SPT7824 10-BIT, 40 MSPS, TTL OUTPUT A/D CONVERTER FEATURES APPLICATIONS • • • • • • • • • • • • • Monolithic 40 MSPS Converter On-Chip Track/Hold Bipolar ±2.0 V Analog Input 57 dB SNR @ 3.58 MHz Input Low Power (1.0 W Typical) 5 pF Input Capacitance TTL Outputs Medical Imaging Professional Video Radar Receivers Instrumentation Electronic Warfare Digital Communications GENERAL DESCRIPTION The SPT7824 A/D converter is a 10-bit monolithic converter capable of word rates a minimum of 40 MSPS. On board track/hold function assures excellent dynamic performance without the need for external components. Drive requirement problems are minimized with an input capacitance of only 5 pF. Inputs and outputs are TTL compatible to interface with TTL logic systems. An overrange output signal is provided to indicate overflow conditions. Output data format is straight binary. Power dissipation is very low at only 1.0 watt with power supply voltages of +5.0 and -5.2 volts. The SPT7824 also provides a wide input voltage swing of ±2.0 volts. The SPT7824 is available in 28-lead ceramic sidebrazed DIP, PDIP and SOIC packages over the commercial, industrial and military temperature ranges. Consult the factory for availability of die and /833 versions. BLOCK DIAGRAM Coarse A/D 4 Analog Prescaler AAAAAAAAAAAAAAA AAAAAAAAAAAAAAA AAAAAAAAAAAAAAA AAAAAAAAAAAAAAA AAAAAAAAAAAAAAA T/H Amplifier Bank Successive Interpolation Stage i Successive Interpolation Stage i+1 Successive Interpolation Stage N Decoding Network Analog Input Digital Output 10 ABSOLUTE MAXIMUM RATINGS (Beyond which damage may occur)1 25 °C Supply Voltages VCC ........................................................................... +6 V VEE ........................................................................... -6 V Output Digital Outputs .......................................... +30 to -30 mA Temperature Operating Temperature ............................ -55 to +125 °C Junction Temperature1 .............................................. +175 °C Lead Temperature, (soldering 10 seconds) ........ +300 °C Storage Temperature ................................ -65 to +150 °C Input Voltages Analog Input ............................................... VFB≤VIN≤VFT VFT, VFB .............................................................. +3.0 V, -3.0 V Reference Ladder Current ..................................... 12 mA CLK Input .................................................................. VCC Note: 1. Operation at any Absolute Maximum Rating is not implied. See Electrical Specifications for proper nominal applied conditions in typical applications. ELECTRICAL SPECIFICATIONS TA=TMIN - TMAX, VCC=+5.0 V, VEE=-5.2 V, DVCC=+5.0 V, VIN=±2.0 V, VSB=-2.0 V, VST=+2.0 V, fCLK=40 MHz, 50% clock duty cycle, unless otherwise specified. PARAMETERS TEST CONDITIONS TEST LEVEL Resolution MIN SPT7824A TYP MAX 10 DC Accuracy (+25 °C) Integral Nonlinearity Differential Nonlinearity No Missing Codes ±Full Scale 100 kHz Sample Rate Analog Input Input Voltage Range Input Bias Current Input Bias Current Input Resistance Input Resistance Input Capacitance Input Bandwidth +FS Error -FS Error fCLK=1 MHz VIN=0 V TA=-55 to +125 °C TA=-55 to +125 °C 3 dB Small Signal 10 V V VI ±1.0 ±0.5 Guaranteed V VI IV VI IV V V V V ±2.0 30 ±1.5 ±0.75 Guaranteed ±2.0 LSB LSB 100 75 300 300 5 120 ±2.0 ±2.0 100 75 300 300 5 120 ±2.0 ±2.0 800 0.8 500 800 0.8 Ω Ω/°C 20 MHz ns 1 5 12 1 Clock Cycle 18 ns ns ps-RMS ns 8.2 8.2 6.9 Bits Bits Bits VI V 500 Timing Characteristics Maximum Conversion Rate Overvoltage Recovery Time Pipeline Delay (Latency) Output Delay Aperture Delay Time Aperture Jitter Time Acquisition Time VI V IV V V V V 40 Dynamic Performance Effective Number of Bits fIN=1 MHz fIN=3.58 MHz fIN=10.0 MHz Bits V 60 µA 75 µA kΩ kΩ pF MHz LSB LSB Reference Input fCLK=1 MHz Reference Ladder Resistance Reference Ladder Tempco TA=+25 °C TA=+25 °C TA=+25 °C TA=+25 °C SPT7824B TYP MAX UNITS MIN 60 75 30 40 20 14 1 5 12 8.7 8.7 7.3 1 18 14 Typical thermal impedances (unsoldered, in free air): 28L sidebrazed DIP: θja = 50 °C/W, 28L plastic DIP: θja = 50°C/W, 28L SOIC: θja = 100 °C/W. SPT7824 2 3/11/97 ELECTRICAL SPECIFICATIONS TA=TMIN-TMAX, VCC=+5.0 V, VEE=-5.2 V, DVCC=+5.0 V, VIN=±2.0 V, VSB=-2.0 V, VST=+2.0 V, fCLK=40 MHz, 50% clock duty cycle unless otherwise specified. PARAMETERS Dynamic Performance Signal-To-Noise Ratio (without Harmonics) fIN=1 MHz TEST CONDITIONS TEST LEVEL MIN SPT7824A TYP MAX MIN SPT7824B TYP MAX UNITS TA=+25 °C TA=0 to +70, -25 to +85 °C TA=-55 to +125 °C* TA=+25 °C TA=0 to 70, -25 to +85 °C TA=-55 to +125 °C* TA=+25 °C TA=0 to 70, -25 to +85 °C TA=-55 to +125 °C* I IV IV I IV IV I IV IV 55 53 49 55 53 49 48 45 41 57 55 51 57 55 51 50 47 43 52 50 46 52 50 46 46 43 39 54 52 48 54 52 48 48 45 41 dB dB dB dB dB dB dB dB dB TA=+25 °C TA=0 to 70, -25 to +85 °C TA=-55 to +125 °C* TA=+25 °C TA=0 to 70, -25 to +85 °C TA=-55 to +125 °C* TA=+25 °C TA=0 to 70, -25 to +85 °C TA=-55 to +125 °C* I IV IV I IV IV I IV IV 54 51 50 54 51 50 46 45 44 56 53 52 56 53 52 48 47 46 52 49 48 52 49 48 43 41 40 54 51 50 54 51 50 45 44 42 dB dB dB dB dB dB dB dB dB I IV IV I IV IV I IV IV V V V 52 49 48 52 49 48 44 43 40 54 49 46 45 49 46 45 41 40 37 51 dB dB dB dB dB dB dB dB dB dB Digital Inputs fCLK=1 MHz Logic 1 Voltage Logic 0 Voltage Maximum Input Current Low TA=+25 °C Maximum Input Current High TA=+25 °C Pulse Width Low (CLK) Pulse Width High (CLK) VI VI I I IV IV 2.4 Digital Outputs Logic "1" Voltage Logic "0" Voltage VI VI 2.4 IV IV IV I I I I V 4.75 4.75 -4.95 fIN=3.58 MHz fIN=10.0 MHz Harmonic Distortion fIN=1 MHz fIN=3.58 MHz fIN=10.0 MHz Signal-to-Noise and Distortion TA=+25 °C fIN=1 MHz TA=0 to 70, -25 to +85 °C TA=-55 to +125 °C* fIN=3.58 MHz TA=+25 °C TA=0 to 70, -25 to +85 °C TA=-55 to +125 °C* fIN=10.0 MHz TA=+25 °C TA=0 to 70, -25 to +85 °C TA=-55 to +125 °C* Spurious Free Dynamic Range TA=+25 °C, fIN=1 MHz TA=+25 °C, fIN = 3.58 & 4.35 MHz Differential Phase Differential Gain TA=+25 °C, fIN = 3.58 & 4.35 MHz Power Supply Requirements Voltages VCC DVCC -VEE Currents ICC DICC -IEE Power Dissipation Power Supply Rejection 54 46 67 0.2 0.5 0 0 10 10 +5 +5 51 43 67 0.2 0.7 4.5 0.8 +20 +20 300 2.4 0 0 10 10 +5 +5 Degree % 4.5 0.8 +20 +20 V V µA µA ns 300 ns fCLK=1 MHz TA=+25 °C TA=+25 °C TA=+25 °C TA=+25 °C +5 V ±0.25 V, -5.2 V ±0.25 V 2.4 V 0.6 V 0.6 5.0 -5.2 118 40 40 1.0 1.0 5.25 5.25 -5.45 145 55 57 1.3 4.75 4.75 -4.95 5.0 -5.2 118 40 40 1.0 1.0 5.25 5.25 -5.45 145 55 57 1.3 V V V mA mA mA W LSB *Temperature tested /883 only. SPT7824 3 3/11/97 TEST LEVEL CODES TEST LEVEL All electrical characteristics are subject to the following conditions: All parameters having min/max specifications are guaranteed. The Test Level column indicates the specific device testing actually performed during production and Quality Assurance inspection. Any blank section in the data column indicates that the specification is not tested at the specified condition. TEST PROCEDURE I 100% production tested at the specified temperature. II 100% production tested at TA = +25 °C, and sample tested at the specified temperatures. III QA sample tested only at the specified temperatures. IV Parameter is guaranteed (but not tested) by design and characterization data. V Parameter is a typical value for information purposes only. VI 100% production tested at TA = +25 °C. Parameter is guaranteed over specified temperature range. Figure 1A - Timing Diagram A A A A A A A CLK Output Data N-2 AA A AA AA AA AA N+1 N tpwH A A A AA N+2 tpwL td N-1 Data Valid N Data Valid N+1 Figure 1B - Single Event Clock CLK A A A A A AAAAAAAAAAA A AAAAAAAAAAA td Output Data Data Valid Table I - Timing Parameters PARAMETERS DESCRIPTION MIN TYP MAX UNITS td CLK to Data Valid Prop Delay - 14 18 ns tpwH CLK High Pulse Width 10 - 300 ns tpwL CLK Low Pulse Width 10 - - ns SPT7824 4 3/11/97 TYPICAL PERFORMANCE CHARACTERISTICS THD vs Input Frequency SNR vs Input Frequency 80 80 70 fs = 40 MSPS fs = 40 MSPS 60 Signal-to-Noise Ratio (dB) Total Harmonic Distortion (dB) 70 50 40 30 60 50 40 30 20 20 100 101 100 102 Input Frequency (MHz) 80 80 70 70 SNR, THD, SINAD (dB) Signal-to-Noise and Distortion (dB) SINAD vs Input Frequency fs =40 MSPS 60 50 40 30 60 50 20 40 20 102 101 A A A A A A A SNR, THD, SINAD vs Sample Rate SNR SINAD fIN = 1 MHz 30 100 102 101 Input Frequency (MHz) 100 Input Frequency (MHz) Spectral Response THD 101 102 Sample Rate (MSPS) SNR, THD, SINAD vs Temperature 65 0 SNR, THD, SINAD (dB) fS = 40 MSPS fIN = 1 MHz Amplitude (dB) -30 -60 60 SNR 55 THD SINAD 50 fS = 40 MSPS fIN = 1 MHz -90 45 -120 0 1 2 3 4 5 6 7 8 9 10 Input Frequency (MHz) 40 -25 0 +25 +50 +75 Temperature (°C) SPT7824 5 3/11/97 AGND and DGND are the two grounds available on the SPT7824. These two internal grounds are isolated on the device. The use of ground planes is recommended to achieve optimum device performance. DGND is needed for the DVCC return path (40 mA typical) and for the return path for all digital output logic interfaces. AGND and DGND should be separated from each other and connected together only at the device through a ferrite bead. TYPICAL INTERFACE CIRCUIT The SPT7824 requires few external components to achieve the stated operation and performance. Figure 2 shows the typical interface requirements when using the SPT7824 in normal circuit operation. The following section provides a description of the pin functions and outlines critical performance criteria to consider for achieving the optimal device performance. A Schottky or hot carrier diode connected between AGND and VEE is required. The use of separate power supplies between VCC and DVCC is not recommended due to potential power supply sequencing latch-up conditions. Using the recommended interface circuit shown in figure 2 will provide optimum device performance for the SPT7824. POWER SUPPLIES AND GROUNDING The SPT7824 requires -5.2 V and +5 V analog supply voltages. The +5 V supply is common to analog VCC and digital DVCC. A ferrite bead in series with each supply line is intended to reduce the transient noise injected into the analog VCC. These beads should be connected as closely as possible to the device. The connection between the beads and the SPT7824 should not be shared with any other device. Each power supply pin should be bypassed as closely as possible to the device. Use 0.1 µF for VEE and VCC, and 0.01 µF for DVCC (chip caps are preferred). Figure 2 - Typical Interface Circuit R1 CLK CLK 100 Ω ± 2.5 V Max VIN 6 5 + Trim 10 kΩ 1 µF C2 .01 µF 30 kΩ 2R C3 .01 µF 10 kΩ + IC2 OP-07 8 +5 V - 5.2 V 2R D7 D6 D5 D4 D3 D2 4 D1 .01 µF 30 kΩ C4 .01 µF 2R D0 (LSB) VSB SUCCESSIVE INTERPOLATION STAGE # N 7 R 6 1 µF + C5 .01 µF VFB AGND -2.5 V VEE .01 µF D8 C6 .1 µF C8 C7 .1 µF C9 DGND 1 2 SUCCESSIVE INTERPOLATION STAGE # 1 2R VRM DGND 3 ANALOG PRESCALER R VST DVCC GND VFT C1 .01 µF DVCC 4 +2.5 V VOUT (REF-03) D9 (MSB) VCC IC1 VIN AGND + VEE C19 1 µF D10 (Overrange) D I G IT A L O U 2 +5V 4 COARSE A/D VCC VIN (±2 V) DECODING NETWORK (TTL) C10 .01 µF C11 .01 µF Notes to prevent latch-up due to power sequencing: FB FB FB 1) D1 = Schottky or hot carrier diode, P/N IN5817. D1 2) FB = Ferrite bead, Fair Rite P/N 2743001111 10 µF to be mounted as close to the device as possible. The ferrite bead to the ADC connection should not be shared with any other device. 3) C1-C11 = Chip cap (recommended) mounted as close to the device's pin as possible. 4) Use of a separate supply for VCC and DVCC is not recommended. -5.2 V (Analog) 5) R1 provides current limiting to 45 mA. 6) C6, C7, C8 and C9 should be ten times larger than C10 and C11. 7) C8 = C9 = a 0.1 µF cap in parallel with a 4.7 µF cap. 10 µF + AGND + +5 V (Analog) DGND SPT7824 6 3/11/97 VOLTAGE REFERENCE ever, because the device is laser trimmed to optimize performance with ± 2.5 V references, the accuracy of the device will degrade if operated beyond a ± 2% range. The SPT7824 requires the use of two voltage references: VFT and VFB. VFT is the force for the top of the voltage reference ladder (+2.5 V typ), VFB (-2.5 V typ) is the force for the bottom of the voltage reference ladder. Both voltages are applied across an internal reference ladder resistance of 800 ohms. The +2.5 V voltage source for reference VFT must be current limited to 20 mA maximum if a different driving circuit is used in place of the recommended reference circuit shown in figures 2 and 3. In addition, there are three reference ladder taps (VST, VRM and VSB). VST is the sense for the top of the reference ladder (+2.0 V), VRM is the midpoint of the ladder (0.0 V typ) and VSB is the sense for the bottom of the reference ladder (-2.0 V). The voltages seen at VST and VSB are the true full scale input voltages of the device when VFT and VFB are driven to the recommended voltages (+2.5 V and -2.5 V typical respectively). These points should be used to monitor the actual full scale input voltage of the device and should not be driven to the expected ideal values as is commonly done with standard flash converters. When not being used, a decoupling capacitor of .01 uF (chip carrier preferred) connected to AGND from each tap is recommended to minimize high frequency noise injection. The following errors are defined: +FS error = top of ladder offset voltage = ∆(+FS -VST+1 LSB) -FS error = bottom of ladder offset voltage = ∆(-FS -VSB -1 LSB) where the +FS (full scale) input voltage is defined as the output transition between 1-10 and 1-11 and the -FS input voltage is defined as the output transition between 0-00 and 0-01. ANALOG INPUT VIN is the analog input. The full scale input range will be 80% of the reference voltage or ±2 V with VFB=-2.5 V and VFT=+2.5 V. The drive requirements for the analog inputs are minimal when compared to conventional Flash converters due to the SPT7824’s extremely low input capacitance of only 5 pF and very high input resistance of 300 kΩ. For example, for an input signal of ± 2 V p-p with an input frequency of 10 MHz, the peak output current required for the driving circuit is only 628 µA. CLOCK INPUT Figure 3 - Analog Equivalent Input Circuit The SPT7824 is driven from a single-ended TTL input (CLK). The CLK pulse width (tpwH) must be kept between 10 ns and 300 ns to ensure proper operation of the internal track-andhold amplifier. (See timing diagram.) When operating the SPT7824 at sampling rates above 3 MSPS, it is recommended that the clock input duty cycle be kept at 50% to optimize performance. (See figure 4.) The analog input signal is latched on the rising edge of the CLK. VCC Analog Prescaler VIN A A A A VFT AA AA The clock input must be driven from fast TTL logic (VIH ≤4.5 V, TRISE <6 ns). In the event the clock is driven from a high current source, use a 100 Ω resistor in series to current limit to approximately 45 mA. VEE Figure 4 - SNR vs Clock Duty Cycle An example of a reference driver circuit recommended is shown in figure 2. IC1 is REF-03, the +2.5 V reference with a tolerance of 0.6% or +/- 0.015 V. The potentiometer R1 is 10 kΩ and supports a minimum adjustable range of up to 150 mV. IC2 is recommended to be an OP-07 or equivalent device. R2 and R3 must be matched to within 0.1% with good TC tracking to maintain a 0.3 LSB matching between VFT and VFB. If 0.1% matching is not met, then potentiometer R4 can be used to adjust the VFB voltage to the desired level. VFT and VFB should be adjusted such that VST and VSB are exactly +2.0 V and -2.0 V respectively. 59 Signal-to-Noise Ratio (dB) 57 55 53 Duty tpwH = Cycle tpwL 51 AA AA AA 49 tpwH 47 45 The analog input range will scale proportionally with respect to the reference voltage if a different input range is required. The maximum scaling factor for device operation is ± 20% of the recommended reference voltages of VFT and VFB. How- tpwL 43 30 35 40 45 50 55 60 65 70 75 Duty Cycle of Positive Clock Pulse (%) SPT7824 7 3/11/97 DIGITAL OUTPUTS OVERRANGE OUTPUT The format of the output data (D0-D9) is straight binary. (See table II.) The outputs are latched on the rising edge of CLK with a propagation delay of 14 ns (typ). There is a one clock cycle latency between CLK and the valid output data. (See timing diagram.) The OVERRANGE OUTPUT (D10) is an indication that the analog input signal has exceeded the positive full scale input voltage by 1 LSB. When this condition occurs, D10 will switch to logic 1. All other data outputs (D0 to D9) will remain at logic 1 as long as D10 remains at logic 1. This feature makes it possible to include the SPT7824 into higher resolution systems. Table II - Output Data Information ANALOG INPUT OVERRANGE D1O OUTPUT CODE D9-DO >+2.0 V + 1/2 LSB 1 11 1111 1111 +2.0 V -1 LSB O 11 1111 111Ø 0.0 V O ØØ ØØØØ ØØØØ -2.0 V +1 LSB O OO OOOO OOOØ <-2.0 V O OO OOOO OOOO EVALUATION BOARD The EB7824 Evaluation Board is available to aid designers in demonstrating the full performance of the SPT7824. This board includes a reference circuit, clock driver circuit, output data latches and an on-board reconstruction of the digital data. An application note describing the operation of this board as well as information on the testing of the SPT7824 is also available. Contact the factory for price and availability. (Ø indicates the flickering bit between logic 0 and 1). The rise times and fall times of the digital outputs are not symmetrical. The propagation delay of the rise time is typically 14 ns and the fall time is typically 6 ns. (See figure 5.) The nonsymmetrical rise and fall times create approximately 8 ns of invalid data. Figure 5 - Digital Output Characteristics N CLK In 2.4 V N+1 AAA AAA AAA AAA AAA AAA Data Out (Actual) 3.5 V 2.4 V (N-2) 0.8 V 0.5 V Invalid Data (N-1) tpd1 (14 ns typ.) Data Out (Equivalent) (N-2) Invalid Data AA AA AA AA AA AA Rise Time 6 nsec 6 ns typ. (N-1) Invalid Data Invalid Data (N) (N-1) SPT7824 8 3/11/97 PACKAGE OUTLINES 28-Lead Sidebrazed 28 MILLIMETERS MIN MAX SYMBOL A 0.077 0.093 1.96 2.36 0.016 0.095 J B C D E F G H I J 0.020 0.105 .050 typ 0.060 0.235 1.412 0.605 0.012 0.620 0.41 2.41 0.00 1.02 5.46 35.26 14.86 0.23 15.24 0.51 2.67 1.27 1.52 5.97 35.86 15.37 0.30 15.75 I 1 INCHES MIN MAX H G A 0.040 0.215 1.388 0.585 0.009 0.600 E F C B D 28-Lead Plastic DIP SYMBOL INCHES MIN MAX A K B C D E F G H I J K 28 I 1 MILLIMETERS MIN MAX 0.200 0.120 0.170 0.135 0.020 0.100 0.067 0.013 0.180 0.622 0.555 1.460 0.085 5.08 3.05 4.32 3.43 0.51 2.54 1.70 0.33 4.57 15.80 14.10 37.08 2.16 J H G A B F C D E SPT7824 9 3/11/97 PACKAGE OUTLINES 28-Lead SOIC SYMBOL 28 I H 1 INCHES MIN MAX MILLIMETERS MIN MAX A B C 0.696 0.004 0.712 0.012 .050 typ 17.68 0.10 0.00 18.08 0.30 1.27 D E F 0.014 0.009 0.080 0.019 0.012 0.100 0.36 0.23 2.03 0.48 0.30 2.54 G H I 0.016 0.394 0.291 0.050 0.419 0.299 0.41 10.01 7.39 1.27 10.64 7.59 A F B C D G E SPT7824 10 3/11/97 PIN ASSIGNMENTS PIN FUNCTIONS Name Function DGND Digital Ground D0-D9 TTL Outputs (D0=LSB) D10 TTL Output Overrange CLK Clock VEE -5.2 V Supply (Analog) AGND Analog Ground VCC +5.0 V Supply (Analog) VIN Analog Input V FT DVCC Digital +5.0 V Supply V VRM Middle of Voltage Reference Ladder VFT Force for Top of Reference Ladder VST Sense for Top of Reference Ladder VFB Force for Bottom of Reference Ladder VSB Sense for Bottom of Reference Ladder DGND 1 28 D0 2 27 V D1 3 26 AGND D2 4 25 V D3 5 24 V D4 6 23 V SB D5 7 22 V D6 8 21 V D7 9 20 V ST D8 10 19 D9 11 18 D10 12 17 DGND 13 16 V DV CC 14 15 CLK DIP/PDIP/SOIC DVCC EE CC FB RM IN CC AGND EE ORDERING INFORMATION PART NUMBER TEMPERATURE RANGE PACKAGE TYPE SPT7824AIJ -25 to +85 °C SPT7824BIJ -25 to +85 °C 28L Sidebrazed DIP SPT7824ACN 0 to +70 °C 28L Plastic DIP SPT7824BCN 0 to +70 °C 28L Plastic DIP SPT7824ACS 0 to +70 °C 28L SOIC SPT7824BCS 0 to +70 °C 28L SOIC SPT7824AMJ -55 to +125 °C 28L Sidebrazed DIP SPT7824BMJ -55 to +125 °C 28L Sidebrazed DIP 28L Sidebrazed DIP SPT7824 11 3/11/97