LTC6431-20 20dB Gain Block, 50Ω IF Amplifier FEATURES DESCRIPTION 50Ω Matched 20MHz to 1400MHz n20.8dB Power Gain n46.2dBm OIP3 at 240MHz Into 50Ω n NF = 2.6dB at 240MHz n0.6nV/√Hz Total Input Noise n S11 < –10dB Up to 2.0GHz n S22 < –10dB Up to 1.4GHz n>2.0V P-P Linear Output Swing n P1dB = 22.0dBm n50Ω Single-Ended Input/Output n Insensitive to V CC Variation n A-Grade 100% OIP3 Tested at 240MHz n Input/Output Internally Matched to 50Ω n Single 5V Supply The LTC®6431-20 is a gain block amplifier exhibiting excellent linearity at frequencies beyond 1000MHz and with low associated output noise. n The unique combination of linearity, low noise and low power dissipation make this an ideal candidate for many signal-chain applications. The LTC6431-20 is easy to use, requiring a minimum of external components. It is internally input/output matched to 50Ω and it draws only 93mA from a single 5V supply. On-chip bias and temperature compensation maintain performance over environmental changes. The LTC6431-20 uses a high performance SiGe BiCMOS process for excellent repeatability compared with similar GaAs amplifiers. All A-grade LTC6431-20 devices are tested and guaranteed for OIP3 at 240MHz. The LTC6431-20 is housed in a 4mm × 4mm 24-lead QFN package with an exposed pad for thermal management and low inductance. APPLICATIONS Single-Ended IF Amplifier ADC Driver n CATV n n LTC6431 FAMILY GAIN LTC6431-15 15.5dB LTC6431-20 20.8dB L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION OIP3 vs Frequency Single-Ended IF Amplifier VCC = 5V 52 50 5V 48 OIP3 (dBm) RF CHOKE 560nH LTC6431-20 50Ω 1000pF 1000pF 50Ω 643120 TA01a 46 44 42 VCC = 5V TA = 25°C POUT = 2dBm/TONE 38 fSPACE = 1MHz ZIN = ZOUT = 50Ω 36 200 400 0 40 600 FREQUENCY (MHz) 800 1000 643120 TA01b 643120f For more information www.linear.com/LTC6431-20 1 LTC6431-20 PIN CONFIGURATION Total Supply Voltage (VCC to GND)...........................5.5V Amplifier Output Current (+OUT)..........................120mA RF Input Power, Continuous, 50Ω (Note 2)..........15dBm RF Input Power, 100µs Pulse, 50Ω (Note 2).........20dBm Operating Case Temperature Range (TCASE)......................................................–40°C to 85°C Storage Temperature Range................... –65°C to 150°C Junction Temperature (TJ)..................................... 150°C DNC DNC DNC VCC GND IN TOP VIEW 24 23 22 21 20 19 DNC 1 18 OUT DNC 2 17 GND DNC 3 16 T_DIODE 25 GND DNC 4 15 DNC DNC 5 14 DNC DNC 6 13 DNC DNC DNC 9 10 11 12 DNC 8 VCC 7 DNC (Note 1) GND ABSOLUTE MAXIMUM RATINGS UF PACKAGE 24-LEAD (4mm × 4mm) PLASTIC QFN TJMAX = 150°C, θJC = 54°C/W EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC6431AIUF-20#PBF LTC6431AIUF-20#TRPBF 43120 24-Lead (4mm × 4mm) Plastic QFN –40°C to 85°C TCASE LTC6431BIUF-20#PBF LTC6431BIUF-20#TRPBF 43120 24-Lead (4mm × 4mm) Plastic QFN –40°C to 85°C TCASE 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 nonstandard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ DC ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, ZSOURCE = ZLOAD = 50Ω. Typical measured DC electrical performance using Test Circuit A. SYMBOL PARAMETER VS Operating Supply Range IS(TOT) Total Supply Current IS(OUT) ICC Total Supply Current to OUT Pin Current to VCC Pin CONDITIONS MIN TYP MAX UNITS l 4.75 5.0 5.25 V 75 68 93 l 113 129 mA mA 55 51 75 l 95 115 mA mA 15 12.5 18 l 21 21.5 mA mA All VCC Pins Plus OUT Current to OUT Either VCC Pin May Be Used 643120f 2 For more information www.linear.com/LTC6431-20 LTC6431-20 AC ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C (Note 3). VCC = 5V, ZSOURCE = ZLOAD = 50Ω unless otherwise noted. Measurements are performed using Test Circuit A, measuring from 50Ω SMA to 50Ω without de-embedding (Note 4). SYMBOL PARAMETER CONDITIONS –3dB Bandwidth De-embedded to Package (Low Frequency Cutoff = 20MHz) MIN TYP MAX UNITS Small Signal BW 2000 MHz S11 Input Return Loss 20MHz to 2000MHz De-embedded to Package –10 dB S21 Forward Power Gain 50MHz to 1000MHz De-embedded to Package 20.8 dB S12 Reverse Isolation 20MHz to 3000MHz De-embedded to Package –23 dB S22 Output Return Loss 20MHz to 1400MHz De-embedded to Package –10 dB Frequency = 50MHz S21 Power Gain De-embedded to Package 21.1 dB OIP3 Output Third-Order Intercept Point POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade 48.2 47.2 dBm dBm IM3 Third-Order Intermodulation POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade –92.4 –90.4 dBc dBc dBc HD2 Second Harmonic Distortion POUT = 6dBm –53.5 HD3 Third Harmonic Distortion POUT = 6dBm –93.6 dBc P1dB Output 1dB Compression Point 23.5 dBm NF Noise Figure De-embedded to Package 2.6 dB Frequency = 140MHz S21 Power Gain De-embedded to Package 21.0 dB OIP3 Output Third-Order Intercept Point POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade 48.8 47.8 dBm dBm IM3 Third-Order Intermodulation POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade –93.6 –91.6 dBc dBc HD2 Second Harmonic Distortion POUT = 6dBm –55.8 dBc HD3 Third Harmonic Distortion POUT = 6dBm –96.6 dBc 23.0 dBm 2.7 dB P1dB Output 1dB Compression Point NF Noise Figure De-embedded to Package Frequency = 240MHz S21 Power Gain De-embedded to Package l 19.4 19.0 21.0 42.2 46.2 45.7 OIP3 Output Third-Order Intercept Point POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade IM3 Third-Order Intermodulation POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade –90.4 –87.4 21.4 21.5 dB dB dBm dBm –80.4 dBc dBc HD2 Second Harmonic Distortion POUT = 6dBm –50.5 dBc HD3 Third Harmonic Distortion POUT = 6dBm –92.5 dBc 22.0 dBm 2.6 dB P1dB Output 1dB Compression Point NF Noise Figure De-embedded to Package 643120f For more information www.linear.com/LTC6431-20 3 LTC6431-20 AC ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C (Note 3). VCC = 5V, ZSOURCE = ZLOAD = 50Ω unless otherwise noted. Measurements are performed using Test Circuit A, measuring from 50Ω SMA to 50Ω without de-embedding (Note 4). SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Frequency = 300 MHz S21 Power Gain De-embedded to Package 20.9 dB OIP3 Output Third-Order Intercept Point POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade 45.9 44.8 dBm dBm IM3 Third-Order Intermodulation POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade –87.8 –85.6 dBc dBc HD2 Second Harmonic Distortion POUT = 6dBm –50.5 dBc HD3 Third Harmonic Distortion POUT = 6dBm –83.0 dBc P1dB Output 1dB Compression Point 21.8 dBm NF Noise Figure De-embedded to Package 2.7 dB Frequency = 380MHz S21 Power Gain De-embedded to Package 20.9 dB OIP3 Output Third-Order Intercept Point POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade 45.0 44.0 dBm dBm IM3 Third-Order Intermodulation POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade –86.0 –84.0 dBc dBc HD2 Second Harmonic Distortion POUT = 6dBm –50.4 dBc HD3 Third Harmonic Distortion POUT = 6dBm –77.4 dBc P1dB Output 1dB Compression Point NF Noise Figure 21.7 dBc De-embedded to Package 2.8 dB Frequency = 500MHz S21 Power Gain De-embedded to Package 20.8 dB OIP3 Output Third-Order Intercept Point POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade 43.9 42.9 dBm dBm IM3 Third-Order Intermodulation POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade –83.8 –81.8 dBc dBc HD2 Second Harmonic Distortion POUT = 6dBm –47.8 dBc HD3 Third Harmonic Distortion POUT = 6dBm –72.6 dBc P1dB Output 1dB Compression Point NF Noise Figure 21.8 dBm De-embedded to Package 2.9 dB Frequency = 600MHz S21 Power Gain De-embedded to Package 20.8 dB OIP3 Output Third-Order Intercept Point POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade 41.9 40.9 dBm dBm IM3 Third-Order Intermodulation POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade –79.8 –77.8 dBc dBc HD2 Second Harmonic Distortion POUT = 6dBm –43.7 dBc HD3 Third Harmonic Distortion POUT = 6dBm –64.0 dBc P1dB Output 1dB Compression Point 21.6 dBm NF Noise Figure 3.0 dB De-embedded to Package 643120f 4 For more information www.linear.com/LTC6431-20 LTC6431-20 AC ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C (Note 3). VCC = 5V, ZSOURCE = ZLOAD = 50Ω unless otherwise noted. Measurements are performed using Test Circuit A, measuring from 50Ω SMA to 50Ω without de-embedding (Note 4). SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Frequency = 700 MHz S21 Power Gain De-embedded to Package 20.8 dB OIP3 Output Third-Order Intercept Point POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade 40.7 39.7 dBm dBm IM3 Third-Order Intermodulation POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade –77.4 –75.4 dBc dBc HD2 Second Harmonic Distortion POUT = 6dBm –42.1 dBc HD3 Third Harmonic Distortion POUT = 6dBm –60.7 dBc P1dB Output 1dB Compression Point 21.4 dBm NF Noise Figure De-embedded to Package 3.2 dB Frequency = 800MHz S21 Power Gain De-embedded to Package 20.8 dB OIP3 Output Third-Order Intercept Point POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade 39.2 38.2 dBm dBm IM3 Third-Order Intermodulation POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade –74.4 –72.4 dBc dBc HD2 Second Harmonic Distortion POUT = 6dBm –40.5 dBc HD3 Third Harmonic Distortion POUT = 6dBm –63.1 dBc P1dB Output 1dB Compression Point NF Noise Figure 21.3 dBm De-embedded to Package 3.4 dB Frequency = 900MHz S21 Power Gain De-embedded to Package 20.8 dB OIP3 Output Third-Order Intercept Point POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade 38.5 37.5 dBm dBm IM3 Third-Order Intermodulation POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade –73.0 –71.0 dBc dBc HD2 Second Harmonic Distortion POUT = 6dBm –37.1 dBc HD3 Third Harmonic Distortion POUT = 6dBm –60.4 dBc P1dB Output 1dB Compression Point NF Noise Figure 21.1 dBm De-embedded to Package 3.7 dB Frequency = 1000MHz S21 Power Gain De-embedded to Package 20.8 dB OIP3 Output Third-Order Intercept Point POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade 37.5 36.5 dBm dBm IM3 Third-Order Intermodulation POUT = 2dBm/Tone, ∆f = 1MHz, A-Grade POUT = 2dBm/Tone, ∆f = 1MHz, B-Grade –71.0 –69.0 dBc dBc HD2 Second Harmonic Distortion POUT = 6dBm –36.9 dBc HD3 Third Harmonic Distortion POUT = 6dBm –55.1 dBc P1dB Output 1dB Compression Point 20.8 dBc NF Noise Figure 3.8 dB De-embedded to Package Note 1: 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 2: Guaranteed by design and characterization. This parameter is not tested. Note 3: The LTC6431-20 is guaranteed functional over the case operating temperature range of –40°C to 85°C. Note 4: Small-signal parameters S and noise are de-embedded to the package pins, while large-signal parameters are measured directly from the circuit. 643120f For more information www.linear.com/LTC6431-20 5 LTC6431-20 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, VCC = 5V, ZSOURCE = ZLOAD = 50Ω unless otherwise noted. Measurements are performed using Test Circuit A, measuring from 50Ω SMA to 50Ω without de-embedding (Note 4). Stability Factor K vs Frequency Over Temperature S Parameters vs Frequency 25 10 20 9 S21 15 6 0 –5 S22 –10 S11 –15 –20 7 TCASE = 100°C 85°C 70°C 50°C 30°C 0°C –20°C –40°C 6 5 4 3 2 –25 S12 –30 0 500 1000 1500 2000 FREQUENCY (MHz) NOISE FIGURE (dB) STABILITY FACTOR K 5 MAG (dB) 7 8 10 –35 NF vs Frequency Over Case Temperature 2500 3000 0 4 3 2 TCASE = 85°C 25°C –40°C 1 1 0 5 0 4000 2000 1000 3000 FREQUENCY (MHz) 0 400 643120 G02 643120 G01 S11 vs Frequency Over Temperature 643120 G03 S21 vs Frequency Over Temperature 0 S12 vs Frequency Over Temperature 25 0 TCASE = 100°C 85°C 70°C 50°C 30°C 0°C –20°C –40°C –5 20 TCASE = 100°C 85°C 70°C 50°C 30°C 0°C –20°C –40°C –15 –20 –25 0 500 1000 1500 2000 FREQUENCY (MHz) 2500 3000 –10 MAG S12 (dB) –10 MAG S21 (dB) MAG S11 (dB) –5 15 TCASE = 100°C 85°C 10 70°C 50°C 30°C 5 0°C –20°C –40°C 0 0 500 1000 1500 2000 FREQUENCY (MHz) 2500 –40 3000 0 500 1000 1500 2000 FREQUENCY (MHz) 2500 3000 643120 G07 6 1000 1500 2000 2500 3000 OIP3 vs Power Out Over Frequency 54 52 50 48 48 46 46 OIP3 (dBm) OIP3 (dBm) MAG S22 (dB) –25 500 643120 G06 50 TCASE = 100°C 85°C 70°C 50°C 30°C 0°C –20°C –40°C 0 FREQUENCY (MHz) OIP3 vs Frequency –5 –20 –25 –35 52 –15 –20 643120 G05 0 –10 –15 –30 643120 G04 S22 vs Frequency Over Temperature 2000 1200 1600 800 FREQUENCY (MHz) 44 42 VCC = 5V 40 TA = 25°C POUT = 2dBm/TONE 38 fSPACE = 1MHz ZIN = ZOUT = 50Ω 36 400 200 0 600 FREQUENCY (MHz) 44 42 40 38 36 34 32 800 1000 643120 G08 For more information www.linear.com/LTC6431-20 30 –10 –8 –6 –4 –2 0 2 4 6 RF POWER OUT (dBm/TONE) 50MHz 100MHz 200MHz 240MHz 300MHz 400MHz 500MHz 600MHz 8 10 643120 G09 700MHz 800MHz 900MHz 1000MHz 643120f LTC6431-20 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, VCC = 5V, ZSOURCE = ZLOAD = 50Ω unless otherwise noted. Measurements are performed using Test Circuit A, measuring from 50Ω SMA to 50Ω without de-embedding (Note 4). OIP3 vs Frequency Over VCC Voltage 52 OIP3 vs Tone Spacing Over Frequency 50 TA = 25°C POUT = 2dBm/TONE fSPACE = 1MHz ZIN = ZOUT = 50Ω 50 48 50 46 45 44 44 42 40 40 38 4.5V 4.75V 5V 5.25V 5.5V 38 36 0 200 OIP3 (dBm) 42 OIP3 (dBm) OIP3 (dBm) 55 48 46 34 36 34 32 600 400 FREQUENCY (MHz) 30 1000 800 0 643120 G10 HD2 vs Frequency Over POUT HD3 (dBc) HD2 (dBc) –20 –30 –40 RF POUT = 4dBm 6dBm 8dBm 10dBm –60 10 643120 G12 HD4 vs Input Frequency Over POUT –10 –10 –20 –20 –30 –30 –40 –40 –50 –60 –70 RF POUT = 4dBm 6dBm 8dBm 10dBm –90 –100 –110 –60 –70 –90 –100 –110 Total Current vs RF Input Power 100 VCC = 5V 110 95 100 90 90 TOTAL CURRENT (mA) 90 80 ITOT (mA) 70 70 60 50 40 30 60 643120 G16 0 –50 80 75 70 65 55 10 6 85 60 20 4.25 4.5 4.75 5 5.25 5.5 5.75 VCC (V) 0 100 200 300 400 500 600 700 800 900 1000 INPUT FREQUENCY (MHz) 643120 G15 Total Current (ITOT) vs Temperature TCASE = 25°C 4 –50 –80 0 100 200 300 400 500 600 700 800 900 1000 INPUT FREQUENCY (MHz) 120 80 RF POUT = 4dBm 6dBm 8dBm 10dBm 643120 G14 Total Current (ITOT) vs VCC ITOT (mA) 700MHz 800MHz 900MHz 1000MHz 0 643120 G13 50 TCASE = 85°C 70°C 50°C 30 VCC = 5V 28°C POUT = 2dBm/TONE 0°C 25 fSPACE = 1MHz –20°C ZIN = ZOUT = 50Ω –40°C 20 0 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (MHz) 35 0 –80 0 100 200 300 400 500 600 700 800 900 1000 INPUT FREQUENCY (MHz) 100 45 50 643120 G11 HD4 (dBc) –10 –50 15 20 25 30 35 40 TONE SPACING (MHz) 50MHz 300MHz 100MHz 400MHz 200MHz 500MHz 240MHz 600MHz 5 40 HD3 vs Input Frequency Over POUT 0 –70 OIP3 vs Frequency Over Case Temperature –25 0 25 50 TEMPERATURE (°C) 75 100 643120 G17 VSUP = 5V TA = 25°C FREQ = 200MHz 50 –15 –10 0 5 –5 RF INPUT POWER (dBm) 10 643120 G18 643120f For more information www.linear.com/LTC6431-20 7 LTC6431-20 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, VCC = 5V, ZSOURCE = ZLOAD = 50Ω unless otherwise noted. Measurements are performed using Test Circuit A, measuring from 50Ω SMA to 50Ω without de-embedding (Note 4). Gain vs Output Power Over Frequency 22 22 21 20 16 14 12 10 8 –10 –8 –6 –4 –2 0 2 4 INPUT POWER (dBm) 6 24 23 20 50MHz 100MHz 200MHz 300MHz 400MHz 500MHz 600MHz 700MHz 800MHz 900MHz 1000MHz 18 18 17 16 8 10 22 50MHz 100MHz 200MHz 300MHz 400MHz 500MHz 600MHz 700MHz 800MHz 900MHz 1000MHz 19 15 P1dB vs Frequency 25 12 P1dB (dBm) 24 GAIN (dB) OUTPUT POWER (dBm) Output Power vs Input Power Over Frequency 20 19 18 17 16 18 16 20 14 OUTPUT POWER (dBm) 22 24 643120 G20 643120 G19 21 15 0 200 600 400 FREQUENCY (MHz) 800 1000 643120 G21 PIN FUNCTIONS DNC (Pins 1 to 7, 10 to 15, 19 to 21): Do Not Connect. Do not connect these pins, allow them to float. Failure to float these pins may impair operation of the LTC6431-20. T_DIODE (Pin 16): Optional Diode. The T_DIODE can be forward biased to ground with 1mA of current. The measured voltage will be an indicator of chip temperature. GND (Pins 8, 17, 23, Exposed Pad Pin 25): Ground. For best RF performance, all ground pins should be connected to the printed circuit board ground plane. The exposed pad (Pin 25) should have multiple via holes to an underlying ground plane for low inductance and good thermal dissipation. Out (Pin 18): Amplifier Output Pin. A choke inductor is necessary to provide power from the 5V supply and to provide RF isolation. For best performance select a choke with low loss and high self-resonant frequency (SRF). A DC blocking capacitor is also required. See Applications Information Section for specific recommendations. VCC (Pins 9, 22): Positive Power Supply. Either or both VCC pins should be connected to the 5.0V supply. Bypass the VCC pin with 1000pF and 0.1µF capacitors. The 1000pF capacitor should be physically close to Pin 22. IN (Pin 24): Signal input pin with internally generated 2.0V DC bias. A DC blocking capacitor is required. See Applications Information Section for specific recommendations. 643120f 8 For more information www.linear.com/LTC6431-20 LTC6431-20 BLOCK DIAGRAM VCC 9, 22 BIAS AND TEMPERATURE COMPENSATION 24 IN OUT 20dB GAIN 18 T_DIODE 16 GND 8, 17, 23, 25 (EXPOSED PAD) 643122 BD TEST CIRCUIT A DNC DNC VCC DNC IN OUT DNC GND DNC T_DIODE DNC DNC DNC VCC DNC C3 1000pF PORT OUTPUT DNC DNC GND VCC = 5V DNC LTC6431-20 DNC C6 0.1µF L1 560nH DNC DNC OPTIONAL STABILITY NETWORK GND + R1 350Ω C5 1nF + C1 60pF + C7 1000pF + + PORT INPUT DNC 643120 F01 643120f For more information www.linear.com/LTC6431-20 9 LTC6431-20 OPERATION The LTC6431-20 is a highly linear, fixed-gain amplifier that is configured to operate single ended. Its core signal path consists of a single amplifier stage, minimizing stability issues. The input is a Darlington pair for high input impedance and high current gain. Additional circuit enhancements increase the output impedance and minimize the effects of internal Miller capacitance. The LTC6431-20 starts with a classic RF gain block topology but adds enhancements to dramatically improve linearity. Shunt and series feedback are added to lower the input/output impedance and match them simultaneously to the 50Ω source and load. Meanwhile, an internal bias controller optimizes the internal operating point for peak linearity over environmental changes. This circuit architecture provides low noise, excellent RF power handling capability and wide bandwidth — characteristics that are desirable for IF signal chain applications. APPLICATIONS INFORMATION The LTC6431-20 is a highly linear fixed gain amplifier which is designed for ease of use. Implementing an RF gain stage is often a multi-step project. Typically an RF designer must choose a bias point and design a bias network. Next we need to address impedance matching with input and output matching networks and finally add stability networks to ensure stable operation in and out of band. These tasks are handled internally within the LTC6431-20. The LTC6431-20 has an internal self-biasing network which compensates for temperature variation and keeps the device biased for optimal linearity. Therefore input and output DC blocking capacitors are required. Both the input and output are internally impedance matched to 50Ω from 20MHz to 1400MHz. Similarly, an RF choke is required at the output to deliver DC current to the device. The RF choke acts as a high impedance (isolation) to the DC supply which is at RF ground. Thus, the internal LTC6431-20 impedance matching is unaffected by the biasing network. The open-collector output topology can deliver much more power than an amplifier whose collector is biased through a resistor or active load. Choosing the Right RF Choke Not all choke inductors are created equal. It is always important to select an inductor with low RLOSS, as this will drop the available voltage to the device. Also look for an inductor with high self-resonant frequency (SRF) as this will limit the upper frequency where the choke is useful. Above the SRF, the parasitic capacitance dominates and the choke impedance will drop. For these reasons, wire wound inductors are preferred, and multilayer ceramic chip inductors should be avoided for an RF choke. Since the LTC6431-20 is capable of such wideband operation, a single choke value will probably not result in optimized performance across its full frequency band. Table 1 lists target frequency bands and suggested corresponding inductor values: Table 1. Target Frequency Bands and Suggested Inductor Values FREQUENCY BAND INDUCTOR (MHz) VALUE (nH) 20 to100 1500nH MODEL NUMBER 0603LS 100 to 500 560nH 0603LS 500 to1000 100nH 0603LS 1000 to 2000 51nH 0603LS MANUFACTURER Coilcraft www.coilcraft.com DC Blocking Capacitor The role of a DC blocking capacitor is straightforward; block the path of DC current and allow a low series impedance path for the AC signal. Lower frequencies require a higher value of DC blocking capacitance. Generally, 1000pF to 10000pF will suffice for operation down to 20MHz. The LTC6431-20 is relatively insensitive to the choice of blocking capacitor. RF Bypass Capacitor RF bypass capacitors act to shunt AC signals to ground with a low impedance path. It is best to place them as close as possible to the DC power supply pins of the device. Any extra distance translates into additional series inductance which lowers the self-resonant frequency and 643120f 10 For more information www.linear.com/LTC6431-20 LTC6431-20 APPLICATIONS INFORMATION useful bandwidth of the bypass capacitor. The suggested bypass capacitor network consists of two capacitors: a low value 1000pF capacitor to handle high frequencies in parallel with a larger 0.1µF capacitor to handle lower frequencies. Use ceramic capacitors of an appropriate physical size for each capacitance value (e.g., 0402 for the 1000pF and 0805 for the 0.1µF) to minimize the equivalent series resistance (ESR) of the capacitor. Low Frequency Stability Most RF gain blocks suffer from low frequency instability. To avoid any stability issues, the LTC6431-20 has an internal feedback network that lowers the gain and matches the input and output impedances at frequencies above 20MHz. This feedback network contains a series capacitor so if at some low frequency the feedback fails, the gain increases and gross impedance mismatches occur — indeed a recipe for instability. Luckily this situation is easily resolved with a parallel capacitor and resistor network on the input as seen in Test Circuit A. This network provides resistive loss at low frequencies and is bypassed by the parallel capacitor within the desired band of operation. However, if the LTC6431-20 is preceded by a low frequency termination, such as a choke, the stability network is NOT required. Test Circuit The test circuit shown in Figure 2 is designed to allow evaluation of the LTC6431-20 with standard single-ended 50Ω test equipment. The circuit requires a minimum of external components. Since the LTC6431-20 is a wideband part, the evaluation test circuit is optimized for wideband operation. Obviously, for narrowband applications the circuit can be further optimized. As mentioned earlier, input and output DC blocking capacitors are required as this device is internally biased for optimal operation. A frequency appropriate choke and decoupling capacitors are required to provide DC bias to the RF OUT node. A 5V supply should also be applied to both of the VCC pins on the device. A suggested parallel 60pF, 350Ω network has been added to the input to ensure low frequency stability. The 60pF capacitance can be increased to improve low frequency (<150MHz) performance. However, the designer needs to be sure that the impedance presented at low frequency will not create instability Please note that a number of DNC pins are connected on the demo board. These connections are not necessary for normal circuit operation. Exposed Pad and Ground Plane Considerations As with any RF device, minimizing ground inductance is critical. Care should be taken with board layout using these exposed pad packages. The maximum allowable number of minimum diameter via holes should be placed underneath the exposed pad and connected to as many ground plane layers as possible. This will provide good RF ground and low thermal impedance. Maximizing the copper ground plane will also improve heat spreading and lower inductance. It is a good idea to cover the via holes with a solder mask on the back side of the PCB to prevent solder from wicking away from the critical PCB to exposed pad interface. The LTC6431-20 is a wide bandwidth part but it is not intended for operation down to DC. The lower frequency cutoff (20MHz) is limited by on-chip matching elements. 643120f For more information www.linear.com/LTC6431-20 11 LTC6431-20 DEMO BOARD 5 4 3 2 1 D D 4 B 5 C A B C TECHNOLOGY 2 A 3 1 Figure 2. DC2077A Demo Board Schematic Figure 3. Demo Board 643120f 12 For more information www.linear.com/LTC6431-20 LTC6431-20 S PARAMETERS FREQUENCY (MHZ) 15 60 105 150 195 240 285 330 375 420 465 510 555 600 645 690 735 780 825 870 915 960 1005 1050 1095 1140 1185 1230 1275 1320 1365 1410 1455 1500 1545 1590 1635 1680 1725 1770 1815 1860 1905 1950 1995 S11 (MAG) –12.34 –14.04 –14.03 –14.08 –14.07 –14.15 –14.28 –14.39 –14.29 –14.21 –14.16 –14.23 –14.33 –14.44 –14.54 –14.61 –14.72 –14.82 –15.09 –15.49 –15.70 –16.07 –16.34 –16.85 –17.27 –17.95 –18.45 –19.02 –19.50 –19.85 –20.08 –19.95 –19.77 –19.51 –18.89 –18.24 –17.42 –16.67 –15.83 –15.05 –14.19 –13.50 –12.85 –12.24 –11.67 5V, 95mA, Z = 50Ω, TA = 25°C de-embedded to package pins S11 (PH) –134.00 –170.60 –179.35 175.80 172.39 167.78 163.28 160.26 156.48 153.43 149.55 146.15 141.99 138.03 132.96 129.14 125.47 121.92 117.58 113.60 109.88 106.95 104.03 102.41 100.19 98.62 97.87 98.94 101.29 104.33 106.87 109.72 113.75 117.49 119.17 119.82 119.84 117.91 117.38 116.13 114.01 111.51 109.19 106.89 104.26 S21 (MAG) 21.65 21.09 21.03 21.01 20.98 20.98 20.94 20.90 20.86 20.83 20.84 20.81 20.83 20.82 20.83 20.82 20.81 20.83 20.82 20.86 20.85 20.87 20.83 20.87 20.86 20.82 20.83 20.77 20.79 20.60 20.62 20.45 20.46 20.24 20.18 19.98 19.95 19.72 19.66 19.36 19.28 18.90 19.01 18.52 18.70 S21 (PH) 166.01 171.15 168.79 165.71 162.19 158.68 155.06 151.22 147.90 144.33 140.79 137.22 133.57 129.91 126.20 122.55 118.75 115.24 111.33 107.36 103.72 99.43 95.71 91.50 87.64 82.93 79.39 74.51 70.33 65.52 61.84 57.31 52.82 48.67 44.22 40.21 35.90 31.69 27.35 23.32 18.99 15.44 11.94 6.50 3.97 S12 (MAG) –23.63 –23.46 –23.49 –23.53 –23.53 –23.51 –23.57 –23.56 –23.60 –23.66 –23.66 –23.73 –23.74 –23.76 –23.82 –23.82 –23.88 –23.90 –23.92 –23.98 –23.99 –24.11 –24.09 –24.18 –24.20 –24.28 –24.34 –24.42 –24.49 –24.57 –24.67 –24.78 –24.90 –25.03 –25.18 –25.35 –25.53 –25.69 –25.93 –26.10 –26.43 –26.53 –26.93 –27.03 –27.55 S12 (PH) 9.07 –1.42 –5.14 –8.75 –11.98 –14.70 –17.52 –20.65 –23.49 –26.30 –28.96 –31.97 –34.94 –37.66 –40.56 –43.37 –46.23 –49.23 –51.95 –55.23 –58.08 –61.03 –64.35 –67.08 –70.22 –73.37 –76.81 –79.94 –83.51 –86.55 –90.04 –93.19 –96.97 –100.45 –103.92 –107.23 –111.01 –113.96 –118.14 –121.42 –124.76 –128.07 –131.53 –135.18 –137.80 S22 (MAG) –14.61 –18.21 –18.66 –18.62 –18.41 –18.30 –18.41 –18.26 –18.15 –17.84 –17.57 –17.39 –17.34 –17.19 –17.18 –16.95 –16.82 –16.71 –16.62 –16.57 –16.46 –16.09 –15.67 –15.20 –14.69 –14.08 –13.51 –12.81 –12.18 –11.49 –11.02 –10.42 –9.99 –9.41 –8.92 –8.50 –8.07 –7.78 –7.51 –7.13 –6.90 –6.72 –6.58 –6.51 –6.39 S22 (PH) –124.25 –175.38 166.03 154.22 143.47 133.71 123.42 114.75 108.36 100.90 92.84 84.51 77.29 68.45 61.23 51.45 43.84 35.20 26.73 16.50 6.76 –3.10 –12.60 –21.77 –31.60 –40.57 –48.89 –57.15 –65.26 –72.53 –79.96 –87.02 –93.77 –100.97 –108.10 –114.08 –120.18 –126.41 –132.99 –139.50 –145.49 –151.16 –157.57 –164.06 –170.92 GTU (MAX) 22.07 21.33 21.26 21.24 21.22 21.22 21.17 21.13 21.09 21.07 21.09 21.06 21.07 21.06 21.06 21.06 21.05 21.07 21.05 21.08 21.07 21.08 21.05 21.10 21.09 21.06 21.09 21.06 21.11 20.96 21.02 20.91 20.97 20.82 20.83 20.71 20.76 20.60 20.63 20.44 20.45 20.14 20.31 19.89 20.14 STABILITY (K) 0.92 0.98 0.98 0.98 0.98 0.98 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 1.00 1.00 1.00 1.00 1.00 1.00 1.01 1.01 1.01 1.01 1.01 1.01 1.01 1.02 1.01 1.02 1.01 1.01 1.01 1.01 1.01 1.01 1.00 1.00 1.00 1.00 1.00 1.02 1.02 1.04 1.05 643120f For more information www.linear.com/LTC6431-20 13 LTC6431-20 S PARAMETERS FREQUENCY (MHZ) 2040 2085 2130 2175 2220 2265 2310 2355 2400 2445 2490 2535 2580 2625 2670 2715 2760 2805 2850 2895 2940 2985 3030 3075 3120 3165 3210 3255 3300 3345 3390 3435 3480 3525 3570 3615 3660 3705 3750 3795 3840 3885 3930 3975 4020 S11 (MAG) –11.14 –10.64 –10.00 –9.61 –9.17 –8.83 –8.46 –8.16 –7.83 –7.53 –7.27 –6.92 –6.70 –6.41 –6.27 –6.03 –5.89 –5.67 –5.50 –5.46 –5.30 –5.19 –5.01 –4.92 –4.91 –4.82 –4.75 –4.68 –4.59 –4.55 –4.56 –4.51 –4.45 –4.43 –4.41 –4.40 –4.38 –4.34 –4.29 –4.26 –4.23 –4.21 –4.20 –4.15 –4.11 5V, 95mA, Z = 50Ω, TA = 25°C de-embedded to package pins S11 (PH) 100.90 97.70 94.35 91.25 88.10 84.64 81.25 77.66 74.62 71.16 68.07 64.84 61.73 58.18 55.57 52.10 49.48 45.63 42.67 39.67 36.08 33.25 30.47 27.89 24.65 22.03 18.92 16.03 13.26 10.73 8.20 5.01 2.35 –0.44 –2.83 –5.71 –8.39 –11.28 –13.61 –16.54 –18.89 –21.65 –23.89 –26.81 –29.36 S21 (MAG) 17.88 18.36 17.25 17.78 17.05 16.93 16.78 16.61 16.50 16.06 16.20 15.35 16.03 14.68 15.67 14.17 15.57 13.93 15.09 13.89 14.37 13.99 13.73 13.65 13.20 13.19 12.70 12.57 12.24 11.84 11.62 10.89 11.06 10.16 9.99 9.68 8.93 9.26 8.25 8.99 7.52 8.40 7.12 7.91 6.95 S21 (PH) -0.72 -5.52 -6.06 -14.20 -12.16 -20.90 -18.18 -27.54 -25.19 -34.94 -31.94 -40.99 -39.80 -45.37 -47.21 -49.38 -53.97 -53.77 -63.32 -58.19 -72.34 -65.16 -77.37 -74.73 -83.66 -82.28 -90.39 -89.72 -97.59 -98.06 -103.89 -101.79 -111.51 -107.21 -117.04 -110.63 -121.14 -114.41 -123.30 -119.02 -126.22 -125.79 -125.77 -131.37 -128.17 S12 (MAG) –27.55 –28.08 –28.25 –28.58 –29.10 –29.21 –29.86 –29.98 –30.69 –30.51 –31.57 –31.02 –32.38 –32.09 –32.97 –32.98 –33.09 –34.22 –33.44 –35.33 –34.24 –35.94 –35.59 –36.56 –36.86 –37.44 –38.12 –38.72 –39.34 –39.73 –40.66 –41.66 –43.12 –42.93 –45.97 –44.49 –47.04 –46.78 –48.84 –48.49 –50.09 –51.80 –50.77 –50.96 –49.54 S12 (PH) –142.12 –143.56 –150.27 –149.92 –156.51 –157.46 –162.26 –162.93 –167.63 –168.53 –172.15 –175.82 –175.70 176.58 179.37 169.92 175.85 163.49 166.56 159.61 156.24 156.17 148.57 148.06 137.09 140.21 129.33 129.83 121.95 119.68 109.67 111.26 101.22 99.02 89.65 84.10 75.52 68.74 61.49 43.03 36.00 18.74 12.06 2.88 –0.70 S22 (MAG) –6.26 –6.12 –6.05 –6.02 –5.98 –5.82 –5.78 –5.73 –5.69 –5.62 –5.67 –5.56 –5.57 –5.50 –5.63 –5.56 –5.27 –5.21 –5.17 –5.18 –5.09 –5.09 –4.97 –4.90 –4.91 –4.93 –4.92 –4.86 –4.83 –4.77 –4.74 –4.81 –4.88 –4.93 –4.84 –4.90 –5.05 –5.08 –5.19 –5.23 –5.24 –5.26 –5.34 –5.43 –5.41 S22 (PH) –177.67 176.54 170.42 163.95 156.51 149.75 143.79 137.46 131.27 125.41 118.93 113.08 107.60 101.45 95.57 90.99 85.87 80.99 75.72 70.71 65.83 61.31 56.55 53.19 49.53 45.90 41.35 37.27 33.29 29.79 27.13 24.06 20.14 15.63 11.54 8.34 3.84 –0.41 –4.64 –10.04 –14.83 –19.77 –24.50 –30.21 –36.65 GTU (MAX) 19.40 19.97 18.94 19.53 18.87 18.85 18.78 18.68 18.64 18.30 18.47 17.75 18.49 17.24 18.23 16.82 18.39 16.86 18.10 16.91 17.50 17.17 17.04 17.03 16.59 16.61 16.17 16.09 15.82 15.48 15.26 14.53 14.70 13.79 13.68 13.33 12.53 12.86 11.84 12.58 11.12 12.01 10.70 11.49 10.56 STABILITY (K) 1.10 1.08 1.18 1.14 1.27 1.26 1.34 1.35 1.45 1.45 1.60 1.59 1.70 1.87 1.85 2.16 1.75 2.40 1.84 2.69 2.14 2.74 2.62 2.92 3.20 3.42 3.90 4.20 4.64 5.05 5.79 7.15 8.34 9.10 13.14 11.53 17.24 16.05 23.09 20.33 29.00 31.89 33.05 30.86 29.01 643120f 14 For more information www.linear.com/LTC6431-20 LTC6431-20 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. UF Package 24-Lead Plastic QFN (4mm × 4mm) (Reference LTC DWG # 05-08-1697 Rev B) 0.70 ±0.05 4.50 ±0.05 2.45 ±0.05 3.10 ±0.05 (4 SIDES) PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 4.00 ±0.10 (4 SIDES) BOTTOM VIEW—EXPOSED PAD R = 0.115 TYP 0.75 ±0.05 PIN 1 NOTCH R = 0.20 TYP OR 0.35 × 45° CHAMFER 23 24 PIN 1 TOP MARK (NOTE 6) 0.40 ±0.10 1 2 2.45 ±0.10 (4-SIDES) (UF24) QFN 0105 REV B 0.200 REF 0.00 – 0.05 0.25 ±0.05 0.50 BSC NOTE: 1. DRAWING PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGD-X)—TO BE APPROVED 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE, IF PRESENT 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 643120f 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 itsinformation circuits as described herein will not infringe on existing patent rights. For more www.linear.com/LTC6431-20 15 LTC6431-20 TYPICAL APPLICATION 0.1µF VCC = 5V RSOURCE 50Ω 5V 9, 22 C = 1000pF 24 LTC6431-20 18 RF CHOKE, L = 560nH 1000pF 8, 17, 23, 25 C =1000pF RLOAD 50Ω 643120 TA02 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS Fixed Gain IF Amplifiers/ADC Drivers LTC6431-15 15dB Gain 50Ω Gain Block IF Amplifier — Single Ended OIP3 = 47dBm at 240MHz, 20MHz to 1700MHz Bandwidth, 3.3dB NF LTC6430-15 15dB Gain Block IF Amplifier — Differential OIP3 = 50dBm at 240MHz, 20MHz to 1700MHz Bandwidth, 3.3dB NF LTC6417 1.6GHz Low Noise High Linearity Differential OIP3 = 41dBm at 300MHz, Can Drive 50Ω Differential Output, Buffer/ADC Driver High Speed Voltage Clamping Protects Subsequent Circuitry LTC6416 2GHz, 16-Bit Differential ADC Buffer –72dBc IM2 at 300MHz 2VP-P Composite, IS = 42mA, eN = 2.8nV/√Hz, AV = 0dB, 300MHz LTC6410-6 1.4GHz Differential IF Amplifier with Configurable OIP3 = 36dBm at 70MHz, Flexible Interface-to-Mixer IF Port Input Impedance LTC6400-8/LTC6400-14/ 1.8GHz Low Noise, Low Distortion Differential –71dBc IM3 at 240MHz 2VP-P Composite, IS = 90mA, AV = 8dB, 14dB, 20dB, 26dB LTC6400-20/LTC6400-26 ADC Drivers LTC2420-20 Dual 1.8GHz Low Noise, Low Distortion Differential Dual Version of the LTC6400-20, AV = 20dB ADC Drivers Variable Gain IF Amplifiers/ADC Drivers LTC6412 800MHz, 31dB Range Analog-Controlled VGA OIP3 = 35dBm at 240MHz, Continuously-Adjustable Gain Control Baseband Differential Amplifiers LTC6409 1.1nV√Hz Single Supply Differential Amplifier/ADC 88dB SFDR at 100MHz, AC- or DC-Coupled Inputs Driver LT6411 Low Power Differential ADC Driver/Dual Selectable –83dBc IM3 at 70MHz 2VP-P Composite, AV = 1, –1 or 2, 16mA, Gain Amplifier Excellent for Single-Ended to Differential Conversion LTC6406 3GHz Rail-to-Rail Input Differential Amplifier/ –65dBc IM3 at 50MHz 2VP-P Composite, Rail-to-Rail Inputs, eN = 1.6nV/√Hz, 18mA ADC Driver LTC6404-1/LTC6404-2 Low Noise Rail-to-Rail Output Differential Amplifier/ 16-Bit SNR, SFDR at 10MHz, Rail-to-Rail Outputs, eN = 1.5nV/√Hz, LTC6404-1 Is Unity-Gain Stable, LTC6404-2 Is Gain-of-2 Stable ADC Driver LTC6403-1 Low Noise Rail-to-Rail Output Differential Amplifier/ 16-Bit SNR, SFDR at 3MHz, Rail-to-Rail Outputs, eN = 2.8nV/√Hz ADC Driver High Speed ADCs LTC2208/LTC2209 16-Bit, 130Msps/160Msps ADCs 74.0dBFS Noise Floor, SFDR > 89dB at 140MHz, 2.25VP-P Input LTC2259-16 16-Bit, 80Msps 1.8V ADC 72.0dBFS Noise Floor, SFDR > 82dB at 140MHz, 2.00VP-P Input LTC2160-16/LTC2161-16/ 16-Bit, 25Msps/40Msps/60Msps ADC Low Power 77dBFS Noise Floor, SFDR > 84dB at 140MHz, 2.00VP-P Input LTC2162-16 LTC2155-14/LTC2156-14/ 14-Bit, 170Msps/210Msps/250Msps/310Msps ADC 69dBFS Noise Floor, SFDR > 80dB at 140MHz, 1.50VP-P Input, >1GHz Input BW LTC2157-14/LTC2158-14 2-Channel LTC2216 16-Bit, 80Msps ADC 79dBFS Noise Floor, SFDR > 91dB at 140MHz, 75VP-P Input 643120f 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LTC6431-20 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTC6431-20 LT 0314 • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2014