LMH6555

LMH6555 Low Distortion 1.2 GHz Differential Driver PRELIMINARY November 2006 LMH6555 Low Distortion 1.2 GHz Differential Driver General Description The LMH6555 is an ultra high speed differential line driver with 50 dB SFDR at 750 MHz. The LMH6555 features a fixed gain of 13.6 dB. An input to the device allows the output common mode voltage to be set independent of the input common mode voltage in order to simplify the interface to high speed differential input ADC’s . A unique architecture allows the device to operate as a fully differential driver or as a singleended to differential converter. The outstanding linearity and drive capability (100Ω differential load) of this device is a perfect match for driving high speed analog-to-digital converters. When combined with the ADC081000/ ADC08D1500, the LMH6555 forms an excellent 8-bit data acquisition system with analog bandwidths exceeding 1 GHz. The LMH6555 is offered in a space saving 16-pin LLP package. Features Typical Unless Otherwise Specified: ■ −3 dB bandwidth (VOUT = 0.80PP) ■ ±0.5 dB gain flatness (VOUT = 0.80 VPP) ■ Slew rate ■ 2nd/3rd Harmonics (750 MHz) ■ Fixed gain ■ Supply current ■ Single supply operation ■ Adjustable common-mode output voltage 1.2 GHz 500 MHz 3000 V/μs −53/−54 dBc 13.6 dB 120 mA 3.3V ±10% Applications ■ Differential ADC driver ■ National Semiconductor ADC081000/ ADC08D1500 ■ ■ ■ ■ ■ driver Single ended to differential converter Differential driver Intermediate frequency (IF) amplifier Communication receivers Oscilloscope front end Block Diagram 20127704 Single Ended to Differential Conversion © 2006 National Semiconductor Corporation 201277 www.national.com LMH6555 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance (Note 5) Human Body Model Machine Model VS Output Short Circuit Duration (one pin to ground) Common Mode Input Voltage 2000V 200V TBD Infinite −1V to TBD (Note 2) Maximum Junction Temperature Storage Temperature Range Soldering Information Infrared or Convection (20 sec.) Wave Soldering (10 sec.) +150°C −65°C to +150°C 235°C 260°C Operating Ratings Temperature Range (Note 4) Supply Voltage Range (Note 1) −40°C to +85°C +3.3V ±10% 65°C/W Package Thermal Resistance (θJA)(Note 4) 16-Pin LLP 3.3V Electrical Characteristics Unless otherwise specified, all limits are guaranteed for TA= 25°C, VCM_REF = 1.2V, both inputs tied to 0.3V through 50Ω (RS1 & RS2) each (Note 11), VS = 3.3V, RL = 100Ω differential, VOUT = 0.8 VPP; See Notes section for definition of terms used throughout the datasheet. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (Note 8) Typ (Note 7) 1200 1200 500 TBD 320 14 3000 TBD TBD TBD 13.6 TBD TBD dB Max (Note 8) Units Differential AC Performance SSBW LSBW GF_0.5 Ph_Delta TRS/TRL OS SR ts AV_DIFF ±0.5 dB Gain Flatness Phase Delta Rise/ Fall Time Overshoot Slew Rate Settling Time Insertion Gain (|S21|) −3 dB Bandwidth VOUT = 0.25 VPP VOUT = 0.8 VPP VOUT = 0.8 VPP Output Differential Phase Difference, f = 400 MHz VOUT = 0.4 VPP VOUT = 0.4 VPP 0.8V Step, 10% to 90%,(Note 6) 0.8V Step, VOUT within ±0.1% MHz MHz deg pS % V/µs ns AV_VAR Insertion Gain Variation VCM_REF Input Varied from 0.95V to 1.45V, VOUT = 0.8 VPP 250 MHz (Note 12) 500 MHz (Note 12) 750 MHz (Note 12) ±TBD ±TBD dB Distortion And Noise Response HD2_L HD2_M HD2_H HD3_L HD3_M HD3_H OIP3_L OIP3_H OIM3 eno NF RIN RIN_DIFF CIN Third Order Intermodulation Distortion Output Referred Voltage Noise Noise Figure Input Resistance Differential Input Resistance Input Capacitance Output 3rd Order Intercept 3rd Harmonic Distortion 2nd Harmonic Distortion −60 −62 −53 −67 −61 −54 TBD TBD TBD 24 TBD TBD TBD 50 80 0.3 TBD TBD dBm dBc nV/ dB Ω Ω pF dBc dBc 250 MHz (Note 12) 500 MHz (Note 12) 750 MHz (Note 12) 70 MHz (Note 12) 250 MHz (Note 12) f1 = 70 MHz, f2 = 70 MHz + 10 kHz, PIN = TBD (Note 12) >1 MHz Relative to Differential Inputs Single Ended Input Drive Differential Input Drive Each Input to GND Input Characteristics www.national.com 2 LMH6555 Symbol Output Characteristics CMVR VOOS TCVOOS RO VOUT VO_CM BAL_Error_DC Parameter Conditions Min (Note 8) 0 Typ (Note 7) Max (Note 8) TBD Units Input Common Mode Voltage Range Output Offset Voltage Output Offset Voltage Average Drift Output Resistance AV_DIFF – AV_CM ≥ 30 dB Differential Mode (Note 9) RT1 and RT2 V TBD ±200 TBD TBD TBD 0.95 TBD TBD 50 800 ±100 TBD TBD TBD mV μV/°C Ω mV Differential Output Voltage Swing ΔAV_DIFF ≤ 1 dB Output Common Mode Voltage Range Output Balance Error VCM_REF Input Varied, VOUT = 0.80 VPP 1.45 TBD TBD V BAL_Error_AC TBD dB AV_CM Common Mode Gain DC, ΔVO_CM/ΔVI_CM TBD TBD TBD TBD TBD ±50 TBD dB VCM_REF Characteristics VOS_CM IB_CM RIN_CM Gain_VCM_REF Power Supply IS PSRR PSRR_CM Supply Current Differential Power Supply Rejection Ratio Common Mode PSRR RS1 & RS2 Open (Note 3) DC, ΔVS = ±0.3V, ΔVOUT/ΔVS DC, ΔVS = ±0.3V, ΔVO_CM/ΔVS TBD TBD TBD TBD TBD TBD 120 76 TBD TBD TBD mA dB dB Output CM Offset Voltage VCM_REF Bias Current VCM_REF Input Resistance VCM_REF Input Gain to Output ΔVO_CM/ΔVCM_REF TBD VOS_CM = VO_CM – VCM_REF 0.95V ≤ VCM_REF ≤ 1.45V (Note 10) TBD −100 TBD 0.99 TBD mV μA kΩ V/V Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications, see the Electrical Characteristics tables. Note 2: Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of the device such that TJ = TA. No guarantee of parametric performance is indicated in the electrical tables under conditions of internal self-heating where TJ > TA. Note 3: Total supply current is affected by the input voltages connected through RS1 and RS2. Supply current tested with input removed. Note 4: The maximum power dissipation is a function of TJ(MAX), θJA and TA. The maximum allowable power dissipation at any ambient temperature is PD= (TJ (MAX) — TA)/ θJA. All numbers apply for package soldered directly into a 2 layer PC board with zero air flow. Note 5: Human Body Model, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC) Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC). Note 6: Slew Rate is the average of the rising and falling edges. Note 7: Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will also depend on the application and configuration. The typical values are not tested and are not guaranteed on shipped production material. Note 8: Limits are 100% production tested at 25°C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control (SQC) methods. Note 9: Drift determined by dividing the change in parameter at temperature extremes by the total temperature change. Note 10: Positive current is current flowing into the device. Note 11: Quiescent device common mode input voltage is 0.3V. Note 12: Distortion data taken under single ended input condition. 3 www.national.com LMH6555 Ordering Information Package 16-Pin LLP Part Number LMH6555SQ LMH6555SQX Package Marking L6555SQ Transport Media 1k Units Tape and Reel 4.5k Units Tape and Reel NSC Drawing SQA16A Definition of Terms and Specifications (Alphabetical order) Unless otherwise specified, VCM_REF = 1.2V 1. 2. 3. 4. 5. 1. AV_CM (dB) AV_DIFF (dB) ΔAV_DIFF (dB) AV_VAR (dB) CMVR (V) Change in the output common mode voltage (ΔVO_CM ) with respect to the change in input common mode voltage (ΔVI_CM) Insertion gain from a single ended 50Ω (or 100Ω differential) source to the differential output (ΔVOUT) Variation in insertion gain (AV_DIFF) with input signal change (ΔVIN ) Variation of insertion gain (AV_DIFF) with VCM_REF input change (ΔVCM_REF). Calculated as the change in AV_DIFF (dB) at various VCM_REF Range of input common mode voltage (VI_CM) where the insertion gain (AV_DIFF) is 30 dB larger than common mode gain (AV_CM) and hence the amplifier’s output is dominated by its differential output Variation in output common mode voltage (ΔVO_CM) with respect to change in VCM_REF input (ΔVCM_REF) with maximum differential output 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. Pin (dBm referenced to 50Ω) PSRR (dB) PSRR_CM (dB) RIN (Ω) RIN_DIFF (Ω) RL (Ω) RO (Ω) RS1, RS2 (Ω) RT1, RT2 (Ω) VCM_REF (V) ΔVCM_REF (V) VI_CM (V) ΔVI_CM (V) VIN+, VIN− (V) ΔVIN (V) VO_CM (V) ΔVO_CM (V) Input power associated with each of the tones for OIM3 testing Differential output change (ΔVOUT) with respect to the power supply voltage change (ΔVS) with nominal differential output Output common mode voltage change (ΔVO_CM) with respect to the change in the power supply voltage (ΔVS) Single ended input impedance to ground Differential input impedance Differential output load Equivalent to RT1 & RT2 Source impedance to VIN+ and VIN− respectively Output impedance looking into each output Device input pin voltage which controls output common mode Change in the VCM_REF input voltage DC average of the inputs (VIN+, VIN−) Variation in input common mode voltage (VI_CM) Device input pin voltages Terminated (50Ω for single ended and 100Ω for differential) generator voltage Output common mode voltage (DC average of VOUT+ and VOUT−) Variation in output common mode voltage (VO_CM) Balance Error. Measure of the output swing balance of VOUT+ and VOUT−, as reflected on the output common mode voltage (VO_CM), relative to the differential output swing (VOUT). Calculated as output common mode voltage change (ΔVO_CM) divided into the output differential voltage change (ΔVOUT) 25. AC version of the DC balance error 26. VOOS (V) test 6. Gain_VCM_REF (V/V) DC Offset Voltage. Differential output voltage measured with both inputs grounded through 50Ω 4 www.national.com LMH6555 27. 28. 29. 30. 31. 32. VOS_CM (V) VOUT (V) ΔVOUT (V) VOUT+, VOUT− (V) VS (V) ΔVS (V) Difference between the output common mode voltage (VO_CM) and the voltage on the VCM_REF input, for the allowable VCM_REF range Differential Output Voltage (VOUT+ - VOUT−) (Corrected for DC offset (VOOS)) Change in the differential output voltage (Corrected for DC offset (VOOS)) Device output pin voltages Supply Voltage (V+ - V−) Change in VCC supply voltage Connection Diagram 16-Pin LLP 20127705 Application Information The LMH6555 consists of three individual amplifiers: The VOUT+ driver, VOUT− driver, and the common mode amplifier. Being a differential amplifier, the LMH6555 will not respond to the input common mode input (as long as it is within its input common mode range) and instead the output common mode is forced by the built-in common mode amplifier with VCM_REF as its input. As shown in Figure 1 below, the VCMO of most differential high speed ADC’s will be tied to the VCM_REF input of the LMH6555 for direct output common mode control. In some cases, the output drive capability of the ADC VCMO output may need an external buffer (not shown) to increase its current capability in order to drive the VCM_REF pin. The LMH6555 Electrical Characteristics table shows the gain (AV_CM) and the offset (VOS_CM) from the VCM_REF to the device output common mode. 20127704 FIGURE 1. Single Ended to Differential Conversion 5 www.national.com LMH6555 The single ended AC input and output impedance of the LMH6555 I/O pins are close to 50Ω and are also specified in the Electrical Characteristics table (RIN and RO). With differential input drive, the differential input impedance (RIN_DIFF) will be close to 80Ω. The device nominal input common mode voltage is close to 0.3V at VIN+ and VIN− with a weak relationship to the VCM_REF voltage. Thus, the input source will experience a DC current which is dependant on its DC voltage. Because of this, the differential output offset voltage is influenced by the matching between RS1 and RS2 under DC and AC conditions. So, for example, in a single ended input condition, if the signal source is AC coupled to one input, the undriven input needs to also be AC coupled. In applications where very low output offset is required, adjusting the value of RS2 (the input which is not driven) can be an effective method of trimming the output offset voltage of the LMH6555 in a single ended input configuration. The nominal value of RS1 and RS2 on the other hand will affect the insertion gain. The LMH6555 can also be used with the input signal AC coupled. In this case, the coupling capacitors need to be large enough to not block the frequency content below (1/2πRINC)Hz. The single ended output impedance of the LMH6555 is 50Ω. The LMH6555 Electrical Characteristics shows the device performance with 100Ω differential output load, as would be the case if a device such as the ADC081000 were being driven. As shown in Figure 2 below, some applications can benefit from using the LMH6555 to interface a Class A type differential output device (U1) to a high speed ADC. In this application, the LMH6555 performs the task of buffering and amplifying the signal to properly drive the 100Ω differential input impedance of the ADC. 20127706 FIGURE 2. Differential Buffering and Amplification In this application, U1’s DC common mode output will be affected by the LMH6555 input common mode voltage through RG and RL. The equivalent load to the driver Collector within U1 would be the combination of R L and RIN_DIFF (≅80Ω). Series isolation resistors (not shown) between U1 outputs and LMH6555 input pins would offer additional isolation at the expense of more signal loss. Alternatively, input AC coupling could have been used to alleviate the common mode concerns. EXPOSED PAD LLP PACKAGE The LMH6555 is packaged in a thermally enhanced package. The exposed pad (device bottom) is connected to the GND pins. It is recommended, but not necessary, that the exposed pad be connected to the supply ground plane. The thermal dissipation of the device is largely dependent on the connection of this pad. The exposed pad should be attached to as much copper on the circuit board as possible, preferably external copper. However, it is very important to maintain good high speed layout practices when designing a system board. Here is a link to more information on the National 16 pin LLP package: http://www.national.com/packaging/folders/sqa16a.html www.national.com 6 LMH6555 Physical Dimensions inches (millimeters) unless otherwise noted 16-Pin LLP NS Package Number SQA16A 7 www.national.com LMH6555 Low Distortion 1.2 GHz Differential Driver Notes THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS, IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS DOCUMENT. TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT NATIONAL’S PRODUCT WARRANTY. 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All other brand or product names may be trademarks or registered trademarks of their respective holders. Copyright© 2006 National Semiconductor Corporation For the most current product information visit us at www.national.com National Semiconductor Americas Customer Support Center Email: new.feedback@nsc.com Tel: 1-800-272-9959 National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530-85-86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +49 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: ap.support@nsc.com National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: jpn.feedback@nsc.com Tel: 81-3-5639-7560 www.national.com