® ADS-926 ® 14-Bit, 500kHz, Low-Power Sampling A/D Converters PRODUCT OVERVIEW The ADS-926 is a high-performance, 14-bit, 500kHz sampling A/D converter. This device accurately samples full-scale input signals up to Nyquist frequencies with no missing codes and exhibits outstanding dynamic performance that surpasses most 16-bit, 500kHz sampling A/D's. THD and SNR, for example, are typically –90dB and 80dB when converting fullscale input signals up to 100kHz. Housed in a small 24-pin DDIP or SMT (gullwing) package, the functionally complete ADS-926 contains a fast-settling sample-hold amplifier, a subranging (two-pass) A/D converter, a precise voltage reference, timing/control logic, and error- FEATURES 14-bit resolution 500kHz sampling rate correction circuitry. Digital input and output levels are TTL. Requiring ±15V (or ±12V) and +5V supplies, the ADS-926 dissipates only 1.75W (1.6W for ±12V), maximum. The unit is offered with a bipolar input (–5V to +5V). Models are available for use in either commercial (0 to +70°C), industrial (–40 to +100°C), or HI-REL (–55 to +125°C) operating temperature ranges. Applications include radar, sonar, spectrum analysis, and graphic/medical imaging. Contact DATEL for information on devices screened to MIL-STD-883. INPUT/OUTPUT CONNECTIONS PIN FUNCTION PIN FUNCTION 1 BIT 14 (LSB) 24 –12V/–15V SUPPLY 2 BIT 13 23 ANALOG GROUND 3 BIT 12 22 +12V/+15V SUPPLY 4 BIT 11 21 +10V REFERENCE OUT 5 BIT 10 20 ANALOG INPUT 6 BIT 9 19 ANALOG GROUND 7 BIT 8 18 BIT 1 (MSB) Outstanding dynamic performance 8 BIT 7 17 BIT 2 Bipolar ±5V input range (for unipolar 0 to 10V input range see ADS-916) 9 BIT 6 16 START CONVERT 10 BIT 5 15 EOC 11 BIT 4 14 DIGITAL GROUND 12 BIT 3 13 +5V SUPPLY Functionally complete; No missing codes Small 24-pin DDIP or SMT package Operates from ±15V or ±12V supplies +5V supply Low power, 1.75 Watts maximum Samples up to Nyquist frequencies BLOCK DIAGRAM DAC 18 BIT 1 (MSB) 17 BIT 2 +10V REF. OUT 21 REF 12 BIT 3 FLASH ADC S/H ANALOG INPUT 20 S1 BUFFER – REGISTER + 11 BIT 4 DIGITAL CORRECTION LOGIC REGISTER S2 10 BIT 5 9 BIT 6 8 BIT 7 7 BIT 8 6 BIT 9 5 BIT 10 4 BIT 11 3 BIT 12 2 BIT 13 1 BIT 14 (LSB) START CONVERT 16 TIMING AND CONTROL LOGIC EOC 15 13 14 22 19, 23 24 +5V SUPPLY DIGITAL GROUND +12V/+15V SUPPLY ANALOG GROUND –12V/–15V SUPPLY Figure 1. ADS-926 Functional Block Diagram DATEL • 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 • www.datel.com • e-mail: [email protected] 17 Apr 2013 MDA_ADS-926.C02 Page 1 of 9 ® ADS-926 ® 14-Bit, 500kHz, Low-Power Sampling A/D Converters ABSOLUTE MAXIMUM RATINGS PARAMETERS LIMITS +12V/+15V Supply (Pin 22) 0 to +16 –12V/–15V Supply (Pin 24) 0 to –16 +5V Supply (Pin 13) 0 to +6 Digital Input (Pin 16) –0.3 to +VDD +0.3 Analog Input (Pin 20) –4 to +17 Lead Temperature (10 seconds) +300 PHYSICAL/ENVIRONMENTAL PARAMETERS MIN. TYP. MAX. UNITS Operating Temp. Range, Case ADS-926MC, GC, MC-C, GC-C 0 — +70 °C ADS-926ME, GE, ME-C, GE-C –40 — +100 °C ADS-926MM, GM, MM-C, GM-C –55 — +125 °C ADS-926MM-QL, 883, MM-QL-C, 883-C –55 — +125 °C Thermal Impedance — 6 — °C/Watt θjc — 24 — °C/Watt θca Storage Temperature Range –65 — +150 °C Package Type 24-pin, metal-sealed, ceramic DDIP or SMT Weight 0.42 ounces (12 grams) UNITS Volts Volts Volts Volts Volts °C FUNCTIONAL SPECIFICATIONS (TA = +25°C, ±VCC = ±15V (or ±12V), +VDD = +5V, 500kHz sampling rate, and a minimum 1 minute warmup ➀ unless otherwise specified.) 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 (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 Peak Harmonics (–0.5dB) dc to 100kHz 100kHz to 250kHz Total Harmonic Distortion (–0.5dB) dc to 100kHz 100kHz to 250kHz Signal-to-Noise Ratio (w/o distortion, –0.5dB) dc to 100kHz 100kHz to 250kHz Signal-to-Noise Ratio (& distortion, –0.5dB) ➃ dc to 100kHz 100kHz to 250kHz Two-tone Intermodulation Distortion (fin = 100kHz, 240kHz, fs = 500kHz –0.5dB) Noise Input Bandwidth (–3dB) Small Signal (–20dB input) Large Signal (–0.5dB input) Feedthrough Rejection (fin = 250kHz) 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 DATEL • MIN. — — — +25°C TYP. ±5 1 7 MAX. — — 15 MIN. — — — 0 TO +70°C TYP. ±5 1 7 MAX. — — 15 MIN. — — — +2.0 — — — 175 — — — — 200 — +0.8 +20 –20 225 +2.0 — — — 175 — — — — 200 — +0.8 +20 –20 225 +2.0 — — — 175 — — — — 200 — +0.8 +20 –20 225 Volts Volts μA μA ns — — — — — — — 14 14 ±0.5 ±0.5 ±0.08 ±0.05 ±0.05 ±0.1 — — — +0.95 ±0.15 ±0.1 ±0.1 ±0.15 — — — — — — — — 14 14 ±0.75 ±0.5 ±0.15 ±0.1 ±0.1 ±0.15 — — — ±0.95 ±0.25 ±0.25 ±0.25 ±0.25 — — — — — — — — 14 14 ±1.5 ±0.75 ±0.3 ±0.15 ±0.25 ±0.25 — — — +0.99 ±0.5 ±0.3 ±0.5 ±0.5 — Bits LSB LSB %FSR %FSR %FSR %FSR Bits — — –92 –90 –88 –85 — — –90 –90 –85 –85 — — –88 –86 –81 –80 dB dB — — –90 –87 –86 –82 — — –89 –87 –82 –82 — — –87 –81 –78 –76 dB dB 78 78 80 80 — — 78 78 80 80 — — 74 74 78 77 — — dB dB 77 77 79 79 — — 77 77 79 79 — — 74 73 78 77 — — dB dB — — –87 300 — — — — –86 300 — — — — –85 350 — — dB μVrms — — — — — — 7 3 84 ±40 ±20 50 — — — — — — — — — — — — 7 3 84 ±40 ±20 50 — — — — — — — — — — — — 7 3 84 ±40 ±20 50 — — — — — — MHz MHz dB V/μs ns ps rms 1335 — 500 1390 1400 — 1445 2000 — 1335 — 500 1390 1400 — 1445 2000 — 1335 — 500 1390 1400 — 1445 2000 — ns ns MHz 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 • –55 TO +125°C TYP. MAX. ±5 — 1 — 7 15 www.datel.com • UNITS Volts kΩ pF e-mail: [email protected] 17 Apr 2013 MDA_ADS-926.C02 Page 2 of 9 ® ADS-926 ® 14-Bit, 500kHz, Low-Power Sampling A/D Converters ANALOG OUTPUT Internal Reference Voltage Drift External Current DIGITAL OUTPUTS Logic Levels Logic "1" Logic "0" Logic Loading "1" Logic Loading "0" Delay, Falling Edge of EOC to Output Data Valid Output Coding POWER REQUIREMENTS , ±15V Power Supply Ranges +15V Supply –15V Supply +5V Supply Power Supply Currents +15V Supply –15V Supply +5V Supply Power Dissipation Power Supply Rejection POWER REQUIREMENTS, ±12V Power Supply Ranges +12V Supply –12V Supply +5V Supply Power Supply Currents +12V Supply –12V Supply +5V Supply Power Dissipation ±12V Power Dissipation ±15V Power Supply Rejection MIN. +25°C TYP. MAX. MIN. 0 TO +70°C TYP. MAX. MIN. +9.95 — — +10.0 ±5 — +10.05 — 1.5 +9.95 — — +10.0 ±5 — +10.05 — 1.5 +9.95 — — +10.0 ±5 — +10.05 — 1.5 Volts ppm/°C mA +2.4 — — — — — — — — — — +0.4 –4 +4 35 +2.4 — — — — +2.4 — — — — — — — — — — +0.4 –4 +4 35 Volts Volts mA mA ns +14.5 –14.5 +4.75 +15.0 –15.0 +5.0 +15.5 –15.5 +5.25 +14.5 –14.5 +4.75 +15.0 –15.0 +5.0 +15.5 –15.5 +5.25 +14.5 –14.5 +4.75 +15.0 –15.0 +5.0 +15.5 –15.5 +5.25 Volts Volts Volts — — — — — +41 –23 +71 1.4 — +63 –40 +85 1.75 ±0.02 — — — — — +41 –23 +71 1.4 — +63 –40 +85 1.75 ±0.02 — — — — — +41 –23 +71 1.4 — +63 –40 +85 1.75 ±0.02 mA mA mA Watts %FSR/%V +14.5 –14.5 +4.75 +15.0 –15.0 +5.0 +15.5 –15.5 +5.25 +14.5 –14.5 +4.75 +15.0 –15.0 +5.0 +15.5 –15.5 +5.25 +14.5 –14.5 +4.75 +15.0 –15.0 +5.0 +15.5 –15.5 +5.25 Volts Volts Volts — — — — — — +41 –23 +71 1.15 1.3 — +60 –40 +85 1.6 1.8 ±0.02 — — — — — — +41 –23 +71 1.15 1.3 — +60 –40 +85 1.6 1.8 ±0.02 — — — — — — +41 –23 +71 1.15 1.3 — +60 –40 +85 1.6 1.8 ±0.02 mA mA mA Watts Watts %FSR/%V UNITS ➃ Effective bits is equal to: 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 See Ordering Information for 0 to +10V input range. Contact DATEL for availability of other input voltage ranges. ➂ A 500kHz clock with a 200ns wide start convert pulse is used for all production testing. For applications requiring less than a 500kHz sampling rate, wider start convert pulses can be used. See Timing Diagram for more details. TECHNICAL NOTES 1. Obtaining fully specified performance from the ADS-926 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 23) directly to a large analog ground plane beneath the package. Bypass all power supplies and the REFERENCE OUTPUT (pin 21) 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. If the userinstalled offset and gain adjusting circuit shown in Figure 2 is used, also locate it as close to the ADS-926 as possible. 2. The ADS-926 achieves its specified accuracies without the need for external calibration. If required, the device's small initial offset and gain errors DATEL — — — +0.4 — –4 — +4 — 35 Offset Binary –55 TO +125°C TYP. MAX. • (SNR + Distortion) – 1.76 + Full Scale Amplitude Actual Input Amplitude 20 log 6.02 ➄ This is the time required before the A/D output data is valid after the analog input is back within the specified range. can be reduced to zero using the input circuit of Figure 2. When using this circuit, or any similar offset and gain-calibration hardware, make adjustments following warmup. To avoid interaction, always adjust offset before gain. 3. When operating the ADS-926 from ±12V supplies, do not drive external circuitry with the REFERENCE OUTPUT. The reference's accuracy and drift specifications may not be met, and loading the circuit may cause accuracy errors within the converter. 4. Applying a start convert pulse while a conversion is in progress (EOC = logic "1") initiates a new and inaccurate conversion cycle. Data from the interrupted and subsequent conversions will be invalid. 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 • www.datel.com • e-mail: [email protected] 17 Apr 2013 MDA_ADS-926.C02 Page 3 of 9 ® ADS-926 ® 14-Bit, 500kHz, Low-Power Sampling A/D Converters CALIBRATION PROCEDURE (Refer to Figures 2 and 3) 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 circuit of Figure 2 are guaranteed to compensate for the ADS-926's initial accuracy errors and may not be able to compensate for additional system errors. All fixed resistors in Figure 2 should be metal-film types, and multiturn potentiometers should have TCR’s of 100ppm/°C or less to minimize drift with temperature. 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. For the ADS-926, offset adjusting 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 (+305μV). 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 (+4.999085V). Zero/Offset Adjust Procedure 1. Apply a train of pulses to the START CONVERT input (pin 16) so the converter is continuously converting. If using LED's on the outputs, a 200kHz conversion rate will reduce flicker. 2. Apply +305μV to the ANALOG INPUT (pin 20). 3. Adjust the offset potentiometer until the output bits are a 1 and all 0's and the LSB flickers between 0 and 1. Gain Adjust Procedure 1. 1. Apply +4.999085V to the ANALOG INPUT (pin 20). 2. Adjust the gain potentiometer until the output bits are all 1's and the LSB flickers between 1 and 0. Table 1. Zero and Gain Adjust +15V ZERO/ OFFSET ADJUST 20k –15V SIGNAL INPUT 1.2M 2k GAIN ADJUST INPUT VOLTAGE RANGE ZERO ADJUST +½ LSB GAIN ADJUST +FS –1½ LSB ±5V +305μV +4.999085V Table 2. Output Coding +15V OUTPUT CODING 1.98k 50 INPUT RANGE ±5V BIPOLAR SCALE 11 1111 1111 1111 +4.99939 +FS –1 LSB 11 1000 0000 0000 +3.75000 +3/4 FS 11 0000 0000 0000 +2.50000 +1/2FS 10 0000 0000 0000 0.00000 0 01 0000 0000 0000 –2.50000 –1/2FS 00 1000 0000 0000 –3.75000 –3/4FS 00 0000 0000 0001 –4.99939 –FS +1 LSB 00 0000 0000 0000 –5.00000 –FS MSB To Pin 20 of ADS-926 –15V Figure 2. ADS-926 Calibration Circuit LSB Coding is offset binary; 1LSB = 610μV. 18 BIT 1 (MSB) +5V 4.7μF + 13 17 BIT 2 12 BIT 3 14 DIGITAL GROUND 11 BIT 4 10 BIT 5 9 BIT 6 0.1μF 24 –12V/–15V 4.7μF 4.7μF +12V/+15V + + 0.1μF 8 BIT 7 7 BIT 8 ANALOG 19, 23 GROUND 6 BIT 9 5 BIT 10 4 BIT 11 22 3 BIT 12 2 BIT 13 0.1μF ANALOG 20 INPUT –5V to +5V 0.1μF ADS-926 4.7μF + 1 BIT 14 (LSB) 15 EOC 21 +10V REF. OUT START 16 CONVERT Figure 3. Typical ADS-926 Connection Diagram DATEL • 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 • www.datel.com • e-mail: [email protected] 17 Apr 2013 MDA_ADS-926.C02 Page 4 of 9 ® ADS-926 ® 14-Bit, 500kHz, Low-Power Sampling A/D Converters THERMAL REQUIREMENTS 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. 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. N START CONVERT N+1 200ns ±25ns 10ns typ. Acquisition Time Hold 610ns typ. INTERNAL S/H 1390ns ±55ns 10ns typ. 70ns ±10ns Conversion Time EOC 480ns ±20ns 35ns max. 115ns max. OUTPUT DATA Data N Valid (1885ns min.) Data (N – 1) Valid Invalid Data Notes: 1. fs = 500kHz. 2. The ADS-926 is a pulse-triggered device. Its internal operations are triggered by both the rising and falling edges of the start convert pulse. When sampling at 500kHz, the start pulse must be between 175 and 225nsec wide. For lower sampling rates, wider start pulses may be used, however, a 50nsec minimum pulse width low must be maintained. Figure 4. ADS-926 Timing Diagram DATEL • 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 • www.datel.com • e-mail: [email protected] 17 Apr 2013 MDA_ADS-926.C02 Page 5 of 9 ® ADS-926 ® Figure 5. ADS-926 Evaluation Board Schematic 14-Bit, 500kHz, Low-Power Sampling A/D Converters DATEL • 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 • www.datel.com • e-mail: [email protected] 17 Apr 2013 MDA_ADS-926.C02 Page 6 of 9 ® ADS-926 ® 14-Bit, 500kHz, Low-Power Sampling A/D Converters 0 Amplitude Relative to Full Scale (dB) –10 –20 –30 –40 –50 –60 –70 –80 –90 –100 –110 –120 –130 –140 –150 0 25 50 75 100 125 150 175 200 225 250 Frequency (kHz) (fs = 500kHz, fin = 240kHz, Vin = –0.5dB, 16,384-point FFT) Figure 6. ADS-926 FFT Analysis +0.59 DNL (LSB's) Number of Occurrences 0 –0.57 0 0 16,384 Digital Output Code 16,384 Digital Output Code Figure 7. ADS-926 Histogram and Differential Nonlinearity DATEL • 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 • www.datel.com • e-mail: [email protected] 17 Apr 2013 MDA_ADS-926.C02 Page 7 of 9 ® ADS-926 ® 14-Bit, 500kHz, Low-Power Sampling A/D Converters MECHANICAL DIMENSIONS - INCHES (mm) 1.31 MAX. (33.27) 24-Pin DDIP Versions 24 ADS-926MC ADS-926ME ADS-926MM ADS-926/883 ADS-926MC-C ADS-926ME-C ADS-926MM-C ADS-926-C/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) PIN 1 INDEX 0.200 MAX. (5.080) 0.010 (0.254) 0.190 MAX. (4.826) 0.100 (2.540) 0.018 ±0.002 (0.457) 24-Pin Surface Mount Versions 0.600 ±0.010 (15.240) SEATING PLANE 0.025 (0.635) 0.040 (1.016) 0.100 (2.540) 1.31 MAX. (33.02) Dimension Tolerances (unless otherwise indicated): 2 place decimal (.XX) ±0.010 (±0.254) 3 place decimal (.XXX) ±0.005 (±0.127) 13 24 ADS-926GC ADS-926GE ADS-926GM ADS-926G/883 ADS-926GC-C ADS-926GE-C ADS-926GM-C ADS-926G-C/883 0.80 MAX. (20.32) 1 0.190 MAX. (4.826) Lead Material: Kovar alloy Lead Finish: 50 microinches (minimum) gold plating over 100 microinches (nominal) nickel plating 12 0.020 TYP. (0.508) 0.060 TYP. (1.524) 0.100 TYP. (2.540) • 0.015 (0.381) MAX. radius for any pin 0.130 TYP. (3.302) PIN 1 INDEX 0.100 (2.540) DATEL +0.002 –0.001 0.020 (0.508) 0.010 TYP. (0.254) 0.040 (1.016) 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA • Tel: (508) 339-3000 • www.datel.com • e-mail: [email protected] 17 Apr 2013 MDA_ADS-926.C02 Page 8 of 9 ® ADS-926 ® 14-Bit, 500kHz, Low-Power Sampling A/D Converters MODEL NUMBER ADS-926MC ADS-926MC-C ORDERING INFORMATION OPERATING PACKAGE TEMP. RANGE 0 to +70°C DDIP RoHS No 0 to +70°C DDIP Yes ADS-926ME –40 to +100°C DDIP No ADS-926ME-C –40 to +100°C DDIP Yes ADS-926MM –55 to +125°C DDIP No ADS-926MM-C –55 to +125°C DDIP Yes ADS-926MM-QL –55 to +125°C DDIP No ADS-926MM-QL-C –55 to +125°C DDIP Yes ADS-926/883 –55 to +125°C DDIP No ADS-926-C/883 –55 to +125°C DDIP Yes ADS-926GC 0 to +70°C SMT No ADS-926GC-C 0 to +70°C SMT Yes ADS-926GE –40 to +100°C SMT No ADS-926GE-C –40 to +100°C SMT Yes ADS-926GM –55 to +125°C SMT No ADS-926GM-C –55 to +125°C SMT Yes ADS-926G/883 –55 to +125°C SMT No ADS-926G-C/883 –55 to +125°C SMT Yes For unipolar analog input 0 to 10V see ADS-916 data sheet. DATEL 11 Cabot Boulevard, Mansfield, MA 02048-1151 USA ITAR and ISO 9001/14001 REGISTERED . 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. © 2013 www.datel.com • e-mail: [email protected] 17 Apr 2013 MDA_ADS-926.C02 Page 9 of 9