LMX2531 Frequency Synthesizer System with Integrated VCO
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The LMX2531 is a frequency synthesizer system with an integrated voltage-controlled oscillator (VCO) that offers several advantages over discrete and module solutions. It provides a frequency range of 553 to 2790 MHz with up to 10 dB better performance than competitors. The LMX2531 features a fractional-N phase-locked loop, low power consumption, high output power, and fast locking for applications such as 3G and 4G cellular base stations, wireless LAN, broadband wireless, and more. It is available in a small 6x6mm LLP package.
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LMX2531 Frequency Synthesizer System with Integrated VCO
- 4. Target Applications ■ 3G Cellular Base Stations (WCDMA, TDSCDMA, CDMA2000) ■ 2G Cellular Base Stations (GSM/GPRS, EDGE, CDMA1xRTT) ■ Wireless LAN ■ Broadband Wireless Access ■ Satellite Communications ■ Wireless Radio ■ Automotive ■ CATV Equipment ■ Instrumentation and Test Equipment ■ RFID Readers
- 6. Typical Performance Characteristics OSCin Input Impedance
- 8. Serial Data Timing Diagram
- 9. Mobile Radio and Handset Applications LMX2531 Enhances Performance and Frequency Coverage
- 10. Some Of The Typical Applications Wireless Base Station Applications Used as a local oscillator for up and down covert mixers in the radio, the LMX2531 can reduce synthesizer footprint and current consumption while improving the overall signal-to-noise ratio. The LMX2531 is suitable for variety of wireless standards including Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS), Worldwide interoperability for Microwave Access (WiMAX) and Code Division Multiple Access (CDMA). Wireless Meter Reading Applications Featuring an agile fractional-N PLL, the LMX2531 can be programmed to emulate frequency-shift-keying modulation for wireless concentrators in meter-reading applications. High-Speed Data Converter Clocking As a high-speed frequency clock source for giga sample data converters such as the ADC081500, the LMX2531 can maximize the Effective Number of Bits (ENOB) and enhance overall system performance.
Editor's Notes
- Welcome to the training module on the LMX2531 Frequency Synthesizer System with Integrated VCO by National Semiconductor.
- This training module gives an Overview on the LMX2531 including features and target applications, functional block diagrams, performance characteristics and the serial data timing diagram.
- The LMX2531 is a low power, high performance frequency synthesizer system which includes a fully integrated delta sigma PLL and VCO with fully integrated tank circuit. The third and fourth poles are also integrated and adjustable. Included are integrated ultra-low noise and high precision LDOs for the PLL and VCO, which gives higher supply noise immunity and a more consistent performance. National Semi’s LMX2531 family of frequency synthesizers, provide superior phase noise performance at low-power consumption. Featuring a fully integrated fractional-N Phase-Locked Loop (PLL), the LMX2531 is the ideal choice for low-power Radio Frequency (RF) and high-speed data converter applications.
- The following are some of the typical applications where the LMX LMX2531 can be used. They include 3G cellular base stations, wireless LAN, Satellite communications, wireless radio, Cable TV equipment, RFID readers and so on.
- This is the functional block diagram of LMX2531 device: It has a VCO or Vreg block, multiplexer, R-divider, N-divider, Pre-scaler, sigma-delta comparator, serial interface control, charge pump and fast lock block. The R divider divides the OSCin frequency down to the phase detector frequency. The R divider value, R, is restricted to the values of 1, 2, 4, 8, 16, and 32. The N divider in the LMX2531 includes fractional compensation and can achieve any fractional denominator between 1 and 4,194,303. The phase detector compares the outputs of the R and N dividers and puts out a correction current, corresponding to the phase error. It integrates the third pole (formed by R3 and C3) and fourth pole (formed by R4 and C4) of the loop filter. The values for C3, C4, R3, and R4 can also be programmed independently through the MICROWIRE interface and also R3 and R4 can be changed during FastLock™, for minimum lock time. It includes a fully integrated VCO, including the inductors. For optimum phase noise performance, this VCO has frequency and phase noise calibration algorithms. It has option of dividing the VCO output by two to get half of the VCO frequency at the Fout pin.
- The diagrams show typical performance characteristics of OSCin input impedance. And on the other side we show phase noise graph v/s frequency offset.
- This figure shows the typical connection diagram along with Microcontroller, power supply, and other capacitor connections.
- Here is the serial data timing diagram of this device. The DATA is clocked into a shift register on each rising edge of the CLK signal. On the rising edge of the LE signal, the data is sent from the shift registers to an actual counter. A slew rate of at least 30 V/μs is recommended for these signals. After the programming is complete, the CLK, DATA, and LE signals should be returned to a low state. LE can be kept high if bit R5[23] is changed to 0.
- This is a typical application of LMX2531. As a low power but high performance RF synthesizer, the LMX2531 can bring the much needed flexibility and performance to enhance integrated RF transceivers. In Long Term Evolution or WiMax mobile applications, the LMX2531 can not only improve the radio performance in the mobile device but also enable frequency bands not normally supported by the RF transceiver.
- This slide shows different applications that are implemented using LMX2531 device: like Wireless base station applications, wireless meter reading applications, high speed data converter clocking…Etc.
- Thank you for taking the time to view this presentation on LMX2531 . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simple call our sales hotline. For more technical information you may either visit the National Semiconductor site http://www.national.com/analog/timing/pll/lmx2531_devices or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility.