LMX2491 Low-Noise Fractional-N PLL

By Texas Instruments 42

LMX2491 Low-Noise Fractional-N PLL

Texas Insturments' LMX2491 device is a low-noise, 6.4 GHz, wideband, delta-sigma fractional-N PLL with ramp and chirp generation. It consists of a phase frequency detector, programmable charge pump, and high-frequency input for the external VCO. The LMX2491 supports a broad and flexible class of ramping capabilities including FSK, PSK, and configurable, piecewise, linear FM modulation profiles of up to eight segments. It supports fine PLL resolution and fast ramp with up to a 200 MHz phase detector rate. The LMX2491 allows any of its registers to be read back. The LMX2491 can operate with a single 3.3 V supply. Moreover, supporting up to a 5.25 V charge pump can eliminate the need of an external amplifier, leading to a simpler solution with improved phase noise performance.

Features
  • -227 dBc/Hz normalized PLL noise
  • 500 MHz to 6.4 GHz wideband PLL
  • 3.15 V to 5.25 V charge pump PLL supply
  • Versatile ramp and chirp generation
  • 200 MHz maximum phase detector frequency
  • FSK / PSK modulation pin
  • Digital lock detect
  • Single 3.3 V supply capability

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