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a
Dual, 12-Bit, 40 MSPS MCM A/D Converter with Analog Input Signal Conditioning AD10242
The AD10242 operates with 5.0 V for the analog signal conditioning with a separate +5.0 V supply for the analog-to-digital conversion. Each channel is completely independent allowing operation with independent encode or analog inputs. The AD10242 also offers the user a choice of analog input signal ranges to minimize additional signal conditioning required for multiple functions within a single system. The heart of the AD10242 is the AD9042 which is designed specifically for applications requiring wide dynamic range. The AD10242 is manufactured by Analog Devices on our MIL-PRF-38534 MCM line and is completely qualified. Units are packaged in a custom cofired ceramic 68-lead gull wing package and specified for operation from -55C to +125C. Contact the factory for additional custom options including those which allow the user to ac couple the ADC directly, bypassing the front end amplifier section. Also see the AD9042 data sheet for additional details on ADC performance.
PRODUCT HIGHLIGHTS
FEATURES Two Matched ADCs with Input Signal Conditioning Selectable Bipolar Input Voltage Range ( 0.5 V, 1.0 V, 2.0 V) Full MIL-STD-883B Compliant 80 dB Spurious-Free Dynamic Range Trimmed Channel-Channel Matching APPLICATIONS Radar Processing Communications Receivers FLIR Processing Secure Communications Any I/Q Signal Processing Application
PRODUCT DESCRIPTION
The AD10242 is a complete dual signal chain solution including onboard amplifiers, references, ADCs, and output buffering providing unsurpassed total system performance. Each channel is laser trimmed for gain and offset matching and provides channelto-channel crosstalk performance better than 80 dB. The AD10242 utilizes two each of the AD9631, OP279, and the AD9042 in a custom MCM to gain space, performance, and cost advantages over solutions previously available.
1. Guaranteed sample rate of 40 MSPS. 2. Dynamic performance specified over entire Nyquist band; spurious signals @ 80 dBc for -1 dBFS input signals. 3. Low power dissipation: <2 W off 5.0 V supplies. 4. User defined input amplitude. 5. Packaged in 68-lead ceramic leaded chip carrier.
FUNCTIONAL BLOCK DIAGRAM
AIN3
8
AIN2
7
AIN1
6
UNEG
56
UCOM
55
UPOS
57
AIN3
64
AIN2
63
AIN1
62
UPOS 12 OP279 OP279 AD9631 AD9631
UCOM
4
UNEG
3
OP279 (LSB) D0A 17 D1A 18 D2A 19 D3A 20 D4A
21
AD9042 VREF
OP279
AD9042 TIMING VREF
52 51
ENC ENC
12 9 OUTPUT BUFFERING
AD10242
49
D11B (MSB) D10B D9B D8B D7B
12 5 OUTPUT BUFFERING 7
48 47 46 45
D5A 22 D6A 23 D7A 24 D8A 25
28 29
TIMING
31 32 37 40 42
33
36
38
39
41
ENC
ENC
D9A
D10A D11A (MSB)
D0B (LSB)
D1B
D2B
D3B
D4B
D5B
D6B
REV. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 617/329-4700 World Wide Web Site: http://www.analog.com Fax: 617/326-8703 (c) Analog Devices, Inc., 1997
AD10242-SPECIFICATIONS
Electrical Characteristics
Parameter RESOLUTION DC ACCURACY No Missing Codes Offset Error Offset Error Channel Match Gain Error1 Gain Error Channel Match ANALOG INPUT (AIN) Input Voltage Range AIN1 AIN2 AIN3 Input Resistance AIN1 AIN2 AIN3 Input Capacitance2 Analog Input Bandwidth3 ENCODE INPUT4, 5 Logic Compatibility Logic "1" Voltage Logic "0" Voltage Logic "1" Current (VINH = 5 V) Logic "0" Current (VINL = 0 V) Input Capacitance SWITCHING PERFORMANCE Maximum Conversion Rate6 Minimum Conversion Rate 6 Aperture Delay (tA) Aperture Delay Matching Aperture Uncertainty (Jitter) ENCODE Pulse Width High ENCODE Pulse Width Low Output Delay (tOD) SNR7 Analog Input @ 1.2 MHz @ 4.85 MHz @ 9.9 MHz @ 19.5 MHz SINAD8 Analog Input @ 1.2 MHz @ 4.85 MHz @ 9.9 MHz @ 19.5 MHz Full +25C Full Full +25C Full Full VI I VI V I VI V 1, 2, 3 1 2, 3 1 2, 3
(AVCC = +5 V; AVEE = -5.0 V; DVCC = +5 V; applies to each ADC unless otherwise noted)
Temp Test Level Mil Subgroup Min AD10242BZ/TZ Typ 12 Guaranteed 0.05 1.0 0.1 0.5 0.8 0.1 Max Units Bits
-0.5 -2.0 -1.0 -1.5
+0.5 +2.0 +1.0 +1.5
% FS % FS % % FS % FS %
Full Full Full Full Full Full +25C Full
I I I IV IV IV IV V 12 12 12 12 99 198 396 0
0.5 1.0 2 100 200 400 4.0 60 101 202 404 7.0
V V V pF MHz
Full Full Full Full +25C Full Full +25C +25C +25C +25C +25C Full +25C +25C Full +25C Full +25C Full +25C +25C Full +25C Full +25C Full
I I I I V VI V V V V IV IV IV V I II I II I II V I II I II I II
1, 2, 3 1, 2, 3 1, 2, 3 1, 2, 3 12 4, 5, 6 12
2.0 0 -400
TTL/CMOS 5.0 0.8 625 800 -300 7.0 50 5 1.0 2.0 1 10 10 12 68 66 66 65 65 63 62 67 65 64 64 63 61 60
V V A A pF MSPS MSPS ns ns ps rms ns ns ns dB dB dB dB dB dB dB dB dB dB dB dB dB dB
40
12 12 12
12 10
41 14
4 5, 6 4 5, 6 4 5, 6
63 62 63 62 60 59
4 5, 6 4 5, 6 4 5, 6
62 61 60 60 58 58
-2-
REV. A
AD10242
Parameter SPURIOUS-FREE DYNAMIC RANGE 9 Analog Input @ 1.2 MHz @ 4.85 MHz @ 9.9 MHz @ 19.5 MHz TWO-TONE IMD REJECTION 10 F1, F2 @ -7 dBFS CHANNEL-TO-CHANNEL ISOLATION11 TRANSIENT RESPONSE LINEARITY Differential Nonlinearity (Encode = 20 MHz) Integral Nonlinearity Temp +25C +25C Full +25C Full +25C Full Full +25C +25C +25C Full +25C Test Level I I II I II I II II IV V IV IV V 12 12 Mil Subgroup Min AD10242BZ/TZ Typ Max 81 80 79 70 69 67 66 76 80 10 0.3 0.5 0.3 1.0 1.25 Units dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBc dB ns LSB LSB
4 5, 6 4 5, 6 4 5, 6 4, 5, 6 12
70 70 63 63 60 60 70 75
(Encode = 20 MHz)
OVERVOLTAGE RECOVERY TIME 12 VIN = 2.0 x FS VIN = 4.0 x FS DIGITAL OUTPUTS Logic Compatibility Logic "1" Voltage13 Logic "0" Voltage14 Output Coding POWER SUPPLY AVCC Supply Voltage I (AVCC) Current AVEE Supply Voltage I (AVEE) Current DVCC Supply Voltage I (DVCC) Current ICC (Total) Supply Current Power Dissipation (Total)
Full
Full
V
IV 12
0.5
50 100
LSB LSB
ns
Full
IV
12
75
200
ns
Full Full
I I
1, 2, 3 1, 2, 3
3.5
CMOS 4.2 0.45 0.65 Twos Complement +5.0 260 -5.0 55 +5.0 25 350 1.75
V V
Full Full Full Full Full Full Full Full
VI V VI V VI V I I
1, 2, 3 1, 2, 3
400 2.0
V mA V mA V mA mA W
Power Supply Rejection Ratio (PSRR) Pass Band Ripple to 10 MHz
Full Full
I IV
7, 8 12
0.01
0.02 0.2
% FSR/% VS dB
NOTES 1 Gain tests are performed on A IN3 over specified input voltage range. 2 Input capacitance specifications combines AD9631 die capacitance + ceramic package capacitance. 3 Full power bandwidth is the frequency at which the spectral power of the fundamental frequency (as determined by FFT analysis) is reduced by 3 dB. 4 ENCODE (Pin 4) driven by single-ended source; ENCODE (Pin 5) bypassed to ground through 0.01 F capacitor. 5 ENCODE (Pin 4) may also be driven differentially in conjunction with ENCODE (Pin 5); see "Encoding the AD10242" for details. 6 Minimum and maximum conversion rates allow for variation in Encode Duty Cycle of 50% 5%. 7 Analog Input signal power at -1 dBFS; signal-to-noise ratio (SNR) is the ratio of signal level to total noise (first 5 harmonics removed). Encode = 40.0 MSPS. 8 Analog Input signal power at -1 dBFS; signal-to-noise and distortion (SINAD) is the ratio of signal level to total noise + harmonics. Encode = 40.0 MSPS. 9 Analog Input signal equal -1 dBFS; SFDR is ratio of converter full scale to worst spur. 10 Both input tones at -7 dBFS; two tone intermodulation distortion (IMD) rejection is the rati o of either tone to the worst 3rd order intermod product. f1 = 10.0 MHz 100 kHz, 50 kHz f1 - f2 300 kHz. 11 Channel-to-channel isolation tested with A channel grounded and a full-scale signal applied to B channel (AIN1). 12 Input driven to 2x and 4x AIN1 range for >4 clock cycles. Output recovers inband in specified time with Encode = 40 MSPS. No foldover guaranteed. 13 Outputs are sourcing 10 A. 14 Outputs are sinking 10 A. All specifications guaranteed within 100 ms of initial power up regardless of sequencing. Specifications subject to change without notice.
REV. A
-3-
AD10242
ABSOLUTE MAXIMUM RATINGS 1 Parameter ELECTRICAL VCC Voltage VEE Voltage Analog Input Voltage Analog Input Current Digital Input Voltage (ENCODE) ENCODE, ENCODE Differential Voltage Digital Output Current ENVIRONMENTAL 2 Operating Temperature (Case) Maximum Junction Temperature Lead Temperature (Soldering, 10 sec) Storage Temperature Range (Ambient) Min 0 -7 VEE -10 0 -40 -55 Max 7 0 VCC +10 VCC 4 +40 +125 +175 +300 +150 Units V V V mA V V mA C C C C Table I. Output Coding
MSB
LSB
Base 10 2047 +1 0 -1 2048
Input +FS 0.0 V -FS
0111111111111 0000000000001 0000000000000 1111111111111 1000000000000
EXPLANATION OF TEST LEVELS
Test Level
I - 100% Production Tested. II - 100% production tested at +25C, and sample tested at specified temperatures. AC testing done on sample basis. III - Sample Tested Only. IV - Parameter is guaranteed by design and characterization testing. V - Parameter is a typical value only. VI - All devices are 100% production tested at +25C; sample tested at temperature extremes.
-65
NOTES 1 Absolute maximum ratings are limiting values to be applied individually, and beyond which the serviceability of the circuit may be impaired. Functional operability is not necessarily implied. Exposure to absolute maximum rating conditions for an extended period of time may affect device reliability. 2 Typical thermal impedances for "Z" package: JC = 11oC/W; JA = 30oC/W.
ORDERING GUIDE
Model
Temperature Range -40C to +85C (Case) -55C to +125C (Case) -55C to +125C (Case) -55C to +125C (Case) +25C
Package Description 68-Pin Ceramic Leaded Chip Carrier 68-Pin Ceramic Leaded Chip Carrier 68-Pin Ceramic Leaded Chip Carrier 68-Pin Ceramic Leaded Chip Carrier Evaluation Board with AD10242BZ
Package Option Z-68A Z-68A Z-68A Z-68A
AD10242BZ AD10242TZ AD10242TZ/883B 5962-9581501HXA AD10242/PCB
CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD10242 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
-4-
REV. A
AD10242
PIN FUNCTION DESCRIPTIONS
Pin No. 1 2, 5, 9-11, 26-27 3 4 6 7 8 12 13 14 15-16 17-25, 31-33 28 29 30 34-35 36-42, 45-49 43-44, 53-54 58-61, 65, 68 50 51 52 55 56 57 62 63 64 66 67
Name SHIELD GNDA UNEGA UCOMA AINA1 AINA2 AINA3 UPOSA AVEE AVCC NC D0A-D11A ENCODEA ENCODEA DVCC NC D0B-D11B GNDB DVCC ENCODEB ENCODEB UCOMB UNEGB UPOSB AINB1 AINB2 AINB3 AVCC AVEE
Function Internal Ground Shield between channels. A Channel Ground. A and B grounds should be connected as close to the device as possible. Unipolar Negative. Unipolar Common. Analog Input for A side ADC (nominally 0.5 V). Analog Input for A side ADC (nominally 1.0 V). Analog Input for A side ADC (nominally 2.0 V). Unipolar Positive. Analog Negative Supply Voltage (nominally -5.0 V or -5.2 V). Analog Positive Supply Voltage (nominally +5.0 V). No Connect. Digital Outputs for ADC A. D0 (LSB). ENCODE is complement of ENCODE. Data conversion initiated on rising edge of ENCODE input. Digital positive supply voltage (nominally +5.0 V). No Connect. Digital Outputs for ADC B. D0 (LSB). B Channel Ground. A and B grounds should be connected as close to the device as possible. Digital Positive Supply Voltage (nominally +5.0 V). Data conversion initiated on rising edge of ENCODE input. ENCODE is complement of ENCODE. Unipolar Common. Unipolar Negative. Unipolar Positive. Analog Input for B side ADC (nominally 0.5 V). Analog Input for B side ADC (nominally 1.0 V). Analog Input for B side ADC (nominally 2.0 V). Analog Positive Supply Voltage (nominally +5.0 V). Analog Negative Supply Voltage (nominally -5.0 V or -5.2 V).
PIN CONFIGURATION 68-Lead Ceramic Leaded Chip Carrier
UCOMA UNEGA GNDA SHIELD GNDB AVEE AVCC GNDA AINA3 AINA2 AINA1 GNDA GNDB AINB3 AINB2 AINB1 GNDB
9
8
7
6
5
43
2
1 68 67 66 65 64 63 62 61 60 59 58 57
GNDA GNDA UPOSA AVEE AVCC NC NC (LSB) D0A D1A D2A D3A D4A D5A D6A D7A D8A GNDA
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
PIN 1
GNDB GNDB
GNDB UPOSB 56 UNEGB
55 54 53 52 51 50 49 48 47 46 45 44
AD10242
TOP VIEW (Not to Scale)
UCOMB GNDB GNDB ENCODEB ENCODEB DVCC D11B (MSB) D10B D9B D8B D7B GNDB
GNDA ENCODEA
NC = NO CONNECT
REV. A
D9A D10A (MSB) D11A NC NC (LSB) D0B D1B D2B D3B D4B D5B D6B GNDB
ENCODEA DVCC
-5-
AD10242
DEFINITION OF SPECIFICATIONS Analog Bandwidth Overvoltage Recovery Time
The analog input frequency at which the spectral power of the fundamental frequency (as determined by the FFT analysis) is reduced by 3 dB.
Aperture Delay
The amount of time required for the converter to recover to 0.02% accuracy after an analog input signal of the specified percentage of full scale is reduced to midscale.
Power Supply Rejection Ratio
The delay between the 50% point of the rising edge of the ENCODE command and the instant at which the analog input is sampled.
Aperture Uncertainty (Jitter)
The ratio of a change in input offset voltage to a change in power supply voltage.
Signal-to-Noise-and-Distortion (SINAD)
The sample-to-sample variation in aperture delay.
Differential Nonlinearity
The ratio of the rms signal amplitude (set at 1 dB below full scale) to the rms value of the sum of all other spectral components, including harmonics but excluding dc.
Signal-to-Noise Ratio (without Harmonics)
The deviation of any code from an ideal 1 LSB step.
Encode Pulse Width/Duty Cycle
Pulse width high is the minimum amount of time that the ENCODE pulse should be left in logic "1" state to achieve rated performance; pulse width low is the minimum time ENCODE pulse should be left in low state. At a given clock rate, these specs define an acceptable Encode duty cycle.
Harmonic Distortion
The ratio of the rms signal amplitude (set at 1 dB below full scale) to the rms value of the sum of all other spectral components, excluding the first five harmonics and dc.
Spurious-Free Dynamic Range
The ratio of the rms signal amplitude to the rms value of the worst harmonic component.
Integral Nonlinearity
The ratio of the rms signal amplitude to the rms value of the peak spurious spectral component. The peak spurious component may or may not be a harmonic. May be reported in dBc (i.e., degrades as signal levels is lowered) or in dBFS (always related back to converter full scale).
Transient Response
The deviation of the transfer function from a reference line measured in fractions of 1 LSB using a "best straight line" determined by a least square curve fit.
Minimum Conversion Rate
The time required for the converter to achieve 0.02% accuracy when a one-half full-scale step function is applied to the analog input.
Two-Tone Intermodulation Distortion Rejection
The encode rate at which the SNR of the lowest analog signal frequency drops by no more than 3 dB below the guaranteed limit.
Maximum Conversion Rate
The ratio of the rms value of either input tone to the rms value of the worst third order intermodulation product; reported in dBc.
Two-Tone SFDR
The encode rate at which parametric testing is performed.
Output Propagation Delay
The delay between the 50% point of the rising edge of ENCODE command and the time when all output data bits are within valid logic levels.
The ratio of the rms value of either input tone to the rms value of the peak spurious component. The peak spurious component may or may not be an IMD product. May be reported in dBc (i.e., degrades as signal levels is lowered) or in dBFS (always related back to converter full scale).
-6-
REV. A
AD10242
N N+1 N+2 N+3 N+4 N+5 TTL CLOCK f 10MHz AIN3 ENC ENC AIN
tA = 1.0ns TYP
ENCODE
AIN2 AIN1
1/2 AD10242 SHOWN
tOD = 12ns TYP
DIGITAL OUTPUTS N-2 N-1 N N+1 N+2 NOTE: ALL 5V SUPPLY PINS BYPASSED TO GND WITH A 0.1F CAPACITOR
D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Figure 1. Timing Diagram
Figure 2. Equivalent Burn-In Circuit
EQUIVALENT CIRCUITS
AIN3 AIN2 R3 100 AIN1 R2 21 TO AD9631 R1 79 R4 200
DVCC
CURRENT MIRROR
DVCC VREF D0 - D11
Figure 3. Analog Input Stage
AVCC
AVCC
R1 17k
R1 17k
AVCC
CURRENT MIRROR
ENCODE R2 8k TIMING CIRCUITS R2 8k
ENCODE
Figure 5. Digital Output Stage
Figure 4. Encode Inputs
REV. A
-7-
AD10242-Typical Performance Characteristics
0 0 POWER RELATIVE TO FULL SCALE - dB -10 -20 -30 -40 -50 -60 -70 -80 -90 0 2 4 6 8 10 12 14 FREQUENCY - MHz 16 18 20 ENCODE = 40.0 MSPS AIN1 = 9.8 MHz AIN1 = -7 dBFs AIN2 = 10.1 MHz AIN2 = -7 dBFs SFDR = 76.0 dBc
POWER RELATIVE TO FULL SCALE - dB
-10 -20 -30 -40 -50 -60 -70 -80 -90
ENCODE = 40.0 MSPS AIN = 4.85 MHz AIN = -1 dBFs SNR = 66.4 dB SFDR = 72.8 dBc
-100 0 2 4 6 8 10 12 14 FREQUENCY - MHz 16 18 20
-100
Figure 6. Single Tone @ 4.85 MHz
Figure 9. Two Tone FFT @ 9.8/10.1 MHz
0
0
POWER RELATIVE TO FULL SCALE - dB
-10 -20 -30 -40 -50 -60 -70 -80 -90 2 4 6 8 10 12 14 FREQUENCY - MHz 16 18 20 ENCODE = 40.0 MSPS AIN = 9.9 MHz AIN = -1 dBFs SNR = 66.0 dB SFDR = 65.7 dBc
POWER RELATIVE TO FULL SCALE - dB
-10 -20 -30 -40 -50 -60 -70 -80 -90 0 2 4 6
ENCODE = 40.0 MSPS AIN1 = 19.5 MHz AIN1 = -7 dBFs AIN2 = 19.7 MHz AIN2 = -7 dBFs SFDR = 70.6 dBc
-100 0
-100
8 10 12 14 FREQUENCY - MHz
16
18
20
Figure 7. Single Tone @ 9.9 MHz
Figure 10. Two Tone FFT @ 19.5/19.7 MHz
0 POWER RELATIVE TO FULL SCALE - dB -10 -20 -30 -40 -50 -60 -70 -80 -90 0 2 4 6 8 10 12 14 FREQUENCY - MHz 16 18 20
WORST CASE HARMONIC - dB
76 74 ENCODE = 40.0 MSPS AIN = 19.5 MHz AIN = -1 dBFs SNR = 64.3 dB SFDR = 63.3 dBc 72 70 T = +125 C 68 T = +25 C 66 T = -55 C 64 62 60 58 5 10 ANALOG INPUT FREQUENCY - MHz 20
ENCODE = 40.0 MSPS AIN = -1 dBFs
-100
Figure 8. Single Tone @ 19.5 MHz
Figure 11. Harmonics vs. AIN
-8-
REV. A
AD10242
67 66.5 66 65.5 T = +25 C 64.5 T = +125 C 64 63.5 63 62.5 62 61.5 5 10 ANALOG INPUT FREQUENCY - MHz 20 ENCODE = 40.0 MSPS AIN = -1 dBFs
-70 IN B3 IN A3 -90 IN A1 IN B1
T = -55 C
-80
ISOLATION - dB
65 SNR - dB
-60 -50 -40 -30 -20 -10 0 10
ENCODE = 40.0 MSPS AIN = -1 dBFs
15
20 25 30 35 ANALOG INPUT FREQUENCY - MHz
40
Figure 12. SNR vs. AIN
Figure 15. Isolation vs. Frequency
70 AIN = 9.9 MHz 68 SFDR AIN = -1 dBFs
90
WORST CASE SPURIOUS - dBc, dBFs
80 SFDR (dBFs) 70 60 50 40 30 20 10 0 -70 ENCODE = 40 MSPS AIN = 9.98 MHz -60 -50 -40 -30 -20 -10 ANALOG INPUT POWER LEVEL - dBFs 0 SFDR = 75dB SFDR (dBc)
SNR, WORST SPUR - dB, dBc
66 SNR 64
62
60
58 5 10 15 20 25 30 35 SAMPLE RATE - MSPS 40 45 50
Figure 13. SNR and Harmonics vs. Encode Rate
Figure 16. Single Tone SFDR (AIN @ 9.98) vs. Power Level
2.0 1.5 1.0 GAIN
ERROR IN % FS
100 WORST CASE SPURIOUS - dBc, dBFs 90 80 SFDR (dBFs) 70 60 50 40 30 20 10 0 -70 -60 ENCODE = 40 MSPS AIN = 19.9 MHz -50 -40 -30 -20 -10 ANALOG INPUT POWER LEVEL - dBFs 0 SFDR = 75dB SFDR (dBc)
0.5 0 -0.5 -1.5 -1.5 -2.0 -55 OFFSET
-35
-15
5
25
45
65
85
105
125
TEMPERATURE - C
Figure 14. Offset and Gain Error vs. Temperature
Figure 17. Single Tone SFDR (AIN @ 19.9) vs. Power Level
REV. A
-9-
AD10242-Typical Performance Characteristics
80 70 -0.5 0 SNR (dB)
FUNDAMENTAL LEVELS - dBFS
SNR, WORST SPUR - dB, dBc
ENCODE = 40 MSPS 0.5
60 50 40 30 20 10 0 5 10 20 29.2 34.5 52.5 60.95 ANALOG INPUT FREQUENCY - MHz ENCODE = 40 MSPS AIN = 1dBFs SFDR (dBFS)
1
1.5 2
2.5 3 0 5 10 15 20 25 30 35 40 INPUT FREQUENCY - MHz 45 50 55
Figure 18. SNR/Harmonics to AIN > Nyquist MSPS
Figure 19. Gain Flatness vs. Input Frequency
THEORY OF OPERATION
Refer to the block diagram. The AD10242 employs three monolithic ADI components per channel (AD9631, OP279, and AD9042), along with multiple passive resistor networks and decoupling capacitors to fully integrate a complete 12-bit analogto-digital converter. The input signal is first passed through a precision laser trimmed resistor divider allowing the user to externally select operation with a full scale signal of 0.5 V, 1.0 V, or 2.0 V by choosing the proper input terminal for the application. The result of the resistor divider is to apply a full-scale input of approximately 0.4 V to the noninverting input of the internal AD9631 amplifier. The AD9631 provides the dc coupled level shift circuit required for operation with the AD9042 ADC. Configuring the amplifier in a noninverting mode the ac signal gain can be trimmed to provide a constant input to the ADC centered around the internal reference voltage of the AD9042. This allows the converter to be used in multiple system applications without the need for external gain and level shift circuitry normally requiring trim. The AD9631 was chosen for its superior ac performance and input drive capabilities which have limited the ability of many amplifiers to drive high performance ADCs. As new amplifiers are developed, pin compatible improvements are planned to incorporate the latest operational amplifier technology. The OP279 provides the buffer and inversion of the internal reference of the AD9042 in order to supply the summing node of the AD9631 input amplifier. This dc voltage is then summed with the input voltage and applied to the input of the AD9042 ADC. The reference voltage of the AD9042 is designed to track internal offsets and drifts of the ADC and is used to ensure matching over an extended temperature range of operation.
APPLYING THE AD10242 Encoding the AD10242
The AD10242 is designed to interface with TTL and CMOS logic families. The source used to drive the ENCODE pin(s) must be clean and free from jitter. Sources with excessive jitter will limit SNR and overall performance.
AD10242
TTL OR CMOS SOURCE ENCODE ENCODE 0.01F
Figure 20. Single-Ended TTL/CMOS Encode
The AD10242 encode inputs are connected to a differential input stage (see Figure 4 under EQUIVALENT CIRCUITS). With no input connected to either the ENCODE or input, the voltage divider bias the inputs to 1.6 volts. For TTL or CMOS usage, the encode source should be connected to ENCODE (Pins 29 and/or 51). ENCODE (Pins 28 and/or 52) should be decoupled using a low inductance or microwave chip capacitor to ground. Devices such as AVX 05085C103MA15, a 0.01 F capacitor, work well.
Performance Improvements
It is possible to improve the performance of the AD10242 slightly by taking advantage of the internal characteristics of the amplifier and converter combination. By increasing the +5 V supply slightly, the user may be able to gain up to a 5 dB improvement in SFDR over the entire frequency range of the converter. It is not recommended to exceed +5.5 V on the analog supplies as there are no performance benefits beyond that range and care should be taken to avoid the absolute maximum ratings.
-10-
REV. A
AD10242
If a logic threshold other than the nominal 1.6 V is required, the following equations show how to use an external resistor, RX, to raise or lower the trip point (see Figure 4, R1 = 17 k, R2 = 8 k).
V1 = 5R2R X to lower logic threshold. R1R2 + R1R X + R2R X
+5V R1 ENCODE R2
ENCODE
If no TTL source is available, a clean sine wave may be substituted. In the case of the sine source, the matching network is shown below. Since the matching transformer specified is a 1:1 impedance ratio, R, the load resistor should be selected to match the source impedance. The input impedance of the AD9042 is negligible in most cases.
T1-1T R
ENCODE SOURCE
SINE SOURCE
ENCODE
ENCODE
AD10242
Vl
0.01F RX
AD10242
Figure 24. Sine Source--Differential Encode Figure 21. Lower Threshold for Encode
V1 = 5R2 R1R X to raise logic threshold. R2 + R1+ R X
AVCC RX ENCODE SOURCE +5V ENCODE R1 ENCODE R2
If a low jitter ECL clock is available, another option is to accouple a differential ECL signal to the encode input pins as shown below. The capacitors shown here should be chip capacitors but do not need to be of the low inductance variety.
0.1F ENCODE ECL GATE 0.1F ENCODE 510 510
AD10242
Vl
0.01F
AD10242
-VS
Figure 25. Differential ECL for Encode Figure 22. Raise Logic Threshold for Encode
While the single ended encode will work well for many applications, driving the encode differentially will provide increased performance. Depending on circuit layout and system noise, a 1 dB to 3 dB improvement in SNR can be realized. It is recommended that the encode signal be ac-coupled into the ENCODE and ENCODE pins. The simplest option is shown below. The low jitter TTL signal is coupled with a limiting resistor, typically 100 , to the primary side of an RF transformer (these transformers are inexpensive and readily available; Part No. in figure is from MiniCircuits). The secondary side is connected to the ENCODE and ENCODE pins of the converter. Since both encode inputs are self-biased, no additional components are required.
100 TTL T1-1T
As a final alternative, the ECL gate may be replaced by an ECL comparator. The input to the comparator could then be a logic signal or a sine signal.
AD96687 (1/2)
0.1F ENCODE 50 510 0.1F ENCODE 510
AD10242
-VS
Figure 26. ECL Comparator for Encode
ENCODE
AD10242
ENCODE
Care should be taken not to overdrive the encode input pin when ac coupled. Although the input circuitry is electrically protected from over or under voltage conditions, improper circuit operations may result from overdriving the encode input pin.
Figure 23. TTL Source--Differential Encode
REV. A
-11-
AD10242
USING THE FLEXIBLE INPUT
The AD10242 has been designed with the user's ease of operation in mind. Multiple input configurations have been included on board to allow the user to have a choice of input signal levels and input impedance. While the standard inputs are 0.5 V, 1.0 V, and 2.0 V, the user can select the input impedance of the AD10242 on any input by using the other inputs as alternate locations for GND or an external resistor. The following chart summarizes the impedance options available at each input location: AIN1 = 100 when AIN2 and AIN3 Are Open. AIN1 = 75 when AIN3 Is Shorted to GND. AIN1 = 50 when AIN2 Is Shorted to GND. AIN2 = 200 when AIN3 Is Open. AIN2 = 100 when AIN3 Is Shorted to GND. AIN2 = 75 when AIN2 to AIN3 Has an External Resistor of AIN2 = 300 , with AIN 3 Shorted to GND. AIN2 = 50 when AIN2 to AIN3 Has an External Resistor of AIN2 = 100 , with AIN3 Shorted to GND. AIN3 = 400 . AIN3 = 100 when AIN3 Has an External Resistor of 133 to GND. AIN3 = 75 when AIN3 Has an External Resistor of 92 to GND. AIN3 = 50 when AIN3 Has an External Resistor of 57 to GND. While the Analog inputs of the AD10242 are designed for dc coupled bipolar inputs, the AD10242 has the ability to use unipolar inputs in a user selectable mode through the addition of a external resistor. This allows for 1 V, 2 V, and 4 V full-scale unipolar signals to be applied to the various inputs (AIN1, AIN2, and AIN3 respectively). Placing a 2.43 k resistor (typical, offset calibration required) between UPOS and UCOM shifts the reference voltage setpoint to allow a unipolar positive voltage to be applied at the inputs of the device. To calibrate offset a midscale dc voltage should be applied to the converter while adjusting the unipolar resistor for a midscale output transition.
AIN 1 AIN 2 AIN 3 UNEG 2.67k UCOM
AD10242
Figure 28. Unipolar Negative
GROUNDING AND DECOUPLING Analog and Digital Grounding
Proper grounding is essential in any high speed, high resolution system. Multilayer printed circuit boards (PCBs) are recommended to provide optimal grounding and power schemes. The use of ground and power planes offers distinct advantages: 1. The minimization of the loop area encompassed by a signal and its return path. 2. The minimization of the impedance associated with ground and power paths. 3. The inherent distributed capacitor formed by the power plane, PCB insulation, and ground plane. These characteristics result in both a reduction of electromagnetic interference (EMI) and an overall improvement in performance. It is important to design a layout that prevents noise from coupling to the input signal. Digital signals should not be run in parallel with input signal traces and should be routed away from the input circuitry. The AD10242 does not distinguish between analog and digital ground pins as the AD10242 should always be treated like an analog component. All ground pins should be connected together directly under the AD10242. The PCB should have a ground plane covering all unused portions of the component side of the board to provide a low impedance path and manage the power and ground currents. The ground plane should be removed from the area near the input pins to reduce stray capacitance.
LAYOUT INFORMATION
AIN 1 AIN 2 AIN 3 UPOS 2.43k UCOM
AD10242
Figure 27. Unipolar Positive
To operate with -1 V, -2 V, or -4 V full-scale unipolar signals place a 2.67 k resistor (typical, offset calibration required) between UNEG and UCOM. This again shifts the reference voltage setpoint to allow a unipolar negative voltage to be applied at the inputs of the device. To calibrate offset a midscale dc voltage should be applied to the converter while adjusting the unipolar resistor for a midscale output transition.
The schematic of the evaluation board (Figure 29) represents a typical implementation of the AD10242. The pinout of the AD10242 is very straightforward and facilitates ease of use and the implementation of high frequency/high resolution design practices. It is recommended that high quality ceramic chip capacitors be used to decouple each supply pin to ground directly at the device. All capacitors except the one placed on ENCODE can be standard high quality ceramic chip capacitors. The capacitor used on ENCODE pin must be a low inductance chip capacitor as referenced previously in the data sheet.
-12-
REV. A
AD10242
+5VA C1 0.1F U1 K1115 +5VA R9 470 R10 470 C14 0.1F 14 VCC OUT VEE 7 8 U5 AD9696KN 8 2 3 7 5 GND SMA J1 SMA JA H2DM J15 2 SMA JC +5VA C2 0.1F U2 K1115 +5VA H2DM J17 1 2 R11 470 BUFLATA T1 T1 - 1T 4 3 2 1 1:1 PULSE A IN SMA J11 PULSE A OUT SMA J12 6 2 R7 49.9 5 VLOW R5 470 R8 49.9 2 5 VLOW R6 470 -5.2V E2 VLOW VLOW VHIGH PULSE B IN SMA J13 6 ENCA R12 470 ENCAB C5 0.1F 14 VCC OUT VEE 7 8 U5 AD9696KN 8 2 3 7 5 GND SMA SMA J8 JB H2DM J16 2 SMA JD
1 51 E5
1 51 E5 1
H2DM J18 2
BUFLATB T2 T1 - 1T 4 3 2 1 1:1 6 ENCB
ENCBB
A SECTION
R1 100
B SECTION
R2 100
U3 AD8036Q VHIGH 3 8
U4 AD8036Q VHIGH 3 8 6
PULSE B OUT SMA J14 +5VA E1
B JACKS
E3 GND GND +5VA
E4 +5VD (MSB) D11A D10A D9A D8A D7A D6A D5A D4A BUFLATA D3A D2A D1A (LSB) D0A GND GND GND GND GND
-5.2V VHIGH
R3 470
R4 470
VHIGH U4 C22 0.1F U3 C21 0.1F
+5V U4 C17 0.1F -5.2V U3 C18 0.1F DUT C9 0.1F C23 10F U5 C12 0.1F U6 C3 0.1F DUT C8 0.1F
VLOW U3 C19 0.1F U4 C20 0.1F
U3 C15 0.1F
U4 C16 0.1F
C24 10F
DUT C10 0.1F +5VD
U5 C13 0.1F
U6 C4 0.1F
DUT C11 0.1F
SMA J2 AINA1
SMA J3 AINA2
SMA J4 AINA3
SMA J5 AINB1
SMA J6 AINB2
SMA J7 AINB3
DUT C7 0.1F
C25 10F
DUT C6 0.1F
H40DM J9 1 40 GND 2 39 GND 3 38 GND 4 37 GND 5 36 GND 6 35 GND 7 34 GND 8 33 GND 9 32 GND 10 31 GND 30 11 GND 12 29 GND 13 1 28 GND 14 27 GND 15 26 GND 16 25 GND 17 24 GND 18 23 GND 19 22 GND 20 21 GND
9
8
7
6
5
4
3
2
1
68 67 66 65 64 63 62 61
NOTES; 1) UNIPOLAR OPERATION A SIDE + CONNECT 2.43k RES. FROM TP1 TO TP5. A SIDE - CONNECT 2.67k RES. FROM TP5 TO TP6. B SIDE + CONNECT 2.43k RES. FROM TP2 TO TP4. B SIDE - CONNECT 2.67k RES. FROM TP4 TO TP3. 2) ABOVE UNIPOLAR RESISTOR VALUES ARE NOMINAL & MAY HAVE TO BE ADJUSTED DEPENDING ON OFFSET OF DUT. 3) ENCODE SOURCES A) FOR NORMAL OPERATION, A 40MHz TTL CLOCK OSCILLATOR IS INSTALLED IN U1 & U2. THERE IS A 51 RESISTOR BETWEEN J15 & J16. J17 & J18 ARE OPEN. B) FOR EXTERNAL SQUAREWARE ENCODE, INPUT SIGNAL AT J1 & J8, REMOVE U1, U2, JUMPERS J15 & J16. CONNECT JUMPERS J17 & J18. C) FOR EXTERNAL SINEWAVE ENCODE, INPUT SIGNAL AT J1 & J8, REMOVE U1, U2, R9, R11, JUMPERS J15 & J16. CONNECT JUMPERS J17 & J18. 4) POWER (+5VD) FOR DIGITAL OUTPUTS OF THE AD10242 IS SUPPLIED VIA PIN 1 OF EITHER J9 OR J10 (THE DIGITAL INTERFACES). TO POWER THE EVAL. BOARD WITH ONE +5V SUPPLY, JUMPER A WIRE FROM E1 TO E4 (CONNECTED AT FACTORY).
25 26
GNDA ENCAB ENCA +5VDA D9A D10A D11A (MSBA) NCB NCB D0B (LSBB) D1B D2B D3B D4B
GND GND TP1 -5.2V +5VA GND GND D0A D1A D2A D3A D4A D5A D6A D7A D8A GND
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
GNDA GNDA UNIPOSA -5.2VAA +5VAA NCA NCA D0A (LSBA) D1A D2A D3A D4A D5A D6A D7A D8A GNDA
DUT AD10242
GNDB GNDB GNDB UNIPOSB UNINEGB UNICOMB GNDB GNDB ENCBB ENCB +5VDB (MSBB) D11B D10B D9B D8B D7B GNDB D5B D6B GNDB
60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44
GND GND GND TP2 TP3 TP4 GND GND ENCBB ENCB +5VD D11B D10B D9B D8B D7B GND
+5VD (MSB) D11B D10B D9B D8B D7B D6B D5B D4B BUFLATB D3B D2B D1B (LSB) D0B GND GND GND GND GND
H40DM J10 40 39 38 37 36 35 34 33 32 31 30 11 12 29 28 13 27 14 1 2 3 4 5 6 7 8 9 10 15 16 17 18 19 20 26 25 24 23 22 21
GND GND GND GND GND GND GND GND GND GND GND GND GND GND GND GND GND GND GND GND
AIN A2 AIN A1 GNDA UNICOMA UNINEGA GNDA
SHIELD GNDB -5.2VAB +5VAB GNDB AIN B3 AIN B2 AIN B1
GNDA AIN A3
GNDB
GND AIN A3 AIN A2 AIN A1 GND TP5 TP6 GND GND GND -5.2V +5VA GND AIN B3 AIN B2 AIN B1 GND
TEST POINTS
TP1 TP2 TP3 TP4 TP5 TP1 TP2 TP3 TP4 TP6 TP7 TP8 TP9 TP6 ENCAB ENCA ENCBB ENCB
27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
GND ENCAB ENCA +5VD D9A D10A D11A GND GND D0B D1B D2B
D3B D4B
D5B D6B GND
TP5 TP10
Figure 29. Evaluation Board Schematic
REV. A
-13-
AD10242
Care should be taken when placing the digital output runs. Because the digital outputs have such a high slew rate, the capacitive loading on the digital outputs should be minimized. Circuit traces for the digital outputs should be kept short and connect directly to the receiving gate. Internal circuitry buffers the outputs of the AD9042 ADC through a resistor network to eliminate the need to externally isolate the device from the receiving gate.
EVALUATION BOARD
analog-to-digital converter. The board encompasses everything needed to ensure the highest level of performance for evaluating the AD10242. Power to the analog supply pins is connected via banana jacks. The analog supply powers the crystal oscillator, the associated components and amplifiers, and the analog section of the AD10242. The Digital outputs of the AD10242 are powered via Pin 1 of either J9 or J10 found on the digital interface connector. To power the evaluation board with one +5 V supply a jumper wire is required from test point E1 to E4. Contact the factory if additional layout or applications assistance is required.
The AD10242 evaluation board (see Figure 30) is designed to provide optimal performance for evaluation of the AD10242
Figure 30. Evaluation Board Mechanical Layout
-14-
REV. A
AD10242
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
68-Lead Ceramic Leaded Chip Carrier (Z-68A)
1.180 (29.97) SQ 0.950 (24.13) SQ 0.060 (1.52)
10 PIN 1 9 61 60
0.800 (20.32)
TOP VIEW
(PINS DOWN)
26 27 43
44
0.240 (6.096)
0.050 (1.27)
0.018 (0.457)
REV. A
-15-
-16-
C2161a-4-3/97
PRINTED IN U.S.A.
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