Multiphase Oscillator with Spread Spectrum Frequency Modulation

The LTC6902 is a precision, low power and easy-to-use oscillator that provides multiphase outputs in a small package. The oscillator frequency is set by a single external resistor (RSET). The LTC6902 also provides an optional spread spectrum frequency modulation (SSFM) capability that can be activated and controlled by an additional external resistor (RMOD).

The LTC6902's master oscillator is controlled by the RSET resistor and has a range of 100kHz and 20MHz. In order to accommodate a wider output frequency range, a programmable divider (divide by 1, 10 or 100) is included. The integrated programmable multiphase circuit provides either 2-, 3- or 4-phase waveforms.

The LTC6902's SSFM capability modulates the oscillator's frequency by a pseudorandom noise (PRN) signal to spread the oscillator's energy over a wide frequency band. This spreading decreases the peak electromagnetic radiation level and improves electromagnetic compatibility (EMC) performance. The amount of frequency spreading is programmable by a single additional external resistor (RMOD) and is disabled by grounding the MOD pin.

Applications

* Switching Power Supply Clock Reference

* Portable and Battery-Powered Equipment

* PDAs

* Cell Phones

* Clocking Switched Capacitor Filters

* 2-, 3- or 4-Phase Outputs

* Optional Spread Spectrum Frequency Modulation for Improved EMC Performance

* 5kHz to 20MHz Frequency Range

* One External Resistor Sets the Frequency

* One External Resistor Sets Percent Frequency Spreading

* 400µA Typical Supply Current, VS = 3V, 1MHz

* Frequency Error < 1.5% Max, 5kHz to 10MHz (TA = 25°C)

* Frequency Error < 2% Max, 5kHz to 10MHz (TA = 0°C to 70°C)

* ±40ppm/°C Temperature Stability

* Fast Start-Up Time: 50µs to 1.5ms

* 100Ω CMOS Output Driver

* Operates from a Single 2.7V to 5.5V Supply

* Available in 10-Lead MS Package