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AN487

APPLICATION NOTE

November 2003

Switched mode techniques led to the development of high efficiency circuits offering space saving and a

reduction in costs, mainly of the heatsink and output LC filter. For these applications a new technology,

called MULTIPOWER-BCD, has been developed which allows the integration on the same chip of isolated

power DMOS elements, Bipolar transistors and CMOS logic.

The technology is particularly suitable for the problems rising in the switch mode field, due to the charac-

teristics of high efficiency, fast switching speed, no secondary breakdown of the power DMOS element.

The great flexibility that we have at our disposal for the choice of the signal and driving sections compo-

nents allows optimization and compactness of the system. With MULTIPOWER-BCD it has been possible

to implement the family L497X, a new series of fully integrated switching regulators suitable for DC-DC

converters working in Buck configuration. The complete family consists of five devices which differ each

other only by the output current value (2A, 3.5A, 5A, 7A, 10A) they can deliver to the load. The devices

rated at 2A and 3.5A are assembled in Power Dip (16+2+2), while the others are assembled in the

Multiwatt15 package. Each device integrates a DMOS output power stage, a control section, limiting cur-

rent and supervisor functions like Reset and Power Fail signal for microprocessors applications.

Output voltage can be adjusted starting from the internal reference voltage (5.1V) up to 40V, allowing a

maximum output power of 80W for the 2A version and of 400W for the 10A version. Maximum operating

supply voltage is 55V.

THE TECHNOLOGY

The technology architecture is based on the vertical DMOS silicon gate process that allows a channel

length of 1.5 micron ; using a junction isolation technique it has been possible to mix on the same chip

Bipolar and CMOS transistors along with the DMOS power components (Fig. 2). Figure 1 shows how this

process brings a rapid increase in power IC complexity compared to conventional bipolar technology.

Figure 1. BCD process and increase in power ICs complexity.

by C. Diazzi

INTRODUCTION TO A 10A MONOLITHIC SWITCHING

REGULATOR IN MULTIPOWER-BCD TECHNOLOGY

The L497X series of high current switching regulator ICs exploit Multipower-BCD technology to achieve

very high output currents with low power dissipation – up to 10A in the Multiwatt power package and

3.5A in a DIP package.