LTC GHz Low Noise, Low Distortion Differential ADC Driver for 300MHz IF FEATURES DESCRIPTION APPLICATIONS TYPICAL APPLICATION

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1 FEATURES.8GHz db Bandwidth Fixed Gain of V/V (db) 9dBc IMD at 7MHz (Equivalent OIP = dbm) 6dBc IMD at MHz (Equivalent OIP = 6.dBm) nv/ Hz Internal Op Amp Noise.nV/ Hz Total Input Noise 6.dB Noise Figure Differential Inputs and Outputs Ω Input Impedance.8V to.v Supply Voltage 9mA Supply Current (7mW) V to.6v Output Common Mode Voltage, Adjustable DC- or AC-Coupled Operation Max Differential Output Swing.V P-P Small 6-Lead mm mm.7mm QFN Package APPLICATIONS Differential ADC Driver Differential Driver/Receiver Single Ended to Differential Conversion IF Sampling Receivers SAW Filter Interfacing DESCRIPTION LTC6-.8GHz Low Noise, Low Distortion Differential ADC Driver for MHz IF The LTC 6- is a high-speed differential amplifier targeted at processing signals from DC to MHz. The part has been specifically designed to drive -, - and 6-bit ADCs with low noise and low distortion, but can also be used as a general-purpose broadband gain block. The LTC6- is easy to use, with minimal support circuitry required. The output common mode voltage is set using an external pin, independent of the inputs, which eliminates the need for transformers or AC-coupling capacitors in many applications. The gain is internally fixed at db (V/V). The LTC6- saves space and power compared to alternative solutions using IF gain blocks and transformers. The LTC6- is packaged in a compact 6-lead mm mm QFN package and operates over the C to 8 C temperature range., LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION Single-Ended to Differential ADC Driver.V 6 Equivalent Output IP vs Frequency (NOTE 7).V INPUT 66.Ω pf 9Ω V OCM F LTC6- F V ENABLE db GAIN Ω Ω AIN + AIN V CM LTC8 V DD LTC8 Msps 6-Bit ADC 6 TAa OUTPUT IP (dbm) 6 TAb 6f

2 LTC6- ABSOLUTE MAXIMUM RATINGS (Note ) Supply Voltage ( V )...6V Input Current (Note )...±ma Operating Temperature Range (Note )... C to 8 C Specifi ed Temperature Range (Note )... C to 8 C Storage Temperature Range... 6 C to C Maximum Junction Temperature... C Lead Temperature (Soldering, sec)... C PIN CONFIGURATION V OCM V TOP VIEW F F V ENABLE 9 V UD PACKAGE 6-LEAD (mm mm) PLASTIC QFN T JMAX = C, θ JA = 68 C/W, θ JC =. C/W EXPOSED PAD (PIN 7) IS V, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC6CUD-#PBF LTC6CUD-#TRPBF LCCS 6-Lead (mm mm) Plastic QFN C to 7 C LTC6IUD-#PBF LTC6IUD-#TRPBF LCCS 6-Lead (mm mm) Plastic QFN C to 8 C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based fi nish parts. For more information on lead free part marking, go to: For more information on tape and reel specifi cations, go to: LTC6 AND LTC6 SELECTOR GUIDE Please check each datasheet for complete details. PART NUMBER GAIN (db) GAIN (V/V) Z IN (DIFFERENTIAL) (Ω) LTC6-9 LTC6- In addition to the LTC6 family of amplifi ers, a lower power LTC6 family is available. The LTC6 is pin compatible to the LTC6, and has the same low noise performance. The lower power consumption of the LTC6 comes at the expense of slightly higher non-linearity, especially at input frequencies above MHz. Please refer to the separate LTC6 data sheets for complete details. Other gain versions from 8dB to 6dB will follow. I S (ma) 6f

3 DC ELECTRICAL CHARACTERISTICS LTC6- The denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at T A = C. = V, V = V, = = V OCM =.V, E N A B L E = V, No R L unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Input/Output Characteristic G DIFF Gain V IN = ±mv Differential 9..6 db TC GAIN Gain Temperature Drift V IN = ±mv Differential. mdb/ C V SWINGMIN Output Swing Low Each Output, V IN = ±6mV Differential 8 mv V SWINGMAX Output Swing High Each Output, V IN = ±6mV Differential..6 V V OUTDIFFMAX Maximum Differential Output Swing db Compressed. V P-P I OUT Output Current Drive Each Output ma V OSDIFF Input Differential Offset Voltage mv TCV OSDIFF Input Differential Offset Voltage Drift T MIN to T MAX. μv/ C I VRMIN Input Common Mode Voltage Range, MIN V I VRMAX Input Common Mode Voltage Range, MAX.6 V R INDIFF Input Resistance (, ) Differential 7 Ω C INDIFF Input Capacitance (, ) Differential, Includes Parasitic pf R OUTDIFF Output Resistance (, ) Differential 8 Ω R OUTFDIFF Filtered Output Resistance (F, F) Differential 8 Ω C OUTFDIFF Filtered Output Capacitance (F, F) Differential, Includes Parasitic.7 pf CMRR Common Mode Rejection Ratio Input Common Mode Voltage.V~.V 6 db Output Common Mode Voltage Control G CM Common Mode Gain V OCM = V to.6v V/V V OCMMIN Output Common Mode Range, MIN V. V V OCMMAX Output Common Mode Range, MAX.6 V. V V OSCM Common Mode Offset Voltage V OCM =.V to.v mv TCV OSCM Common Mode Offset Voltage Drift T MIN to T MAX 6 μv/ C IV OCM V OCM Input Current μa E N A B L E Pin V IL E N A B L E Input Low Voltage.8 V V IH E N A B L E Input High Voltage. V I IL E N A B L E Input Low Current E N A B L E =.8V. μa I IH E N A B L E Input High Current E N A B L E =.V. μa Power Supply V S Operating Supply Range.8. V I S Supply Current E N A B L E =.8V 7 9 ma I SHDN Shutdown Supply Current E N A B L E =.V ma PSRR Power Supply Rejection Ratio (Differential =.8V to.v 86 db Outputs) 6f

4 LTC6- AC ELECTRICAL CHARACTERISTICS E N A B L E = V, No R L unless otherwise noted. Specifi cations are at T A = C. = V, V = V, V OCM =.V, SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS dbbw db Bandwidth mv P-P,OUT (Note 6).8 GHz.dBBW Bandwidth for.db Flatness mv P-P,OUT (Note 6). GHz.dBBW Bandwidth for.db Flatness mv P-P,OUT (Note 6).7 GHz /f /f Noise Corner. khz SR Slew Rate Differential (Note 6). V/ns t S% % Settling Time V P-P,OUT (Note 6).8 ns t OVDR Overdrive Recovery Time.9V P-P,OUT (Note 6) ns t ON Turn-On Time, Within % of Final Values 8 ns t OFF Turn-Off Time I CC Falls to % of Nominal 9 ns dbbw VOCM V OCM Pin Small Signal db BW.V P-P at V OCM, Measured Single-Ended at MHz Output (Note 6) MHz Input Signal HD,M /HD,M Second/Third Order Harmonic V P-P,OUT, R L = Ω 97/ 9 dbc Distortion V P-P,OUT, No R L 98/ 97 dbc V P-P,OUTFILT, No R L / 98 dbc IMD,M Third-Order Intermodulation V P-P,OUT Composite, R L = Ω 9 dbc (f = 9.MHz f =.MHz) V P-P,OUT Composite, No R L 99 dbc V P-P,OUTFILT Composite, No R L dbc OIP,M Third-Order Output Intercept Point V P-P,OUT Composite, No R L (Note 7).8 dbm (f = 9.MHz f =.MHz) P db,m db Compression Point R L = 7Ω (Notes, 7) 8 dbm NF M Noise Figure R L = 7Ω (Note ) 6. db e IN,M Input Referred Voltage Noise Density Includes Resistors (Short Inputs). nv/ Hz e ON,M Output Referred Voltage Noise Density Includes Resistors (Short Inputs).7 nv/ Hz 7MHz Input Signal HD,7M /HD,7M Second/Third Order Harmonic V P-P,OUT, R L = Ω 86/ 8 dbc Distortion V P-P,OUT, No R L 88/ 87 dbc V P-P,OUTFILT, No R L 86/ 88 dbc IMD,7M Third-Order Intermodulation V P-P,OUT Composite, R L = Ω 9 dbc (f = 69.MHz f = 7.MHz) V P-P,OUT Composite, No R L 9 dbc V P-P,OUTFILT Composite, No R L 9 dbc OIP,7M Third-Order Output Intercept Point V P-P,OUT Composite, No R L (Note 7) dbm (f = 69.MHz f = 7.MHz) P db,7m db Compression Point R L = 7Ω (Notes, 7) 8 dbm NF 7M Noise Figure R L = 7Ω (Note ) 6. db e IN,7M Input Referred Voltage Noise Density Includes Resistors (Short Inputs). nv/ Hz e ON,7M Output Referred Voltage Noise Density Includes Resistors (Short Inputs) nv/ Hz 6f

5 AC ELECTRICAL CHARACTERISTICS E N A B L E = V, No R L unless otherwise noted. LTC6- Specifi cations are at T A = C. = V, V = V, V OCM =.V, SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS MHz Input Signal HD,M /HD,M Second/Third Order Harmonic V P-P,OUT, R L = Ω 7/ 7 dbc Distortion V P-P,OUT, No R L 7/ 8 dbc V P-P,OUTFILT, No R L 77/ 76 dbc IMD,M Third-Order Intermodulation V P-P,OUT Composite, R L = Ω 9 dbc (f = 9.MHz f =.MHz) V P-P,OUT Composite, No R L 87 dbc V P-P,OUTFILT Composite, No R L 89 dbc OIP,M Third-Order Output Intercept Point V P-P,OUT Composite, No R L (Notes 7) 7.7 dbm (f = 9.MHz f =.MHz) P db,m db Compression Point R L = 7Ω (Notes, 7) 8. dbm NF M Noise Figure R L = 7Ω (Note ) 6. db e IN,M Input Referred Voltage Noise Density Includes Resistors (Short Inputs). nv/ Hz e ON,M Output Referred Voltage Noise Density Includes Resistors (Short Inputs). nv/ Hz MHz Input Signal HD,M /HD,M Second-Order Harmonic Distortion V P-P,OUT, R L = Ω 66/ 8 dbc V P-P,OUT, No R L 6/ 6 dbc V P-P,OUTFILT, No R L 6/ 8 dbc IMD,M Third-Order Intermodulation V P-P,OUT Composite, R L = Ω 7 dbc (f = 9.MHz f =.MHz) V P-P,OUT Composite, No R L 7 dbc V P-P,OUTFILT Composite, No R L 67 dbc OIP,M Third-Order Output Intercept Point V P-P,OUT Composite, No R L (Note 7) dbm (f = 9.MHz f =.MHz) P db,m db Compression Point R L = 7Ω (Notes, 7) 7.9 dbm NF M Noise Figure R L = 7Ω (Note ) 7. db e N, M Input Referred Voltage Noise Density Includes Resistors (Short Inputs).9 nv/ Hz e ON,M Output Referred Voltage Noise Density Includes Resistors (Short Inputs).7 nv/ Hz 6f

6 LTC6- AC ELECTRICAL CHARACTERISTICS E N A B L E = V, No R L unless otherwise noted. Specifi cations are at T A = C. = V, V = V, V OCM =.V, SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS MHz Input Signal HD,M /HD,M Second-Order Harmonic Distortion V P-P,OUT, R L = Ω 6/ dbc V P-P,OUT, No R L 6/ dbc V P-P,OUTFILT, No R L 6/ 6 dbc IMD,M Third-Order Intermodulation V P-P,OUT Composite, R L = Ω 6 dbc (f = 99.MHz f =.MHz) V P-P,OUT Composite, No R L 6 dbc V P-P,OUTFILT Composite, No R L 8 dbc OIP,M Third-Order Output Intercept Point V P-P,OUT Composite, No R L (Note 7) 6.6 dbm (f = 99.MHz f =.MHz) P db,m db Compression Point R L = 7Ω (Notes, 7) 7. dbm NF M Noise Figure R L = 7Ω (Note ) 7. db e N,M Input Referred Voltage Noise Density Includes Resistors (Short Inputs).8 nv/ Hz e ON,M Output Referred Voltage Noise Density Includes Resistors (Short Inputs) nv/ Hz IMD,8M/M Third-Order Intermodulation (f = 8MHz f = MHz) Measure at 6MHz V P-P,OUT Composite, R L = 7Ω 6 7 dbc Note : Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note : Input pins (, ) are protected by steering diodes to either supply. If the inputs go beyond either supply rail, the input current should be limited to less than ma. Note : The LTC6C and LTC6I are guaranteed functional over the operating temperature range of C to 8 C. Note : The LTC6C is guaranteed to meet specifi ed performance from C to 7 C. It is designed, characterized and expected to meet specifi ed performance from C to 8 C but is not tested or QA sampled at these temperatures. The LTC6I is guaranteed to meet specifi ed performance from C to 8 C. Note : Input and output baluns used. See Test Circuit A. Note 6: Measured using Test Circuit B. Note 7: Since the LTC6- is a feedback amplifi er with low output impedance, a resistive load is not required when driving an AD converter. Therefore, typical output power is very small. In order to compare the LTC6- with amplifi ers that require Ω output load, the LTC6- output voltage swing driving a given R L is converted to OIP and P db as if it were driving a Ω load. Using this modifi ed convention, V P-P is by defi nition equal to dbm, regardless of actual R L. 6 6f

7 TYPICAL PERFORMANCE CHARACTERISTICS LTC6- GAIN (db) Frequency Response TEST CIRCUIT B 6 G GAIN FLATNESS (db) Gain.dB Flatness TEST CIRCUIT B. 6 G PHASE (DEGREE) S Phase and Group Delay vs Frequency TEST CIRCUIT B PHASE GROUP DELAY G GROUP DELAY (ns) S PARAMETERS (db) Input and Output Refl ection and Reverse Isolation vs Frequency TEST CIRCUIT B S S S 6 G IMPEDANCE MAGNITUDE (Ω) Input and Output Impedance vs Frequency Z IN Z OUT Z IN PHASE IMPEDANCE MAGNITUDE Z OUT 6 G PHASE (DEGREES) PSRR, CMRR (db) PSRR and CMRR vs Frequency CMRR PSRR 6 G6 NOISE FIGURE (db) Noise Figure and Input Referred Noise Voltage vs Frequency Small Signal Transient Response Large Signal Transient Response NOISE FIGURE EN 6 G7 6 INPUT REFERRED NOISE VOLTAGE (nv/ Hz) OUTPUT VOLTAGE (V)..... R L = 87.Ω PER OUTPUT 6 8 TIME (ns) 6 G8 OUTPUT VOLTAGE (V)..... R L = 87.Ω PER OUTPUT 6 8 TIME (ns) 6 G9 6f 7

8 LTC6- TYPICAL PERFORMANCE CHARACTERISTICS OUTPUT VOLTAGE (V)..... Overdrive Recovery Time R L = 87.Ω PER OUTPUT TIME (ns) 6 G SETTLING (%) % Settling Time for V Output Step R L = 87.Ω PER OUTPUT TIME (ns) 6 G HARMONIC DISTORTION (dbc) Harmonic Distortion (Unfi ltered) vs Frequency DIFFERENTIAL INPUT V OUT = V P-P HD NO R L HD Ω R L HD NO R L HD Ω R L 6 G HARMONIC DISTORTION (dbc) Harmonic Distortion (Filtered) vs Frequency DIFFERENTIAL INPUT V OUT = V P-P NO R L 9 HD HD 6 G THIRD ORDER IMD (dbc) Third Order Intermodulation Distortion vs Frequency UNFILTERED NO R L UNFILTERED Ω R L FILTERED NO R L DIFFERENTIAL INPUT V OUT = V P-P COMPOSITE 6 G HARMONIC DISTORTION (dbc) 6 7 Harmonic Distortion (Unfi ltered) vs Frequency SINGLE-ENDED INPUT V OUT = V P-P 8 HD NO R L 9 HD Ω R L HD NO R L HD Ω R L 6 G HARMONIC DISTORTION (dbc) Harmonic Distortion (Filtered) vs Frequency SINGLE-ENDED INPUT V OUT = V P-P NO R L 9 HD HD 6 G6 THIRD ORDER IMD (dbc) Third Order Intermodulation Distortion vs Frequency UNFILTERED NO R L UNFILTERED Ω R L FILTERED NO R L 9 SINGLE-ENDED INPUT V OUT = V P-P COMPOSITE 6 G7 HARMONIC DISTORTION (dbc) Harmonic Distortion vs Output Common Mode Voltage (Unfi ltered Outputs) V OUT = V P-P at MHz R L = Ω HD HD OUTPUT COMMON MODE VOLTAGE (V) 6 G8 6f

9 TYPICAL PERFORMANCE CHARACTERISTICS LTC6- OUTPUT db COMPRESSION (dbm) Output db Compression Point vs Frequency DIFFERENTIAL INPUT R L = Ω (NOTE 7) 6 G9 OUTPUT IP (dbm) 6 Output Third Order Intercept vs Frequency DIFFERENTIAL INPUT V OUT = V P-P COMPOSITE (NOTE 7) UNFILTERED NO R L UNFILTERED Ω R L FILTERED NO R L 6 G. Turn-On Time Turn-Off Time. R L = 87.Ω PER OUTPUT.. VOLTAGE (V)..... I CC 8 6 R L = 87.Ω PER OUTPUT ENABLE. TIME (ns) 6 G SUPPLY CURRENT (ma) VOLTAGE (V) I CC ENABLE. TIME (ns) 6 G SUPPLY CURRENT (ma) 6f 9

10 LTC6- PIN FUNCTIONS (Pins,, ): Positive Power Supply (Normally tied to V or.v). All three pins must be tied to the same voltage. Bypass each pin with pf and capacitors as close to the pins as possible. V OCM (Pin ): This pin sets the output common mode voltage. A external bypass capacitor is recommended. V (Pins, 9,, 7): Negative Power Supply (GND). All four pins must be connected to same voltage/ground., (Pins, 8): Unfi ltered Outputs. These pins have series resistors, R OUT.Ω. F, F (Pins 6, 7): Filtered Outputs. These pins have Ω series resistors and a.7pf shunt capacitor. E N A B L E (Pin ): This pin is a logic input referenced to V EE. If low, the part is enabled. If high, the part is disabled and draws approximately ma supply current. (Pins, ): Positive Input. Pins and are internally shorted together. (Pins, 6): Negative Input. Pins and 6 are internally shorted together. Exposed Pad (Pin 7): V. The Exposed Pad must be connected to same voltage/ground as pins, 9,. BLOCK DIAGRAM V ENABLE 9 V BIAS CONTROL R G Ω R F Ω R OUT.Ω 8 IN+ IN OUT OUT+ R FILT Ω R FILT Ω F 7 C FILT.7pF F 6 6 R G Ω R F Ω R OUT.Ω k.pf COMMON MODE CONTROL V OCM V 6 BD 6f

11 APPLICATIONS INFORMATION Circuit Operation The LTC6 is a low noise and low distortion fully differential op amp/adc driver with: Operation from DC to.8ghz ( db bandwidth) Fixed gain of V/V (db) Differential input impedance Ω Differential output impedance Ω On-Chip 9MHz output fi lter The LTC6 is composed of a fully differential amplifier with on chip feedback and output common mode voltage control circuitry. Differential gain and input impedance are set by Ω/Ω resistors in the feedback network. Small output resistors of.ω improve the circuit stability over various load conditions. They also provide a possible external filtering option, which is often desirable when the load is an ADC. Filter resistors of Ω are available for additional filtering. Lowpass/bandpass filters are easily implemented with just a couple of external components. Moreover, they offer single-ended Ω matching in wideband applications and no external resistor is needed. The LTC6- is very fl exible in terms of I/O coupling. It can be AC- or DC-coupled at the inputs, the outputs or both. Due to the internal connection between input and output, users are advised to keep input common mode voltage between V and.6v for proper operation. If the inputs are AC-coupled, the input common mode voltage is automatically biased close to V OCM and thus no external circuitry is needed for bias. The LTC6- provides an output common mode voltage set by V OCM, which allows driving an ADC directly without external components such as a transformer or AC coupling capacitors. The input signal can be either single-ended or differential with only minor differences in distortion performance. Input Impedance and Matching The differential input impedance of the LTC6- is Ω. If a Ω source impedance is unavailable, then the differential inputs may need to be terminated to a lower LTC6- value impedance, e.g. Ω, in order to provide an impedance match for the source. Several choices are available. One approach is to use a differential shunt resistor (Figure ). Another approach is to employ a wide band transformer (Figure ). Both methods provide a wide band impedance match. The termination resistor or the transformer must be placed close to the input pins in order to minimize the reflection due to input mismatch. Alternatively, one could apply a narrowband impedance match at the inputs of the LTC6- for frequency selection and/or noise reduction. Referring to Figure, LTC6- can be easily configured for single-ended input and differential output without a balun. The signal is fed to one of the inputs through a matching network while the other input is connected to the same matching network and a source resistor. Because the return ratios of the two feedback paths are equal, the two outputs have the same gain and thus symmetrical + Ω V IN Ω 66.Ω Ω Ω IN+ IN Ω OUT OUT+ Ω.Ω LTC6-.Ω F F 6 F Figure. Input Termination for Differential Ω Input Impedance Using Shunt Resistor + Ω V IN Ω : 6 6 IN+ IN OUT OUT+ Figure. Input Termination for Differential Ω Input Impedance Using a : Balun Ω Ω.7pF LTC6- Ω Ω.Ω Ω Ω Ω Ω.Ω F.7pF F 6 F f

12 LTC6- APPLICATIONS INFORMATION Figure. Input Termination for Single-Ended Ω Input Impedance swing. In general, the single-ended input impedance and termination resistor R T are determined by the combination of R S, R G and R F. For example, when R S is Ω, it is found that the single-ended input impedance is Ω and R T is 66.Ω in order to match to a Ω source impedance. The LTC6- is unconditionally stable. However, the overall differential gain is affected by both source impedance and load impedance as shown in Figure : A + V R S Ω V IN R T 66.Ω R S Ω R T 66.Ω VOUT R = = L V R + + R IN 6 S Ω Ω IN+ IN Ω The noise performance of the LTC6- also depends upon the source impedance and termination. For example, an input : balun transformer in Figure improves SNR by adding 6dB of voltage gain at the inputs. A trade-off between gain and noise is obvious when constant noise figure circle and constant gain circle are plotted within the same input Smith Chart, based on which users can choose the optimal source impedance for a given gain and noise requirement. + / R S V IN / R S 6 IN+ IN OUT OUT+ Ω.Ω OUT OUT+ Figure. Calculate Differential Gain L LTC6-.Ω Ω Ω 8 F 7.7pF LTC6- Ω Ω.Ω Ω Ω Ω Ω.Ω 8 6 F F 6 6 F F 7 V OUT.7pF F 6 / R L / R L Output Match and Filter The LTC6- can drive an ADC directly without external output impedance matching. Alternatively, the differential output impedance of Ω can be matched to higher value impedance, e.g. Ω, by series resistors or an LC network. The internal low pass filter outputs at F/F have a db bandwidth of 9MHz. External capacitors can reduce the low pass filter bandwidth as shown in Figure. A bandpass filter is easily implemented with only a few components as shown in Figure 6. Three 9pF capacitors and a 6nH inductor create a bandpass filter with 6MHz center frequency, db frequencies at 8MHz and MHz. Output Common Mode Adjustment The output common mode voltage is set by the V OCM pin, which is a high impedance input. The output common mode voltage is capable of tracking V OCM in a range from V to 6 LTC6- Ω Ω.Ω IN+ IN OUT OUT+ Ω Ω.Ω 6 F Figure. LTC6- Internal Filter Topology Modifi ed for Low Filter Bandwidth (Three External Capacitors) 6 IN+ IN OUT OUT+ Ω Ω LTC6- Ω Ω.Ω Ω Ω Ω Ω.Ω 6 F6 8 F 7.7pF 8 F 7.7pF F 6 F 6 9pF pf 8.pF FILTERED OUTPUT (87.MHz) 8.pF Figure 6. LTC6- Internal Filter Topology Modifi ed for Bandpass Filtering (Three External Capacitors, One External Inductor) Ω 6nH Ω 9pF.99Ω 9pF.99Ω LTC8 6f

13 APPLICATIONS INFORMATION.6V. The bandwidth of V OCM control is typically MHz, which is dominated by a low pass filter connected to the V OCM pin and is aimed to reduce common mode noise generation at the outputs. The internal common mode feedback loop has a db bandwidth around MHz, allowing fast common mode rejection at the outputs of the LTC6-. The V OCM pin should be tied to a DC bias voltage with a bypass capacitor. When interfacing with A/D converters such as the LTxx families, the V OCM pin can be connected to the V CM pin of the ADC. Driving A/D Converters The LTC6- has been specifi cally designed to interface directly with high speed A/D converters. In Figure 7, an example schematic shows the LTC6- with a single-ended input driving the LTC8, which is a 6-bit, Msps ADC. Two external Ω resistors help eliminate potential resonance associated with stray capacitance of PCB traces and bond wires of either the ADC input or the driver output. V OCM of the LTC6- is connected to V CM of the LTC8 V CM pin at.v. Alternatively, a single-ended input signal can be converted to differential signal via a balun and fed to the input of the LTC6-. The balun also converts input impedance to match Ω source impedance. Figure 8 summarizes the spurious free dynamic range (SFDR) for IMD of the whole system in Figure 7. SFDR (db) LTC6-7 6 F8 Figure 8. SFDR for the Combination of LTC6- and LTC8 specifications, two test circuits are used to generate the information in this datasheet. Test Circuit A is DC987B, a two-port demonstration circuit for the LTC6 family. The schematic and silkscreen are shown below. This circuit includes input and output transformers (baluns) for single-ended-to-differential conversion and impedance transformation, allowing direct hook-up to a -port Top Silkscreen Test Circuits Due to the fully-differential design of the LTC6 and its usefulness in applications with differing characteristic.v IF IN 66.Ω 9Ω V OCM F LTC6- F ENABLE db GAIN Ω Ω AIN V CM LTC8 AIN + LTC8 Msps 6-Bit ADC 6 F7 Figure 7. Single-Ended Input to LTC6- and LTC8 6f

14 LTC6- APPLICATIONS INFORMATION network analyzer. There are also series resistors at the output to present the LTC6 with a 7Ω differential load, optimizing distortion performance. Due to the input and output transformers, the db bandwidth is reduced from.8ghz to approximately.ghz. Test Circuit B uses a -port network analyzer to measure S-parameters and gain/phase response. This removes the effects of the wideband baluns and associated circuitry, for true picture of the >GHz S-parameters and AC characteristics. TYPICAL APPLICATIONS Demo Circuit 987B Schematic (Test Circuit A) ENABLE DIS JP R6 Ω V CC V CC C7 pf C8 J J R6 Ω R () db R () R Ω T () R () R () C C R () C V CC SL () 6 9 V ENABLE V LTC6- F F V OCM V R 86.6Ω R8 () R7 () R9 86.6Ω V CC C C SL () C T R () R Ω R Ω R () J SL () J TP V OCM V CC R k R9.k C C9 pf C7 C pf C J6 TEST IN R7 Ω R Ω T TCM :9 : C9 C C R () C C6 R () C T TCM :9 : R8 Ω R6 Ω J7 TEST OUT V CC TP V CC.8V TO.V TP GND C.7μF C μf () VERSION IC R R T SL SL SL -C LTC6CUD- OPEN OPEN MINI-CIRCUITS TCM-9 (:) 6dB db db SL = SIGNAL LEVEL NOTE: UNLESS OTHERWISE SPECIFIED. () DO NOT STUFF. 6 TA 6f

15 TYPICAL APPLICATIONS Test Circuit B, -Port Analysis pf LTC6- V ENABLE 9 V BIAS CONTROL / AGILENT EO7A PORT (Ω) Ω R G Ω IN+ IN R F Ω OUT OUT+ R OUT.Ω R FILT Ω R FILT Ω 7.Ω 8 F 7 C FILT.7pF F 6 PORT (Ω) / AGILENT EO7A PORT (Ω) 6 R G Ω R F Ω COMMON MODE CONTROL R OUT.Ω 7.Ω PORT (Ω) V OCM V 6 TA pf V OCM PACKAGE DESCRIPTION UD Package 6-Lead Plastic QFN (mm mm) (Reference LTC DWG # -8-69) BOTTOM VIEW EXPOSED PAD.7 ±.. ±. ( SIDES) PIN TOP MARK (NOTE 6).7 ±. R =. TYP 6 PIN NOTCH R =. TYP OR. CHAMFER. ±.. ±.. ±.. ±. ( SIDES). ±. (-SIDES). ±.. BSC PACKAGE OUTLINE RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS. REF.. NOTE:. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO- VARIATION (WEED-). DRAWING NOT TO SCALE. ALL DIMENSIONS ARE IN MILLIMETERS. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED.mm ON ANY SIDE. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN LOCATION ON THE TOP AND BOTTOM OF PACKAGE (UD6) QFN 9. ±.. BSC Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 6f

16 LTC6- RELATED PARTS PART NUMBER DESCRIPTION COMMENTS High-Speed Differential Amplifiers/Differential Op Amps LT 99-8MHz Differential Amplifi er/adc Driver A V = V/V, OIP = 8dBm at 7MHz LT99-9MHz Differential Amplifi er/adc Driver A V = V/V, OIP = dbm at 7MHz LT99-7MHz Differential Amplifi er/adc Driver A V = V/V, OIP = dbm at 7MHz LT99 Low Noise, Low Distortion Differential Op Amp 6-Bit SNR and SFDR at MHz, Rail-to-Rail Outputs LT Ultralow Distortion IF Amplifi er/adc Driver with Digitally OIP = 7dBm at MHz, Gain Control Range.dB to db Controlled Gain LT Low Distortion IF Amplifi er/adc Driver with Digitally OIP = dbm at MHz, Gain Control Range.dB to 7dB Controlled Gain LTC6-.GHz Low Noise, Low Distortion, Differential ADC Driver A V = db, ma Supply Current, IMD = 7dBc at MHz LT6-6 MHz Differential Amplifi er/adc Driver A V = 6dB, Distortion < 8dBc at MHz LT6- MHz Differential Amplifi er/adc Driver A V = db, Distortion < 8dBc at MHz LT6- MHz Differential Amplifi er/adc Driver A V = db, Distortion < 8dBc at MHz LTC66 GHz Rail-to-Rail Input Differential Op Amp.6nV/ Hz Noise, 7dBc Distortion at MHz, 8mA LT6 Low Power Differential ADC Driver/Dual Selectable Gain Amplifi er 6mA Supply Current, IMD = 8dBc at 7MHz, A V =, or High-Speed Single-Ended Output Op Amps LT8/LT8/ High Slew Rate Low Cost Single/Dual/Quad Op Amps 8nV/ Hz Noise, 7V/μs, ma Supply Current LT8 LT8/LT86/ Very High Slew Rate Low Cost Single/Dual/Quad Op Amps 6nV/ Hz Noise, V/μs, 6.mA Supply Current LT87 LT88/LT89 Ultra High Slew Rate Low Cost Single/Dual Op Amps 6nV/ Hz Noise, V/μs, 9mA Supply Current LT6/LT6 Rail-to-Rail Input and Output Low Noise Single/Dual Op Amps.9nV/ Hz Noise, 6MHz GBW, Distortion = 8dBc at MHz LT6/LT6/ LT6 LT6/LT6/ LT6 LT6/LT6/ LT6 Rail-to-Rail Input and Output Low Noise Single/Dual/Quad Op Amps Rail-to-Rail Output Low Noise Single/Dual/Quad Op Amps Rail-to-Rail Output Low Noise Single/Dual/Quad Op Amps.9nV/ Hz Noise, ma Supply Current, MHz GBW.nV/ Hz Noise,.mA Supply Current, MHz GBW.9nV/ Hz Noise,.mA Supply Current, 6MHz GBW Integrated Filters LTC6- Very Low Noise, 8th Order Filter Building Block Lowpass and Bandpass Filters up to khz LT68 Very Low Noise, th Order Filter Building Block Lowpass and Bandpass Filters up to MHz LTC69-7 Linear Phase, Tunable th Order Lowpass Filter Single-Resistor Programmable Cut-Off to khz LT66-. Very Low Noise Differential.MHz Lowpass Filter SNR = 86dB at V Supply, th Order Filter LT66- Very Low Noise Differential MHz Lowpass Filter SNR = 8dB at V Supply, th Order Filter LT66- Very Low Noise Differential MHz Lowpass Filter SNR = 8dB at V Supply, th Order Filter LT66- Very Low Noise Differential MHz Lowpass Filter SNR = 76dB at V Supply, th Order Filter LT66- Very Low Noise Differential MHz Lowpass Filter SNR = 76dB at V Supply, th Order Filter 6 LT 77 PRINTED IN USA Linear Technology Corporation 6 McCarthy Blvd., Milpitas, CA 9-77 (8) -9 FAX: (8) -7 LINEAR TECHNOLOGY CORPORATION 7 6f