Multi-Phase Architecture Fortifies Interleaved Buck Converters

Designed for interleaved buck dc/dc converters that require one or more phases, the XPhase scalable, multi-phase architecture consists of the IR3081 control IC and the IR3086 phase chip. In a 28-lead MLPQ package, the IR3081 communicates with the phase device using a five-wire bus. Phases can be added or removed without design changes. The device contains all one-per-converter circuitry, including VID pull-up resistors, a PWM ramp oscillator, error amplifier, bias voltage, and fault detection. The IR3086 phase chip comes in a 20-lead MLPQ package and both drives and monitors a single phase. It provides all one-per-phase circuitry, such as gate drivers, a PWM comparator and latch, over-voltage protection, and current sensing and sharing. Programmable VTHOT over-temperature detection is also included. The phase device employs a patent-pending, body-braking control feature that turns off the synchronous rectifier MOSFET when load current decreases significantly. This feature is said to allow for larger inductance values and decreased output capacitor requirements. According to the company, a 100A, six-phase VRM 10.0-compliant converter that employs the XPhase chipset can attain an efficiency up to 84% with less than 4% variation in phase current and average current per phase. The IR3081 and IR3086 are priced at $1.65 and $1.25, respectively, each/10,000. INTERNATIONAL RECTIFIER CORP., El Segundo, CA. (310) 252-7105.