PDF RFMD2081 Data sheet ( Hoja de datos )

Número de pieza	RFMD2081
Descripción	45MHz TO 2700MHz IQ MODULATOR
Fabricantes	RFMD
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No Preview Available ! RFMD2081RFMD2081 45MHz TO 2700MHz IQ MODULATOR WITH SYNTHESIZER/VCO Package: QFN, 32-Pin, 5mm x 5mm Features  RF Output Frequency Range 45MHz to 2700MHz  Fractional-N Synthesizer with Very Low Spurious Levels  Typical Step Size 1.5Hz  Fully Integrated Wideband VCOs and LO Buffers  Integrated Phase Noise <0.2° rms at 1GHz  -40dBc Unadjusted Carrier Suppression  -40dBc Unadjusted Sideband Suppression  100MHz Baseband Input 3dB Bandwidth  Very Low Noise Floor -162dBm/Hz Typical  Output P1dB + 4dBm  Output IP3 + 17dBm  2.7V to 3.3V Power Supply  135mA Typical Current Consumption  Serial Programming Interface Applications  Satellite Communications  QPSK/QAM Modulators  Wireless Broadband  Point-to-Point  Software Defined Radios Phase det . Synth Ref. divider Functional Block Diagram Product Description The RFMD2081 is a low power, wideband, IQ modulator with integrated fractional-N synthesizer and voltage controlled oscillator (VCO). The modulator features an input 3dB bandwidth of 100MHz, and can generate output frequencies of between 45MHz and 2700MHz, making it suitable for a wide range of applications. The fractional-N synthesizer takes advantage of an advanced sigma-delta architecture that delivers ultra-fine step sizes and low spurious products. The synthesizer/VCO, combined with an external loop filter, allows the user to generate local oscillator (LO) signals from 90MHz to 5400MHz. The LO signal is buffered and routed to a high accuracy quadrature divider (/2) that drives the balanced I and Q mixers. The output of the mixers are summed and applied to a dif- ferential RF output stage. This device also features a differential input for an external VCO or LO source. Device programming is achieved via a simple 3-wire serial interface. In addition, a unique pro- gramming mode allows up to four devices to be controlled from a common serial bus. This elim- inates the need for separate chip-select control lines between each device and the host controller. Up to six general purpose outputs are provided, which can be used to access internal signals (the LOCK signal, for example) or to control front end components. The device is opti- mized for low power operation, consuming typically only 135mA from a 3V supply. DS140110 Optimum Technology Matching® Applied GaAs HBT GaAs MESFET InGaP HBT SiGe BiCMOS Si BiCMOS SiGe HBT GaAs pHEMT Si CMOS Si BJT GaN HEMT RF MEMS LDMOS RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ are trademarks of RFMD, LLC. BLUETOOTH is a trade- mark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks and registered trademarks are the property of their respective owners. ©2011, RF Micro Devices, Inc. 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 1 of 18 Free Datasheet http://www.Datasheet4U.com 1 page RFMD2081 Theory of Operation The RFMD2081 is a wideband IQ modulator with integrated fractional-N synthesizer and a low noise VCO core. It features a high accuracy LO quadrature divider followed by buffer circuits which drive the I and Q mixers of the modulator with the quadra- ture LO signals. The RFMD2081 has an integrated voltage reference and low drop out regulators supplying critical circuit blocks such as the VCOs and synthesizer. Synthesizer programming, device configuration and control are achieved through a mixture of hardware and software controls. All on-chip registers are programmed through a simple three-wire serial interface. VCO The VCO core in the RFMD2081 consists of three VCOs which, in conjunction with the integrated LO dividers of /1 to /32, cover the frequency range of 90MHz to 5400MHz. The modulator quadrature divider provides a further fixed divide by two to give the center frequency range at the modulator output of 45MHz to 2700MHz. Each VCO has 128 overlapping bands which are used to achieve low VCO gain and optimal phase noise performance across the whole tuning range. The chip automatically selects the correct VCO (VCO auto-select) and the correct VCO band (VCO coarse tuning) to generate the desired LO frequency based on the values programmed into the PLL1 and PLL2 registers banks. The VCO auto-select and VCO coarse tuning are triggered every time ENBL is taken high, or if the PLL re-lock self clearing bit is programmed high. Once the correct VCO and band have been selected the PLL will lock onto the correct frequency. During the band selection process fixed capacitance elements are progressively connected to the VCO resonant circuit until the VCO is oscillating at approximately the correct frequency. The output of this band selection, CT_CAL, is made available in the read- back register. A value of 127 or 0 in this register indicates that the coarse tuning was unsuccessful, and this should also be indicated by the CT_FAILED flag also available in the read-back register. A value between 1 and 126 indicates a successful cal- ibration, the actual value being dependent on the desired frequency as well as process variation for a particular device. The band select process will center the VCO tuning voltage at about 0.8V, compensating for manufacturing tolerances and pro- cess variation as well as environmental factors including temperature. In applications where the device is left enabled at the same LO frequency for some time it is recommended that automatic band selection be performed for every 30°C change in temperature. This assumes an active loop filter. The RFMD2081 features a differential LO input to allow the mixer to be driven from an external LO source. The fractional-N PLL can be used with an external VCO driven into this LO input, which may be useful to reduce phase noise in some applications. This may also require an external op-amp, dependant on the tuning voltage required by the external VCO. Fractional-N PLL The RFMD2081 contains a charge-pump based fractional-N phase locked loop (PLL) for controlling the three VCOs. The PLL includes automatic calibration systems to counteract the effects of process and environmental variations, ensuring repeatable loop response and phase noise performance. As well as the VCO auto-select and coarse tuning, there is a loop filter calibration mechanism which can be enabled if required. This operates by adjusting the charge pump current to maintain loop bandwidth. This can be useful for applications where the LO is tuned over a wide frequency range. The PLL has been designed to use a reference frequency of between 10MHz and 104MHz from an external source, which is typically a temperature controlled crystal oscillator (TCXO). A reference divider (divide by 1 to divide by 7) is supplied and should be programmed to limit the frequency at the phase detector to a maximum of 52MHz. Two PLL programming banks are provided, the first bank is preceded by the label PLL1 and the second bank is preceded by the label PLL2. The active register bank is selected by the state of the MODE pin, low for PLL1 and high for PLL2. The VCO outputs are first divided down in a high frequency prescalar. The output of this high frequency prescalar then enters the N divider, which is a fractional divider containing a dual-modulus prescalar and a digitally spur-compensated fractional sequence generator. This allows very fine frequency steps and minimizes fractional spurs. The fractional energy is randomized and appears as fractional noise at frequency offsets above 100kHz which will be attenuated by the loop filter. An external loop filter is used, giving flexibility in setting loop bandwidth for optimizing phase noise and lock time for example. DS140110 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 5 of 18 Free Datasheet http://www.Datasheet4U.com 5 Page Application Schematic RFMD2081 9 MODE/GP06 10 REF_IN 11 NC 12 TM 13 RF_OUT_N 14 RF_OUT_P 15 GPO1/ADD1 16 GPO2/ADD2 33 GND SDATA SCLK ENX RESETX NC NC GPO4/LD/DO GPO3/FM 32 31 30 29 28 27 26 25 DS140110 2 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 11 of 18 Free Datasheet http://www.Datasheet4U.com 11 Page

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