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LT5512 1kHz-3GHz High Signal Level Active Mixer U FEATURES DESCRIPTIO ■ The LT®5512 is an active double-balanced mixer IC, optimized for high linearity HF, VHF and UHF applications. The IC includes an integrated LO buffer amplifier to drive the mixer and an RF buffer amplifier for improved LO-RF isolation. Internal bias circuits eliminate the need for precision external resistors and allow the device to be powered-down using the enable control (EN) pin. ■ ■ ■ ■ ■ ■ ■ ■ ■ Broadband RF, LO and IF Operation High Input IP3: >20dBm from 30MHz to 900MHz +17dBm at 1900MHz Typical Conversion Gain: 1dB SSB Noise Figure: 11dB at 900MHz 14dB at 1900MHz Integrated LO Buffer: Insensitive to LO Drive Level Single-Ended or Differential LO Drive High LO-RF Isolation Enable Function 4.5V to 5.25V Supply Voltage Range 4mm × 4mm QFN Package The externally matched RF and IF ports allow the mixer to be used at very low frequencies, below 1MHz or up to 3GHz. The differential LO input is designed for single-ended or a differential input drive. The LT5512 is a high-linearity alternative to passive diode mixers. Unlike passive mixers, which have conversion loss and require high LO drive levels, the LT5512 delivers conversion gain and requires significantly lower LO drive levels. U APPLICATIO S ■ ■ ■ ■ ■ HF/VHF/UHF Mixer Cellular/PCS/UMTS Infrastructure High Linearity Mixer Applications ISM Band Receivers Wireless Medical Telemetry System (WMTS) , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. U TYPICAL APPLICATIO Conv Gain, IIP3, NF and LO Leakage vs LO Power High Signal-Level Downmixer for 600MHz Wireless Medical Telemetry System 6.8nH + 19 LO– LT5512 RF + 8:1 + IF IFOUT 45MHz 50Ω 1.8pF RFIN 608MHz TO 614MHz 50Ω 6.8pF 6.8nH 6.8pF 47nH EN 5V RF – BIAS IF – EN VCC2 VCC1 0.01µF 20 21 0.01µF IIP3 TA = 25°C RF = 610MHz 0 HIGH-SIDE LO IF = 45MHz 17 15 –20 13 11 SSB NF 9 –40 LO-IF 7 5 LO LEAKAGE (dBm) LO 100Ω GC, SSB NF (dB), IIP3 (dBm) 0.01µF LOIN –5dBm TYP –60 LO-RF 3 1 –11 1µF GC –80 –9 VCC 4.5V TO 5.25V –5 –3 –7 LO POWER (dBm) –1 1 5512 TA01a 5512 TA01 www.BDTIC.com/Linear 5512fa 1 LT5512 U W U PACKAGE/ORDER I FOR ATIO U W W W ABSOLUTE AXI U RATI GS (Note 1) NC LO – NC LO+ TOP VIEW Supply Voltage (VCC1, VCC2, IF+, IF–)........................5.5V Enable Voltage .................................–0.3V to VCC + 0.3V LO+ to LO– Differential Voltage ..............................±1.5V .................................................... (+6dBm equivalent) + RF to RF– Differential Voltage ...............................±0.7V .................................................. (+11dBm equivalent) Operating Temperature Range ................. –40°C to 85°C Storage Temperature Range................... –65°C to 125°C Junction Temperature (TJ) .................................... 125°C 16 15 14 13 12 GND NC 1 RF + 2 RF – 11 IF+ 17 10 IF – 3 NC 4 6 7 8 EN VCC1 VCC2 NC 9 5 GND UF PACKAGE 16-LEAD (4mm × 4mm) PLASTIC QFN TJMAX = 125°C, θJA = 37°C/W EXPOSED PAD IS GROUND (PIN 17) (MUST BE SOLDERED TO PCB) ORDER PART NUMBER PART MARKING LT5512EUF 5512 Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. DC ELECTRICAL CHARACTERISTICS (Test Circuit Shown in Figure 2) VCC = 5V, EN = High, TA = 25°C (Note 3), unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Enable (EN) Low = Off, High = On Turn On Time 3 μs Turn Off Time 13 μs 50 μA Input Current VENABLE = 5V Enable = High (On) 3 V Enable = Low (Off) 0.3 V 5.25 V Power Supply Requirements (VCC) Supply Voltage 4.5 Supply Current Shutdown Current 56 EN = Low 74 mA 100 μA MAX UNITS AC ELECTRICAL CHARACTERISTICS PARAMETER CONDITIONS RF Input Frequency Range Requires Appropriate Matching 0.001 to 3000 MHz LO Input Frequency Range Requires Appropriate Matching 0.001 to 3000 MHz IF Output Frequency Range Requires Appropriate Matching 0.001 to 2000 MHz LO Input Power 1kHz to 1700MHz (Resistive Match) 1200MHz to 3000MHz (Reactive Match) 2 MIN –11 –18 www.BDTIC.com/Linear TYP –5 –10 1 –2 dBm dBm 5512fa LT5512 AC ELECTRICAL CHARACTERISTICS Downmixer Applications: (Test Circuits Shown in Figures 1 and 2) VCC = 5V, EN = High, TA = 25°C, PRF = –10dBm (–10dBm/tone for two-tone IIP3 tests, Δf = 200kHz), High-Side LO at –5dBm for 45MHz, 140MHz and 450MHz tests, Low-Side LO at –10dBm for 900MHz, 1900MHz and 2450MHz tests, unless otherwise noted. (Note 2, 3 and 4) PARAMETER CONDITIONS Conversion Gain RF = 45MHz, IF = 2MHz RF = 140MHz, IF = 10MHz RF = 450MHz, IF = 70MHz RF = 900MHz, IF = 170MHz RF = 1900MHz, IF = 170MHz RF = 2450MHz, IF = 240MHz MIN Conversion Gain vs Temperature TA = –40°C to 85°C, RF = 900MHz Input 3rd Order Intercept –1 TYP 1 2 1.1 0 1 2 MAX UNITS dB dB dB dB dB dB –0.011 dB/°C RF = 45MHz, IF = 2MHz RF = 140MHz, IF = 10MHz RF = 450MHz, IF = 70MHz RF = 900MHz, IF = 170MHz RF = 1900MHz, IF = 170MHz RF = 2450MHz, IF = 240MHz 20.4 20.7 21.3 21 17 13 dBm dBm dBm dBm dBm dBm Single-Sideband Noise Figure RF = 140MHz, IF = 10MHz RF = 450MHz, IF = 70MHz RF = 900MHz, IF = 170MHz RF = 1900MHz, IF = 170MHz RF = 2450MHz, IF = 240MHz 10.3 10.3 11 14 13.4 dB dB dB dB dB LO to RF Leakage fLO = 250kHz to 700MHz (Figure 1) fLO = 700MHz to 2500MHz (Figure 2) ≤–63 ≤–50 dBm dBm LO to IF Leakage fLO = 250kHz to 500MHz (Figure 1) fLO = 500MHz to 1250MHz (Figure 1) fLO = 700MHz to 1500MHz (Figure 2) fLO = 1500MHz to 1950MHz (Figure 2) fLO = 1950MHz to 2500MHz (Figure 2) ≤–35 ≤–40 ≤–45 ≤–40 ≤–32 dBm dBm dBm dBm dBm RF to LO Isolation fRF = 250kHz to 800MHz (Figure 1) fRF = 700MHz to 1200MHz (Figure 2) fRF = 1200MHz to 1700MHz (Figure 2) fRF = 1700MHz to 2500MHz (Figure 2) >61 >49 >46 >43 dB dB dB dB 2RF-2LO Output Spurious Product (fRF = fLO + fIF/2) 900MHz: fRF = 815MHz at –12dBm, fIF = 170MHz 1900MHz: fRF = 1815MHz at –12dBm, fIF = 170MHz –66 –59 dBc dBc 3RF-3LO Output Spurious Product (fRF = fLO + fIF/3) 900MHz: fRF = 786.67MHz at –12dBm, fIF = 170MHz 1900MHz: fRF = 1786.67MHz at –12dBm, fIF = 170MHz –83 –58 dBc dBc Input 1dB Compression RF = 10MHz to 500MHz (Figure 1) RF = 900MHz (Figure 2) RF = 1900MHz (Figure 2) 10.5 10.1 6.2 dBm dBm dBm Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: 45MHz, 140MHz and 450MHz performance measured on the test circuit shown in Figure 1. 900MHz, 1900MHz and 2450MHz performance measured on the test circuit shown in Figure 2. Note 3: Specifications over the –40°C to 85°C temperature range are assured by design, characterization and correlation with statistical process control. Note 4: SSB Noise Figure measurements performed with a small-signal noise source and bandpass filter on RF input and no other RF signal applied. www.BDTIC.com/Linear 5512fa 3 LT5512 U W TYPICAL DC PERFOR A CE CHARACTERISTICS Supply Current vs Supply Voltage (Test Circuit Shown Figure 2) Shutdown Current vs Supply Voltage 60 100 59 SUPPLY CURRENT (mA) SHUTDOWN CURRENT (µA) TA = 85°C 58 57 TA = 25°C 56 55 54 TA = –40°C 53 52 TA = 85°C 10 TA = 25°C 1 TA = –40°C 51 50 4.75 5.25 5.0 SUPPLY VOLTAGE (V) 4.5 0.1 4.5 5.5 5.0 5.25 4.75 SUPPLY VOLTAGE (V) 5512 G01 5.5 5512 G02 U W TYPICAL AC PERFOR A CE CHARACTERISTICS HF/VHF/UHF Downmixer Application VCC = 5V, EN = High, PRF = –10dBm (–10dBm/tone for 2-tone IIP3 tests, Δf = 200kHz), High-Side LO, PLO = –5dBm, unless otherwise noted. Test Circuit Shown in Figure 1. Conv Gain, IIP3 and NF vs LO Power (140MHz App) 22 –10 20 –20 18 IIP3 16 LO-IF 14 12 –30 –40 –50 IF = 10MHz 10 –60 LO-RF 8 –70 –40°C –80 25°C 85°C –90 –100 6 4 GC 2 90 115 140 165 RF FREQUENCY (MHz) 12 10 SSB NF 8 6 4 20 –20 18 16 –30 14 –40 LO-IF –50 LO-RF –60 8 –70 6 4 2 –40°C –80 25°C –90 85°C –100 GC 0 400 425 450 475 RF FREQUENCY (MHz) –110 500 5512 G06 4 GC, SSB NF (dB), IIP3 (dBm) 22 –10 LO LEAKAGE (dBm) GC, SSB NF (dB), IIP3 (dBm) 0 20 12 12 10 –40°C 25°C 85°C 8 6 2 GC 0 –9 4.5 1 –7 –5 –3 –1 LO INPUT POWER (dBm) 5.5 4.75 5 5.25 SUPPLY VOLTAGE (V) 5512 G05 Conv Gain, IIP3 and NF vs LO Power (450MHz App) IF = 70MHz PLO = –5dBm RF = 140MHz IF = 10MHz 5512 G04 22 10 16 14 4 GC 0 –11 Conv Gain, IIP3 and LO Leakage vs RF Frequency (450MHz App) IIP3 IIP3 18 14 5512 G03 18 20 TA = 25°C RF = 140MHz IF = 10MHz 16 2 –110 190 0 22 IIP3 Conv Gain and IIP3 vs Supply Voltage (450MHz App) 22 IIP3 20 18 TA = 25°C RF = 450MHz IF = 70MHz 16 14 12 GC (dB), IIP3 (dBm) 18 Conv Gain and IIP3 vs Supply Voltage (140MHz App) GC (dB), IIP3 (dBm) 0 20 GC, SSB NF (dB), IIP3 (dBm) 22 LO LEAKAGE (dBm) GC, SSB NF (dB), IIP3 (dBm) Conv Gain, IIP3 and LO Leakage vs RF Frequency (140MHz App) SSB NF 10 8 6 0 –11 PLO = –5dBm RF = 450MHz IF = 70MHz 14 12 10 –40°C 25°C 85°C 8 6 4 4 2 IIP3 16 GC GC 2 0 –9 –7 –5 –3 –1 LO INPUT POWER (dBm) 1 4.5 5512 G07 www.BDTIC.com/Linear 4.75 5 5.25 SUPPLY VOLTAGE (V) 5.5 5512 G08 5512fa LT5512 U W TYPICAL PERFOR A CE CHARACTERISTICS (1900MHz Downmixer Application) VCC = 5V, EN = High, TA = 25°C, 1900MHz RF input matching, PRF = –10dBm (–10dBm/tone for 2-tone IIP3 tests, Δf = 200kHz), Low-Side LO, PLO = –10dBm, IF output measured at 170MHz, unless otherwise noted. Test circuit shown in Figure 2. Conv Gain and IIP3 Conv Gain and IIP3 vs Temperature Conv Gain, IIP3 and NF vs Supply Voltage RF = 1900MHz, IF = 170MHz vs RF Frequency 14 17 LOW-SIDE LO HIGH-SIDE LO 10 SSB NF 16 15 8 14 6 13 4 TA = 25°C 12 IF = 170MHz 11 2 GC 0 1700 16 IIP3 10 8 6 4 CONV GAIN TA = 25°C TA = –40°C 2 TA = 85°C 20 10 19 0 4.75 5.25 5.0 SUPPLY VOLTAGE (V) 14 17 12 –40°C 16 25°C 85°C 15 SSB NF 14 13 6 GC 0 –18 –16 –14 –12 –10 –8 –6 LO INPUT POWER (dBm) –4 –30 –60 11 –80 TA = 25°C TA = –40°C IM3 SPUR LEVEL (dBm) POUT (RF = 1900MHz) 2RF-2LO (RF = 1815MHz) –1 2 5512 G15 LO-IF –40 –45 –55 –60 –18 –16 –14 –12 –10 –8 –6 LO INPUT POWER (dBm) 3 PRF = –10dBm –75 –50 TA = 25°C fLO = 1730MHz fRF = 1786.67MHz –55 –60 –65 PRF = –10dBm –70 –75 –80 PRF = –16dBm –90 –18 –16 –14 –12 –10 –8 –6 LO INPUT POWER (dBm) –2 5512 G14 TA = 25°C fLO = 1730MHz fRF = 1815MHz –65 –70 –4 3RF-3LO Spur Level vs LO Input Power PRF = –16dBm –85 –85 –110 –22 –19 –16 –13 –10 –7 –4 RF INPUT POWER (dBm) –35 LO-RF TA = 25°C –60 –80 –90 fLO = 1730MHz TA = 25°C 5512 G13 –55 100 –50 –90 0 –21 –18 –15 –12 –9 –6 –3 RF INPUT POWER (dBm/TONE) –50 75 –30 TA = 85°C 2RF-2LO (Half-IF) Spur Level vs LO Input Power –50 0 25 50 TEMPERATURE (°C) 5512 G11 TA = 85°C –50 –70 10 –2 3RF-3LO (RF = 1786.67MHz) –25 LO-IF and LO-RF Leakage vs LO Input Power –40 12 10 IF OUTPUT POWER (dBm) HIGH-SIDE LO LOW-SIDE LO –25 –20 IF Output Power, 2RF-2LO and 3RF-3LO vs RF Input Power –70 CONV GAIN 4 –20 5512 G12 –30 6 –50 5.5 SPUR LEVEL (dBm) 10 TA = 25°C fLO = 1730MHz –10 PLO = –10dBm 8 TA = –40°C –10 POUT POUT, IM3 (dBm/TONE) 18 SSB NF (dB) GC (dB), IIP3 (dBm) IIP3 16 2 10 Output IF Power and Output IM3 vs RF Input Power (2 Input Tones) 20 4 HIGH-SIDE LO 12 5512 G10 Conv Gain, IIP3 and NF vs LO Input Power 8 LOW-SIDE LO 14 0 4.5 5512 G09 18 IIP3 16 2 0 10 2100 1800 2000 1900 RF FREQUENCY (MHz) TA = 85°C 14 12 18 TA = –40°C LO LEAKAGE (dBm) 12 TA = 25°C CONV GAIN (dB), IIP3 (dBm) 18 CONV GAIN (dB), IIP3 (dBm) 16 IIP3 20 18 19 SSB NF (dB) GC (dB), IIP3 (dBm) 18 –4 –2 5512 G16 –90 –18 –16 –14 –12 –10 –8 –6 LO INPUT POWER (dBm) www.BDTIC.com/Linear –4 –2 5512 G17 5512fa 5 LT5512 U U U PI FU CTIO S NC (Pins 1, 4, 8, 13, 16): Not connected internally. These pins should be grounded on the circuit board for improved LO to RF and LO to IF isolation. RF+, RF– (Pins 2, 3): Differential Inputs for the RF Signal. These pins must be driven with a differential signal. Each pin must be connected to a DC ground capable of sinking 15mA (30mA total). This DC bias return can be accomplished through the center-tap of a balun, or with shunt inductors. An impedance transformation is required to match the RF input to 50Ω (or 75Ω). EN (Pin 5): Enable Pin. When the input voltage is higher than 3V, the mixer circuits supplied through Pins 6, 7, 10, and 11 are enabled. When the input voltage is less than 0.3V, all circuits are disabled. Typical enable pin input current is 50μA for EN = 5V and 0μA when EN = 0V. VCC1 (Pin 6): Power Supply Pin for the LO Buffer Circuits. Typical current consumption is 22mA. This pin should be externally connected to the other VCC pins, and decoupled with 0.01μF and 1μF capacitors. VCC2 (Pin 7): Power Supply Pin for the Bias Circuits. Typical current consumption is 4mA. This pin should be externally connected to the other VCC pins, and decoupled with 0.01μF and 1μF capacitors. GND (Pins 9 and 12): Ground. These pins are internally connected to the backside ground for better isolation. They should be connected to RF ground on the circuit board, although they are not intended to replace the primary grounding through the backside contact of the package. IF–, IF+ (Pins 10, 11): Differential Outputs for the IF Signal. An impedance transformation may be required to match the outputs. These pins must be connected to VCC through impedance matching inductors, RF chokes or a transformer center-tap. LO–, LO+ (Pins 14, 15): Differential Inputs for the Local Oscillator Signal. They can also be driven single-ended by connecting one to an RF ground through a DC blocking capacitor. These pins are internally biased to 2V; thus, DC blocking capacitors are required. An impedance transformation or matching resistor is required to match the LO input to 50Ω (or 75Ω). GROUND (Pin 17): (Backside Contact): Circuit Ground Return for the Entire IC. This must be soldered to the printed circuit board ground plane. W BLOCK DIAGRA BACKSIDE GROUND 17 RF + 2 LINEAR AMPLIFIER DOUBLE-BALANCED MIXER 15mA 15mA RF – 3 12 GND 11 IF + 10 IF – 9 GND LO + 15 HIGH-SPEED LO BUFFER LO– 14 BIAS 5 EN 6 VCC1 6 7 VCC2 5512 BD www.BDTIC.com/Linear 5512fa LT5512 TEST CIRCUITS C6 16 6 RFIN T1 1:1 NC 1 2 2 C4 RF GND + IF GND RF INPUT MATCHING T1 L1, L2 WBC4-4L --47nH 27nH WBC1-1TL 12nH 6.8nH 5.6nH 4.7nH 1 C3 10 6 IFOUT 0.1MHz TO 100MHz 2 4 3 9 VCC1 VCC2 NC 5 EN 5V C4 39pF 100pF 68pF 33pF 18pF 12pF 10pF T2 8:1 12 + 11 IF – NC EN RF(MHz) 0.25 - 250 45 70 140 240 380 450 13 LO– NC RF – 4 L2 14 + LT5512 3 3 4 15 LO NC L1 1 C7 R1 LOIN –5dBm 6 7 8 VCC 4.5V TO 5.25V C1 C2 5512 F01 REF DES VALUE SIZE PART NUMBER REF DES VALUE SIZE PART NUMBER R1 100Ω 0402 AAC CR05-101J C4 See Table 0402 AVX 0402 C1, C6, C7 See Table 0402 Toko LL1005-FH 0.01µF 0402 AVX 04023C103JAT L1, L2 C2 1µF 0603 AVX 0603ZD105KAT T1 1:1 Coilcraft WBC1-1TL C3 1.8pF 0402 AVX 04025A1R8BAT T2 8:1 Mini-Circuits TC8-1 Figure 1. Test Schematic for HF/VHF/UHF Downmixer Applications C6 C7 LOIN –10dBm 17 16 T1 1 4 1 ZO = 72Ω L = 2mm 2 C4 3 3 5 4 ZO = 72Ω L = 2mm NC DC 15 LO + 14 0.018" 13 LO– NC NC RF GND T2 L1 IF LT5512 IF – RF – GND NC 5 EN GND 12 + 11 + EN RF GND 0.062" L3 RFIN ER = 4.4 0.018" 6 IFOUT 2 C3 10 1 C5 4 3 L2 9 VCC1 VCC2 NC 6 7 8 R1 VCC APPLICATION (MHz) 900 RF/170 IF 1900 RF/170 IF 2450 RF/240 IF T1 (MURATA) LDB21881M05C-001 LDB211G9010C-001 LDB212G4020C-001 C4 3.9pF 1.5pF 1.2pF L3 22nH 5.6nH 4.7nH C3 6.8pF 6.8pF 3.3pF C1 C2 5512 F02 REF DES VALUE SIZE PART NUMBER REF DES VALUE SIZE PART NUMBER C5, C6, C7 100pF 0402 Murata GRP1555C1H101J L1, L2 47nH 0402 Coilcraft 0402CS-47NX C1 0.01µF 0402 Murata GRP155R71C103K L3 See Table 0402 Toko LL1005-FH C2 1.0µF 0603 Taiyo Yuden LMK107F105ZA R1 10 0402 C4 See Table 0402 Murata GRP1555C T1 See Table C3 See Table 0402 Murata GRP1555C T2 8:1 Murata LDB21 Series Mini-Circuits TC8-1 Figure 2. Test Schematic for 900MHz to 2.5GHz Downmixer Applications www.BDTIC.com/Linear 5512fa 7 LT5512 U U W U APPLICATIO S I FOR ATIO The LT5512 consists of a double-balanced mixer, RF buffer amplifier, high-speed limiting LO buffer and bias/enable circuits. The differential RF, LO and IF ports require simple external matching which allows the mixer to be used at very low frequencies, below 1MHz, or up to 3GHz. Low side or high side LO injection can be used. capable of sinking 15mA. This can be accomplished with the center-tap of a balun as shown in Figure 3, or with bias chokes connected from Pins 2 and 3 to ground, if a differential RF input signal is available. The value of the bias chokes should be high enough to avoid reducing the input impedance at the frequency of interest. Two evaluation circuits are available. The HF/VHF/UHF evaluation circuit is shown in Figure 1 and the 900MHz to 2.5GHz evaluation circuit is shown in Figure 2. The corresponding demo board layouts are shown in Figures 10 and 11, respectively. Table 1 lists the differential input impedance and differential reflection coefficient between Pins 2 and 3 for several common RF frequencies. As shown in Figures 3 and 4, low-pass impedance matching is used to transform the differential input impedance up to the desired value for the balun input. The following example shows how to design the low-pass impedance transformation network for the RF input. RF Input Port A simplified schematic of the differential RF input is shown in Figure 3, with the associated external impedance matching elements for a 450MHz application. Each RF input requires a low resistance DC return to ground LT5512 VBIAS From Table 1, the differential input impedance at 450MHz is 18.1 + j5.2. As shown in Figure 4, the 5.2Ω reactance is split, with one half on each side of the 18.1Ω load resistor. The matching network will consist of additional inductance in series with the internal inductance and a capacitor in parallel with the desired 50Ω source impedance. The capacitance (C4) and inductance are calculated as follows. VCC 15mA Q = (RS / RL ) – 1 = (50 / 18 . 1) – 1 = 1 . 328 15mA 2 C4 = 3 L1 4.7nH Q 1 . 328 = = 9 . 4pF (use 10pF ) ωRS 2π • 450MHz • 50 L2 4.7nH C4 10pF L1, L2 = 1 8 . 1 • 1 . 328 RL • Q = 2 • 2π • 450MHz 2ω = 4 . 2nH (use 4 . 7nH) Table 1. RF Input Differential Impedance 1:1 RFIN 50Ω 5512 F03 Figure 3. RF Input with External Matching for a 450MHz Application L1 2 RS 50Ω C4 3 Differential S11 Mag Angle 10 18.2 + j0.14 0.467 179.6 44 18 + j0.26 0.470 178.6 240 18.1 + j2.8 0.471 172.6 450 18.1 + j5.2 0.473 166.3 j2.6 950 18.7 + j11.3 0.479 150.8 1900 20.6 + j22.8 0.503 124.3 2150 21.4 + j26.5 0.512 116.9 2450 22.5 + j30.5 0.522 109.2 2700 24.1 + j34.7 0.530 101.7 RL 18.1Ω j2.6 LT5512 5512 F04 Figure 4. 450MHz RF Input Matching 8 Differential Input Impedance 1/2 XINT 1/2 XINT L2 Frequency (MHz) www.BDTIC.com/Linear 5512fa LT5512 U U W U APPLICATIO S I FOR ATIO RF PORT RETURN LOSS (dB) 0 Table 2. LO Input Differential Impedance –5 Frequency (MHz) Differential Input Impedance –10 –15 900MHz –20 –25 140MHz 450MHz 1900MHz –30 50 100 1000 RF FREQUENCY (MHz) 3000 5512 F05 Figure 5. RF Input Return Loss (140MHz, 450MHz, 900MHz and 1900MHz Matching) At high frequencies (greater than 900MHz), this same matching technique is used, but it is important to consider the IC’s input reactance when calculating the external inductance. As shown in Figure 2, the high-frequency evaluation board uses short (2mm) 72Ω microstrip lines to realize the required inductance, instead of chip inductors. External matching values for several frequencies, ranging from 45MHz to 2.45GHz are shown in Figures 1 and 2. Measured RF input return losses are plotted in Figure 5. LO Input Port The LO buffer amplifier consists of high-speed limiting differential amplifiers, designed to drive the mixer quad for high linearity. The LO+ and LO– pins are designed for differential or single-ended drive. Both LO pins are internally biased to 2VDC. LO + 15 C6 0.01µF 200Ω 2V R1 100Ω VCC Angle 750 263 + j172 0.766 –10.2 213 + j178 0.760 –13.4 1250 175 + j173 0.752 –16.6 1500 146 + j164 0.743 –19.8 1750 125 + j153 0.733 –22.8 2000 108 + j142 0.722 –25.8 2250 95 + j131 0.709 –28.9 2500 86 + j122 0.695 –31.8 2750 78 + j133 0.68 –34.6 A simplified schematic of the LO input is shown in Figure 6 with simple resistive matching and DC blocking capacitors. This is the preferred matching for LO frequencies below 1.5GHz. The internal (DC) resistance is 400Ω. The required LO drive at the IC is 150mVRMS (typical) which can come from a 50Ω source, or a higher impedance source such as PECL. The external matching resistor is required only to reduce the amplitude of the LO signal at the IC, although the input stage will tolerate 10dB of overdrive without significant performance degradation. Resistive LO port matching is used on the low-frequency evaluation board (see Figure 1). Above 1.5GHz, the internal capacitance becomes significant and reactive matching to 50Ω with a single series inductor and DC blocking capacitors is preferred. A schematic is shown in Figure 7. Table 2 lists the differential input LOIN 50Ω –10dBm C7 0.01µF Mag 1000 200Ω LOIN –5dBm Differential S11 L3 LO + 15 C6 100pF 2V 200Ω 200Ω VCC C7 100pF 14 LO – 14 LO – LT5512 LT5512 5512 F07 5512 F06 Figure 6. LO Input with Resistive Matching Figure 7. LO Input with Reactive Matching www.BDTIC.com/Linear 5512fa 9 LT5512 U U W U APPLICATIO S I FOR ATIO close as possible to the IF+/IF– pins. Even small amounts of inductance in series with C3 (such as through a via) can significantly degrade IIP3. The value of C3 should be reduced by the value of internal capacitance (see Table 3). This matching network is simple and offers good selectivity for narrow band IF applications. 0 RETURN LOSS (dB) –5 –10 4.7nH 5.6nH 6.8nH –15 –20 8.2nH –25 10nH –30 0 500 1000 1500 2000 2500 3000 3500 4000 FREQUENCY (MHz) 1573 F08 Figure 8. Single-Ended LO Port Return Loss vs Frequency for Various Values of L3 impedance and differential reflection coefficient between the LO+ and LO– pins. This information can be used to compute the value of the series matching inductor, L3. Alternatively, Figure 8 shows measured LO input return loss versus frequency for various values of L3. Reactive LO port matching is used on the high-frequency evaluation board (see Figure 2). IF Output Port The differential IF outputs, IF+ and IF–, are internally connected to the collectors of the mixer switching transistors as shown in Figure 9. These outputs should be combined externally through an RF balun or 180° hybrid to achieve optimum performance. Both pins must be biased at the supply voltage, which can be applied through matching inductors (see Figure 2), or through the center-tap of an output transformer (see Figure 1). These pins are protected with ESD diodes; the diodes allow peak AC signal swing up to 1.3V above VCC. As shown in Table 3, the IF output differential impedance is approximately 390Ω in parallel with 0.44pF. A simple band-pass IF matching network suitable for wireless applications is shown in Figure 9. Here, L1, L2 and C3 set the desired IF output frequency. The 390Ω differential output can then be applied directly to a differential filter, or an 8:1 balun for impedance transformation down to 50Ω. To achieve maximum linearity, C3 should be located as 10 For IF frequencies below 100MHz, the simplest IF matching technique is an 8:1 transformer connected across the IF pins as shown in Figure 1. DC bias to the IF+ and IF– pins is provided through the transformer’s center-tap. A small value IF capacitor (C3) improves the LO-IF leakage and attenuates the undesired image frequency. No inductors are required. Table 3. IF Output Differential Impedance (Parallel Equivalent) Frequency (MHz) Differential Output Impedance Differential S11 Mag Angle 10 396 II - j10k 0.766 0 70 394 II - j5445 0.775 –1.1 170 393 II - j2112 0.774 –2.8 240 392 II - j1507 0.773 –3.9 450 387 II - j798 0.772 –7.3 750 377 II - j478 0.768 –12.2 860 371 II - j416 0.766 –14.0 1000 363 II - j359 0.762 –16.2 1250 363 II - j295 0.764 –19.6 1500 346 II -j244 0.756 –23.6 1900 317 II - j192 0.743 –29.9 LT5512 11 IF+ L1 400Ω TO VCC DIFFERENTIAL FILTER OR BALUN C3 L2 10 IF– 5512 F09 Figure 9. IF Output Equivalent Circuit with Band-Pass Matching Elements www.BDTIC.com/Linear 5512fa LT5512 U PACKAGE DESCRIPTIO UF Package 16-Lead Plastic QFN (4mm × 4mm) (Reference LTC DWG # 05-08-1692) 0.72 ±0.05 4.35 ± 0.05 2.15 ± 0.05 2.90 ± 0.05 (4 SIDES) PACKAGE OUTLINE 0.30 ±0.05 0.65 BCS RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS BOTTOM VIEW—EXPOSED PAD 4.00 ± 0.10 (4 SIDES) 0.75 ± 0.05 R = 0.115 TYP 0.55 ± 0.20 15 16 PIN 1 1 2.15 ± 0.10 (4-SIDES) 2 (UF) QFN 0102 0.200 REF 0.00 – 0.05 0.30 ± 0.05 0.65 BSC NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGC) 2. ALL DIMENSIONS ARE IN MILLIMETERS 3. 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 4. EXPOSED PAD SHALL BE SOLDER PLATED www.BDTIC.com/Linear 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. 5512fa 11 LT5512 U W U U APPLICATIO S I FOR ATIO LO LO RF IF RF Figure 10. HF/VHF/UHF Evaluation Board Layout (DC933A) IF Figure 11. High-Frequency Evaluation Board Layout (DC478B) RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT5511 High Linearity Upconverting Mixer RF Output to 3GHz, 17dBm IIP3, Integrated LO Buffer LT5514 Ultralow Distortion, IF Amplifier/ADC Driver with Digitally Controlled Gain 850MHz Bandwidth, 47dBm OIP3 at 100MHz, 10.5dB to 33dB Gain Control Range LT5515 1.5GHz to 2.5GHz Direct Conversion Quadrature Demodulator 20dBm IIP3, Integrated LO Quadrature Generator LT5516 0.8GHz to 1.5GHz Direct Conversion Quadrature Demodulator 21.5dBm IIP3, Integrated LO Quadrature Generator LT5517 40MHz to 900MHz Quadrature Demodulator 21dBm IIP3, Integrated LO Quadrature Generator LT5519 0.7GHz to 1.4GHz High Linearity Upconverting Mixer 17.1dBm IIP3 at 1GHz, Integrated RF Output Transformer with 50Ω Matching, Single-Ended LO and RF Ports Operation LT5520 1.3GHz to 2.3GHz High Linearity Upconverting Mixer 15.9dBm IIP3 at 1.9GHz, Integrated RF Output Transformer with 50Ω Matching, Single-Ended LO and RF Ports Operation LT5521 10MHz to 3700MHz High Linearity Upconverting Mixer 24.2dBm IIP3 at 1.95GHz, NF = 12.5dB, 3.15V to 5.25V Supply, Single-Ended LO Port Operation LT5522 400MHz to 2.7GHz High Signal Level Downconverting Mixer 4.5V to 5.25V Supply, 25dBm IIP3 at 900MHz, NF = 12.5dB, 50Ω Single-Ended RF and LO Ports LT5524 Low Power, Low Distortion ADC Driver with Digitally Programmable Gain 450MHz Bandwidth, 40dBm OIP3, 4.5dB to 27dB Gain Control LT5525 High Linearity, Low Power Downconverting Mixer Single-Ended 50Ω RF and LO Ports, 17.6dBm IIP3 at 1900MHz, ICC = 28mA LT5526 High Linearity, Low Power Downconverting Mixer 3V to 5.3V Supply, 16.5dBm IIP3, 100kHz to 2GHz RF, NF = 11dB, ICC = 28mA, –65dBm LO-RF Leakage LT5527 400MHz to 3.7GHz High Signal Level Downconverting Mixer Single-Ended 50Ω RF and LO Ports, 23.5dBm IIP3 at 1.9GHz LT5528 1.5GHz to 2.4GHz High Linearity Direct I/Q Modulator 21.8dBm OIP3 at 2GHz, –159dBm/Hz Noise Floor, 50Ω Interface at all Ports Infrastructure Corporation www.BDTIC.com/Linear 12 Linear Technology 5512fa LT/LT 1005 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005