Electronic Design

Application-Specific MOSFETs Target Multiphase DC-DC Converters

The IRLR8103 and IRLR8503 have been designed for use in multiphase synchronous buck dc-dc converters operating at 1 MHz and above. Developed by International Rectifier, these n-channel 30-V HEXFETs represent an application-specific approach to MOSFET design. Both devices have been optimized for critical parameters like on-resistance, gate charge, and C.dv/dt induced turn-on immunity.

Features of the IRLR8103 include low drain-source on-resistance RDS(ON) and high C.dv/dt immunity for synchronous FET applications. The IRLR8503 presents a low combination of switch charge (QSW) and RDS(ON) for reduced losses in control FET applications. Unique to IR data sheets, QSW is a combination of post-threshold gate-source charge and gate-drain charge.

Hence, typical RDS(ON) for the IRLR8103 is 8 mΩ at 4.5-V gate-source voltage (VGS) with a QSW of 20.3 nC (typical). Similarly, IRLR8503 offers typical RDS(ON) of 14 mΩ at 4.5-V gate-source voltage, while its QSW is rated at 5.4 nC (typical). According to IR, a four-phase dc-dc converter built using these optimized MOSFETs demonstrates 80% full-load efficiency at a 1.6-V, 60-A output. The operating frequency is 1 MHz per phase and the input voltage is 5 V.

In production, the new MOSFETs are housed in DPAKs. In quantities of 100,000, the optimized IRLR8103/8503 MOSFET set is priced at $1.35 each.

International Rectifier, 233 Kansas St., El Segundo, CA 90245; (310) 252-7105; www.irf.com.

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