ANALOG DEVICES AD8350

Low Distortion a 1.0 GHz Differential Amplifier AD8350 FEATURES FUNCTIONAL BLOCK DIAGRAM High Dynamic Range 8-Lead SOIC and �SOIC Packages (with Enable) Output IP3: +28 dBm: Re 50 � @ 250 MHz Low Noise Figure: 5.9 dB @ 250 MHz IN+ 1 8 IN– Two Gain Versions: AD8350-15: 15 dB – ENBL 2 + 7 GND AD8350-20: 20 dB V GND 3 6 CC –3 dB Bandwidth: 1.0 GHz OUT+ 4 5 OUT– Single Supply Operation: 5 V to 10 V AD8350 Supply Current: 28 mA Input/Output Impedance: 200 � Single-Ended or Differential Input Drive 8-Lead SOIC Package and 8-Lead microSOIC Package APPLICATIONS Cellular Base Stations Communications Receivers RF/IF Gain Block Differential A-to-D Driver SAW Filter Interface Single-Ended-to-Differential Conversion High Performance Video High Speed Data Transmission PRODUCT DESCRIPTION The amplifier can be operated down to 5 V with an OIP3 of The AD8350 series are high performance fully-differential +28 dBm at 250 MHz and slightly reduced distortion perfor- amplifiers useful in RF and IF circuits up to 1000 MHz. The mance. The wide bandwidth, high dynamic range and temperature amplifier has excellent noise figure of 5.9 dB at 250 MHz. It stability make this product ideal for the various RF and IF offers a high output third order intercept (OIP3) of +28 dBm frequencies required in cellular, CATV, broadband, instrumen- at 250 MHz. Gain versions of 15 dB and 20 dB are offered. tation and other applications. The AD8350 is designed to meet the demanding performance The AD8350 is offered in an 8-lead single SOIC package and requirements of communications transceiver applications. It µSOIC package. It operates from 5 V and 10 V power supplies, enables a high dynamic range differential signal chain, with drawing 28 mA typical. The AD8350 offers a power enable func- exceptional linearity and increased common-mode rejection. tion for power-sensitive applications. The AD8350 is fabricated The device can be used as a general purpose gain block, an using Analog Devices’ proprietary high speed complementary A-to-D driver, and high speed data interface driver, among bipolar process. The device is available in the industrial (–40°C to other functions. The AD8350 input can also be used as a single- +85°C) temperature range. ended-to-differential converter. REV. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. use, nor for any infringements of patents or other rights of third parties that Tel: 781/329-4700 www.analog.com may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781/326-8703 © Analog Devices, Inc., 2001 (@ 25�C, V = 5 V, G = 15 dB, unless otherwise noted. All specifications refer to S differential inputs and differential outputs unless noted.) AD8350–SPECIFICATIONS Parameter Conditions Min Typ Max Unit DYNAMIC PERFORMANCE –3 dB Bandwidth V = 5 V, V = 1 V p-p 0.9 GHz S OUT V = 10 V, V = 1 V p-p 1.1 GHz S OUT Bandwidth for 0.1 dB Flatness V = 5 V, V = 1 V p-p 90 MHz S OUT V = 10 V, V = 1 V p-p 90 MHz S OUT Slew Rate V = 1 V p-p 2000 V/µs OUT Settling Time 0.1%, V = 1 V p-p 10 ns OUT 1 Gain (S21) V = 5 V, f = 50 MHz 14 15 16 dB S Gain Supply Sensitivity V = 5 V to 10 V, f = 50 MHz 0.003 dB/V S Gain Temperature Sensitivity T to T –0.002 dB/°C MIN MAX 1 Isolation (S12) f = 50 MHz –18 dB NOISE/HARMONIC PERFORMANCE 50 MHz Signal Second Harmonic V = 5 V, V = 1 V p-p –66 dBc S OUT V = 10 V, V = 1 V p-p –67 dBc S OUT Third Harmonic V = 5 V, V = 1 V p-p –65 dBc S OUT V = 10 V, V = 1 V p-p –70 dBc S OUT 2 Output Second Order Intercept V = 5 V 58 dBm S V = 10 V 58 dBm S 2 Output Third Order Intercept V = 5 V 28 dBm S V = 10 V 29 dBm S 250 MHz Signal Second Harmonic V = 5 V, V = 1 V p-p –48 dBc S OUT V = 10 V, V = 1 V p-p –49 dBc S OUT Third Harmonic V = 5 V, V = 1 V p-p –52 dBc S OUT V = 10 V, V = 1 V p-p –61 dBc S OUT 2 Output Second Order Intercept V = 5 V 39 dBm S V = 10 V 40 dBm S 2 Output Third Order Intercept V = 5 V 24 dBm S V = 10 V 28 dBm S 2 1 dB Compression Point (RTI) V = 5 V 2 dBm S V = 10 V 5 dBm S Voltage Noise (RTI) f = 150 MHz 1.7 nV/√Hz Noise Figure f = 150 MHz 6.8 dB INPUT/OUTPUT CHARACTERISTICS Differential Offset Voltage (RTI) V – V ±1mV OUT+ OUT– Differential Offset Drift T to T 0.02 mV/°C MIN MAX Input Bias Current 15 µA Input Resistance Real 200 Ω CMRR f = 50 MHz –67 dB Output Resistance Real 200 Ω POWER SUPPLY Operating Range 411.0V Quiescent Current Powered Up, V = 5 V 25 28 32 mA S Powered Down, V = 5 V 3 3.8 5.5 mA S Powered Up, V = 10 V 27 30 34 mA S Powered Down, V = 10 V 3 4 6.5 mA S Power-Up/Down Switching 15 ns Power Supply Rejection Ratio f = 50 MHz, V ∆ = 1 V p-p –58 dB S OPERATING TEMPERATURE RANGE –40 +85 °C NOTES 1 See Tables II–III for complete list of S-Parameters. 2 Re: 50 Ω. Specifications subject to change without notice. –2– REV. A AD8350 (@ 25�C, V = 5 V, G = 20 dB, unless otherwise noted. All specifications refer to AD8350-20–SPECIFICATIONS S differential inputs and differential outputs unless noted.) Parameter Conditions Min Typ Max Unit DYNAMIC PERFORMANCE –3 dB Bandwidth V = 5 V, V = 1 V p-p 0.7 GHz S OUT V = 10 V, V = 1 V p-p 0.9 GHz S OUT Bandwidth for 0.1 dB Flatness V = 5 V, V = 1 V p-p 90 MHz S OUT V = 10 V, V = 1 V p-p 90 MHz S OUT Slew Rate V = 1 V p-p 2000 V/µs OUT Settling Time 0.1%, V = 1 V p-p 15 ns OUT 1 Gain (S21) V = 5 V, f = 50 MHz 19 20 21 dB S Gain Supply Sensitivity V = 5 V to 10 V, f = 50 MHz 0.003 dB/V S Gain Temperature Sensitivity T to T –0.002 dB/°C MIN MAX 1 Isolation (S12) f = 50 MHz –22 dB NOISE/HARMONIC PERFORMANCE 50 MHz Signal Second Harmonic V = 5 V, V = 1 V p-p –65 dBc S OUT V = 10 V, V = 1 V p-p –66 dBc S OUT Third Harmonic V = 5 V, V = 1 V p-p –66 dBc S OUT V = 10 V, V = 1 V p-p –70 dBc S OUT 2 Output Second Order Intercept V = 5 V 56 dBm S V = 10 V 56 dBm S 2 Output Third Order Intercept V = 5 V 28 dBm S V = 10 V 29 dBm S 250 MHz Signal Second Harmonic V = 5 V, V = 1 V p-p –45 dBc S OUT V = 10 V, V = 1 V p-p –46 dBc S OUT Third Harmonic V = 5 V, V = 1 V p-p –55 dBc S OUT V = 10 V, V = 1 V p-p –60 dBc S OUT 2 Output Second Order Intercept V = 5 V 37 dBm S V = 10 V 38 dBm S 2 Output Third Order Intercept V = 5 V 24 dBm S V = 10 V 28 dBm S 2 1 dB Compression Point (RTI) V = 5 V –2.6 dBm S V = 10 V 1.8 dBm S Voltage Noise (RTI) f = 150 MHz 1.7 nV/√Hz Noise Figure f = 150 MHz 5.6 dB INPUT/OUTPUT CHARACTERISTICS Differential Offset Voltage (RTI) V – V ±1mV OUT+ OUT– Differential Offset Drift T to T 0.02 mV/°C MIN MAX Input Bias Current 15 µA Input Resistance Real 200 Ω CMRR f = 50 MHz –52 dB Output Resistance Real 200 Ω POWER SUPPLY Operating Range 411.0V Quiescent Current Powered Up, V = 5 V 25 28 32 mA S Powered Down, V = 5 V 3 3.8 5.5 mA S Powered Up, V = 10 V 27 30 34 mA S Powered Down, V = 10 V 3 4 6.5 mA S Power-Up/Down Switching 15 ns Power Supply Rejection Ratio f = 50 MHz, V ∆ = 1 V p-p –45 dB S OPERATING TEMPERATURE RANGE –40 +85 °C NOTES 1 See Tables II–III for complete list of S-Parameters. 2 Re: 50 Ω. REV. A –3– AD8350 PIN FUNCTION DESCRIPTIONS ABSOLUTE MAXIMUM RATINGS* Supply Voltage, V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 V S Pin Function Description Input Power Differential . . . . . . . . . . . . . . . . . . . . . . +8 dBm Internal Power Dissipation . . . . . . . . . . . . . . . . . . . . 400 mW 1, 8 IN+, IN– Differential Inputs. IN+ and IN– θ SOIC (R) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100°C/W JA should be ac-coupled (pins have a dc θ µSOIC (RM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133°C/W JA bias of midsupply). Differential input Maximum Junction Temperature . . . . . . . . . . . . . . . . . 125°C impedance is 200 Ω. Operating Temperature Range . . . . . . . . . . . –40°C to +85°C 2 ENBL Power-up Pin. A high level (5 V) enables Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C the device; a low level (0 V) puts device Lead Temperature Range (Soldering 60 sec) . . . . . . . . . 300°C in sleep mode. *Stresses above those listed under Absolute Maximum Ratings may cause perma- 3V Positive Supply Voltage. 5 V to 10 V. CC nent damage to the device. This is a stress rating only; functional operation of the 4, 5 OUT+, OUT– Differential Outputs. OUT+ and 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 OUT– should be ac-coupled (pins have conditions for extended periods may affect device reliability. a dc bias of midsupply). Differential input impedance is 200 Ω. PIN CONFIGURATION 6, 7 GND Common External Ground Reference. 1 8 IN– IN+ ENBL 2 AD8350 7 GND TOP VIEW V 3 6 GND CC (Not to Scale) 4 OUT+ 5 OUT– ORDERING GUIDE Model Temperature Range Package Description Package Option Brand Code AD8350AR15 –40°C to +85°C 8-Lead SOIC SO-8 Standard AD8350AR15-REEL –40°C to +85°C 8-Lead SOIC 13" Reel SO-8 Standard AD8350AR15-REEL7 –40°C to +85°C 8-Lead SOIC 7" Reel SO-8 Standard AD8350ARM15 –40°C to +85°C 8-Lead microSOIC RM-8 J2N AD8350ARM15-REEL –40°C to +85°C 8-Lead microSOIC 13" Reel RM-8 J2N AD8350ARM15-REEL7 –40°C to +85°C 8-Lead microSOIC 7" Reel RM-8 J2N AD8350AR20 –40°C to +85°C 8-Lead SOIC SO-8 Standard AD8350AR20-REEL –40°C to +85°C 8-Lead SOIC 13" Reel SO-8 Standard AD8350AR20-REEL7 –40°C to +85°C 8-Lead SOIC 7" Reel SO-8 Standard AD8350ARM20 –40°C to +85°C 8-Lead microSOIC RM-8 J2P AD8350ARM20-REEL –40°C to +85°C 8-Lead microSOIC 13" Reel RM-8 J2P AD8350ARM20-REEL7 –40°C to +85°C 8-Lead microSOIC 7" Reel RM-8 J2P AD8350-EVAL SOIC Evaluation Board CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily WARNING! accumulate on the human body and test equipment and can discharge without detection. Although the AD8350 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are ESD SENSITIVE DEVICE recommended to avoid performance degradation or loss of functionality. –4– REV. A Typical Performance Characteristics–AD8350 20 25 50 V = 10V CC 40 15 20 V = 10V V = 10V CC CC 30 V = 5V CC 10 15 V = 5V CC 20 5 10 10 V = 5V CC 0 0 5 0 –40 –20 20 40 60 80 1 10 100 1k 10k 1 10 100 1k 10k TEMPERATURE – �C FREQUENCY – MHz FREQUENCY – MHz TPC 1. Supply Current vs. TPC 2. AD8350-15 Gain (S21) vs. TPC 3. AD8350-20 Gain (S21) vs. Temperature Frequency Frequency 350 350 500 300 400 300 �SOIC 300 250 250 V = 10V SOIC CC V = 10V CC 200 200 200 V = 5V CC V = 5V CC 100 150 150 0 100 100 0 10 100 1000 1 10 100 1k 1 10 100 1k FREQUENCY – MHz FREQUENCY – MHz FREQUENCY – MHz TPC 4. AD8350-15 Input Imped- TPC 5. AD8350-20 Input Impedance TPC 6. AD8350-15 Output Impedance ance vs. Frequency vs. Frequency vs. Frequency 800 –5 –10 �SOIC 600 –10 –15 V = 10V CC 400 SOIC –15 –20 V = 10V CC 200 –20 –25 V = 5V CC V = 5V CC 0 –25 –30 0 10 100 1000 1 10 100 1k 10k 1 10 100 1k 10k FREQUENCY – MHz FREQUENCY – MHz FREQUENCY – MHz TPC 7. AD8350-20 Output Imped- TPC 8. AD8350-15 Isolation (S12) TPC 9. AD8350-20 Isolation (S12) ance vs. Frequency vs. Frequency vs. Frequency REV. A –5– IMPEDANCE – � IMPEDANCE – � SUPPLY CURRENT – mA ISOLATION – dB IMPEDANCE – � GAIN – dB IMPEDANCE – � ISOLATION – dB GAIN – dB AD8350 –45 –40 –40 F = 50MHz V = 1V p-p O V = 1V p-p OUT OUT –45 HD2 (V = 10V) –45 HD3 (V = 5V) CC CC HD2 (V = 5V) CC HD2 (V = 5V) –55 HD2 (V = 5V) –50 CC –50 CC HD2 (V = 10V) CC –55 –55 HD3 (V = 5V) CC –65 –60 –60 HD2 (V = 10V) CC –65 –65 HD3 (V = 5V) CC HD3 (V = 10V) CC HD3 (V = 10V) CC –70 –75 –70 HD3 (V = 10V) CC –75 –75 –80 –85 –80 0 0 0.5 1 1.5 2 2.5 3 3.5 50 100 150 200 250 300 0 50 100 150 200 250 300 OUTPUT VOLTAGE – V p-p FUNDAMENTAL FREQUENCY – MHz FUNDAMENTAL FREQUENCY – MHz TPC 10. AD8350-15 Harmonic TPC 12. AD8350-15 Harmonic Distor- TPC 11. AD8350-20 Harmonic Dis- Distortion vs. Frequency tion vs. Differential Output Voltage tortion vs. Frequency 66 –45 66 F = 50MHz O HD2 (V = 5V) CC 61 61 HD3 (V = 5V) CC –55 V = 10V CC V = 10V CC 56 56 51 51 –65 HD2 (V = 10V) CC V = 5V V = 5V CC CC 46 46 HD3 (V = 10V) CC –75 41 41 –85 36 36 0 0.5 1 1.5 2 2.5 3 3.5 0 50 100 150 200 250 300 0 50 100 150 200 250 300 OUTPUT VOLTAGE – V p-p FREQUENCY – MHz FREQUENCY – MHz TPC 15. AD8350-20 Output Referred TPC 13. AD8350-20 Harmonic Distor- TPC 14. AD8350-15 Output Referred IP2 vs. Frequency tion vs. Differential Output Voltage IP2 vs. Frequency 41 41 10.0 INPUT REFERRED 36 36 7.5 V = 10V CC V = 10V V = 10V CC CC 31 31 5.0 26 26 2.5 V = 5V CC 21 21 0 V = 5V CC V = 5V CC 16 16 –2.5 11 11 –5.0 0 0 50 100 150 200 250 300 0 50 100 150 200 250 300 100 200 300 400 500 600 FREQUENCY – MHz FREQUENCY – MHz FREQUENCY – MHz TPC 16. AD8350-15 Output Referred TPC 17. AD8350-20 Output Referred TPC 18. AD8350-15 1 dB Compres- IP3 vs. Frequency IP3 vs. Frequency sion vs. Frequency –6– REV. A DISTORTION – dBc DISTORTION – dBc OIP3 – dBm (Re: 50�) DISTORTION – dBc OIP3 – dBm (Re: 50�) OIP2 – dBm (Re: 50�) DISTORTION – dBc 1dB COMPRESSION – dBm (Re: 50�) OIP2 – dBm (Re: 50�) AD8350 10 7.5 10 INPUT REFERRED 5.0 9 9 V = 10V 2.5 CC 8 8 V = 10V CC 0 V = 10V CC 7 7 –2.5 V = 5V CC V = 5V 6 CC V = 5V 6 CC –5.0 –7.5 5 5 0 0 0 100 200 300 400 500 600 50 100 150 200 250 300 350 400 450 500 50 100 150 200 250 300 350 400 450 500 FREQUENCY – MHz FREQUENCY – MHz FREQUENCY – MHz TPC 19. AD8350-20 1 dB Compres- TPC 20. AD8350-15 Noise Figure TPC 21. AD8350-20 Noise Figure sion vs. Frequency vs. Frequency vs. Frequency –20 25 100 AD8350-20 V = 5V CC 20 50 –30 V + (V = 5V) OUT CC 15 0 –40 10 AD8350-15 V – (V = 5V) OUT CC –50 –50 5 AD8350-20 0 –100 –60 V + (V = 10V) OUT CC –5 AD8350-15 –150 –70 –10 V – (V = 10V) OUT CC –200 –80 –15 –20 –250 –90 1 2 3 4 5678 9 10 0 –40 –20 20 40 60 80 1 10 100 1k V – Volts TEMPERATURE – �C CC FREQUENCY – MHz TPC 22. AD8350 Gain (S21) vs. TPC 23. AD8350 Output Offset Volt- TPC 24. AD8350 PSRR vs. Frequency Supply Voltage age vs. Temperature –20 V = 5V V = 5V CC 500mV CC –30 AD8350-20 V OUT –40 –50 AD8350-15 –60 –70 ENBL –80 5V 30ns –90 1 10 100 1k FREQUENCY – MHz TPC 25. AD8350 CMRR vs. Frequency TPC 26. AD8350 Power-Up/Down Response Time REV. A –7– PSRR – dB 1dB COMPRESSION – dBm (Re: 50�) GAIN – dB OUTPUT OFFSET – mV NOISE FIGURE – dB PSRR – dB NOISE FIGURE – dB AD8350 C C L /2 AC AC L /2 APPLICATIONS S S Using the AD8350 87 6 5 Figure 1 shows the basic connections for operating the AD8350. R /2 S A single supply in the range 5 V to 10 V is required. The power AD8350 supply pin should be decoupled using a 0.1 µF capacitor. The C – C P P V R S LOAD ENBL pin is tied to the positive supply or to 5 V (when V = CC 10 V) for normal operation and should be pulled to ground to R /2 S put the device in sleep mode. Both the inputs and the outputs 12 34 have dc bias levels at midsupply and should be ac-coupled. L /2 L /2 S S C C Also shown in Figure 1 are the impedance balancing requirements, AC AC either resistive or reactive, of the input and output. With an 0.1�F ENBL (5V) input and output impedance of 200 Ω, the AD8350 should be driven by a 200 Ω source and loaded by a 200 Ω impedance. A +V (5V TO 10V) S reactive match can also be implemented. Figure 3. Reactively Matching the Input and Output C2 C4 0.001�F 0.001�F SOURCE LOAD C C L AC AC L S S Z = 100� 8 7 6 5 AD8350 87 6 5 R S AD8350 – Z = 200� C – C P P V R S LOAD 1 2 3 4 Z = 100� 12 34 C1 C3 0.001�F 0.001�F C5 C C AC AC 0.1�F ENBL (5V) 0.1�F ENBL (5V) +V (5V TO 10V) S +V (5V TO 10V) S Figure 1. Basic Connections for Differential Drive Figure 4. Single-Ended Equivalent Circuit Figure 2 shows how the AD8350 can be driven by a single- When the source impedance is smaller than the load impedance, ended source. The unused input should be ac-coupled to ground. a step-up matching network is required. A typical step-up network When driven single-endedly, there will be a slight imbalance in is shown on the input of the AD8350 in Figure 3. For purely the differential output voltages. This will cause an increase in resistive source and load impedances the resonant approach may the second order harmonic distortion (at 50 MHz, with V = CC be used. The input and output impedance of the AD8350 can be 10 V and V = 1 V p-p, –59 dBc was measured for the second OUT modeled as a real 200 Ω resistance for operating frequencies less harmonic on AD8350-15). than 100 MHz. For signal frequencies exceeding 100 MHz, classi- LOAD cal Smith Chart matching techniques should be invoked in order to deal with the complex impedance relationships. Detailed S C2 C4 7 8 6 5 0.001�F 0.001�F parameter data measured differentially in a 200 Ω system can be AD8350 found in Tables II and III. – For the input matching network the source resistance is less Z = 200� than the input resistance of the AD8350. The AD8350 has a nominal 200 Ω input resistance from Pins 1 to 8. The reactance 1 2 3 4 of the ac-coupling capacitors, C , should be negligible if 100 nF AC SOURCE capacitors are used and the lowest signal frequency is greater Z = 200� C1 C3 than 1 MHz. If the series reactance of the matching network 0.001�F 0.001�F C5 inductor is defined to be X = 2 π f L , and the shunt reactance S S 0.1�F ENBL (5V) –1 of the matching capacitor to be X = (2 π f C ) , then: P P +V (5V TO 10V) S RR × R S LOAD S X = whereXR=× Figure 2. Basic Connections for Single-Ended Drive S PLOAD (1) X RR – P LOAD S Reactive Matching For a 70 MHz application with a 50 Ω source resistance, and In practical applications, the AD8350 will most likely be matched assuming the input impedance is 200 Ω, or R = R = 200 Ω, LOAD IN using reactive matching components as shown in Figure 3. then X = 115.5 Ω and X = 86.6 Ω, which results in the follow- P S Matching components can be calculated using a Smith Chart or ing component values: by using a resonant approach to determine the matching network 6 –1 that results in a complex conjugate match. In either situation, C = (2 π × 70 × 10 × 115.5) = 19.7 pF and P the circuit can be analyzed as a single-ended equivalent circuit 6 –1 L = 86.6 × (2 π × 70 × 10 ) = 197 nH to ease calculations as shown in Figure 4. S –8– REV. A + + + + AD8350 For the output matching network, if the output source resis- The same results could be found using a Smith Chart as shown tance of the AD8350 is greater than the terminating load in Figure 7. In this example, a shunt capacitor and a series inductor resistance, a step-down network should be employed as shown are used to match the 200 Ω source to a 50 Ω load. For a fre- on the output of Figure 3. For a step-down matching network, quency of 10 MHz, the same capacitor and inductor values the series and parallel reactances are calculated as: previously found using the resonant approach will transform the 200 Ω source to match the 50 Ω load. At frequencies exceeding RR × R 100 MHz, the S parameters from Tables II and III should be S LOAD LOAD X = whereXR=× S PS (2) used to account for the complex impedance relationships. X RR – P S LOAD For a 10 MHz application with the 200 Ω output source resistance of the AD8350, R = 200 Ω, and a 50 Ω load termination, R = S LOAD 50 Ω, then X = 115.5 Ω and X = 86.6 Ω, which results in P S the following component values: 6 –1 C = (2 π × 10 × 10 × 115.5) = 138 pF and P 6 –1 L = 86.6 × (2 π × 10 × 10 ) = 1.38 µH S LOAD SOURCE The same results can be obtained using the plots in Figure 5 and Figure 6. Figure 5 shows the normalized shunt reactance versus the normalized source resistance for a step-up matching SHUNT C network, R < R . By inspection, the appropriate reactance S LOAD SERIES L can be found for a given value of R /R . The series reactance S LOAD is then calculated using X = R R /X The same technique S S LOAD P. can be used to design the step-down matching network using Figure 6. 2 Figure 7. Smith Chart Representation of Step-Down Network 1.8 R SOURCE X S After determining the matching network for the single-ended 1.6 R X LOAD P equivalent circuit, the matching elements need to be applied in a 1.4 differential manner. The series reactance needs to be split such 1.2 that the final network is balanced. In the previous examples, this 1 simply translates to splitting the series inductor into two equal halves as shown in Figure 3. 0.8 Gain Adjustment 0.6 The effective gain of the AD8350 can be reduced using a num- 0.4 ber of techniques. Obviously a matched attenuator network will 0.2 reduce the effective gain, but this requires the addition of a separate component which can be prohibitive in size and cost. 0 The attenuator will also increase the effective noise figure resulting NORMALIZED SOURCE RESISTANCE – R /R in an SNR degradation. A simple voltage divider can be imple- SOURCE LOAD mented using the combination of the driving impedance of the Figure 5. Normalized Step-Up Matching Components previous stage and a shunt resistor across the inputs of the AD8350 as shown in Figure 8. This provides a compact solution but suffers from an increased noise spectral density at the input 3.2 of the AD8350 due to the thermal noise contribution of the R SOURCE X S shunt resistor. The input impedance can be dynamically altered 3 R X LOAD P through the use of feedback resistors as shown in Figure 9. This will result in a similar attenuation of the input signal by virtue 2.8 of the voltage divider established from the driving source imped- ance and the reduced input impedance of the AD8350. Yet 2.6 this technique does not significantly degrade the SNR with the unnecessary increase in thermal noise that arises from a truly 2.4 resistive attenuator network. 2.2 2 NORMALIZED SOURCE RESISTANCE – R /R SOURCE LOAD Figure 6. Normalized Step-Down Matching Components REV. A –9– NORMALIZED REACTANCE – X /R P LOAD NORMALIZED REACTANCE – X /R P LOAD 2 0.01 2.4 0.05 2.8 0.09 0.13 3.2 0.17 3.6 0.21 4 0.25 4.4 0.29 4.8 0.33 5.2 0.37 5.6 0.41 6 0.45 0.49 6.4 0.53 6.8 0.57 7.2 0.61 7.6 0.65 8 0.69 8.4 0.73 8.8 0.77 AD8350 C C AC AC The insertion loss and the resultant power gain for multiple shunt resistor values is summarized in Table I. The source 87 6 5 resistance and input impedance need careful attention when R R S R L SHUNT AD8350 using Equation 1. The reactance of the input impedance of the AD8350 and the ac-coupling capacitors need to be considered – V S before assuming they have negligible contribution. Figure 10 shows the effective power gain for multiple values of R for SHUNT R R S R L SHUNT the AD8350-15 and AD8350-20. 12 34 Table I. Gain Adjustment Using Shunt Resistor, C C AC AC R = 100 � and R = 100 � Single-Ended S IN 0.1�F ENBL (5V) Power Gain–dB +V (5V TO 10V) S R –� IL–dB AD8350-15 AD8350-20 SHUNT Figure 8. Gain Reduction Using Shunt Resistor 50 6.02 8.98 13.98 100 3.52 11.48 16.48 200 1.94 13.06 18.06 R FEXT 300 1.34 13.66 18.66 400 1.02 13.98 18.98 C C AC AC 87 6 5 20 R R S L AD8350 18 – V 16 AD8350-20 S 14 R R S L 12 12 34 AD8350-15 10 0.1�F C C AC AC ENBL 8 (5V) +V S 6 (5V TO 10V) 4 R FEXT 2 Figure 9. Dynamic Gain Reduction 0 0 100 200 300 400 500 600 700 800 R – � SHUNT Figure 8 shows a typical implementation of the shunt divider Figure 10. Gain for Multiple Values of Shunt Resistance concept. The reduced input impedance that results from the for Circuit in Figure 8 parallel combination of the shunt resistor and the input impedance The gain can be adjusted dynamically by employing external of the AD8350 adds attenuation to the input signal effectively feedback resistors as shown in Figure 9. The effective attenua- reducing the gain. For frequencies less than 100 MHz, the input tion is a result of the lowered input impedance as with the shunt impedance of the AD8350 can be modeled as a real 200 Ω resis- resistor method, yet there is no additional noise contribution at tance (differential). Assuming the frequency is low enough to the input of the device. It is necessary to use well-matched resistors ignore the shunt reactance of the input, and high enough such to minimize common-mode offset errors. Quality 1% tolerance that the reactance of moderately sized ac-coupling capacitors resistors should be used along with a symmetric board layout to can be considered negligible, the insertion loss, IL, due to the help guarantee balanced performance. The effective gain for mul- shunt divider can be expressed as: tiple values of external feedback resistors is shown in Figure 11.   R IN   () RR + IN S   IL() dB=× 20 Log 10 RR �  IN SHUNT    () RR � +R IN SHUNT S   where (3) RR × IN SHUNT RR � = and R=− 100Ω single ended IN SHUNT IN RR + IN SHUNT –10– REV. A + + GAIN – dB AD8350 20 Driving Lighter Loads It is not necessary to load the output of the AD8350 with a 18 AD8350-20 200 Ω differential load. Often it is desirable to try to achieve a 16 complex conjugate match between the source and load in order 14 to minimize reflections and conserve power. But if the AD8350 12 is driving a voltage responding device, such as an ADC, it is no longer necessary to maximize power transfer. The harmonic 10 distortion performance will actually improve when driving AD8350-15 8 loads greater than 200 Ω. The lighter load requires less cur- 6 rent driving capability on the output stages of the AD8350 resulting in improved linearity. Figure 12 shows the improve- 4 ment in second and third harmonic distortion for increasing 2 differential load resistance. 0 0 500 1000 1500 2000 –66 R – � FEXT –68 Figure 11. Power Gain vs. External Feedback Resistors for the AD8350-15 and AD8350-20 with R = 100 Ω and S –70 R = 100 Ω L HD3 –72 The power gain of any two-port network is dependent on the source and load impedance. The effective gain will change if the –74 differential source and load impedance is not 200 Ω. The single- ended input and output resistance of the AD8350 can be modeled –76 using the following equations: –78 HD2 RR + FL –80 R = IN RR +  FL (4) ++ 1gR × mL   –82  R  200 300 400 500 600 700 800 900 1000 INT R – � LOAD and Figure 12. Second and Third Harmonic Distortion vs. Differential Load Resistance for the AD8350-15 with 1 V = 5 V, f = 70 MHz, and V = 1 V p-p S OUT R + F 11 + RR + RR FS S INT R = ≈ for R ≤ 1kΩ OUT S   1+×gR mS   1 (5) 1+× g m   11   + RR  S INT where R =R //R F FEXT FINT R = R Feedback External FEXT R = 662 Ω for the AD8350-15 FINT = 1100 Ω for the AD8350-20 R = 25000 Ω INT g = 0.066 mhos for the AD8350-15 m = 0.110 mhos for the AD8350-20 R = R Source (Single-Ended) S R = R Load (Single-Ended) L R = R Input (Single-Ended) IN R = R Output (Single-Ended) OUT The resultant single-ended gain can be calculated using the following equation: Rg××R−1 () Lm F G = V (6) RR++R+R×R×g LS F L S m REV. A –11– GAIN – dB DISTORTION – dBc AD8350 EVALUATION BOARD To drive and load the board differentially, transformers T1 and Figure 13 shows the schematic of the AD8350 evaluation board, T2 should be removed and replaced with four 0 Ω resistors for SOIC, as it is shipped from the factory. The board is config- (0805 size); Resistors R1 and R4 (0 Ω) should also be removed. ured to allow easy evaluation using single-ended 50 Ω test This yields a circuit with a broadband input and output impedance equipment. The input and output transformers have a 4-to-1 of 200 Ω. To match to impedances other than this, matching impedance ratio and transform the AD8350’s 200 Ω input and components (0805 size) can be placed on pads C1, C2, C3, C4, output impedances to 50 Ω. In this mode, 0 Ω resistors (R1 and L1, and L2. R4) are required. To allow compensation for the insertion loss of the transform- ers, a calibration path is provided at Test In and Test Out. This consists of two transformers connected back to back. C1 C3 0.001�F 0.001�F R1 8 7 6 5 R4 T1: TC4-1W 0� 0� T2: TC4-1W (MINI CIRCUITS) AD8350 (MINI CIRCUITS) 61 R2 R3 IN– OUT– 0� – 0� L2 L1 (OPEN) (OPEN) 1 6 IN+ OUT+ 1 3 2 4 C2 C4 0.001�F 0.001�F C5 A 3 0.1�F +V SW1 S 1 2 B +V S T3: TC4-1W T4: TC4-1W (MINI CIRCUITS) (MINI CIRCUITS) 61 TEST IN TEST OUT 16 Figure 13. Evaluation Board –12– REV. A + AD8350 Table II. Typical Scattering Parameters for the AD8350-15: V = 5 V, Differential Input and Output, Z (diff) = 200 �, CC SOURCE Z (diff) = 200 � LOAD Frequency – MHz S11 S12 S21 S22 25 0.015∠–48.8° 0.119∠176.3° 5.60∠–4.3° 0.034∠–4.8° 50 0.028∠–65.7° 0.119∠171.1° 5.61∠–8.9° 0.032∠–14.3° 75 0.043∠–75.3° 0.119∠166.9° 5.61∠–13.5° 0.036∠–30.2° 100 0.057∠–87.5° 0.120∠163.5° 5.61∠–17.9° 0.043∠–39.6° 125 0.073∠–91.8° 0.119∠159.8° 5.65∠–22.6° 0.053∠–40.6° 150 0.080∠–95.6° 0.120∠154.8° 5.68∠–27.0° 0.058∠–37° 175 0.100∠–97.4° 0.117∠151.2° 5.73∠–31.8° 0.072∠–45.1° 200 0.111∠–99.1° 0.121∠147.3° 5.78∠–36.3° 0.077∠–47.7° 225 0.128∠–103.2° 0.120∠143.7° 5.83∠–41.0° 0.091∠–52.5° 250 0.141∠–106.7° 0.120∠140.3° 5.90∠–45.6° 0.104∠–55.1° 275 0.151∠–109.7° 0.120∠136.6° 6.02∠–50.2° 0.108∠–54.2° 300 0.161∠–111.9° 0.123∠132.9° 6.14∠–55.1° 0.122∠–51.5° 325 0.179∠–114.7° 0.121∠130.7° 6.19∠–60.2° 0.135∠–55.6° 350 0.187∠–117.4° 0.122∠126.6° 6.27∠–65.0° 0.150∠–56.9° 375 0.194∠–121° 0.123∠123.6° 6.43∠–70.1° 0.162∠–60.9° 400 0.199∠–121.2° 0.124∠120.1° 6.61∠–75.8° 0.187∠–60.3° 425 0.215∠–122.6° 0.126∠117.2° 6.77∠–81.7° 0.215∠–63.3° 450 0.225∠–127.0° 0.126∠113.9° 6.91∠–87.6° 0.242∠–63.9° 475 0.225∠–127.7° 0.126∠112° 7.06∠–93.8° 0.268∠–65.2° 500 0.244∠–129.9° 0.128∠108.1° 7.27∠–99.8° 0.304∠–68.2° Table III. Typical Scattering Parameters for the AD8350-20: V = 5 V, Differential Input and Output, Z (diff) = 200 �, CC SOURCE Z (diff) = 200 � LOAD Frequency – MHz S11 S12 S21 S22 25 0.017∠–142.9° 0.074∠174.9° 9.96∠–4.27° 0.023–16.6° 50 0.033∠–114.9° 0.074∠171.0° 9.98∠–8.9° 0.022∠–2.7° 75 0.055∠–110.6° 0.075∠167.0° 9.98∠–13.3° 0.023∠–23.5° 100 0.073∠–109.4° 0.075∠163.1° 10.00∠–17.7° 0.029∠–22.7° 125 0.089∠–112.1° 0.075∠159.2° 10.12∠–22.1° 0.037∠–18.0° 150 0.098∠–116.5° 0.076∠153.8° 10.20∠–26.4° 0.045∠–3.2° 175 0.124∠–118.1° 0.075∠150.2° 10.34∠–30.9° 0.055∠–15.7° 200 0.141∠–119.4° 0.076∠147.2° 10.50∠–35.6° 0.065∠–15.6° 225 0.159∠–122.6° 0.077∠142.2° 10.65∠–40.1° 0.080∠–17.7° 250 0.170∠–128.5° 0.078∠139.5° 10.80∠–44.7° 0.085∠–22.4° 275 0.186∠–131.6° 0.078∠135.8° 11.14∠–49.3° 0.096∠–23.5° 300 0.203∠–132.9° 0.080∠132.5° 11.45∠–54.7° 0.116∠–25.9° 325 0.215∠–135.0° 0.080∠129.3° 11.70∠–60.3° 0.139∠–29.6° 350 0.222∠–136.9° 0.082∠125.9° 11.93∠–65.0° 0.161∠–32.2° 375 0.242∠–142.4° 0.082∠123.6° 12.39∠–70.3° 0.173∠–38.6° 400 0.240∠–145.2° 0.084∠120.3° 12.99∠–76.8° 0.207∠–37.6° 425 0.267∠–146.7° 0.084∠117.3° 13.34∠–84.0° 0.241∠–48.1° 450 0.266∠–150.7° 0.086∠115.1° 13.76∠–90.1° 0.265∠–49.7° 475 0.267∠–153.7° 0.087∠112.8° 14.34∠–97.5° 0.317∠–53.5° 500 0.285∠–161.1° 0.088∠110.9° 14.89∠–105.0° 0.359∠–59.2° REV. A –13– AD8350 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 8-Lead Plastic SOIC (SO-8) 0.1968 (5.00) 0.1890 (4.80) 85 0.1574 (4.00) 0.2440 (6.20) 0.1497 (3.80) 0.2284 (5.80) 1 4 PIN 1 0.0500 (1.27) 0.0196 (0.50) � 45� BSC 0.0099 (0.25) 0.0688 (1.75) 0.0098 (0.25) 0.0532 (1.35) 0.0040 (0.10) 8� 0.0192 (0.49) 0� 0.0500 (1.27) 0.0098 (0.25) SEATING 0.0138 (0.35) 0.0160 (0.41) PLANE 0.0075 (0.19) 8-Lead microSOIC Package (RM-8) 0.122 (3.10) 0.114 (2.90) 85 0.122 (3.10) 0.199 (5.05) 0.114 (2.90) 0.187 (4.75) 1 4 PIN 1 0.0256 (0.65) BSC 0.120 (3.05) 0.120 (3.05) 0.112 (2.84) 0.112 (2.84) 0.043 (1.09) 0.006 (0.15) 0.037 (0.94) 0.002 (0.05) 33� 0.018 (0.46) 27� 0.028 (0.71) 0.011 (0.28) SEATING 0.008 (0.20) 0.016 (0.41) PLANE 0.003 (0.08) –14– REV. A –15– –16– PRINTED IN U.S.A. C01014–1.5–6/01(A)