Santa Clara, Calif.--July 22, 1997--With the introduction of the LM2662 and LM2663 charge-pump voltage converters, National Semiconductor Corp. (Santa Clara, Calif.) doubled the current-output generated by switched capacitors in an SO-8 surface-mount package.
Both new ICs are rated 200 mA output current, with a typical output impedance of just 3.5 ohms. Unlike other types of switchers, switched capacitor circuits require no external inductor.
The LM2662 and LM2663 convert a range of supply voltages from 1.5V to 5.5V at a typical efficiency of greater than 86 percent. The output impedance of 3.5 ohms limits the voltage droop to 0.35V at 100mA.
The LM2662/63 are designed for use in handheld battery-operated equipment in the PC and wireless markets, including PCMCIA cards and hard disk drives.
A frequency control pin on the LM2662 permits the designer to select oscillator frequencies of either 20 kHz or 150 kHz. Frequency of the LM2663 is set at 150 kHz. The LM2663 also includes a low-current shutdown mode that disables the device and reduces the quiescent current to 10 mA.
Switched capacitors generate negative power rails from positive supplies or operate as a positive voltage doubler. Although two capacitors are required to provide the output current, the LM2662/63 does not require the external inductor and does not generate high EMI associated with inductor-based switchers.
The LM2662M and LM2663M (SO-8 package) are priced at $2.10 each in 1,000-piece lots and are available in production quantities.
Santa Clara, CA
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