LT5568-2 GSM/EDGE Optimized, High Linearity Direct Quadrature Modulator DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ The LT®5568-2 is a direct I/Q modulator designed for high performance wireless applications, including wireless infrastructure. It allows direct modulation of an RF signal using differential baseband I and Q signals. It supports GSM, EDGE, CDMA, CDMA2000 and other systems that operate in the 850MHz to 965MHz band. It may be configured as an image reject upconverting mixer, by applying 90° phase-shifted signals to the I and Q inputs. The I/Q baseband inputs consist of voltage-to-current converters that in turn drive double-balanced mixers. The outputs of these mixers are summed and applied to an on-chip RF transformer, which converts the differential mixer signals to a 50Ω single-ended output. The four balanced I and Q baseband input ports are intended for DC coupling from a source with a common mode voltage level of about 0.5V. The LO path consists of an LO buffer with single-ended input, and precision quadrature generators that produce the LO drive for the mixers. The supply voltage range is 4.5V to 5.25V. Optimized Image Rejection for 850MHz to 965MHz High OIP3: +22.9dBm at 900MHz Low Output Noise Floor at 5MHz Offset: No RF: –159.4dBm/Hz POUT = 4dBm: –153dBm/Hz Integrated LO Buffer and LO Quadrature Phase Generator 50Ω AC-Coupled Single-Ended LO and RF Ports 50Ω DC Interface to Baseband Inputs Low Carrier Leakage: –43dBm at 900MHz High Image Rejection: –52dBc at 900MHz 16-Lead 4mm × 4mm QFN Package U APPLICATIO S ■ ■ ■ Infrastructure Tx for GSM/Cellular Bands Image Reject Up-Converters for Cellular Bands Low-Noise Variable Phase-Shifter for 700MHz to 1050MHz Local Oscillator Signals RFID Reader , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. U ■ TYPICAL APPLICATIO GSM EVM and Noise vs RF Output Power at 900MHz 850MHz to 965MHz Direct Conversion Transmitter Application LT5568-2 V-I I-CHANNEL PA 0° EN 90° Q-CHANNEL Q-DAC BALUN 5 –96 4 –98 3 –100 NOISE 2 V-I –102 EVM –104 1 BASEBAND GENERATOR 55682 TA01 VCO/SYNTHESIZER 0 –10 NOISE FLOOR AT 6MHz OFFSET (dBc/100kHz) I-DAC 5V 100nF x2 RF = 850MHz TO 965MHz EVM (%RMS) VCC 4 –8 –6 –4 –2 0 2 GSM RF OUTPUT POWER (dBm) 6 –106 55682 TA02 55682f 1 LT5568-2 U W W W ABSOLUTE AXI U RATI GS PIN CONFIGURATION (Note 1) VCC BBPI BBMI GND TOP VIEW Supply Voltage .........................................................5.5V Common Mode Level of BBPI, BBMI and BBPQ, BBMQ .......................................................2.5V Operating Ambient Temperature (Note 2) ............................................... –40°C to 85°C Storage Temperature Range................... –65°C to 125°C Voltage on Any Pin Not to Exceed...................... –500mV to VCC + 500mV 16 15 14 13 12 GND EN 1 GND 2 11 RF 17 LO 3 10 GND GND 4 GND 6 7 8 BBMQ GND BBPQ VCC 9 5 UF PACKAGE 16-LEAD (4mm × 4mm) PLASTIC QFN TJMAX = 125°C, θJA = 37°C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB CAUTION: This part is sensitive to ESD. It is very important that proper ESD precautions be observed when handling the LT5568-2. ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT5568-2EUF#PBF LT5568-2EUF#TRPBF 55682 16-Lead (4mm × 4mm) Plastic QFN –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on non-standard 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/ ELECTRICAL CHARACTERISTICS VCC = 5V, EN = High, TA = 25°C, fLO = 900MHz, fRF = 902MHz, PLO = 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.54VDC, Baseband Input Frequency = 2MHz, I&Q 90° shifted (upper side-band selection). PRF, OUT = –10dBm, unless otherwise noted. (Note 3) SYMBOL PARAMETER CONDITIONS fRF RF Frequency Range RF Frequency Range –3dB Bandwidth –1dB Bandwidth S22, ON RF Output Return Loss S22, OFF MIN TYP MAX UNITS RF Output (RF) 0.6 to 1.1 0.7 to 1 GHz GHz EN = High (Note 6) –16 dB RF Output Return Loss EN = Low (Note 6) –18 dB NFloor RF Output Noise Floor No Input Signal (Note 8) POUT = 4dBm (Note 9) POUT = 4dBm (Note 10) GP Conversion Power Gain POUT/PIN, I&Q GV Conversion Voltage Gain 20 • Log (VOUT, 50Ω/VIN, DIFF, I or Q) –6.8 dB POUT Absolute Output Power 1VP-P DIFF CW Signal, I and Q –2.8 dBm G3LO vs LO 3 • LO Conversion Gain Difference (Note 17) –23 dB OP1dB Output 1dB Compression (Note 7) 8.6 dBm OIP2 Output 2nd Order Intercept (Notes 13, 14) 59 dBm OIP3 Output 3rd Order Intercept (Notes 13, 15) 22.9 dBm –159.4 –153 –152.6 –9 –6.8 dBm/Hz dBm/Hz dBm/Hz –3 dB 55682f 2 LT5568-2 ELECTRICAL CHARACTERISTICS VCC = 5V, EN = High, TA = 25°C, fLO = 900MHz, fRF = 902MHz, PLO = 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.54VDC, Baseband Input Frequency = 2MHz, I&Q 90° shifted (upper side-band selection). PRF, OUT = –10dBm, unless otherwise noted. (Note 3) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS IR Image Rejection fBB = 100kHz (Note 16) –52 dBc LOFT Carrier Leakage (LO Feedthrough) EN = High, PLO = 0dBm (Note 16) EN = Low, PLO = 0dBm (Note 16) –43 –65 dBm dBm 0.6 to 1.1 GHz LO Input (LO) fLO LO Frequency Range PLO LO Input Power S11, ON LO Input Return Loss EN = High (Note 6) –15 dB S11, OFF LO Input Return Loss EN = Low (Note 6) –2.5 dB NFLO LO Input Referred Noise Figure (Note 5) at 900MHz 14.7 dB GLO LO to RF Small Signal Gain (Note 5) at 900MHz 14.7 dB IIP3LO LO Input 3rd Order Intercept (Note 5) at 900MHz –3 dBm MHz –10 0 5 dBm Baseband Inputs (BBPI, BBMI, BBPQ, BBMQ) BWBB Baseband Bandwidth –3dB Bandwidth 380 VCMBB DC Common Mode Voltage (Note 4) 0.54 V RIN, SE Single-Ended Input Resistance (Note 4) 47 Ω PLO2BB Carrier Feedthrough on BB POUT = 0 (Note 4) –38 dBm IP1dB Input 1dB Compression Point Differential Peak-to-Peak (Notes 7, 18) 4.3 VP-P, DIFF Power Supply (VCC) VCC Supply Voltage ICC, ON Supply Current EN = High 4.5 5 5.25 V 80 110 145 mA ICC, OFF Supply Current, Sleep Mode EN = 0V 100 µA tON Turn-On Time EN = Low to High (Note 11) 0.3 µs tOFF Turn-Off Time EN = High to Low (Note 12) 1.4 µs 245 V µA Enable (EN), Low = Off, High = On Enable Sleep Input High Voltage Input High Current EN = High EN = 5V Input Low Voltage Input Low Current EN = Low EN = 0V 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: Specifications over the –40°C to 85°C temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Tests are performed as shown in the configuration of Figure 7. Note 4: On each of the four baseband inputs BBPI, BBMI, BBPQ and BBMQ. Note 5: V(BBPI) – V(BBMI) = 1VDC, V(BBPQ) – V(BBMQ) = 1VDC. Note 6: Maximum value within 850MHz to 965MHz. Note 7: An external coupling capacitor is used in the RF output line. Note 8: At 20MHz offset from the LO signal frequency. Note 9: At 20MHz offset from the CW signal frequency. 1.0 0.5 0.01 V µA Note 10: At 5MHz offset from the CW signal frequency. Note 11: RF power is within 10% of final value. Note 12: RF power is at least 30dB lower than in the ON state. Note 13: Baseband is driven by 2MHz and 2.1MHz tones. Drive level is set in such a way that the two resulting RF tones are –10dBm each. Note 14: IM2 measured at LO frequency + 4.1MHz. Note 15: IM3 measured at LO frequency + 1.9MHz and LO frequency + 2.2MHz. Note 16: Amplitude average of the characterization data set without image or LO feedthrough nulling (unadjusted). Note 17: The difference in conversion gain between the spurious signal at f = 3 • LO – BB versus the conversion gain at the desired signal at f = LO + BB for BB = 2MHz and LO = 900MHz. Note 18: The input voltage corresponding to the output P1dB. 55682f 3 LT5568-2 U W TYPICAL PERFOR A CE CHARACTERISTICS VCC = 5V, EN = High, TA = 25°C, fLO = 900MHz, PLO = 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.54VDC, Baseband Input Frequency fBB = 2MHz, I&Q 90° shifted. fRF = fBB + fLO (upper sideband selection). PRF, OUT = –10dBm (–10dBm/tone for 2-tone measurements), unless otherwise noted. (Note 3) RF Output Power vs LO Frequency at 1VP-P Differential Baseband Drive Supply Current vs Supply Voltage 120 Voltage Gain vs LO Frequency 0 –4 –2 –6 –4 –8 25°C 110 –40°C 100 –6 –8 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C –10 –12 90 4.5 5 SUPPLY VOLTAGE (V) –14 550 5.5 VOLTAGE GAIN (dB) RF OUTPUT POWER (dBm) SUPPLY CURRENT (mA) 85°C 650 –10 –12 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C –14 –16 –18 550 750 850 950 1050 1150 1250 LO FREQUENCY (MHz) 55682 G02 650 750 850 950 1050 1150 1250 LO FREQUENCY (MHz) 55682 G03 55682 G01 Output IP3 vs LO Frequency 26 70 fBB, 1 = 2MHz fBB, 2 = 2.1MHz 24 Output 1dB Compression vs LO Frequency Output IP2 vs LO Frequency 10 fIM2 = fBB, 1 + fBB, 2 + fLO fBB, 1 = 2MHz fBB, 2 = 2.1MHz 65 8 20 18 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C 16 14 12 550 650 OP1dB (dBm) OIP2 (dBm) OIP3 (dBm) 22 60 55 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C 50 45 550 750 850 950 1050 1150 1250 LO FREQUENCY (MHz) 650 55682 G04 –45 –40 –50 –42 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C –44 –46 550 650 750 850 950 1050 1150 1250 LO FREQUENCY (MHz) 55682 G07 2 550 750 850 950 1050 1150 1250 LO FREQUENCY (MHz) 55682 G05 650 750 850 950 1050 1150 1250 LO FREQUENCY (MHz) 55682 G06 3 • LO Leakage to RF Output vs 3 • LO Frequency –45 –50 P(3 • LO) (dBm) –38 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C 4 2 • LO Leakage to RF Output vs 2 • LO Frequency P(2 • LO) (dBm) LO FEEDTHROUGH (dBm) LO Feedthrough to RF Output vs LO Frequency 6 –55 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C –60 –65 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2 • LO FREQUENCY (GHz) –55 –60 –65 2.5 55682 G08 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C –70 1.65 1.95 2.25 2.55 2.85 3.15 3.45 3.75 3 • LO FREQUENCY (GHz) 55682 G09 55682f 4 LT5568-2 U W TYPICAL PERFOR A CE CHARACTERISTICS VCC = 5V, EN = High, TA = 25°C, fLO = 900MHz, PLO = 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.54VDC, Baseband Input Frequency fBB = 2MHz, I&Q 90° shifted. fRF = fBB + fLO (upper sideband selection). PRF, OUT = –10dBm (–10dBm/tone for 2-tone measurements), unless otherwise noted. (Note 3) Noise Floor vs RF Frequency –30 –160 –161 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C –163 –163 550 650 –35 –45 –55 550 650 –40 550 750 850 950 1050 1150 1250 LO FREQUENCY (MHz) 55682 G11 PRF = –10dBm fBB = 100kHz 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C – 48 –50 –20 –16 –12 –8 –4 0 4 LO INPUT POWER (dBm) –16 55682 G13 –12 –8 –4 0 4 LO INPUT POWER (dBm) 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C –16 –20 55682 G14 10 10 –12 –8 –4 0 4 LO INPUT POWER (dBm) 8 55682 G16 HD2 (dBc), HD3 (dBc) 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C 25°C 25°C 85°C –40 85°C –10 –20 25°C HD3 –50 HD2 –40°C –30 –40 –60 85°C –70 –80 0 1 2 3 4 5 I AND Q BASEBAND VOLTAGE (VP–P, DIFF) HD2 = MAX POWER AT fLO + 2 • fBB OR fLO – 2 • fBB HD3 = MAX POWER AT fLO + 3 • fBB OR fLO – 3 • fBB 0 –20 5V –30 –40 –60 –80 5.5V HD2 –30 4.5V –40 –50 –60 0 55682 G17 –20 5V –60 –70 –10 HD3 –50 –50 4.5V RF CW OUTPUT POWER (dBm) 19 8 55682 G15 –10 RF CW OUTPUT POWER (dBm) 0 –40°C –12 –8 –4 0 4 LO INPUT POWER (dBm) RF –20 –30 –16 RF CW Output Power, HD2 and HD3 vs CW Baseband Voltage and Supply Voltage RF 21 –16 –12 8 –40°C 15 –10 –14 –10 fBB, 1 = 2MHz fBB, 2 = 2.1MHz 17 –8 RF CW Output Power, HD2 and HD3 vs CW Baseband Voltage and Temperature 23 13 –20 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C –50 Output IP3 vs LO Power 25 –6 –45 –55 –20 8 750 850 950 1050 1150 1250 RF FREQUENCY (MHz) 55682 G12 –40 VOLTAGE GAIN (dB) IMAGE REJECTION (dBc) –46 650 RF PORT, EN = HIGH, No LO –4 –40 –44 RF PORT, EN = HIGH, PLO = 0dBm Voltage Gain vs LO Power –35 –42 RF PORT, EN = LOW LO PORT, EN = HIGH, PLO = 10dBm Image Rejection vs LO Input Power –38 LO FEEDTHROUGH (dBm) –20 fBB = 100kHz LO Feedthrough to RF Output vs LO Input Power LO PORT, EN = HIGH, PLO = 0dBm –30 –50 750 850 950 1050 1150 1250 RF FREQUENCY (MHz) LO PORT, EN = LOW –10 –40 55682 G10 0IP3 (dBm) 0 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C HD2 (dBc), HD3 (dBc) NOISE FLOOR (dBm/Hz) IMAGE REJECTION (dBc) fLO = 900MHz (FIXED) NO RF S11 (dB) –158 –159 LO and RF Port Return Loss vs RF Frequency Image Rejection vs LO Frequency 5 1 2 3 4 I AND Q BASEBAND VOLTAGE (VP–P, DIFF) HD2 = MAX POWER AT fLO + 2 • fBB OR fLO – 2 • fBB HD3 = MAX POWER AT fLO + 3 • fBB OR fLO – 3 • fBB 55682 G18 55682f 5 LT5568-2 U W TYPICAL PERFOR A CE CHARACTERISTICS VCC = 5V, EN = High, TA = 25°C, fLO = 900MHz, PLO = 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.54VDC, Baseband Input Frequency fBB = 2MHz, I&Q 90° shifted. fRF = fBB + fLO (upper sideband selection). PRF, OUT = –10dBm (–10dBm/tone for 2-tone measurements), unless otherwise noted. (Note 3) RF Two-Tone Power (Each Tone), IM2 and IM3 vs Baseband Voltage LO Feedthrough to RF Output Image Rejection and Temperature vs CW Baseband Voltage vs CW Baseband Voltage –42 –44 –50 fBB = 100kHz –55 0 4.5V, 25°C 5.5V, 25°C 1 2 3 4 5 I AND Q BASEBAND VOLTAGE (VP-P,DIFF) 0 0.5 1 1.5 2 2.5 I AND Q BASEBAND VOLTAGE (VP-P,DIFF) 4.5V 5V, 5.5V –30 –40 IM3 –50 IM2 –70 –80 5V 5.5V 4.5V –60 1 10 0.1 I AND Q BASEBAND VOLTAGE (VP–P, DIFF, EACH TONE) IM2 = POWER AT fLO + 4.1MHz IM3 = MAX POWER AT fLO + 1.9MHz OR fLO + 2.2MHz 15 10 25°C IM3 –50 –40°C –60 IM2 –70 85°C fBBI = 2MHz, 2.1MHz, 0° fBBQ = 2MHz, 2.1MHz, 90° –40°C 25°C 85°C 25 20 15 10 5 0 –9 –8.5 –8 –7.5 –7 –6.5 GAIN (dB) –6 0 –160.4 –5.5 55682 G23 LO Leakage Distribution 35 85°C 5 fBBI = 2MHz, 2.1MHz, 0° fBBQ = 2MHz, 2.1MHz, 90° 40 –30 –40 30 PERCENTAGE (%) 5V, 5.5V 25°C Noise Floor Distribution –40°C 25°C 85°C 20 PERCENTAGE (%) –20 4.5V –40°C 25°C 35 RF 55682 G22 PRF,TONE (dBm), IM2 (dBc), IM3 (dBc) –10 –20 Gain Distribution 25 0 –10 10 1 0.1 I AND Q BASEBAND VOLTAGE (VP–P, DIFF, EACH TONE) IM2 = POWER AT fLO + 4.1MHz IM3 = MAX POWER AT fLO + 1.9MHz OR fLO + 2.2MHz 3 55682 G20 10 85°C –40°C –80 55682 G19 RF Two-Tone Power (Each Tone), IM2 and IM3 vs Baseband Voltage and Supply Voltage RF 0 55682 G21 –40 5V, –40°C 5V, 25°C 5V, 85°C PRF,TONE (dBm), IM2 (dBc), IM3 (dBc) –38 10 –45 5V, –40°C 5V, 25°C 5V, 85°C 4.5V, 25°C 5.5V, 25°C IMAGE REJECTION (dBc) LO FEEDTHROUGH (dBm) –36 –159.6 –159.2 –160 NOISE FLOOR (dBm/Hz) –158.8 55682 G24 Image Rejection Distribution 25 –40°C 25°C 85°C 20 –40°C 25°C 85°C PERCENTAGE (%) PERCENTAGE (%) 30 25 20 15 10 15 10 5 5 0 < –54 –50 –46 –42 –38 LO LEAKAGE (dBm) –34 –30 55682 G25 0 < –70 –66 –62 –58 –54 –50 IMAGE REJECTION (dBc) –46 55682 G26 55682f 6 LT5568-2 U U U PI FU CTIO S EN (Pin 1): Enable Input. When the enable pin voltage is higher than 1V, the IC is turned on. When the input voltage is less than 0.5V, the IC is turned off. BBPQ, BBMQ (Pins 7, 5): Baseband Inputs for the Q-channel, each 50Ω input impedance. Internally biased at about 0.54V. Applied voltage must stay below 2.5V. GND (Pins 2, 4, 6, 9, 10, 12, 15): Ground. Pins 6, 9, 15 and 17 (exposed pad) are connected to each other internally. Pins 2 and 4 are connected to each other internally and function as the ground return for the LO signal. Pins 10 and 12 are connected to each other internally and function as the ground return for the on-chip RF balun. For best RF performance, pins 2, 4, 6, 9, 10, 12, 15 and the Exposed Pad 17 should be connected to the printed circuit board ground plane. VCC (Pins 8, 13): Power Supply. Pins 8 and 13 are connected to each other internally. It is recommended to use 0.1µF capacitors for decoupling to ground on each of these pins. LO (Pin 3): LO Input. The LO input is an AC-coupled singleended input with approximately 50Ω input impedance at RF frequencies. Externally applied DC voltage should be within the range –0.5V to VCC + 0.5V in order to avoid turning on ESD protection diodes. BBPI, BBMI (Pins 14, 16): Baseband Inputs for the I-channel, each with 50Ω input impedance. Internally biased at about 0.54V. Applied voltage must stay below 2.5V. RF (Pin 11): RF Output. The RF output is an AC-coupled single-ended output with approximately 50Ω output impedance at RF frequencies. Externally applied DC voltage should be within the range –0.5V to VCC + 0.5V in order to avoid turning on ESD protection diodes. Exposed Pad (Pin 17): Ground. This pin must be soldered to the printed circuit board ground plane. 55682f 7 LT5568-2 W BLOCK DIAGRA VCC 8 13 LT5568-2 BBPI 14 V-I BBMI 16 11 RF 0° 90° BALUN BBPQ 7 1 EN V-I BBMQ 5 2 4 6 9 3 LO GND 10 12 15 17 55682 BD GND U U W U APPLICATIO S I FOR ATIO The LT5568-2 consists of I and Q input differential voltage-to-current converters, I and Q up-conversion mixers, an RF output balun, an LO quadrature phase generator and LO buffers. LT5568-2 RF C VCC = 5V BALUN FROM Q LOMI R1A 25Ω LOPI R2B 23Ω R1B 23Ω BBPI R2A 25Ω CM 12pF R3 R4 12pF Baseband Interface VREF = 540mV BBMI 55682 F01 GND Figure 1. Simplified Circuit Schematic of the LT5568-2 (Only I-Half is Drawn) External I and Q baseband signals are applied to the differential baseband input pins, BBPI, BBMI, and BBPQ, BBMQ. These voltage signals are converted to currents and translated to RF frequency by means of double-balanced up-converting mixers. The mixer outputs are combined in an RF output balun, which also transforms the output impedance to 50Ω. The center frequency of the resulting RF signal is equal to the LO signal frequency. The LO input drives a phase shifter which splits the LO signal into inphase and quadrature LO signals. These LO signals are then applied to on-chip buffers which drive the up-conversion mixers. Both the LO input and RF output are single-ended, 50Ω-matched and AC coupled. The baseband inputs (BBPI, BBMI), (BBPQ, BBMQ) present a differential input impedance of about 100Ω. At each of the four baseband inputs, a first-order lowpass filter using 25Ω 55682f 8 LT5568-2 U U W U APPLICATIO S I FOR ATIO and 12pF to ground is incorporated (see Figure 1), which limits the baseband bandwidth to approximately 330MHz (–1dB point). The common mode voltage is about 0.54V and is approximately constant over temperature. It is important that the applied common mode voltage level of the I and Q inputs is about 0.54V in order to properly bias the LT5568-2. Some I/Q test generators allow setting the common mode voltage independently. In this case, the common mode voltage of those generators must be set to 0.27V to match the LT5568-2 internal bias, because for DC signals, there is no –6dB source-load voltage division (see Figure 2). 50Ω + – 50Ω 0.27VDC 0.54VDC 50Ω GENERATOR 48Ω 0.54VDC + – 0.54VDC 0.54VDC GENERATOR + – LT5568-2 55682 F02 Figure 2. DC Voltage Levels for a Generator Programmed at 0.27VDC for a 50Ω Load and the LT5568-2 as a Load The baseband inputs should be driven differentially; otherwise, the even-order distortion products will degrade the overall linearity severely. Typically, a DAC will be the signal source for the LT5568-2. Reconstruction filters should be placed between the DAC output and the LT5568-2’s baseband inputs. In Figure 3, a typical baseband interface schematic for GSM is drawn. It shows a ground referenced DAC output interface followed by a 3rd order active OpAmp RC lowpass filter with a 400kHz cutoff frequency (–3dB). The DAC in this example sources a current from 0mA to 20mA, with a voltage compliance range of at least 0V to 1V. This interface is DC coupled, which allows adjustment of the DAC’s differential output current to minimize the LO feedthrough. The voltage swing at the LT5568-2 baseband inputs is about 2VP-P,DIFF, which results in a 1.2dBm GSM RF output power at 900MHz with noise floor of –154.3dBm/Hz at 6MHz offset (= –104.3dBm/100kHz). The RMS EVM is about 0.6%. The LT1819, which houses two LT1818s, can be used instead of U2 and U3. The total current in the positive supply is about 157mA and the current in the negative supply is about 40mA. C3 1nF VCC = 4.5 TO 5.25V R7 200Ω R9 249Ω 3 C1 1.2nF 0mA to 20mA + U2 LT1818 – 2 R5 53.6Ω R14 50Ω 0.54V 7 VCC 0.54V 6 R11 249Ω 4 V SS 0.54V R13 499Ω GND DAC 0mA to 20mA R6 53.6Ω R8 200Ω 2 R10 249Ω C2 1.2nF – 7 VCC U3 LT1818 + 4 V SS R12 249Ω 6 0.54V R15 50Ω LT5568-2 BALUN FROM Q C C5 10nF LOPI LOMI GND BBPI C4 3 1nF VSS = –2V to –5.25V RF = 1.2dBm, GSM C6 10nF R1 45Ω R2 45Ω CM R3 33Ω VREF = 540mV R4 33Ω 16mA BBMI U1 0.54V 55682 F03 GND Figure 3. LT5568-2 GSM Baseband Interface with 3rd Order Lowpass Filter and Ground Referenced DAC (Only I-Channel is Shown) 55682f 9 LT5568-2 U U W U APPLICATIO S I FOR ATIO LO Section The internal LO input amplifier performs single-ended to differential conversion of the LO input signal. Figure 4 shows the equivalent circuit schematic of the LO input. VCC 20pF LO INPUT 51Ω 5568 F04 Figure 4. Equivalent Circuit Schematic of the LO Input The internal, differential LO signal is then split into in-phase and quadrature (90° phase shifted) signals that drive LO buffer sections. These buffers drive the double balanced I and Q mixers. The phase relationship between the LO input and the internal in-phase LO and quadrature LO signals is fixed, and is independent of start-up conditions. The internal phase shifters are designed to deliver accurate quadrature signals. For LO frequencies significantly below 650MHz or above 1.25GHz, however, the quadrature accuracy will diminish, causing the image rejection to degrade. The LO pin input impedance is about 50Ω, and the recommended LO input power is 0dBm. For lower LO input power, the gain, OIP2, OIP3 and noise floor at PRF = 4dBm will degrade, especially for PLO below –2dBm and at TA = 85°C. For high LO input power (e.g., +5dBm), the image rejection will degrade with no improvement in linearity or gain. Harmonics present on the LO signal can degrade the image rejection because they can introduce a small excess phase shift in the internal phase splitter. For the second (at 1.8GHz) and third harmonics (at 2.7GHz) at –20dBc, the resulting signal at the image frequency is about –61dBc or lower, corresponding to an excess phase shift of much less than 1 degree. For the second and third LO harmonics at –10dBc, the introduced signal at the image frequency is about –51dBc. Higher harmonics than the third will have less impact. The LO return loss typically will be better than 11dB over the 700MHz to 1.05GHz range. Table 1 shows the LO port input impedance vs frequency. Table 1. LO Port Input Impedance vs Frequency for EN = High and PLO = 0dBm Frequency MHz Input Impedance Ω Mag S11 Angle 500 600 700 800 900 1000 1100 1200 47.5 + j12.1 59.4 + j8.4 66.2 – j1.14 67.2 – j13.4 61.1 – j23.9 53.3 – j26.8 48.2 – j26.1 42.0 – j27.4 0.126 0.115 0.140 0.185 0.232 0.252 0.258 0.297 95.0 37.8 –3.41 –31.7 –53.2 –68.7 –79.4 –90.0 If the part is in shutdown mode, the input impedance of the LO port will be different. The LO input impedance for EN = Low is given in Table 2. Table 2. LO Port Input Impedance vs Frequency for EN = Low and PLO = 0dBm Frequency MHz Input Impedance Ω Mag S11 Angle 500 600 700 800 900 1000 1100 1200 33.6 + j41.3 59.8 + j69.1 140 + j89.8 225 – j62.6 92.9 – j128 39.8 – j95.9 22.8 – j72.7 16.0 – j57.3 0.477 0.539 0.606 0.659 0.704 0.735 0.755 0.763 85.4 49.8 19.6 –6.8 –29.6 –45.5 –65.6 –79.7 RF Section After up-conversion, the RF outputs of the I and Q mixers are combined. An on-chip balun performs internal differential to single-ended output conversion, while transforming the output signal impedance to 50Ω. Table 3 shows the RF port output impedance vs frequency. Table 3. RF Port Output Impedance vs Frequency for EN = High and PLO = 0dBm Frequency MHz Input Impedance Ω Mag S22 Angle 500 600 700 800 900 1000 1100 1200 22.0 + j5.7 28.2 + j12.5 38.8 + j14.8 49.4 + j7.2 49.3 – j5.1 42.5 – j11.1 36.7 – j11.7 33.0 – j10.3 0.395 0.317 0.206 0.072 0.051 0.143 0.202 0.238 164.2 141.3 117.5 90.6 –94.7 –117.0 –130.7 –141.6 55682f 10 LT5568-2 U U W U APPLICATIO S I FOR ATIO The RF output S22 with no LO power applied is given in Table 4. Table 4. RF Port Output Impedance vs Frequency for EN = High and No LO Power Applied Frequency MHz Input Impedance Ω Mag S22 Angle 500 22.7 + j5.6 0.381 164.0 600 29.7 + j11.6 0.290 142.0 700 40.5 + j11.6 0.164 121.9 800 47.3 + j2.2 0.037 139.6 900 44.1 – j6.7 0.094 –126.9 1000 38.2 – j9.8 0.171 –133.9 1100 34.0 – j9.4 0.218 –143.1 1200 31.5 – j7.8 0.245 –151.6 For EN = Low the S22 is given in Table 5. Table 5. RF Port Output Impedance vs Frequency for EN = Low Frequency MHz Input Impedance Ω Mag S22 Angle 500 21.2 + j5.4 0.409 164.9 600 26.6 + j12.5 0.340 142.5 700 36.6 + j16.6 0.241 118.1 800 49.2 + j11.6 0.116 87.4 900 52.9 – j2.0 0.034 –33.1 1000 46.4 – j11.2 0.121 –101.1 1100 39.3 – j13.2 0.188 –120.6 1200 34.4 – j12.1 0.231 –133.8 VCC Note that an ESD diode is connected internally from the RF output to ground (see Figure 5). For strong output RF signal levels (higher than 3dBm), this ESD diode can degrade the linearity performance if the 50Ω termination impedance is connected directly to ground. To prevent this, a coupling capacitor can be inserted in the RF output line. This is strongly recommended during a 1dB compression measurement. Enable Interface Figure 6 shows a simplified schematic of the EN pin interface. The voltage necessary to turn on the LT5568-2 is 1V. To disable (shut down) the chip, the enable voltage must be below 0.5V. If the EN pin is not connected, the chip is disabled. This EN = Low condition is assured by the 75k on-chip pull-down resistor. It is important that the voltage at the EN pin does not exceed VCC by more than 0.5V. If this should occur, the supply current could be sourced through the EN pin ESD protection diodes, which are not designed to carry the full supply current, and damage may result. VCC EN 75k 25k 21pF RF OUTPUT 7nH 1pF 51Ω 55682 F06 55682 F05 Figure 5. Equivalent Circuit Schematic of the RF Output Figure 6. EN Pin Interface 55682f 11 LT5568-2 U U W U APPLICATIO S I FOR ATIO Evaluation Board Figure 7 shows the evaluation board schematic. A good ground connection is required for the exposed pad. If this is not done properly, the RF performance will degrade. Additionally, the exposed pad provides heat sinking for the part and minimizes the possibility of the chip overheating. J1 R1 (optional) limits the EN pin current in the event that the EN pin is pulled high while the VCC inputs are low. In Figures 8 and 9 the silk screens and the PCB board layout are shown. J2 BBMI BBPI VCC 16 R1 100Ω 1 VCC EN 2 J4 LO IN 3 4 15 14 C2 100nF 13 BBMI GND BBPI VCC EN GND GND RF LT5568-2 LO GND GND GND GND BBMQ GND BBPQ VCC 5 6 7 12 BBMQ RF OUT 10 9 17 8 C1 100nF J5 J3 11 J6 GND BBPQ BOARD NUMBER: DC1178A Figure 7. Evaluation Circuit Schematic 55682 F07 Figure 8. Component Side of Evaluation Board 55682 F09 Figure 9. Bottom Side of Evaluation Board 55682f 12 LT5568-2 U U W U APPLICATIO S I FOR ATIO Application Measurements The LT5568-2 is recommended for base-station applications using various modulation formats. Figure 10 shows a typical application. Figure 11 shows the ACPR performance for CDMA2000 using 1- and 3-carrier modulation. Figures 12 and 13 illustrate the 1- and 3-carrier CDMA2000 RF spectrum. To calculate ACPR, a correction is made for the spectrum analyzer noise floor. If the output power is high, the ACPR will be limited by the linearity performance of the part. If the output power is low, the ACPR will be limited by the noise performance of the part. In the middle, an optimum ACPR is observed. V-I I-CHANNEL 0° 1 EN 11 90° 7 Q-DAC 5 Q-CHANNEL BALUN V-I PA –60 –135 3-CH. ACPR –70 –145 3-CH. AltCPR 1-CH. AltCPR –80 BASEBAND GENERATOR 2, 4, 6, 9, 10, 12, 15, 17 3 VCO/SYNTHESIZER –125 DOWNLINK TEST MODEL 64 DPCH 1-CH. ACPR –155 NOISE FLOOR AT 30MHz OFFSET (dBm/Hz) 16 –50 ACPR, AltCPR (dBc) LT5568-2 14 The ACPR performance is sensitive to the amplitude match of the BBPI and BBMI (or BBPQ and BBMQ) inputs. This is because a difference in AC current amplitude will give rise to a difference in amplitude between the even-order harmonic products generated in the internal V-I converter. As a result, they will not cancel out entirely. Therefore, it is important to keep the currents in those pins exactly 5V 100nF x2 RF = 850MHz TO 965MHz VCC 8, 13 I-DAC Because of the LT5568-2’s very high dynamic range, the test equipment can limit the accuracy of the ACPR measurement. See Application Note 99. Consult the factory for advice on the ACPR measurement, if needed. 3-CH. NOISE 55682 F10 1-CH. NOISE –90 –30 –165 –25 –15 –10 –5 –20 RF OUTPUT POWER PER CARRIER (dBm) 55682 F11 Figure 11. ACPR, AltCPR and Noise CDMA2000 Modulation Figure 10. 850MHz to 965MHz Direct Conversion Transmitter Application POWER IN 30kHz BW (dBm) –40 –50 –60 –70 –80 –90 UNCORRECTED SPECTRUM –100 –30 DOWNLINK TEST MODEL 64 DPCH CORRECTED SPECTRUM –110 DOWNLINK TEST MODEL 64 DPCH –40 POWER IN 30kHz BW (dBm) –30 –50 –60 –70 –80 –90 UNCORRECTED SPECTRUM –100 –110 –120 –120 SPECTRUM ANALYSER NOISE FLOOR –130 896.25 897.75 899.25 900.75 902.25 903.75 RF FREQUENCY (MHz) –130 894 55682 F12 Figure 12. 1-Carrier CDMA2000 Spectrum CORRECTED SPECTRUM 896 SPECTRUM ANALYSER NOISE FLOOR 900 902 904 898 RF FREQUENCY (MHz) 906 55682 F13 Figure 13. 3-Carrier CDMA2000 Spectrum 55682f 13 LT5568-2 U U W U APPLICATIO S I FOR ATIO the same (but of opposite sign). The current will enter the LT5568-2’s common-base stage, and will flow to the mixer upper switches. This can be seen in Figure 1 where the internal circuit of the LT5568-2 is drawn. After calibration when the temperature changes, the LO feedthrough and the image rejection performance will 10 CALIBRATED WITH PRF = –10dBm –70 IMAGE REJECTION LO FEEDTHROUGH –80 EN = High fLO = 900MHz VCC = 5V fRF = fBB + fLO fBBI = 2MHz, 0° PLO = 0dBm fBBQ = 2MHz, 90° –90 40 20 0 80 60 –40 –20 TEMPERATURE (°C) 55682 F14 –10 85°C 25°C –20 –30 –40 85°C LOFT –40°C IR –50 85°C –60 25°C 25°C –70 –40°C –80 –90 55682 F15 –60 –40°C PRF 0 PRF (dBm), LOFT (dBm), IR (dBc) LO FEEDTHROUGH (dBm), IR (dBc) –50 change. This is illustrated in Figure 14. The LO feedthrough and image rejection can also change as a function of the baseband drive level, as is depicted in Figure 15. In Figure 16 the GSM EVM and noise performance vs RF output power is drawn. 0 1 3 4 5 2 I AND Q BASEBAND VOLTAGE (VP-P, DIFF) fBBI = 2MHz, 0° fBBQ = 2MHz, 90° VCC = 5V EN = High Figure 14. LO Feedthrough and Image Rejection vs Temperature after Calibration at 25°C fLO = 900MHz fRF = fBB + fLO PLO = 0dBm 5 –96 4 –98 3 –100 NOISE 2 –102 EVM –104 1 0 –10 NOISE FLOOR AT 6MHz OFFSET (dBc/100kHz) EVM (%RMS) Figure 15. LO Feedthrough and Image Rejection vs Baseband Drive Voltage after Calibration at 25°C 4 –8 –6 –4 –2 0 2 GSM RF OUTPUT POWER (dBm) 6 –106 55682 F16 Figure 16. GSM EVM and Noise vs RF Output Power at 900MHz 55682f 14 LT5568-2 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 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS BOTTOM VIEW—EXPOSED PAD 4.00 ± 0.10 (4 SIDES) 0.75 ± 0.05 R = 0.115 TYP 15 PIN 1 NOTCH R = 0.20 TYP OR 0.35 × 45° CHAMFER 16 0.55 ± 0.20 PIN 1 TOP MARK (NOTE 6) 1 2.15 ± 0.10 (4-SIDES) 2 (UF16) QFN 10-04 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. 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 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 55682f 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. 15 LT5568-2 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS Infrastructure 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 LT5518 1.5GHz to 2.4GHz High Linearity Direct Quadrature Modulator 22.8dBm OIP3 at 2GHz, –158.2dBm/Hz Noise Floor, 50Ω Single-Ended LO and RF Ports, 4-Ch W-CDMA ACPR = –64dBc at 2.14GHz 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 600MHz 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 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 IIP3 = 23.5dBm and NF = 12.5dB at 1900MHz, 4.5V to 5.25V Supply, ICC = 78mA LT5528 1.5GHz to 2.4GHz High Linearity Direct Quadrature Modulator 21.8dBm OIP3 at 2GHz, –159.3dBm/Hz Noise Floor, 50Ω, 0.5VDC Baseband Interface, 4-Ch W-CDMA ACPR = –66dBc at 2.14GHz LT5557 400MHz to 3.8GHz, 3.3V, Very High Linearity Downconverting Mixer IIP3 = 24.7dBm at 1.9GHz, 23.5dBm at 3.5GHz, Conversion Gain = 2.9dB at 1.9GHz, 3.3V at 82mA, –3dB LO Drive LT5558 600MHz to 1100MHz High Linearity Direct Quadrature Modulator 22.4dBm OIP3 at 900MHz, –158dBm/Hz Noise Floor, 3kΩ, 2.1VDC Baseband Interface, 3-Ch CDMA2000 ACPR = –70.4dBc at 900MHz LT5560 Ultra-Low Power Active Mixer 10mA Supply Current, 10dBm IIP3, 10dB NF, Usable as Up- or Down-Converter LT5568 700MHz to 1050MHz High Linearity Direct Quadrature Modulator 22.9dBm OIP3 at 850MHz, –160.3dBm/Hz Noise Floor, 50Ω, 0.5VDC Baseband Interface, 3-Ch CDMA2000 ACPR = –71.4dBc at 850MHz LT5572 1.5GHz to 2.5GHz High Linearity Direct Quadrature Modulator 21.6dBm OIP3 at 2GHz, –158.6dBm/Hz Noise Floor, High-Ohmic 0.5VDC Baseband Interface, 4-Ch W-CDMA ACPR = –67.7dBc at 2.14GHz LT5575 800MHz to 2.7GHz High Linearity Direct Conversion Quadrature Demodulator 28dBm IIP3 and 13.2dBm P1dB at 900MHz, 60dBm IIP2 and 12.7dB NF at 1900MHz RF Power Detectors LTC®5505 RF Power Detectors with >40dB Dynamic Range 300MHz to 3GHz, Temperature Compensated, 2.7V to 6V Supply LTC5507 100kHz to 1000MHz RF Power Detector 100kHz to 1GHz, Temperature Compensated, 2.7V to 6V Supply LTC5508 300MHz to 7GHz RF Power Detector 44dB Dynamic Range, Temperature Compensated, SC70 Package LTC5509 300MHz to 3GHz RF Power Detector 36dB Dynamic Range, Low Power Consumption, SC70 Package LTC5530 300MHz to 7GHz Precision RF Power Detector Precision VOUT Offset Control, Shutdown, Adjustable Gain LTC5531 300MHz to 7GHz Precision RF Power Detector Precision VOUT Offset Control, Shutdown, Adjustable Offset LTC5532 300MHz to 7GHz Precision RF Power Detector Precision VOUT Offset Control, Adjustable Gain and Offset LT5534 50MHz to 3GHz Log RF Power Detector with 60dB Dynamic Range ±1dB Output Variation over Temperature, 38ns Response Time LTC5536 Precision 600MHz to 7GHz RF Detector with Fast 25ns Response Time, Comparator Reference Input, Latch Enable Input, –26dBm to Comparator +12dBm Input Range LT5537 Wide Dynamic Range Log RF/IF Detector Low Frequency to 800MHz, 83dB Dynamic Range, 2.7V to 5.25V Supply 55682f 16 Linear Technology Corporation LT 0307 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2007