LT5528EUF#PBF

LT5528 1.5GHz to 2.4GHz High Linearity Direct Quadrature Modulator DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LT®5528 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 PHS, GSM, EDGE, TD-SCDMA, CDMA, CDMA2000, W-CDMA and other systems. It may also be configured as an image reject up-converting 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. Direct Conversion to 1.5GHz to 2.4GHz High OIP3: 21.8dBm at 2GHz Low Output Noise Floor at 5MHz Offset: No RF: –159.3dBm/Hz POUT = 4dBm: –151.8dBm/Hz 4-Ch W-CDMA ACPR: –66dBc at 2.14GHz 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: –42dBm at 2GHz High Image Rejection: 45dB at 2GHz 16-Lead QFN 4mm × 4mm Package U APPLICATIO S ■ ■ Infrastructure Tx for DCS, PCS and UMTS Bands Image Reject Up-Converters for PCS and UMTS Bands Low-Noise Variable Phase-Shifter for 1.5GHz to 2.4GHz Local Oscillator Signals , LTC and LT are registered trademarks of Linear Technology Corporation. U ■ TYPICAL APPLICATIO 1.5GHz to 2.4GHz Direct Conversion Transmitter Application with LO Feed-Through and Image Calibration Loop 5V VCC 8, 13 –55 V-I EN 90° 5 PA 0° 1 7 Q-DAC 11 Q-CHANNEL BALUN LO FEED-THROUGH CAL OUT V-I IMAGE CAL OUT CAL BASEBAND DSP 4-CH ACPR –65 2-CH AltCPR –70 –150 2-CH ACPR 4-CH AltCPR –155 1-CH ACPR 1-CH AltCPR –75 4-CH NOISE 2, 4, 6, 9, 10, 12, 15, 17 –160 3 VCO/SYNTHESIZER –80 –42 ADC –140 –145 –60 I-CHANNEL ACPR, AltCPR (dBc) 16 DOWNLINK TEST MODEL 64 DPCH RF = 1.5GHz TO 2.4GHz 1-CH NOISE –38 –34 –30 –26 –22 –18 NOISE FLOOR AT 30MHz OFFSET (dBm/Hz) LT5528 14 I-DAC W-CDMA ACPR, AltCPR and Noise vs RF Output Power at 2140MHz for 1, 2 and 4 Channels –165 –14 RF OUTPUT POWER PER CARRIER (dBm) 5528 TA01a 5528 TA01b 5528f 1 LT5528 U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART NUMBER 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 EN 1 LT5528EUF 12 GND GND 2 11 RF 17 LO 3 10 GND GND 4 6 7 8 BBMQ GND BBPQ VCC 9 5 GND UF PART MARKING UF PACKAGE 16-LEAD (4mm × 4mm) PLASTIC QFN 5528A TJMAX = 125°C, θJA = 37°C/W EXPOSED PAD IS GROUND (PIN 17) MUST BE SOLDERED TO PCB. Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS VCC = 5V, EN = High, TA = 25°C, fLO = 2GHz, fRF = 2.002GHz, PLO = 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, Baseband Input Frequency = 2MHz, I&Q 90° shifted (upper sideband selection). PRF, OUT = –10dBm, unless otherwise noted. (Note 3) SYMBOL RF Output (RF) fRF S22, ON S22, OFF NFloor GP GV POUT G3LO vs LO OP1dB OIP2 OIP3 IR LOFT LO Input (LO) fLO PLO S11, ON S11, OFF NFLO GLO IIP3LO PARAMETER CONDITIONS RF Frequency Range RF Frequency Range –3dB Bandwidth –1dB Bandwidth RF Output Return Loss RF Output Return Loss RF Output Noise Floor EN = High (Note 6) EN = Low (Note 6) No Input Signal (Note 8) POUT = 4dBm (Note 9) POUT = 4dBm (Note 10) POUT/PIN, I&Q 20 • Log (VOUT, 50Ω/VIN, DIFF, I or Q) 1VP-P DIFF CW Signal, I and Q (Note 17) (Note 7) (Notes 13, 14) (Notes 13, 15) (Note 16) EN = High, PLO = 0dBm (Note 16) EN = Low, PLO = 0dBm (Note 16) Conversion Power Gain Conversion Voltage Gain Absolute Output Power 3 • LO Conversion Gain Difference Output 1dB Compression Output 2nd Order Intercept Output 3rd Order Intercept Image Rejection Carrier Leakage (LO Feed-Through) LO Frequency Range LO Input Power LO Input Return Loss LO Input Return Loss LO Input Referred Noise Figure LO to RF Small Signal Gain LO Input 3rd Order Intercept MIN MAX 1.5 to 2.4 1.7 to 2.2 1.5 to 2.4 0 –17 –5.5 14.4 20.4 –10 UNITS GHz GHz –15 –12 –159.3 –151.8 –151.8 –6.5 –6 –2.1 –28 7.9 49 21.8 –45 –42 –57.8 –10 EN = High (Note 6) EN = Low (Note 6) (Note 5) at 2GHz (Note 5) at 2GHz (Note 5) at 2GHz TYP dB dB dBm/Hz dBm/Hz dBm/Hz dB dB dBm dB dBm dBm dBm dBc dBm dBm 5 GHz dBm dB dB dB dB dBm 5528f 2 LT5528 ELECTRICAL CHARACTERISTICS VCC = 5V, EN = High, TA = 25°C, fLO = 2GHz, fRF = 2.002GHz, PLO = 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, Baseband Input Frequency = 2MHz, I&Q 90° shifted (upper sideband selection). PRF, OUT = –10dBm, unless otherwise noted. (Note 3) SYMBOL PARAMETER Baseband Inputs (BBPI, BBMI, BBPQ, BBMQ) BWBB Baseband Bandwidth VCMBB RIN, SE PLO2BB IP1dB ΔGI/Q ΔϕI/Q Power Supply (VCC) VCC ICC, ON DC Common Mode Voltage Single-Ended Input Resistance Carrier Feed-Through on BB Input 1dB Compression Point I/Q Absolute Gain Imbalance I/Q Absolute Phase Imbalance CONDITIONS MIN –3dB Bandwidth (Note 4) (Note 4) POUT = 0 (Note 4) Differential Peak-to-Peak (Note 7) Supply Voltage Supply Current ICC, OFF Supply Current, Sleep Mode tON Turn-On Time tOFF Turn-Off Time Enable (EN), Low = Off, High = On Enable Input High Voltage Input High Current Sleep Input Low Voltage 4.5 Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. 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 –1dB bandwidth. 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. MAX 400 0.525 45 –40 3.2 0.05 0.5 EN = High EN = 0V EN = Low to High (Note 11) EN = High to Low (Note 12) EN = High EN = 5V EN = Low TYP UNITS MHz V Ω dBm VP-P, DIFF dB Deg 5 5.25 V 125 0.05 0.25 1.3 145 50 mA µA µs µs 1.0 240 0.5 V µA V 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 feed-through 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 = 2GHz. 5528f 3 LT5528 U W TYPICAL PERFOR A CE CHARACTERISTICS VCC = 5V, EN = High, TA = 25°C, fLO = 2.14GHz, PLO = 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, 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) Gain and Output 1dB Compression vs LO Frequency and Supply Voltage Gain and Output 1dB Compression vs LO Frequency and Temperature Supply Current vs Supply Voltage 140 10 10 85°C 25°C 120 –40°C 110 0 –5 –10 GAIN –15 5.0 SUPPLY VOLTAGE (V) –20 1.3 5.5 1.7 1.9 2.1 2.3 LO FREQUENCY (GHz) 5528 G01 OIP3 (dBm) –148 OIP3 fBB, 1 = 2MHz fBB, 2 = 2.1MHz –150 16 –152 14 –154 12 10 NOISE FLOOR NO BASEBAND SIGNAL 20MHz OFFSET NOISE –156 8 6 1.3 1.5 1.7 1.9 2.1 2.3 LO FREQUENCY (GHz) 2.5 –20 1.3 2.7 22 20 18 1.5 1.7 1.9 2.1 2.3 LO FREQUENCY (GHz) OIP3 fBB, 1 = 2MHz fBB, 2 = 2.1MHz –148 –150 –152 14 –154 12 10 –160 8 6 1.3 NOISE FLOOR NO BASEBAND SIGNAL 20MHz OFFSET NOISE 1.7 1.9 2.1 2.3 LO FREQUENCY (GHz) –156 –158 2.5 –162 2.7 5528 G05 2.7 65 60 55 50 45 40 –160 1.5 2.5 Output IP2 vs LO Frequency 16 –158 –162 2.7 5528 G04 4.5V 5V 5.5V 5528 G03 NOISE FLOOR (dBm/Hz) 18 2.5 –142 4.5V 5V –144 5.5V –146 24 NOISE FLOOR (dBm/Hz) 20 26 OIP3 (dBm) 22 GAIN Output IP3 and Noise Floor vs LO Frequency and Supply Voltage –142 –40°C 25°C –144 85°C –146 24 –10 5528 G02 Output IP3 and Noise Floor vs LO Frequency and Temperature 26 –5 –15 –40°C 25°C 85°C 1.5 OP1dB 0 OIP2 (dBm) 100 4.5 5 OP1dB GAIN (dB), OP1dB (dBm) GAIN (dB), OP1dB (dBm) SUPPLY CURRENT (mA) 5 130 35 1.3 4.5V, 25°C 5V, –40°C 5V, 25°C 5V, 85°C 5.5V, 25°C 1.5 1.7 1.9 2.1 2.3 LO FREQUENCY (GHz) fIM2 = fBB,1 + fBB,2 + fLO fBB, 1 = 2MHz 2.5 2.7 fBB, 2 = 2.1MHz 5528 G06 5528f 4 LT5528 U W TYPICAL PERFOR A CE CHARACTERISTICS VCC = 5V, EN = High, TA = 25°C, fLO = 2.14GHz, PLO = 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, 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) 2 • LO Leakage to RF Output vs 2 • LO Frequency 3 • LO Leakage to RF Output vs 3 • LO Frequency –25 –30 LO to RF Output Feed-Through vs LO Frequency –30 –36 –35 –38 –40 –45 4.5V, 25°C 5V, –40°C 5V, 25°C 5V, 85°C 5.5V, 25°C –50 –55 2.6 3.0 3.4 3.8 4.2 4.6 5.0 2 • LO FREQUENCY (GHz) 5.4 –44 –50 –46 –55 –60 –65 –70 3.9 4.5 0.3 ABSOLUTE I/Q GAIN IMBALANCE (dB) IMAGE REJECTION (dBc) –32 –34 –36 –38 –40 –42 –44 –46 –48 1.3 1.5 1.7 1.9 2.1 2.3 LO FREQUENCY (GHz) 2.5 2.7 5528 G10 8.1 –54 1.3 1.5 1.7 1.9 2.1 2.3 LO FREQUENCY (GHz) Absolute I/Q Phase Imbalance vs LO Frequency 4.5V, 25°C 5V, –40°C 5V, 25°C 5V, 85°C 5.5V, 25°C 0.2 0.1 0 1.3 1.5 1.7 1.9 2.1 2.3 LO FREQUENCY (GHz) 2.5 2.7 2.5 5528 G09 Absolute I/Q Gain Imbalance vs LO Frequency –26 –30 –52 5528 G08 Image Rejection vs LO Frequency 4.5V, 25°C 5V, –40°C 5V, 25°C 5V, 85°C 5.5V, 25°C –50 5.1 5.7 6.3 6.9 7.5 3 • LO FREQUENCY (GHz) 5528 G07 –28 –48 4.5V, 25°C 5V, –40°C 5V, 25°C 5V, 85°C 5.5V, 25°C 2.7 5528 G11 5 ABSOLUTE I/Q PHASE IMBALANCE (DEG) –40 –42 –45 LOFT (dBm) P(3 • LO) (dBm) P(2 • LO) (dBm) –40 –35 4.5V, 25°C 5V, –40°C 5V, 25°C 5V, 85°C 5.5V, 25°C 4.5V, 25°C 5V, –40°C 5V, 25°C 5V, 85°C 5.5V, 25°C 4 3 2 1 0 1.3 1.5 1.7 1.9 2.1 2.3 LO FREQUENCY (GHz) 2.5 2.7 5528 G12 5528f 5 LT5528 U W TYPICAL PERFOR A CE CHARACTERISTICS VCC = 5V, EN = High, TA = 25°C, fLO = 2.14GHz, PLO = 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, 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) Gain vs LO Power RF Output Power, HD2 and HD3 at 2140MHz vs Baseband Voltage and Temperature Output IP3 vs LO Power –4 22 –10 –6 –20 –12 –14 12 10 4.5V, 25°C 5V, –40°C 5V, 25°C 5V, 85°C 5.5V, 25°C –16 –18 –16 –12 –8 –4 0 LO POWER (dBm) 4 HD2, HD3 (dBc) 14 OIP3 (dBm) GAIN (dB) 16 –10 8 4.5V, 25°C 5V, –40°C 5V, 25°C 5V, 85°C 5.5V, 25°C 6 4 2 0 –20 8 –16 –12 –8 –4 0 LO POWER (dBm) 4 –30 –10 –40 –20 HD2 –50 –30 –60 –40°C –40 25°C 85°C –50 1 2 3 4 5 I AND Q BASEBAND VOLTAGE (VP-P, DIFF) –70 8 fBB, 1 = 2MHz fBB, 2 = 2.1MHz 5528 G13 0 HD3 0 RF OUTPUT POWER (dBm) 18 –8 –20 –20 10 RF 20 fBBI = 2MHz, 0° fBBQ = 2MHz, 90° HD2 = MAX POWER AT fLO + 2 • fBB OR fLO – 2 • fBB HD3 = MAX POWER AT fLO + 3 • fBB OR fLO – 3 • fBB 5528 G14 5528 G15 RF Output Power, HD2 and HD3 at 2140MHz vs Baseband Voltage and Supply Voltage –10 LO Feed-Through and Image Rejection at 2140MHz vs Baseband Voltage and Temperature 10 –25 –40°C 25°C 85°C RF 0 HD2, HD3 (dBc) –30 –10 –40 –20 HD2 –50 –30 –60 –70 0 4.5V –40 5V 5.5V –50 1 2 3 4 5 I AND Q BASEBAND VOLTAGE (VP-P, DIFF) fBBI = 2MHz, 0° fBBQ = 2MHz, 90° HD2 = MAX POWER AT fLO + 2 • fBB OR fLO – 2 • fBB HD3 = MAX POWER AT fLO + 3 • fBB OR fLO – 3 • fBB RF OUTPUT POWER (dBm) HD3 –30 LOFT (dBm), IR (dBc) –20 LOFT –35 –40 IR –45 –50 0 1 2 3 4 5 I AND Q BASEBAND VOLTAGE (VP-P, DIFF) fBBI = 2MHz, 0° fBBQ = 2MHz, 90° 5528 G17 5528 G16 5528f 6 LT5528 U W TYPICAL PERFOR A CE CHARACTERISTICS VCC = 5V, EN = High, TA = 25°C, fLO = 2.14GHz, PLO = 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, 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) LO Feed-Through and Image Rejection at 2140MHz vs Baseband Voltage and Supply Voltage 4.5V 5V 5.5V –2 –35 –40 –20 –30 RF PORT, EN = HIGH, PLO = OFF IR –45 –50 1 2 3 4 5 I AND Q BASEBAND VOLTAGE (VP-P, DIFF) fBBI = 2MHz, 0° fBBQ = 2MHz, 90° –50 1.3 LO PORT, EN = HIGH RF PORT, EN = HIGH, PLO = 0dBm –40 0 0 LO PORT, EN = LOW –10 LOFT S11 (dB) LOFT (dBm), IR (dBc) –30 0 1.5 RF OUTPUT POWER (dBm) –25 RF Output Power vs RF Frequency at 1VP-P Differential Baseband Drive LO and RF Port Return Loss vs RF Frequency –4 –6 –8 –10 RF PORT, EN = LOW 1.7 1.9 2.1 2.3 RF FREQUENCY (GHz) 4.5V, 25°C 5V, –40°C 5V, 25°C 5V, 85°C 5.5V, 25°C –12 2.5 2.7 5528 G19 VBBI = 1VP-P, DIFF VBBQ = 1VP-P, DIFF –14 1.3 1.5 1.7 1.9 2.1 2.3 RF FREQUENCY (GHz) 2.5 2.7 5528 G20 5528 G18 U U U PI FU CTIO S EN (Pin 1): Enable Input. When the EN 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 45Ω input impedance. Internally biased at about 0.525V. 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. 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. BBPI, BBMI (Pins 14, 16): Baseband Inputs for the I-channel, each with 45Ω input impedance. These pins are internally biased at about 0.525V. Applied voltage must stay below 2.5V. Exposed Pad (Pin 17): Ground. This pin must be soldered to the printed circuit board ground plane. 5528f 7 LT5528 W BLOCK DIAGRA VCC 8 13 LT5528 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 5528 BD GND U U W U APPLICATIO S I FOR ATIO The LT5528 consists of I and Q input differential voltageto-current converters, I and Q up-conversion mixers, an RF output balun, an LO quadrature phase generator and LO buffers. LT5528 RF C VCC = 5V BALUN FROM Q LOMI R1A 20Ω R1B 23Ω LOPI R2B 23Ω BBPI R2A 20Ω CM 12pF R3 R4 12pF Baseband Interface VREF = 0.52V BBMI 5528 F01 GND Figure 1. Simplified Circuit Schematic of the LT5528 (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 90Ω. At each of the four baseband inputs, a first-order low-pass filter using 20Ω 5528f 8 LT5528 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 0.52V and is approximately constant over temperature. It is important that the applied common-mode voltage level of the I and Q inputs is about 0.52V in order to properly bias the LT5528. 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 0.26V to match the LT5528 internal bias, because for DC signals, there is no –6dB source-load voltage division (see Figure 2). 50Ω + – 50Ω 0.26VDC 0.52VDC 50Ω + – GENERATOR 45Ω 0.52VDC 0.52VDC 0.52VDC GENERATOR + – LT5528 5528 F02 Figure 2. DC Voltage Levels for a Generator Programmed at 0.26VDC for a 50Ω Load and the LT5528 as a Load It is recommended that the part 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 LT5528. To prevent aliasing, a filter should be placed between the DAC output and the LT5528’s baseband inputs. In Figure 3, an example interface schematic shows a commonly used DAC output interface followed by a passive 5th order ladder filter. The DAC in this example sources a current from 0mA to 20mA. The interface may be DC coupled. This allows adjustment of the DAC’s differential output current to minimize the LO feed-through. Optionally, transformer T1 can be inserted to improve the current balance in the BBPI and BBMI pins. This will improve the second-order distortion performance (OIP2). The maximum single sideband CW RF output power at 2GHz using 20mA drive to both I and Q channels with the configuration shown in Figure 3 is about –2.5dBm. The maximum CW output power can be increased by connecting resistors R5 and R6 to –5V instead of GND, and changing their values to 550Ω. In that case, the maximum single sideband CW RF output power at 2GHz will be about 2.3dBm. In addition, the ladder filter component values require adjustment for a higher source impedance. VCC = 5V LT5528 BALUN RF = –2.5dBm, MAX C LOMI 0.5V 0mA TO 20mA L1A L2A C2 GND R6, 50Ω L1B L2B R4 R3 C3 VREF = 0.52V • 0mA TO 20mA R2 45Ω R1 45Ω CM • C1 BBPI T1 1:1 R5, 50Ω DAC OPTIONAL LOPI BBMI 0.5V 5528 F03 GND Figure 3. LT5528 5th Order Filtered Baseband Interface with Common DAC (Only I-Channel is Shown) 5528f 9 LT5528 U W U U APPLICATIO S I FOR ATIO Table 1. LO Port Input Impedance vs Frequency for EN = High 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 ZIN ≈ 57Ω Frequency MHz 1000 1400 1600 1800 2000 2200 2400 2600 Input Impedance Ω 49.9 + j18.5 68.1 + j8.8 71.0 + j2.0 70.0 – j8.6 62.0 – j12.8 53.8 – j13.6 47.3 – j12.4 41.1 – j12.0 S11 Mag 0.182 0.171 0.175 0.182 0.156 0.135 0.128 0.161 Angle 80 22 4.8 –6.6 –40 –66 –95 –119 5528 F04 Figure 4. Equivalent Circuit Schematic of the LO Input The internal, differential LO signal is then split into inphase 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 phase shifters are designed to deliver accurate quadrature signals for an LO frequency near 2GHz. For frequencies significantly below 1.8GHz or above 2.4GHz, 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 dynamicrange will degrade, especially below –5dBm and at TA = 85°C. For high LO input power (e.g. 5dBm), the LO feedthrough will increase 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 4GHz) and third harmonics (at 6GHz) at –20dBc level, the introduced signal at the image frequency is about –56dBc or lower, corresponding to an excess phase shift much below 1 degree. For the second and third harmonics at –10dBc, the introduced signal at the image frequency is about –47dBc. Higher harmonics than the third will have less impact. The LO return loss typically will be better than 17dB over the 1.7GHz to 2.3GHz range. Table 1 shows the LO port input impedance vs. frequency. If the part is in shut-down 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 Frequency MHz 1000 1400 1600 1800 2000 2200 2400 2600 Input Impedance Ω 46.6 + j47.6 136 + j44.5 157 – j24.5 114 – j70.6 70.7 – j72.1 45.3 – j59.0 31.2 – j45.2 22.8 – j34.2 S11 Mag 0.443 0.507 0.526 0.533 0.533 0.528 0.527 0.543 Angle 67.8 13.8 –6.2 –24.6 –43.2 –62.8 –83.5 –103 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 1000 1400 1600 1800 2000 2200 2400 2600 Output Impedance Ω 23.1 + j7.9 34.4 + j20.7 45.8 + j22.3 54.5 + j12.4 48.7 + j1.7 39.1 + j1.0 32.9 + j4.4 29.7 + j7.4 S22 Mag 0.382 0.298 0.231 0.125 0.022 0.123 0.213 0.269 Angle 158 113 87.6 63.2 127 174 163 155 5528f 10 LT5528 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 1000 1400 1600 1800 2000 2200 2400 2600 Output Impedance Ω 23.7 + j8.1 37.7 + j18.5 47.0 + j14.3 46.0 + j5.5 39.2 + j3.7 34.2 + j6.2 31.0 + j9.4 29.6 + j11.6 Enable Interface S22 Mag 0.371 0.248 0.149 0.071 0.127 0.201 0.260 0.292 Angle 157 112 93.6 123 159 154 147 142 For EN = Low the S22 is given in Table 5. Table 5. RF Port Output Impedance vs Frequency for EN = Low Frequency MHz 1000 1400 1600 1800 2000 2200 2400 2600 Output Impedance Ω 22.8 + j7.7 32.4 + j20.8 42.4 + j25.1 54.6 + j20.1 55.3 + j6.0 44.7 + j0.0 36.0 + j1.9 31.3 + j4.8 coupling capacitor can be inserted in the RF output line. This is strongly recommended during a 1dB compression measurement. Figure 6 shows a simplified schematic of the EN pin interface. The voltage necessary to turn on the LT5528 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 guaranteed 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. S22 Mag 0.386 0.321 0.274 0.193 0.076 0.056 0.164 0.237 VCC Angle 158 116 91.7 66.2 45.3 180 171 162 To improve S22 for lower frequencies, a shunt capacitor can be added to the output. At higher frequencies, a shunt inductor can improve the S22. Figure 5 shows the equivalent circuit schematic of the RF output. EN 75k 25k 5528 F06 Figure 6. EN Pin Interface 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. J1 Note that an ESD diode is connected internally from the RF output to ground. 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 J2 BBIM BBIP VCC 16 R1 100Ω 1 VCC EN 2 J4 LO IN 3 4 VCC 15 14 C2 100nF 13 BBMI GND BBPI VCC EN GND GND RF LT5528 LO GND GND GND GND BBMQ GND BBPQ VCC 20pF 5 RF OUTPUT 3nH 21pF 52.5Ω 6 7 12 BBQM RF OUT 10 9 17 8 C1 100nF J5 J3 11 GND J6 BBQP 5528 F05 BOARD NUMBER: DC729A Figure 5. Equivalent Circuit Schematic of the RF Output 5528 F07 Figure 7. Evaluation Circuit Schematic 5528f 11 LT5528 U W U U APPLICATIO S I FOR ATIO Additionally, the exposed pad provides heat sinking for the part and minimizes the possibility of the chip overheating. If improved LO and Image suppression are required, an LO feed-through calibration and an Image suppression calibration can be performed. The evaluation board schematic of the calibration hardware, the calibration procedure and the results are described in an application note. R1 (optional) limits the Enable pin current in the event that the Enable pin is pulled high while the VCC inputs are low. In Figures 8, 9, 10 and 11, the silk screens and the PCB board layout are shown. Figure 8. Component Side Silk Screen of Evaluation Board Figure 9. Component Side Layout of Evaluation Board Figure 10. Bottom Side Silk Screen of Evaluation Board Figure 11. Bottom Side Layout of Evaluation Board 5528f 12 LT5528 U U W U APPLICATIO S I FOR ATIO Application Measurements Because of the LT5528’s very high dynamic-range, the test equipment can limit the accuracy of the ACPR measurement. Consult the factory for advice on the ACPR measurement, if needed. The LT5528 is recommended for base-station applications using various modulation formats. Figure 12 shows a typical application. The CAL box in Figure 12 allows for LO feed-through and Image suppression calibration. The ACPR performance is sensitive to the amplitude match of the BBIP and BBIM (or BBQP and BBQM) 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 the same (but of opposite sign). The current will enter the LT5528’s common-base stage, and will flow to the mixer upper switches. This can be seen in Figure 1 where the Figure 13 shows the ACPR performance for W-CDMA using one, two or four channel modulation. Figures 14, 15 and 16 illustrate the 1-, 2- and 4-channel W-CDMA measurement. 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 obtained. 5V VCC 8, 13 LT5528 EN 90° 7 Q-DAC PA BALUN LO FEED-THROUGH CAL OUT V-I 5 IMAGE CAL OUT CAL BASEBAND GENERATOR 4-CH ACPR –65 2-CH AltCPR –70 1-CH AltCPR –150 2-CH ACPR 4-CH AltCPR –155 1-CH ACPR –75 4-CH NOISE 3 VCO/SYNTHESIZER 2, 4, 6, 9, 10, 12, 15, 17 –80 –42 ADC –140 –145 –60 11 0° Q-CHANNEL DOWNLINK TEST MODEL 64 DPCH 5528 F12 –160 1-CH NOISE NOISE FLOOR AT 30MHz OFFSET (dBm/Hz) I-CHANNEL 1 –55 RF = 1.5GHz TO 2.4GHz V-I 16 ACPR, AltCPR (dBc) 14 I-DAC –165 –26 –22 –18 –14 RF OUTPUT POWER PER CARRIER (dBm) –38 –34 –30 5528 F13 Figure 12. 1.5GHz to 2.4GHz Direct Conversion Transmitter Application with LO Feed-Through and Image Calibration Loop –50 –60 –70 UNCORRECTED SPECTRUM CORRECTED SPECTRUM –90 –100 –110 –120 2127.5 2152.5 5528 F14 Figure 14: 1-Channel W-CDMA Spectrum –40 DOWNLINK TEST –40 MODEL 64 DPCH –50 –60 –70 –80 UNCORRECTED SPECTRUM CORRECTED SPECTRUM –90 –100 –110 SYSTEM NOISE FLOOR 2132.5 2137.5 2142.5 2147.5 RF FREQUENCY (MHz) POWER IN 30kHz BW (dBm) POWER IN 30kHz BW (dBm) –40 –80 –30 DOWNLINK TEST MODEL 64 DPCH –120 2125 2135 2140 2145 2150 RF FREQUENCY (MHz) DOWNLINK –50 TEST MODEL 64 –60 DPCH –70 –80 –90 2155 5528 F15 Figure 15: 2-Channel W-CDMA Spectrum UNCORRECTED SPECTRUM CORRECTED SPECTRUM –100 –110 –120 SYSTEM NOISE FLOOR 2130 POWER IN 30kHz BW (dBm) –30 Figure 13: W-CDMA APCR, AltCPR and Noise vs RF Output Power at 2140MHz for 1, 2 and 4 Channels SYSTEM NOISE FLOOR CORRECTED SPECTRUM –130 2115 2125 2135 2145 2155 RF FREQUENCY (MHz) 2165 5528 F16 Figure 16: 4-Channel W-CDMA Spectrum 5528f 13 LT5528 U W U U APPLICATIO S I FOR ATIO internal circuit of the LT5528 is drawn. For best results, a high ohmic source is recommended; for example, the interface circuit drawn in Figure 3, modified by pulling resistors R5 and R6 to a –5V supply and adjusting their values to 550Ω, with T1 omitted. secondary in combination with the required impedance match. The secondary center tap should not be connected, which allows some voltage swing if there is a singleended input impedance difference at the baseband pins. As a result, both currents will be equal. The disadvantage is that there is no DC coupling, so the LO feed-through calibration cannot be performed via the BB connections. After calibration when the temperature changes, the LO feed-through and the Image Rejection performance will change. This is illustrated in Figure 17. The LO feed-through and Image Rejection can also change as a function of the baseband drive level, as is depicted in Figure 18. The RF output power, IM2 and IM3 vs a two-tone baseband drive are given in Figure 19. Another method to reduce current mismatch between the currents flowing in the BBIP and BBIM pins (or the BBQP and BBQM pins) is to use a 1:1 transformer with the two windings in the DC path (T1 in Figure 3). For DC, the transformer forms a short, and for AC, the transformer will reduce the common-mode current component, which forces the two currents to be better matched. Alternatively, a transformer with 1:2 impedance ratio can be used, which gives a convenient DC separation between primary and –50 –20 LOFT (dBm), IR (dBc) –60 –65 –70 IMAGE REJECTION –75 –80 CALIBRATED WITH PRF = –10dBm –85 –40 –20 0 20 40 TEMPERATURE (°C) EN = HIGH VCC = 5V fBBI = 2MHz, 0° fBBQ = 2MHz, 90° 0 –30 LO FEED-THROUGH 60 –40 fLO = 2.14GHz fRF = fBB + fLO PLO = 0dBm IR –60 Figure 17: LO Feed-Through and Image Rejection vs Temperature after Calibration at 25°C PRF, EACH TONE (dBm), IM2, IM3 (dBm) 10 0 –10 –30 –70 –40 –80 –40°C –50 25°C 85°C –60 1 2 3 4 5 I AND Q BASEBAND VOLTAGE (VP-P, DIFF) 0 EN = HIGH VCC = 5V fBBI = 2MHz, 0° fBBQ = 2MHz, 90° 5528 F18 –10 –20 –50 –90 80 LOFT PRF (dBm) LOFT (dBm), IR (dB) –55 10 PRF fLO = 2.14GHz fRF = fBB + fLO PLO = 0dBm 5528 F18 Figure 18: LO Feed-Through and Image Rejection vs Baseband Drive Voltage after Calibration at 25°C PRF IM3 –20 –30 –40 –50 IM2 –60 –70 –80 –40°C 25°C 85°C –90 1 0.1 10 I AND Q BASEBAND VOLTAGE (VP-P, DIFF EACH TONE) EN = HIGH fLO = 2.14GHz VCC = 5V fRF = fBB + fLO PLO = 0dBm fBBI = 2MHz, 2.1MHz, 0° fBBQ = 2MHz, 2.1MHz, 90° IM2 = POWER AT fLO + 4.1MHz IM3 = MAX POWER AT fLO + 1.9MHz OR fLO + 2.2MHz 5528 F19 Figure 19: RF Two-Tone Power, IM2 and IM3 at 2140MHz vs Baseband Voltage 5528f 14 LT5528 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 PIN 1 TOP MARK (NOTE 6) 0.55 ± 0.20 15 16 1 2.15 ± 0.10 (4-SIDES) 2 (UF) QFN 1103 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 5528f 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 LT5528 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS Infrastructure LT5511 High Linearity Upconverting Mixer RF Output to 3GHz, 17dBm IIP3, Integrated LO Buffer LT5512 DC-3GHz High Signal Level Downconverting Mixer DC 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 20dBm IIP3, Integrated LO Quadrature Generator Demodulator LT5516 0.8GHz to 1.5GHz Direct Conversion Quadrature 21.5dBm IIP3, Integrated LO Quadrature Generator Demodulator 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 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 LT5524 Low Power, Low Distortion ADC Driver with Digitally Programmable Gain 450MHz Bandwidth, 40dBm OIP3, 4.5dB to 27dB Gain Control LT5526 High Linearity, Low Power Downconverting Mixer 3V to 5.3V Supply, 16.5dBm IIP3, 100kHz to 2GHz RF, NF = 11dB, IS = 28mA, –65dBm LO-RF Leakage RF Power Detectors LT5504 800MHz to 2.7GHz RF Measuring Receiver 80dB Dynamic Range, Temperature Compensated, 2.7V to 5.25V Supply LTC5505 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 RF Power Detector with 60dB Dynamic Range ±1dB Output Variation over Temperature, 38ns Response Time Low Voltage RF Building Blocks LT5500 1.8GHz to 2.7GHz Receiver Front End 1.8V to 5.25V Supply, Dual-Gain LNA, Mixer, LO Buffer LT5502 400MHz Quadrature IF Demodulator with RSSI 1.8V to 5.25V Supply, 70MHz to 400MHz IF, 84dB Limiting Gain, 90dB RSSI Range LT5503 1.2GHz to 2.7GHz Direct IQ Modulator and Upconverting Mixer 1.8V to 5.25V Supply, Four-Step RF Power Control, 120MHz Modulation Bandwidth LT5506 500MHz Quadrature Demodulator with VGA 1.8V to 5.25V Supply, 40MHz to 500MHz IF, –4dB to 57dB Linear Power Gain, 8.8MHz Baseband Bandwidth LT5546 500MHz Quadrature Demodulator with VGA and 17MHz Baseband Bandwidth, 40MHz to 500MHz IF, 1.8V to 5.25V Supply, –7dB to 17MHz Baseband Bandwidth 56dB Linear Power Gain Wide Bandwidth ADCs LTC1749 12-Bit, 80Msps 500MHz BW S/H, 71.8dB SNR LTC1750 14-Bit, 80Msps 500MHz BW S/H, 75.5dB SNR 5528f 16 Linear Technology Corporation LT/TP 1104 1K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2004