LMH6554LE-EVAL/NOPB

User's Guide SNOA541C – October 2009 – Revised May 2013 AN-1945 LMH6554LE-EVAL High Speed Differential Amplifier Evaluation Board 1 General Description The LMH6554LE−EVAL evaluation board is designed to aid in the characterization of Texas Instruments LMH6554 fully differential amplifier in an 14 lead UQFN package. The LMH6554 is part of the LMH™ high-speed amplifier family. Use the evaluation board as a guide for high frequency layout and as a tool to aid in device testing and characterization. The evaluation board schematic is shown in Figure 1. For recommended for component values, see the device-specific data sheets. 2 Basic Operation The LMH6554LE−EVAL evaluation board has been set up to provide maximum flexibility for evaluating TI’s differential LMH6554 operational amplifier. The board supports fully differential operation as well as single-ended to differential and single-ended to single-ended operation. For fully differential operation, use resistors R2 and R3 to set the input impedance of the amplifier. The differential input resistance will be equal to 2*R2 || 2*RG_M. Where R2 = R3 and RG_M = RG_P. In this mode resistors RG_M, RG_F, RF_M and RF_P set the gain of the amplifier. Amplifier gain = RF_M/RG_M = RF_P/RG_P where RG_M = RG_P and RF_M = RF_P. For more details on gain component value selections, see Table 2. For single-ended input mode of operation, the input and termination resistance must be properly configured to give the correct gain and input impedance (RIN). For example, in the case of the LMH6554, if a gain of 2 V/V is desired, R2 = R3 = 76.8 Ω, RG_M = RG_P = 90 Ω, RF_M = RF_P = 200 Ω, C2 and R14 = OPEN, C3 = 0.1 µF, and R15 = 50 Ω, which will make RIN = 50 Ω at the most positive node of R3 looking into RG_M. Further details of single-ended input mode calculations can be found in the LMH6554 2.8 GHz Ultra Linear Fully Differential Amplifier Data Sheet (SNOSB30). Components C3= 0.1 µF and R15= 50 Ω should be used to AC-couple and balance the inputs, otherwise can be left empty. In this example the input signal would be connected to the VIN- input. For more details on gain component value selections, see Table 1. For differential output applications, load R6 and R7 with the desired values to match the output load and leave C14 and C15 empty. Typically to match a test equipment, R6 = R7 = 50 Ω. If single-ended output is desired an output transformer such as the TC4-19 from mini circuits can be utilized. The TC4-19 has a 4:1 impedance ratio (2:1 turns/voltage ratio). This is particularly useful for interfacing to a 50 Ω test equipment. When referencing the transformer data sheet, the LMH6554LE−EVAL evaluation board has the primary windings on the output side of the evaluation board and the amplifier is driving the secondary windings. This provides a step down transformation from the differential amplifier output to the test equipment. The center-tapped secondary winding also allows a differential to single ended conversion (Balun). The impedance seen by the differential amplifier = (R6 + R7 + RL*4), where RL is the impedance from pin 4 of the transformer to the load. For example, if RL = 50 Ω for the test equipment, to achieve an impedance of 500 Ω seen by the LMH6554 differential output R6 = R7 = 150 Ω with C14 = C15 = R12 = R13 = 0 Ω. The LMH6554LE−EVAL board is equipped with pads to add additional filtering schemes using C14 - C18 and R8 - R13. LMH, LMH6554LE−EVAL are trademarks of Texas Instruments. All other trademarks are the property of their respective owners. SNOA541C – October 2009 – Revised May 2013 Submit Documentation Feedback AN-1945 LMH6554LE-EVAL High Speed Differential Amplifier Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 1 Layout Considerations www.ti.com Pin 9 on the LMH6554 device is the enable (VEN) pin that can be used to disable the device with an external signal. Pin 11 and 14 have no internal package connections and should be connected to analog ground by using 0 Ω resistors for R4 and R5. For more details, see the LMH6554 2.8 GHz Ultra Linear Fully Differential Amplifier Data Sheet (SNOSB30). 3 Layout Considerations The printed circuit board (PCB) layout and supply bypassing play major roles in determining high frequency performance. Use these evaluation boards as a guide when designing your own board and follow these steps to optimize high frequency performance: 1. Symmetry is of the utmost importance. 2. Use precision resistors 0.1% or 0.01%. 3. Use a ground plane. 4. Include large ( ~ 10 μF) ceramic capacitors on both supplies (C19 and C20). 5. Near the device use ceramic capacitors 0.1 μF for C22–25 and 0.01 μF for C7, C8, C12, and C13 from supplies to ground. 6. Remove the ground and power planes from under and around the part, especially the input and output pins. 7. Minimize all trace lengths. 8. Use terminated and matched transmission lines for long traces. Sample artwork for the LMH6554LE−EVAL evaluation board is shown in Figure 2 and Figure 3. 4 Measurement Hints Balance, CMRR and HD2 are highly dependent on resistor matching. Use 0.1 or 0.01% resistors. The LMH6554LE−EVAL™ evaluation board is designed for differential or single-ended output measurements, but not both at the same time. When not using the transformer make sure to leave C14 and C15 empty. Likewise, when making single-ended output measurements populate components C14, C15, R12 and R13. Many differential amplifiers are optimized for the higher impedances represented by most ADCs. On a differential amplifier both inputs are inverting, keep parasitic capacitance to a minimum on both inputs. Also, using probes of any kind on a differential circuit is not recommended. 2 AN-1945 LMH6554LE-EVAL High Speed Differential Amplifier Evaluation Board SNOA541C – October 2009 – Revised May 2013 Submit Documentation Feedback Copyright © 2009–2013, Texas Instruments Incorporated LMH6554LE_EVAL Schematic www.ti.com 5 LMH6554LE_EVAL Schematic BANANA JACK VCC VCC C12 C19 C7 C23 + C20 + VCC C22 BANANA JACK BANANA JACK VEE GND VEE VEE OUT+ VOCM SMA SMA C4 R4 R14 2 1 U1 6 VIP LMH6554 7 FBM 8 SMA RF_P VIM VCC RG_P VIN+ 5 VIM VEN RG_M NC VIP NC 14 R9 3 T1 OUT 4 13 12 11 C16 2 R11 1 R7 C18 R10 C15 R3 C3 C17 R6 SMA 6 TC4 -19 10 SMA FBP VCC 4 VCM 3 RF_M VEE VIN- C21 R12 C14 VEE R2 9 C2 R13 C10 R8 R15 OUT- SMA EN VCC SMA R5 C1 C13 C25 C8 C24 VEE Figure 1. Board Schematic Table 1. Single-Ended Input Gain Resistor Values for 50 Ω System Gain RF_M = RF_P RG_M=RG_P R3 RM R6 = R7 0dB 200 Ω 191 Ω 62 Ω 27.7 Ω 50 Ω 6dB 200 Ω 91 Ω 76.8 Ω 30.3 Ω 50 Ω 12dB 200 Ω 35.7 Ω 147 Ω 37.3 Ω 50 Ω SNOA541C – October 2009 – Revised May 2013 Submit Documentation Feedback AN-1945 LMH6554LE-EVAL High Speed Differential Amplifier Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 3 LMH6554LE_EVAL Board Layout Views www.ti.com Table 2. Differential Input Gain Resistor Selection for 50 Ω System 6 Gain RF_M = RF_P RG_M = RG_P R2 = R3 R6 = R7 0dB 200 Ω 200 Ω 66.67 Ω 50 Ω 6dB 200 Ω 100 Ω 100 Ω 50 Ω 12dB 200 Ω 50 Ω — 50 Ω LMH6554LE_EVAL Board Layout Views Figure 2. Board Layout Top View Figure 3. Board Layout Bottom View 4 AN-1945 LMH6554LE-EVAL High Speed Differential Amplifier Evaluation Board SNOA541C – October 2009 – Revised May 2013 Submit Documentation Feedback Copyright © 2009–2013, Texas Instruments Incorporated Bill of Materials (BOM) www.ti.com 7 Bill of Materials (BOM) Table 3. LMH6554LE_EVAL BOM Item No P/N Reference Description 1 GRM188F51C224ZA01 D Manufacturer Murata 2 C1,C4 Ceramic cap 0.22 µF 16 V 0603 2 C1608X8R1H103K TDK Corporation 4 C7,C8,C12,C13 Ceramic cap 0.01 µF 50 V 10% 0603 3 C3216X5R1C106M TDK Corporation 2 C19,C10 Ceramic cap 10 µF 16 V 20% 1206 4 C0603C104K4RACTU Kemet 1 C2 Ceramic cap 0.1uF 16 V X7R 0603 5 CC0805KRX7R7BB104 Yageo 4 C22–C25 Ceramic cap 0.1uF 16 V X7R 0805 6 142–0701–806 Emerson (Johnson) 7 EN,OUT,OUT+, OUT-,VIN+, VIN-, VOCM Connector Jack rcpt end launch nickel 7 SPC15363 SPC TECHNOLOGY 1 VCC RED insulated banana jack 8 SPC15182 SPC TECHNOLOGY 1 VEE GREEN insulated banana jack 9 SPC15354 SPC TECHNOLOGY 1 GND BLACK insulated banana jack 10 RC0603FR-0749R9L Yageo 1 R14 Resistor 49.9 Ω 1/10W 1% 0603 SMD 11 RC0603FR-0776R8L Yageo 2 R2,R3 Resistor 76.8 Ω 1/10W 1% 0603 SMD 12 RC0402JR-070RL Yageo 2 R4,R5 Resistor 0 Ω 1/6W 5% 0402 SMD 13 TNPW040249R9BEED Vishay/Dale 2 R6,R7 Resistor 49.9 Ω 1/16W 0.1% 0402 14 ERA-2AEB201X Panasonic 2 RF_M,RF_P Resistor 200 Ω 1/16W 0.1% 0402 SMD 15 ERA-2AEB910X Panasonic 2 RG_M,RG_P Resistor 91 Ω 1/16W 0.1% 0402 SMD 16 TC4–19+ Mini-Circuits 1 T1 Surface Mount RF transformer, 50 Ω, 10 to 1900 MHz 17 LMH6554 Texas Instruments 1 U1 2.5 GHz Fully Differential Amplifier, 14 pin UQFN package SNOA541C – October 2009 – Revised May 2013 Submit Documentation Feedback Qty AN-1945 LMH6554LE-EVAL High Speed Differential Amplifier Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 5 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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