EL SEGUNDO, CA. December 2000 - International Rectifier has introduced the IR1176, an application-specific synchronous rectification IC (SRIC). The new IR1176 simplifies and improves isolated DC-DC converters with voltage output down to 1.5V, powering telecom and broadband network servers.

When used with IR DC-DC converter-specific HEXFET^® power MOSFETs such as the IRF7822, the IR1176 SRIC enhances 1.5 and 1.8V DC-DC converter efficiency ratings. At 40A, in-circuit efficiency is 86% for 1.8V, and 85% for 1.5V output circuits with 48V input. See Figure 1. The new SRIC controls gate drive circuits to minimize losses in secondary-side, isolated DC-DC converter synchronous rectification MOSFETs.

In operation, the IR1176 uses a modified phase lock loop (PLL) to lock the switching frequency of the secondary-side synchronous rectification MOSFETs to the primary-side switching action. This allows the secondary-side MOSFETs to be pre-fired with fully programmable control of turn-on transition lead time, as well as the dead time and overlap between gate drive signals. Pre-firing the MOSFETs eliminates parasitic diode conduction and all output current is now conducted through the active MOSFET channels.

"The IR1176 operates independently of the primary-side topology and can be used to implement simple and low cost diode or resonant reset forward topologies without elaborate or patented circuits such as active clamp or gate drive compensation," said David Tam, Vice President, IR Power IC Group. "The new device works with IR application-specific MOSFETs to enhance isolated synchronous rectification efficiency, especially in the most demanding 1.8 and 1.5-volt applications."

Figure 1. In-circuit 1.5 and 1.8V output DC-DC converter performance of the IR1176 running at 200kHz.

Pricing and More Information

Pricing for IR's new IR1176 begins at US $3.50 each in 10,000-unit quantities. Volume production is scheduled for December 2000.