Sipex Corporation, designer and manufacturer of high-performance analog semiconductors for the battery-powered, portable electronics market, announced the immediate availability of its new SP6639/40/53 family of low voltage DC/DC buck regulators. These buck regulators with their 1 ohm on-chip power MOSFETs, deliver up to 100mA at either fixed (SP6639, 5.0V; SP6640, 3.3V; SP6653, 3.0V) or user adjustable output voltages.

These power management products bring both high power efficiency and low noise to lithium ion and alkaline cell powered portable devices. They can sustain up to 94% efficiency over an extremely wide output current range (10 mA to 100mA) while operating with very low quiescent current (10uA). Switching related noise for each product in the family is minimized due to on-chip inductor damping. This feature helps keep output ripple below 1% and greatly reduces EMI.

"These three new products provide very efficient solutions for power supply requirements in many handheld, portable devices," said Todd Sherman, Manager of Sipexýs Power Management Product Line. "The unique combination of low output ripple and reduced EMI offers our customers a quiet and efficient solution for generating bus voltages from batteries in portable devices."

About the SP6639/40/53

I was first attracted to these parts because of the low EMI resulting from internal inductor damping. But when you look closer you also see some really good efficiency numbers with relatively small inductors and capacitor selections that are extremely wide-ranging. Like some other vendors' parts there is an on-board MOSFET reducing the component count to an inductor, a Schottky and the input/output capacitors. The three versions provide a buck conversion from an input range of 3.3 to 7.5 V down to 5.0, 3.3 and 3.0 V in the SP6639, SP6640, and SP6653, respectively. The drop out voltage is a typical 0.3 V. Any other voltage can be set using a potential divider on the output to derive the correct feedback voltage for each part.

The part uses duty-cycle modulation but I could find no mention of the frequencies of operation in the data sheet. From the size of the inductors for the higher, 100 mA, loads I would hazard that the center frequency is probably around 400 kHz. The data sheet has an extremely well documented guide to using the parts in a practical design. A low battery detector is included and the shutdown mode reduces the quiescent to 10 uA.