National Semi Intros LM3670/LM3671 DC-DC Converters

National Semiconductor Corp. (Santa Clara, CA) introduced its new LM3670 and LM3671, the first two products in a family of miniature, high-efficiency, synchronous, step-down dc-dc converters for portable systems. The LM3670 and LM3671 optimize the efficiency and size of portable devices, including wireless handsets, digital still cameras, MP3 players, PDAs, hard disk drives and wireless LAN products.

The LM3670 and LM3671 feature automatic pulse frequency modulation (PFM) and pulse width modulation (PWM) mode operation; up to 95% efficiency during continuous switching operation; quiescent current at 16 µA typical; less than 5 mV peak-to-peak output voltage ripple; a small 2.2 µH inductor; 10 µF output capacitors; and a SOT-23 package.

The LM3670 requires a small 10 µH inductor and two 4.7 µF capacitors for operation. It is available in 1.8 V, 1.875 V and 1.5 V output voltage options, and an adjustable option for other voltages. The LM3670 is optimized for systems and applications with lower output current requirements. It switches at 1 MHz and has a load capability of up to 300 mA

The LM3671 is available in 3.3 V, 1.875 V, 1.8 V, 1.6 V, 1.5 V, 1.375 V, 1.25 V and 1.2 V output voltage options, as well as an adjustable option for other voltages. The LM3671 powers low-voltage circuits operating from a lithium-ion battery or 2.8 V to 5.5 V voltage rails. It has a load capability of up to 600 mA. The LM3671's 2 MHz oscillator frequency enables the use of three very small external components for operation, including a 2.2 µH inductor and two 10 µF capacitors.

Available now, the LM3670 is priced at $1.40 and the LM3671 is priced at $1.60, both in 1,000-unit quantities. In the spring of 2005, the LM3671 will be available in National's small, proprietary, micro SMD, chip-scale package, measuring 1.4 mm x 1.1 mm.