industry news
Subscribe Now

Ultralow Noise & Spurs 373MHz to 5.79GHz Integer-N Synthesizers with Integrated VCO Improve System Performance

MILPITAS, CA – September 28, 2011 – Linear Technology announces the LTC6946, the first device in a family of high performance integer-N frequency synthesizers with integrated VCO, delivering -226dBc/Hz normalized closed-loop in-band phase noise, superior -274dBc/Hz normalized in-band 1/f noise, and best-in-class -103dBc spurious output. In a typical 900MHz application, these performance attributes help to achieve a closed-loop phase noise of
-100dBc/Hz at 1kHz offset. The device is available in three frequency options: the LTC6946-1 tunes from 2.240GHz to 3.740GHz; the LTC6946-2 from 3.080GHz to 4.910GHz; and the LTC6946-3 covers 3.840GHz to 5.790GHz. In addition, each part has an on-chip output divider that is programmable from 1 through 6 to extend frequency coverage to as low as 373MHz.

This family of devices integrates a low noise 5.7GHz phase-locked loop (PLL), which includes a reference divider, phase-frequency detector (PFD) with phase-locked indicator, ultralow noise charge pump, and integer feedback divider to attain very low noise PLL operation. The PLL circuit is tightly coupled to a low noise VCO as well as internal self-calibration to ensure optimum VCO resonator tuning for best phase noise performance. The VCO requires no external components. The on-chip SPI compatible bidirectional serial port allows frequency tuning and control, and read back of register and loop status information.

The low phase noise and spurious capabilities of this family of frequency synthesizers enhance the performance of multiband basestations supporting LTE, W-CDMA, UMTS, CDMA, GSM and WiMAX standards. Its high frequency capability also supports 
point-to-point broadband wireless access, military, avionics, and high performance test and measurement applications.

The PLLWizard™ comprehensive PC-based design tool software is available to facilitate interactive control and interface with the LTC6946’s evaluation board. Designers can perform simulations and optimization with the PLLWizard software, and then interactively verify their designs on the actual demonstration circuit. The PLLWizard design tool software is available for download free of charge from the Linear Technology website at www.linear.com/synthesizers.

All versions of the LTC6946 are specified over the full case temperature range from -40°C to 105°C. The products are available in a 4mm x 5mm, 28-lead plastic QFN package. Prices start at $5.75 each in 1,000-piece quantities and are available immediately from stock. For more information visit, www.linear.com/product/LTC6946.

Summary of Features: LTC6946

  • Outstanding In-Band Phase Noise:
    -226dBc/Hz (Closed-Loop, Normalized)
  • Best-In-Class In-Band 1/f Noise:
    -274dBc/Hz (Closed-Loop, Normalized)
  • -157dBc/Hz Wideband Output Phase Noise Floor
  • Very Low Spurious Output: -103dBc
  • Temperature Stabilized VCO with 
    Self-Calibration
  • Programmable Charge Pump Up to 11.2mA Output Current
  • PLLWizard™ Design Tool Software Support
  • On-Chip Output Divider Providing Wide Tuning Frequency Range up to 5.79GHz
 
Output Frequency Range (GHz)
 
LTC6946-1
LTC6946-2
LTC6946-3
Internal VCO Frequency
2.240 to 3.740
3.080 to 4.910
3.840 to 5.790
Output Freq. (O DIV=1)
2.240 to 3.740
3.080 to 4.910
3.840 to 5.790
Output Freq. (O DIV=2)
1.120 to 1.870
1.540 to 2.455
1.920 to 2.895
Output Freq. (O DIV=3)
0.747 to 1.247
1.027 to 1.637
1.280 to 1.930
Output Freq. (O DIV=4)
0.560 to 0.935
0.770 to 1.228
0.960 to 1.448
Output Freq. (O DIV=5)
0.448 to 0.748
0.616 to 0.982
0.768 to 1.158
Output Freq. (O DIV=6)
0.373 to 0.623
0.513 to 0.818
0.640 to 0.965


About Linear Technology

Linear Technology Corporation, a member of the S&P 500, has been designing, manufacturing and marketing a broad line of high performance analog integrated circuits for major companies worldwide for three decades. The Company’s products provide an essential bridge between our analog world and the digital electronics in communications, networking, industrial, automotive, computer, medical, instrumentation, consumer, and military and aerospace systems. Linear Technology produces power management, data conversion, signal conditioning, RF and interface ICs, and µModule® subsystems.

LT, LTC, LTM, µModule and  are registered trademarks and PLLWizard is a trademark of Linear Technology Corp. All other trademarks are the property of their respective owners.

Leave a Reply

featured blogs
Apr 24, 2026
A thought experiment in curiosity, confusion, and cosmic consequences....

featured paper

Quickly and accurately identify inter-domain leakage issues in IC designs

Sponsored by Siemens Digital Industries Software

Power domain leakage is a major IC reliability issue, often missed by traditional tools. This white paper describes challenges of identifying leakage, types of false results, and presents Siemens EDA’s Insight Analyzer. The tool proactively finds true leakage paths, filters out false positives, and helps circuit designers quickly fix risks—enabling more robust, reliable chip designs. With detailed, context-aware analysis, designers save time and improve silicon quality.

Click to read more

featured chalk talk

GaN for Humanoid Robots
Sponsored by Mouser Electronics and Infineon
In this episode of Chalk Talk, Eric Persson and Amelia Dalton explore why power is the key driver for efficient and reliable robot movements and how GaN technologies can help motor control solutions be more compact, integrated and efficient. They also investigate the role of field-oriented control in humanoid robotic applications and why the choice of a GaN power transistor can make all the difference in your next humanoid robot project!
Apr 20, 2026
9,964 views