New Generations of Highly Integrated High Temperature DC-DC Converters

This paper presents YELLOWSTONE, a single chip, low-voltage, synchronous Buck DC-DC converter implementing a current mode PWM controller with built-in N & P-channel power MOSFETs. It aims to be used as a Point-of-Load (PoL) switched mode power supply with a maximum output current of 500mA. It generates from a typical +3.3V or +5V voltage input a lower voltage output between +0.9V and +3.3V configurable by an external resistor network. It has been specified and designed for operation at temperatures from −55°C to +225°C. Synchronous rectification increases efficiency and reduces external components count. The circuit achieves power efficiencies in excess of 90%. The chip implements a current mode PWM control which enables a fast response to line and load transient variations. A high switching frequency (1.5MHz typical with internal clock and up to 2MHz with external clock) has been selected enabling a dramatic reduction of the number and size of passive external components. The current mode control made possible to use a simple compensation loop and to integrate it. High integration level, tiny IC package (5mm*5.5mm) and small external passive components, lead to a very small footprint for the complete PoL function, i.e. as small as 0.25inch2 (10mm*15mm).