2 GHz Ultralow Distortion Differential RF/IF Amplifier AD8352

Transcription

1 GHz Ultralow Distortion Differential RF/IF Amplifier AD83 FEATURES 3 db bandwidth of. GHz (AV = 1 db) Single resistor gain adjust: 3 db AV db Single resistor and capacitor distortion adjust Input resistance: 3 kω, independent of gain (AV) Differential or single-ended input to differential output Low noise input stage:.7 nv/ Hz AV = 1 db Low broadband distortion 1 MHz: 86 HD, 8 HD3 7 MHz: 8 HD, 8 HD3 19 MHz: 81 HD, 87 HD3 OIP3 of 1 1 MHz Slew rate: 8 V/ns Fast settling and overdrive recovery of ns Single-supply operation: 3 V to. V Low power dissipation: 37 V Power down capability: V Fabricated using the high speed XFCB3 SiGe process C D R G 6 6 FUNCTIONAL BLOCK DIAGRAM ENB RGP RDP VIP R D VIN RDN RGN BIAS CELL + AD83 Figure 1. VCM VCC VOP VON GND 78-1 APPLICATIONS 7 Differential ADC drivers Single-ended to differential conversion RF/IF gain blocks SAW filter interfacing HD3 () IP3 (dbm) GENERAL DESCRIPTION The AD83 is a high performance differential amplifier optimized for RF and IF applications. It achieves better than 8 db SFDR performance at frequencies up to MHz, and 6 db beyond MHz, making it an ideal driver for high speed 1-bit to 16-bit analog-to-digital converters (ADCs). Unlike other wideband differential amplifiers, the AD83 has buffers that isolate the gain setting resistor (RG) from the signal inputs. As a result, the AD83 maintains a constant 3 kω input resistance for gains of 3 db to db, easing matching and input drive requirements. The AD83 has a nominal 1 Ω differential output resistance Figure. IP3 and Third Harmonic Distortion vs. Frequency, Measured Differentially The device is optimized for wideband, low distortion performance at frequencies beyond MHz. These attributes, together with its wide gain adjust capability, make this device the amplifier of choice for general-purpose IF and broadband applications where low distortion, noise, and power are critical. In particular, it is ideally suited for driving not only ADCs, but also mixers, pin diode attenuators, SAW filters, and multielement discrete devices. The device is available in a compact 3 mm 3 mm, 16-lead LFCSP package and operates over a temperature range of C to +8 C. 78- 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 that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 916, Norwood, MA 6-916, U.S.A. Tel: Fax: Analog Devices, Inc. All rights reserved.

2 TABLE OF CONTENTS Features... 1 Applications... 1 Functional Block Diagram... 1 General Description... 1 Revision History... Specifications... 3 Noise Distortion Specifications... Absolute Maximum Ratings... 6 ESD Caution... 6 Pin Configuration and Function Descriptions... 7 Typical Performance Characteristics... 8 Applications Gain and Distortion Adjustment (Differential Input) Single-Ended Input Operation... 1 Narrow-Band, Third-Order Intermodulation Cancellation.13 High Performance ADC Driving... 1 Layout and Transmission Line Effects... 1 Evaluation Board Evaluation Board Loading Schemes Evaluation Board Schematics Outline Dimensions Ordering Guide REVISION HISTORY 9/6 Rev. to Rev. A Changes to Absolute Maximum Ratings... 6 Inserted Figure 1, Figure 11, and Figure Inserted Figure 17, Figure 18, and Figure Changes to Figure Changes to Table Changes to Figure Changes to Ordering Guide /6 Revision : Initial Version Rev. A Page of

3 SPECIFICATIONS AD83 VS = V, RL = Ω differential, RG = 118 Ω (AV = 1 db), f = 1 MHz, T = C; parameters specified differentially (in/out), unless otherwise noted. CD and RD are selected for differential broadband operation (see Table and Table 6). Table 1. Parameter Conditions Min Typ Max Unit DYNAMIC PERFORMANCE 3 db Bandwidth AV = 6 db, VOUT 1. V p-p MHz AV = 1 db, VOUT 1. V p-p MHz AV = 1 db, VOUT 1. V p-p 18 MHz Bandwidth for.1 db Flatness 3 db AV db, VOUT 1. V p-p 19 MHz Bandwidth for. db Flatness 3 db AV db, VOUT 1. V p-p 3 MHz Gain Accuracy Using 1% resistor for RG, db AV db ±1 db Gain Supply Sensitivity VS ± %.6 db/v Gain Temperature Sensitivity C to +8 C mdb/ C Slew Rate RL = 1 kω, VOUT = V step 9 V/ns RL = Ω, VOUT = V step 8 V/ns Settling Time V step to 1% < ns Overdrive Recovery Time VIN = V to V step, VOUT ±1 mv <3 ns Reverse Isolation (S1) 8 db INPUT/OUTPUT CHARACTERISTICS Common-Mode Nominal VCC/ V Voltage Adjustment Range 1. to 3.8 V Maximum Output Voltage Swing 1 db compressed 6 V p-p Output Common-Mode Offset Referenced to VCC/ 1 + mv Output Common-Mode Drift C to +8 C. mv/ C Output Differential Offset Voltage + mv CMRR 7 db Output Differential Offset Drift C to +8 C.1 mv/ C Input Bias Current ± μa Input Resistance 3 kω Input Capacitance (Single-Ended).9 pf Output Resistance 1 Ω Output Capacitance 3 pf POWER INTERFACE Supply Voltage 3. V ENB Threshold 1. V ENB Input Bias Current ENB at 3 V 7 na ENB at.6 V 1 μa Quiescent Current ENB at 3 V ma ENB at.6 V.3 ma Rev. A Page 3 of

4 NOISE DISTORTION SPECIFICATIONS VS = V, RL = Ω differential, RG = 118 Ω (AV = 1 db),, T = C; parameters specified differentially, unless otherwise noted. CD and RD are selected for differential broadband operation (see Table and Table 6). See the Applications section for single-ended to differential performance characteristics. Table. Parameter Conditions Min Typ Max Unit 1 MHz Second/Third Harmonic Distortion 1 RL = 1 kω, VOUT = V p-p 88/ 9 RL = Ω, VOUT = V p-p 86/ 8 Output Third-Order Intercept RL = Ω, f1 = 9. MHz, f = 1. MHz +38 dbm Third-Order IMD RL = 1 kω, f1 = 9. MHz, f = 1. MHz, 86 RL = Ω, f1 = 9. MHz, f = 1. MHz, 81 Noise Spectral Density (RTI) +.7 nv/ Hz 1 db Compression Point (RTO) +1.7 dbm 7 MHz Second/Third Harmonic Distortion RL = 1 kω, RG = 178 Ω, VOUT = V p-p 83/ 8 RL = Ω, RG = 11 Ω, VOUT = V p-p 8/ 8 Output Third-Order Intercept RL = Ω f1 = 69. MHz, f = 7. MHz + dbm Third-Order IMD RL = 1 kω, f1 = 69. MHz, f = 7. MHz, 91 RL = Ω, f1 = 69. MHz, f = 7. MHz, 83 Noise Spectral Density (RTI) +.7 nv/ Hz 1 db Compression Point (RTO) +1.7 dbm 1 MHz Second/Third Harmonic Distortion RL = 1 kω, VOUT = V p-p 83/ 83 RL = Ω, VOUT = V p-p 8/ 8 Output Third-Order Intercept RL = Ω, f1 = 99. MHz, f = 1. MHz + dbm Third-Order IMD RL = 1 kω, f1 = 99. MHz, f = 1. MHz, 91 RL = Ω, f1 = 99. MHz, f = 1. MHz, 8 Noise Spectral Density (RTI) +.7 nv/ Hz 1 db Compression Point (RTO) +1.6 dbm 1 MHz Second/Third Harmonic Distortion RL = 1 kω, VOUT = V p-p 83/ 8 RL = Ω, VOUT = V p-p 8/ 8 Output Third-Order Intercept RL = Ω, f1 = 139. MHz, f = 1. MHz +1 dbm Third-Order IMD RL = 1 kω, f1 = 139. MHz, f = 1. MHz, 89 RL = Ω, f1 = 139. MHz, f = 1. MHz, 8 Noise Spectral Density (RTI) +.7 nv/ Hz 1 db Compression Point (RTO) +1. dbm Rev. A Page of

5 Parameter Conditions Min Typ Max Unit 19 MHz Second/Third Harmonic Distortion RL = 1 kω, VOUT = V p-p 8/ 8 RL = Ω, VOUT = V p-p 81/ 87 Output Third-Order Intercept RL = Ω, f1 = 18. MHz, f = 19. MHz +39 dbm Third-Order IMD RL = 1 kω, f1 = 18. MHz, f = 19. MHz, 83 RL = Ω, f1 = 18. MHz, f = 19. MHz, 81 Noise Spectral Density (RTI) +.7 nv/ Hz 1 db Compression Point (RTO) +1. dbm MHz Second/Third Harmonic Distortion RL = 1 kω, VOUT = V p-p 8/ 76 RL = Ω, VOUT = V p-p 8/ 73 Output Third-Order Intercept RL = Ω, f1 = 39. MHz, f =. MHz +36 dbm Third-Order IMD RL = 1 kω, f1 = 39. MHz, f =. MHz, 8 RL = Ω, f1 = 39. MHz, f =. MHz, 77 Noise Spectral Density (RTI) +.7 nv/ Hz 1 db Compression Point (RTO) +1.3 dbm 38 MHz Second/Third Harmonic Distortion RL = 1 kω, VOUT = V p-p 7/ 68 RL = Ω, VOUT = V p-p 7/ 69 Output Third-Order Intercept RL = Ω, f1 = 379. MHz, f = 38. MHz +33 dbm Third-Order IMD RL = 1 kω, f1 = 379. MHz, f = 38. MHz, 7 RL = Ω, f1 = 379. MHz, f = 38. MHz, 7 Noise Spectral Density (RTI) +.7 nv/ Hz 1 db Compression Point (RTO) +1.6 dbm MHz Second/Third Harmonic Distortion RL = Ω, VOUT = V p-p 71/ 6 Output Third-Order Intercept RL = Ω, f1 = 99. MHz, f =. MHz +8 dbm Third-Order IMD RL = Ω, f1 = 99. MHz, f =. MHz, 61 Noise Spectral Density (RTI) +.7 nv/ Hz 1 db Compression Point (RTO) dbm 1 When using the evaluation board at frequencies below MHz, replace the Output Balun T1 with a transformer such as Mini-Circuits ADT1-1WT to obtain the low frequency balance required for differential HD cancellation. CD and RD can be optimized for broadband operation below 18 MHz. For operation above 3 MHz, CD and RD components are not required. Rev. A Page of

6 ABSOLUTE MAXIMUM RATINGS Table 3. Parameter Rating Supply Voltage VCC. V VIP, VIN VCC +. V Internal Power Dissipation 1 mw θja 91. C/W Maximum Junction Temperature 1 C Operating Temperature Range C to +8 C Storage Temperature Range 6 C to +1 C Lead Temperature (Soldering 6 sec) 3 C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ESD CAUTION Rev. A Page 6 of

7 VIN GND GND VCC VIP 1 ENB 1 VCM 13 VCC AD83 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS RDP RGP RGN RDN 1 3 PIN 1 INDICATOR AD83 TOP VIEW (Not to Scale) 1 GND 11 VOP 1 VON 9 GND Figure 3. Pin Configuration Table. Pin Function Descriptions Pin No. Mnemonic Description 1 RDP Positive Distortion Adjust. RGP Positive Gain Adjust. 3 RGN Negative Gain Adjust. RDN Negative Distortion Adjust. VIN Balanced Differential Input. Biased to VCM, typically ac-coupled. 6, 7, 9, 1 GND Ground. Connect to low impedance GND. 8, 13 VCC Positive Supply. 1 VON Balanced Differential Output. Biased to VCM, typically ac-coupled. 11 VOP Balanced Differential Output. Biased to VCM, typically ac-coupled. 1 VCM Common-Mode Voltage. A voltage applied to this pin sets the common-mode voltage of the input and output. Typically decoupled to ground with a.1 μf capacitor. With no reference applied, input and output common mode floats to midsupply (VCC/). 1 ENB Enable. Apply positive voltage (1.3 V < ENB < VCC) to activate device. 16 VIP Balanced Differential Input. Biased to VCM, typically ac-coupled Rev. A Page 7 of

8 TYPICAL PERFORMANCE CHARACTERISTICS 3 R G =3Ω R G =Ω 1 1 R G = 1Ω R G = Ω 1 1 R G = 1Ω R G = 18Ω R G = 383Ω R G = 71Ω 1 1 1k 1k Figure. Gain vs. Frequency for a Ω Differential Load with Baluns, AV = 18 db, 1 db, and 6 db k 1k Figure 7. Gain vs. Frequency for a 1 kω Differential Load Without Baluns, RD/CD Open, AV = db, 1 db, 1 db, 6 db, and 3 db R G =6Ω R G = 19Ω R G =3kΩ C +8 C + C C +8 C R L = Ω R G = 118Ω T C =. + C R L =1kΩ R G = 18Ω T C =.db/ C k 1k Figure. Gain vs. Frequency for a 1 kω Differential Load with Baluns, AV = 18 db, 1 db, and 6 db k 1k Figure 8. Gain vs. Frequency over Temperature ( C, + C, +8 C) Without Baluns, AV = 1 db, RL = Ω and 1 kω 78-8 R G =19Ω 7 R L =Ω 1 R G =6Ω 6 1 R G = 118Ω R G = 3Ω CMRR (db) R L =1kΩ R G = 39Ω k 1k Figure 6. Gain vs. Frequency for a Ω Differential Load Without Baluns, RD/CD Open, AV = db, 1 db, 1 db, 6 db, and 3 db Figure 9. CMRR vs. Frequency, RL = Ω and 1 kω, Differential Source Resistance 78-3 Rev. A Page 8 of

9 . 16. NOISE FIGURE (db), IP3 (dbm) OIP3 A V = 6dB A V = 1dB A V = 1dB NOISE FIGURE. A. V = 1dB A V = 1dB SPECTRAL NOISE DENSITY RTI (nv/ Hz) 78-9 OUTPUT P1dB (dbm) MHz 38MHz MHz 1MHz 1MHz 19MHz MHz GAIN SETTING RESISTOR (Ω) 78-1 Figure 1. Noise Figure, OIP3, and Spectral Noise Density vs. Frequency, V p-p Composite, RL = Ω Figure 13. Output 1 db Compression Point vs. RG for Multiple Frequencies, RL = Ω 7MHz 1MHz 1MHz 6 6 OIP3 (dbm) 3 3 MHz 38MHz MHz 19MHz HARMONIC DISTORTION () HD3 HD GAIN SETTING RESISTOR (Ω) Figure 11. Output IP3 vs. RG for Multiple Frequencies, RL = Ω Figure 1. Harmonic Distortion vs. Frequency for V p-p into RL = 1 kω, AV = 1 db, V Supply, RG = 18 Ω, RD = 6.8 kω, CD =.1 pf 78-6 > 3MHz NO C D OR R D USED 6 6 HARMONIC DISTORTION () HD3 V p-p HD3 1V p-p HD V p-p HARMONIC DISTORTION () HD3 HD Figure 1. Third-Order Harmonic Distortion HD3 vs. Frequency, AV = 1 db, RL = Ω Figure 1. Harmonic Distortion vs. Frequency for V p-p into RL = Ω, AV = 1 db, RG = 11 Ω, RD =.3 kω, CD =. pf 78-7 Rev. A Page 9 of

10 .6 1. T RISE (1/9) = 1psec T FALL (1/9) = 1psec. 1. GROUP DELAY (ns) PHASE (Degrees) VOLTAGE (V) Figure 16. Phase and Group Delay vs. Frequency, AV = 1 db, RL = Ω TIME (nsec) Figure 19. Large Signal Output Transient Response, RL = Ω, AV = 1 db INPUT RESISTANCE (Ω) INPUT CAPACITANCE (pf) SETTLING (%) Figure 17. S11 Equivalent RC Parallel Network RG = 11 Ω TIME (nsec) Figure. 1% Settling Time for a V p-p Step Response, AV = 1 db, RL = Ω OUTPUT RESISTANCE (Ω) OUTPUT CAPACITANCE (pf) SPECTRAL NOISE DENSITY RTI (nv/ Hz) NOISE FIGURE (db) Figure 18. S Equivalent RC Parallel Network RG = 11 Ω GAIN SETTING RESISTOR (Ω) Figure 1. Noise Figure and Noise Spectral Density RTI vs. RG, RL = Ω 78- Rev. A Page 1 of

11 APPLICATIONS GAIN AND DISTORTION ADJUSTMENT (DIFFERENTIAL INPUT) Table and Table 6 show the required value of RG for the gains specified at Ω and 1 kω loads. Figure and Figure plot gain vs. RG up to 18 db for both load conditions. For other output loads (RL), use Equation 1 to compute gain vs. RG. A where: VDifferential = ( R RL = single-ended load. RG = gain setting resistor. G RG + R + ) ( R L + 3) + 3 The third-order harmonic distortion can be reduced by using external components RD and CD. Table and Table 6 show the required values for RD and CD for the specified gains to achieve (single tone) third-order distortion reduction at 18 MHz. Figure 3 and Figure show any gain (up to 18 db) vs. CD for Ω and 1 kω loads, respectively. When these values are selected, they result in minimum single tone, third-order distortion at 18 MHz. This frequency point provides the best overall broadband distortion for the specified frequencies below and above this value. For applications above approximately 3 MHz, CD and RD are not required. See the Specifications section and third-order harmonic plots in the Typical Performance Characteristics section for more details. L (1) Table 6. Broadband Selection of RG, CD, and RD: 1 kω Load AV (db) RG (Ω) CD (pf) RD (kω) 3 7 Open Open Open R G (Ω) Figure. Gain vs. RG, RL = Ω 78-6 CD can be further optimized for narrow-band tuning requirements below 18 MHz that result in relatively lower third-order (in-band) intermodulation distortion terms. See the Narrow- Band, Third-Order Intermodulation Cancellation section for more information. Though not shown, single tone, third-order optimization can also be improved for narrow-band frequency applications below 18 MHz with the proper selection of CD, and 3 db to 6 db of relative third-order improvement can be realized at frequencies below approximately 1 MHz. Using the information listed in Table and Table 6, an extrapolated value for RD can be determined for loads between Ω and 1 kω. For loads above 1 kω, use the 1 kω RD values listed in Table 6. Table. Broadband Selection of RG, CD, and RD: Ω Load AV (db) RG (Ω) CD (pf) RD (kω) 3 39 Open Open C D (pf) Figure 3. Gain vs. CD, RL = Ω 78-7 Rev. A Page 11 of

12 18.1µF VIP.1µF Ω AC 6Ω Ω.1µF C D R D R N Ω R G RGP AD83 RGN Figure 6. Single-Ended Schematic.1µF R G (Ω) Figure. Gain vs. RG, RL = 1 kω GAIN, R L =1kΩ GAIN, R L =Ω k 1k R G (Ω) 78-6 Figure 7. Gain vs. RG C D (pf) Figure. Gain vs. CD, RL = 1 kω SINGLE-ENDED INPUT OPERATION The AD83 can be configured as a single-ended to differential amplifier as shown in Figure 6. To balance the outputs when driving only the VIP input, an external resistor (RN) of Ω is added between VIP and RGN. See Equation to determine the single-ended input gain (AVSingle-ended) for a given RG or RL. where: R G + RL A VSingle ended = R + ( ) ( 3) 3 L () R RL + 3 G RL RL = single-ended load. RG = gain setting resistor. Figure 7 plots gain vs. RG for Ω and 1 kω loads. Table 7 and Table 8 show the values of CD and RD required (for 18 MHz broadband, third-order, single tone optimization) for Ω and 1 kω loads, respectively. This single-ended configuration provides 3 db bandwidths similar to input differential drive. Figure 8 through Figure 3 show distortion levels at a gain of 1 db for both Ω and 1 kω loads. Gains from 3 db to 18 db, using optimized CD and RD values, obtain similar distortion levels () NDS, V p-p OUT NDS, 1V p-p OUT Figure 8. Single-Ended, Second-Order Harmonic Distortion, Ω Load This broadband optimization was also performed at 18 MHz. As with differential input drive, the resulting distortion levels at lower frequencies are based on the CD and RD specified in Table 7 and Table 8. As with differential input drive, relative third-order reduction improvement at frequencies below 1 MHz are realized with proper selection of CD and RD Rev. A Page 1 of

13 () RDS, V p-p OUT Table 8. Distortion Cancellation Selection Components (RD and CD) for Required Gain, 1 kω Load AV (db) RG (Ω) CD (pf) RD (kω) 6 3 k Open Open RDS, 1V p-p OUT Figure 9. Single-Ended, Third-Order Harmonic Distortion, Ω Load NARROW-BAND, THIRD-ORDER INTERMODULATION CANCELLATION Broadband, single tone, third-order harmonic optimization does not necessarily result in optimum (minimum) two tone, third-order intermodulation levels. The specified values for CD and RD in Table and Table 6 were determined for minimizing broadband, single tone, third-order levels. () NDS, V p-p OUT NDS, 1V p-p OUT Due to phase-related distortion coefficients, optimizing single tone, third-order distortion does not result in optimum in band (f1 f and f f1), third-order distortion levels. By proper selection of CD (using a fixed.3 kω RD), IP3s of better than dbm are achieved. This results in degraded out-of-band, third-order frequencies (f + f1, f1 + f, 3f1 and 3f). Thus, careful frequency planning is required to determine the tradeoffs Figure 3. Single-Ended, Second-Order Harmonic Distortion, 1 kω Load () RDS, 1V p-p OUT 11 3RDS, V p-p OUT Figure 31. Single-Ended, Third-Order Harmonic Distortion, 1 kω Load Table 7. Distortion Cancellation Selection Components (RD and CD) for Required Gain, Ω Load AV (db) RG (Ω) CD (pf) RD (kω) 3.3 k Open.3 6 Open Figure 3 shows narrow band ( MHz spacing) OIP3 levels optimized at 3 MHz, 7 MHz, 1 MHz, and 18 MHz using the CD values specified in Figure 33. These four data points (the CD value and associated IP3 levels) are extrapolated to provide close estimates of IP3 levels for any specific frequency between 3 MHz and 18 MHz. For frequencies below approximately 1 MHz, narrow-band tuning of IP3 results in relatively higher IP3s (vs. the broadband results shown in Table specifications). Though not shown, frequencies below 3 MHz also result in improved IP3s when using proper values for CD. OIP3 (dbm) A V = 6dB 1dB 1dB 18dB R L = Ω R D =.3kΩ C D =.3pF Figure 3. Third-Order Intermodulation Distortion vs. Frequency for Various Gain Settings 78-3 Rev. A Page 13 of

14 C D (pf) A V = 6dB 1dB 1dB 18dB R L = Ω R D =.3kΩ Figure 33. Narrow-Band CD vs. Frequency for Various Gain Settings HIGH PERFORMANCE ADC DRIVING The AD83 provides the gain, isolation, and balanced low distortion output levels for efficiently driving wideband ADCs such as the AD9. Figure 3 and Figure 3 (single and differential input drive) illustrate the typical front-end circuit interface for the AD83 differentially driving the AD9 1-bit ADC at 1 MSPS. The AD83, when used in the single-ended configuration, shows little or no degradation in overall third-order harmonic performance (vs. differential drive). See the Single-Ended Input Operation section. The 1 MHz FFT plots shown in Figure 36 and Figure 37 display the results for the differential configuration. Though not shown, the single-ended, third-order levels are similar. The Ω resistor shown in Figure 3 provides a Ω differential input impedance to the source for matching considerations. When the driver is less than one eighth of the wavelength from the AD83, impedance matching is not required thereby negating the need for this termination resistor. The output Ω resistors provide isolation from the analog-to-digital input. Refer to the Layout and Transmission Line Effects section for more information. The circuit in Figure 3 represents a singleended input to differential output configuration for driving the AD9. In this case, the input Ω resistor with RN (typically Ω) provide the input impedance match for a Ω system. Again, if input reflections are minimal, this impedance match is not required. A fixed Ω resistor (RN) is required to balance the output voltages that are required for second-order distortion cancellation. RG is the gain setting resistor for the AD83 with the RD and CD components providing distortion cancellation. The AD9 presents approximately kω in parallel with pf/differential load to the AD83 and requires a. V p-p differential signal (VREF = 1 V) between VIN+ and VIN for a full-scale output operation These AD83 simplified circuits provide the gain, isolation, and distortion performance necessary for efficiently driving high linearity converters such as the AD9. This device also provides balanced outputs whether driven differentially or single-ended, thereby maintaining excellent second-order distortion levels. However, at frequencies above approximately 1 MHz, due to phase related errors, single-ended, secondorder distortion is relatively higher. The output of the amplifier is ac-coupled to allow for an optimum common-mode setting at the ADC input. Input ac coupling can be required if the source also requires a common-mode voltage that is outside the optimum range of the AD83. A VCM common-mode pin is provided on the AD83 that equally shifts both input and output common-mode levels. Increasing the gain of the AD83 increases the system noise and, thus, decreases the SNR (3. db at 1 MHz input for Av = 1 db) of the AD9 when no filtering is used. Note that amplifier gains from 3 db to 18 db, with proper selection of CD and RD, do not appreciably affect distortion levels. These circuits, when configured properly, can result in SFDR performance of better than 87 at 7 MHz and 8 at 18 MHz input. Single-ended drive, with appropriate CD and RD, give similar results for SFDR and third-order intermodulation levels shown in these figures. Placing antialiasing filters between the ADC and the amplifier is a common approach for improving overall noise and broadband distortion performance for both band-pass and low-pass applications. For high frequency filtering, matching to the filter is required. The AD83 maintains a 1 Ω output impedance well beyond most applications and is well-suited to drive most filter configurations with little or no degradation in distortion. IF/RF INPUT ADT1-1WT Ω AC Ω Ω.1µF Ω 16 1 C D 3 R D R G.1µF Ω V CC 8, AD83 1.1µF.1µF 1.1µF Ω.1µF Ω Figure 3. Differential Input to the AD83 Driving the AD9 Ω.1µF.1µF C D R D R N Ω R G VIN VIP.1µF VOP 33Ω AD83 VON.1µF 33Ω AD9 VIN+ AD9 VIN Figure 3. Single-Ended Input to the AD83 Driving the AD Rev. A Page 1 of

15 (dbfs) SNR = 67.6 SFDR = NOISE FLOOR = 11.dB FUND = 1.7dBFS SECOND = 83.1 THIRD = Figure 36. Single Tone Distortion AD83 Driving AD9, Encode 1 MHz with 1 MHz (AV = 1 db), See Figure 3 (dbfs) SNR = NOISE FLOOR = 111.dB FUND1 = 7.7dBFS FUND = 7.3dBFS 3 IMD (F-F1) = 89 IMD (F1-F) = Figure 37. Two Tone Distortion AD83 Driving AD9, Encode 1 MHz with 1 MHz (AV = 1 db), Analog In = 98 MHz and 11 MHz, See Figure LAYOUT AND TRANSMISSION LINE EFFECTS High Q inductive drives and loads, as well as stray transmission line capacitance in combination with package parasitics, can potentially form a resonant circuit at high frequencies resulting in excessive gain peaking or possible oscillation. If RF transmission lines connecting the input or output are used, they should be designed such that stray capacitance at the I/O pins is minimized. In many board designs, the signal trace widths should be minimal where the driver/receiver is less than oneeighth of the wavelength from the AD83. This nontransmission line configuration requires that underlying and adjacent ground and low impedance planes be far removed from the signal lines. In a similar fashion, stray capacitance should be minimized near the RG, CD, and RD components and associated traces. This also requires not placing low impedance planes near these components. Refer to the evaluation board layout (Figure 39 and Figure ) for more information. Excessive stray capacitance at these nodes results in unwanted high frequency distortion. The.1 μf supply decoupling capacitors need to be close to the amplifier. This includes Signal Capacitor C through Signal Capacitor C. Parasitic suppressing resistors (R, R6, R7, and R11) can be used at the device I/O pins. Use Ω series resistors (Size ) to adequately de-q the input and output system from most parasitics without a significant decrease in gain. In general, if proper board layout techniques are used, the suppression resistors are not necessarily required. Output Parasitic Suppression Resistor R7 and Output Parasitic Suppression Resistor R11 can be required for driving some switch cap ADCs. These suppressors, with Input C of the converter (and possibly added External Shunt C), help provide charge kickback isolation and improve overall distortion at high encode rates. Rev. A Page 1 of

16 EVALUATION BOARD An evaluation board is available for experimentation of various parameters such as gain, common-mode level, and distortion. The output network can be configured for different loads via minor output component changes. The schematic and evaluation board artwork are presented in Figure 38, Figure 39, and Figure. All discrete capacitors and resistors are Size, except for C1 (38-B). Table 9. Evaluation Board Circuit Components and Functions Component Name Function Additional Information C8, C9 Capacitors C8 and C9 are bypass capacitors. C8 =.1 μf, C9 =.1 μf RD, CD R1, R, R3, R, R, R6, T, C, C3 R7, R8, R9, R11, R1, R13, R1, T1, C, C Distortion Tuning Components Resistors, Transformer, Capacitors Resistors, Transformer, Capacitors Distortion Adjustment Components. Allows for third-order distortion adjustment HD3. Input Interface. R1 and R ground one side of the differential drive interface for single-ended applications. T is a 1-to-1 impedance ratio balun to transform a single-ended input into a balanced differential signal. R and R3 provide a differential Ω input termination. R and R6 can be increased to reduce gain peaking when driving from a high source impedance. The Ω termination provides an insertion loss of 6 db. C and C3 provide ac-coupling. Output Interface. R13 and R1 ground one side of the differential output interface for single-ended applications. T1 is a 1-to-1 impedance ratio balun to transform a balanced differential signal to a singleended signal. R8, R9, and R1 are provided for generic placement of matching components. R7 and R11 allow additional output series resistance when driving capacitive loads. The evaluation board is configured to provide a Ω to Ω impedance transformation with an insertion loss of 11.6 db. C and C provide ac-coupling. R7 and R11 provide additional series resistance when driving capacitive loads. RG Resistor Gain Setting Resistor. Resistor RG is used to set the gain of the device. Refer to Table and Table 6 when selecting the gain resistor. C1, C6, C7 Capacitors Power Supply Decoupling. The supply decoupling consists of a 1 μf capacitor to ground. C6 and C7 are bypass capacitors. Typically, both are open above 3 MHz CD =. pf, RD =.3 kω CD is Panasonic High Q (microwave) Multilayer Chip capacitor T = M/A-COM, Inc. ETC R1 = open, R = Ω, R3 = Ω, R = Ω, R = Ω, R6 = Ω, C =.1 μf, C3 =.1 μf T1= M/A-COM ETC R7 = Ω, R8 = 86.6 Ω, R9 = 7.6 Ω, R11 = Ω, R1 = 86.6 Ω, R13 = Ω, R1 = open C =.1 μf, C =.1 μf RG = 11 Ω (Size ) for a gain of 1 db C1 = 1 μf C6 =.1 μf, C7 =.1 μf EVALUATION BOARD LOADING SCHEMES The AD83 evaluation board is characterized with two load configurations representing the most common ADC input resistance. The loads chosen are Ω and 1 Ω using a broadband resistive match. The loading can be changed via R8, R9, and R1 giving the flexibility to characterize the AD83 evaluation board for the load in any given application. These loads are inherently lossy and thus must be accounted for in overall gain/loss for the entire evaluation board. Measure the gain of the AD83 with an oscilloscope using the following procedure to determine the actual gain: Table 1. Values Used for Ω and 1 Ω Loads Component Ω Load (Ω) 1 Ω Load (Ω) R R R Measure the peak-to-peak voltage at the input node (C or C3).. Measure the peak-to-peak voltage at the output node (C or C). 3. Compute gain using the formula Gain = log(v OUT/V IN ) Rev. A Page 16 of

17 EVALUATION BOARD SCHEMATICS VINP VINN ENBL VCM VPOS R19 Ω YELLOW YELLOW SWITCH_SPDT VCM GND R1 OPEN R Ω T M/A_COM ETC R Ω R3 Ω C D.pF R18 Ω C.1µF C3.1µF R D.3kΩ R Ω R6 Ω SW1 C8.1µF ENB Z1 R Ω C9.1µF VPOS BLACK ENB VCM VCC R G 11Ω RDP RGP RGN RDN 1 3 VIP VIN AD VPOS GND VOP VON GND R7 Ω R11 Ω C.1µF C.1µF R8 86.6Ω R1 86.6Ω R9 7.6Ω GND GND VCC Ω TRACES HIGH IMPEDANCE TRACES (OPEN PLANES UNDER TRACES) CALIBRATION CIRCUIT BYPASS CIRCUIT VPOS J1 J 1 T3 C11.1µF 3 C1.1µF 1 T 3 RED + C1 C6 C7 1µF.1µF.1µF VPOS LOCATE CAPS NEAR DUT 1 3 T1 R1 OPEN M/A_COM ETC R13 Ω Ω TRACES VOUTP VOUTN Figure 38. Preliminary Characterization Board v.a11a Rev. A Page 17 of

18 Figure 39. Component Side Silk Screen Figure. Far Side Showing Ground Plane Pull Back Around Critical Features Rev. A Page 18 of

19 OUTLINE DIMENSIONS PIN 1 INDICATOR 3. BSC SQ TOP VIEW.7 BSC SQ....6 MAX.3 PIN EXPOSED PAD 16 1 INDICATOR * SQ SEATING PLANE 1 MAX.8 MAX.6 TYP. BSC 1. REF 9 (BOTTOM VIEW) 8. MAX. NOM.3. REF.3.18 *COMPLIANT TO JEDEC STANDARDS MO--VEED- EXCEPT FOR EXPOSED PAD DIMENSION. Figure Lead Lead Frame Chip Scale Package [LFCSP_VQ] 3 mm 3 mm Body, Very Thin Quad (CP-16-3) Dimensions shown in millimeters ORDERING GUIDE Model Temperature Range Package Description Package Option AD83ACPZ-WP 1 C to +8 C 16-Lead [LFCSP_VQ] Waffle Pack CP-16-3 AD83ACPZ-R7 1 C to +8 C 16-Lead [LFCSP_VQ] 7 Tape and Reel CP-16-3 AD83-EVALZ 1 Evaluation Board 1 Z = Pb-free part.. MIN Rev. A Page 19 of

20 NOTES 6 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D78--9/6(A) Rev. A Page of