Date: 10/03/2009
Spread spectrum clock oscillator IC to control multiphase switching regulators
Linear Technology has released LTC6909, a precision silicon oscillator to control switching regulators in multiphase power supplies. The LTC6909 has 8 separate outputs, providing up to 8 rail-to-rail 50% duty cycle clock signals. These outputs can be used to enable or disable and phase-synchronize multiple switching regulators. Phase-synchronization offers a number of design advantages, including improved EMI performance, reduced input and output ripple current, and better load transient response. Using 3 logic inputs, the phase relationship between these outputs can be configured from 45° to 120°, or the outputs can be placed in a logic low or high-Z state.
A single resistor selects the output frequency from 12.5kHz to 6.67MHz. The LTC6909 also offers spread spectrum frequency modulation (SSFM), a technique that modulates the clock frequency by a pseudorandom signal. SSFM is easily enabled and offers a method for decreasing peak electromagnetic emissions. The amount of frequency spreading is fixed at ±10% of the center frequency, and the user selects one of 3 modulation rates.
"Incorporating multiple switching regulators into a single system is much simpler with the LTC6909," says Doug LaPorte, design manager for Linear Technology. "The LTC6909 can be used to enable and disable a bank of regulators, to synchronize their operation for improved efficiency and offer vastly better EMI performance through SSFM."
Fully specified over the temperature range of -40°C to 125°C makes LTC6909 rugged and suitable for high-reliability applications. This device also features fast startup and low power consumption.
The other features of LTC6909,
Outputs Can Be Held Low or Muted (Hi-Z)
600uA Supply Current Typical (V+ = 5V)
Operates from a Single 2.7V to 5.5V Supply
260us Start-Up
First Cycle Accurate
Outputs Are High Impedance Until Frequency Settles
Package: 16-lead MSOP package
Available: Now
Price: Each $2.46 in 1K pieces