0.05 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 Offset Binary POWER REQUIREMENTS Power Supply Ranges ➅ +5V Supply –5V Supply Power Supply Currents +5V Supply –5V Supply Power Dissipation Power Supply Rejection Footnotes: ➃ Effective bits is equal to: ➀ 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. (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. This time is only guaranteed if the input does not exceed ±2.2V (S/H saturation voltage). ➂ An 8MHz clock with a 20nsec positive pulse width is used for all production testing. See Timing Diagram, Figure 4, for more details. ➅ The minimum supply voltages of +4.9V and –4.9V for ±VDD are required for –55°C operation only. The minimum limits are +4.75V and –4.75V when operating at +125°C TECHNICAL NOTES 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. 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. 4. A passive bandpass filter is used at the input of the A/D for all production testing. 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. 2kΩ GAIN ADJUST +5V 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. SIGNAL INPUT 1.98kΩ To Pin 21 of ADS-946 50Ω –5V Figure 2. Optional ADS-946 Gain Adjust Calibration Circuit 3 ® ® ADS-946 CALIBRATION PROCEDURE Gain Adjust 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. 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. 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. Table 1. Gain and Zero Adjust INPUT VOLTAGE RANGE 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 +½ LSB (+122µV). ±2V 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. OFFSET BINARY MSB LSB +FS –1 LSB +3/4 FS +1/2 FS 0 –1/2 FS –3/4 FS –FS +1 LSB –FS +1.99976 +1.50000 +1.00000 0.00000 –1.00000 –1.50000 –1.99976 –2.00000 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 ➀ 4.7µF + 4.7µF 4.7µF + + 0.1µF 0.1µF 0.1µF 20 24 21 23 20kΩ ADS-946 22, 13 14 1 2 3 4 5 6 7 8 9 10 11 12 15 16 17 –5V START CONVERT +1.99963V INPUT VOLTAGE (±2V RANGE) +5V ZERO/ OFFSET ADJUST +122µV BIPOLAR SCALE –5V ANALOG INPUT GAIN ADJUST +FS –1½ LSB Table 2. Output Coding for Bipolar Operation 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). 19 ZERO ADJUST +½ LSB 18 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 ➀ 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 4 ® ® ADS-946 THERMAL REQUIREMENTS 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. 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 (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. 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. 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. N START CONVERT N+1 20ns typ. Acquisition Time 10ns typ. INTERNAL S/H 55ns typ. 60ns max. 70ns typ. Hold 20ns typ. EOC 25ns typ. Conversion Time 78ns min., 85ns typ., 90ns max. 10ns typ. OUTPUT DATA Data N-1 Valid Data N Valid 30ns typ. Invalid Data 95ns typ. 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 5 ® ADS-946 0 –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 Frequency (fs = 8MHz, fin = 3.85MHz, Vin = –0.5dB, 16,384-point FFT) Figure 5. FFT Analysis of ADS-946 DNL (LSB's) +0.81 Number of Occurrences Amplitude Relative to Full Scale (dB) –10 –0.57 0 0 Codes Digital Output Code 16,384 16,384 Figure 6. ADS-946 Histogram and Differential Nonlinearity 6 3.6 MHz 4.0 MHz ® ANA. IN SG10 SG3 SG2 SG1 P4 P2 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 ANA. IN 20µH L7 20µH L6 20µH L5 20µH L4 20µH L3 20µH L2 20µH L1 + + C8 0.01µF C9 0.01µF 2.2µF C2 2.2µF +5VF C1 + 0.01µF C12 0.01µF C13 0.01µF 2.2µF C5 2.2µF C6 2.2µF C7 2.2µF 0.01µF C14 C11 0.01µF 2.2µF C4 C10 C3 + + + 7 + R2 +5VA +15V –15V –5VA +5V 5 +15V 10 12 11 13 -15V SG8 0.1µF (Optional) U6 9 8 5 4 13 12 C15 11 0.1µF U5 6 7 GND U5 14 +5VF ANA. IN SG4 0.1µF C26 74HCT86 +5VA –5V 7 8 4 2 3 1 2.2µF HCT7474 ADS-946 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 U1 1 3.2k R3 0.1µF C24 + PR 5 D U6 Q 6 CK Q CLR 7 14 C23 START CONVERT 24 23 22 21 20 19 18 17 16 15 14 13 +5V 15pF C25 SG9 14 +5VF X1 2.2µF C27 8MHz CRYSTAL +5VF 2 3 JPR1 10 9 P3 U5 U5 + 2 3 4 5 6 7 8 9 11 2 3 4 5 6 7 8 9 11 C17 2.2µF 0.1µF 20 Q1 1D 2D Q2 Q3 3D 4D Q4 U2 Q5 5D 6D Q6 Q7 7D Q8 8D OE CE 10 74HCT573 C21 74HCT573 19 18 17 16 15 14 13 12 1 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 + +5VF 3. SEE DATEL DWG A-24546 FOR ADDITIONAL INFORMATION ON ADS-B946 EVALUATION BOARD. 2. CLOSE SG1-SG3, SG9, SG10. 1. UNLESS OTHERWISE SPECIFIED ALL CAPACITORS ARE 50V. C1 - C7 ARE 20V. ALL RESISTORS ARE IN OHMS. 0.1µF 2.2µF C16 C22 3 NOTES: 74HCT86 8 74HCT86 2 1 START CONV. Figure 7. ADS-946 Evaluation Board Schematic (ADS-B946) HCT7474 Q SPARE GATES 0.1µF C19 (Optional) -15V C20 PR D CK CLR 2 R1 C18 0.1µF (Optional) SG6 20k CLC402 HI2541 10 +5VA OFFSET ADJUST -5VA SG7 6 U4 11 +15V +5VF + – SG5 (Optional) 4 –5V OPTION + 2 3 JPR2 1 CE B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 TRIG 2 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 P1 1 33 31 29 27 25 23 21 19 17 15 13 11 9 7 5 3 ® ® ADS-946 ® ® ADS-946 MECHANICAL DIMENSIONS INCHES (mm) 1.31 MAX. (33.27) 24-Pin DDIP Versions 24 ADS-946MC ADS-946MM ADS-946/883 Dimension Tolerances (unless otherwise indicated): 2 place decimal (.XX) ±0.010 (±0.254) 3 place decimal (.XXX) ±0.005 (±0.127) 13 0.80 MAX. (20.32) 1 Lead Material: Kovar alloy Lead Finish: 50 microinches (minimum) gold plating over 100 microinches (nominal) nickel plating 12 0.100 TYP. (2.540) 1.100 (27.940) 0.235 MAX. (5.969) 0.200 MAX. (5.080) +0.002 0.010 –0.001 (0.254) 0.190 MAX. (4.826) 0.100 (2.540) 0.040 (1.016) 0.018 ±0.002 (0.457) 0.600 ±0.010 (15.240) SEATING PLANE 0.025 (0.635) 0.100 (2.540) 1.31 MAX. (33.02) 24-Pin Surface Mount Versions Dimension Tolerances (unless otherwise indicated): 2 place decimal (.XX) ±0.010 (±0.254) 3 place decimal (.XXX) ±0.005 (±0.127) 13 24 Lead Material: Kovar alloy 0.80 MAX. (20.32) ADS-946GC ADS-946GM ADS-946G/883 1 Lead Finish: 50 microinches (minimum) gold plating over 100 microinches (nominal) nickel plating 12 0.020 TYP. (0.508) 0.190 MAX. (4.826) 0.060 TYP. (1.524) 0.130 TYP. (3.302) PIN 1 INDEX 0.100 (2.540) 0.100 TYP. (2.540) 0.020 (0.508) 0.015 (0.381) MAX. radius for any pin 0.010 TYP. (0.254) 0.040 (1.016) ORDERING INFORMATION MODEL OPERATING TEMP. RANGE 24-PIN PACKAGE ADS-946MC ADS-946MM ADS-946/883 ADS-946GC ADS-946GM ADS-946G/883 0 to +70°C –55 to +125°C –55 to +125°C 0 to +70°C –55 to +125°C –55 to +125°C 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. ® ® ISO 9001 R 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:[email protected] Data Sheet Fax Back: (508) 261-2857 E G I S T E R E D DS-0314 03/97 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 München, 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.