PDF RF2512 Data sheet ( Hoja de datos )

Número de pieza	RF2512
Descripción	UHF TRANSMITTER
Fabricantes	RF Micro Devices
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No Preview Available ! 11 Typical Applications • Single- or Dual-Channel LO Source • FM/FSK Transmitter • Wireless Data Transmitters RF2512 UHF TRANSMITTER • 433/868/915MHz ISM Band Systems • Wireless Security Systems Product Description The RF2512 is a monolithic integrated circuit intended for use as a low-cost frequency synthesizer and transmitter. The device is provided in a 24 pin SSOP package and is designed to provide a phased locked frequency source for use in local oscillator or transmitter applications. The chip can be used in FM or FSK applications in the U.S. 915MHz ISM band and European 433MHz or 868MHz ISM band. The integrated VCO, dual-modulus/dual-divide (128/129 or 64/65) prescaler, and reference oscillator require only the addition of an external crystal to provide a complete phase-locked oscillator. A second reference oscillator is available to support two channel applications. 0.157 0.150 1 0.344 0.337 0.012 0.008 0.025 0.2440 0.2284 8°MAX 0°MIN 0.0098 0.0040 0.0688 0.0532 0.050 0.0098 0.016 0.0075 Optimum Technology Matching® Applied üSi BJT GaAs HBT GaAs MESFET Si Bi-CMOS SiGe HBT Si CMOS 7 16 18 20 23 13 Gain Control TX OUT 8 Phase Detector & Charge Pump Prescaler 128/129 or 64/65 321 Ref. Select 24 OSC SEL 12 PRESCL OUT 14 MOD CTRL 15 DIV CTRL Functional Block Diagram Package Style: SSOP-24 Features • Fully Integrated PLL Circuit • 15mW Output Power at 433MHz • 2.7V to 5.0V Supply Voltage • Low Current and Power Down Capability • 300MHz to 1000MHz Frequency Range • Narrowband and Wideband FM Ordering Information RF2512 UHF Transmitter RF2512 PCBA-L Fully Assembled Evaluation Board, 433MHz RF2512 PCBA-M Fully Assembled Evaluation Board, 868MHz RF2512 PCBA-H Fully Assembled Evaluation Board, 915MHz RF Micro Devices, Inc. 7625 Thorndike Road Greensboro, NC 27409, USA Tel (336) 664 1233 Fax (336) 664 0454 http://www.rfmd.com 11 Rev B9 010509 11-11 1 page RF2512 RF2512 Theory of Operation Introduction The RF2512 is a low cost FM/FSK UHF transmitter designed for applications operating within the fre- quency range of 300MHz to 1000MHz. In particular, it is intended for 315/433/868MHz band systems, remote keyless entry systems, and FCC Part 15.231 periodic transmitters. It can also be used as a single- or dual- channel local oscillator signal source. The integrated VCO, phase detector, prescaler, and reference oscilla- tor require only the addition of an external crystal to provide a complete phase-locked loop. The RF2512 is provided in a 24-pin SSOP-24 package and is designed to operate from a supply voltage rang- ing from 2.2V to 5.0V, accommodating designs using three NiCd battery cells, two AAA flashlight cells, or a lithium button battery. The device is capable of provid- ing up to 15mW output power into a 50Ω load (+11.8dBm) and is intended to comply with FCC requirements for unlicensed remote control transmit- ters. RF2512 Functional Blocks A PLL consists of a reference oscillator, a phase detec- tor, a loop filter, a voltage controlled oscillator (VCO), and a programmable divider in the feedback path. The RF2512 includes all of these internally except for the loop filter and the reference oscillator's crystal and two feedback capacitors. The reference oscillators are Colpitts type oscillators. Pin 1 (OSC B2), pin 2 (OSC E), and pin 3 (OSC B1) provide connections to the internal transistors that are used as the reference oscillators. The Colpitts configu- ration is a low parts count topology with reliable perfor- mance and reasonable phase noise. Alternatively, an external signal could be injected into the base of either transistor. The drive level should, in either case, be around 500mVPP. This level prevents overdriving the device and keeps the phase noise and reference spurs to a minimum. The user sets which oscillator is operational by setting pin 24 (OSC SEL) either high or low. This allows the implementation of two channel systems. The prescaler divides the Voltage Controlled Oscilla- tor (VCO) frequency down by either 64/65 or 128/129, using a series of flip-flops, depending upon the logic level present at pin 15 (DIV CTRL). A high logic level will select the 64/65 divisor. A low logic level will select the 128/129 divisor. This divided signal is then fed into Rev B9 010509 the phase detector where it is compared with the refer- ence frequency. In addition to the DIV CTRL setting, one also sets the prescaler modulus by setting pin 14 (MOD CTRL) either high or low. A high logic level will select the 64/ 128 divisor. A low logic level will select the 65/129 divi- sor. Pin 12 (PRESCL OUT) provides access to the pres- caler output. This is used for interfacing to an external PLL IC. The RF2512 contains an onboard phase detector and charge pump. The phase detector compares the phase of the reference oscillator to the phase of the VCO. The phase detector is implemented using flip- flops in a topology referred to as either "digital phase/ frequency detector" or "digital tri-state comparator". The circuit consists of two D flip-flops whose outputs are combined with a NAND gate which is then tied to the reset on each flip-flop. The outputs of the flip-flops are also connected to the charge pump. Each flip-flop output signal is a series of pulses whose frequency is related to the flip-flop input frequency. When both inputs of the flip-flops are identical, the sig- nals are both frequency and phase locked. If they are different, they will provide signals to the charge pump which will either charge or discharge the loop filter or enter into a high impedance state. This is where the name "tri-state comparator" comes from. The main benefit of this type of detector it's ability to correct for errors in both phase and frequency. When locked, the detector uses phase error for correction. When unlocked, it will use the frequency error for cor- rection. This type of detector will lock under all condi- tions. The prescaler and the phase detector bias voltage is brought out through pin 13 (VREF P). This allows bypassing of the of these two circuits to filter the refer- ence crystal frequency. The charge pump consists of two transistors, one for charging the loop filter and the other for discharging the loop filter. It's inputs are the outputs of the phase detector flip-flops. Since there are two flip-flops, there are four possible states. If both amplifier inputs are low, then the amplifier pair goes into a high impedance state, maintaining the charge on the loop filter. The 11 11-15 5 Page RF2512 Evaluation Board Schematic L (433MHz) Board AUDIO R7* 0Ω R5* 0Ω R6* 0Ω X2* D3* D2* 6.612813 MHz C3 100 pF C2* 100 pF PLL ON VCC C4 C5 0.01 uF 22 pF LVL ADJ J1 RF OUT 50 Ω µstrip C18 0.1 uF L1 22 nH C19 8 pF C6 15 pF L2 22 nH C7 8 pF VCC C9 10 nF C10 22 pF C20 3-10 pF X1 6.78 MHz P1-1 P1 1 LVL ADJ 2 GND P1-3 3 PLL ON CON3 P2-1 P2 1 PRESC OUT P3-1 2 GND P2-3 3 TX EN CON3 P3-3 P3 1 AUDIO 2 GND 3 OSCSLT 4 GND P3-5 5 VCC CON5 P4-1 P4 1 DIV 64 2 GND P4-3 3 MOD CTL CON3 C1 100 pF C8 100 pF 1 Ref 2 Select 3 4 Phase 5 Detector/ Charge Pump 6 Gain 7 Control 8 9 10 Prescaler 11 24 OSC SEL 23 L3 22 27 nH 21 D1 SMV 1233-011 20 C15 L4 19 5 pF 27 nH R2 4.3 kΩ C16 47 nF R1 2 kΩ C17 4.7 nF 18 L5 C12 C13 C14 220 nH 10 nF 22 pF 4.7 µF 17 50 Ω µstrip J2 16 MOD IN 15 DIV 64 14 MOD CTL TX EN PRESC OUT R3* TBD 12 13 C11 0.1 µF *Denotes optional. These parts are not normally populated. 2512400A 11 Rev B9 010509 11-21 11 Page

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