LMX2491 - 6.4GHz Low Noise Fractional N PLL With Ramp/Chirp Generation

The 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 8 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 5.25-V charge pump can eliminate the need of external amplifier, leading to a simpler solution with improved phase noise performance.

• –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 / Chirp Generation
• 200-MHz Maximum Phase Detector Frequency
• FSK / PSK Modulation Pin
• Digital Lock Detect
• Single 3.3-V Supply Capability