Electronic Design

Low-Profile Inductorless Charge-Pump IC Suits Cell Phones

The CMOS SP6680 inductorless dc-dc charge-pump IC provides buck/boost performance with up to 96% efficiency. Ceramic capacitors replace large, bulky coils and expensive tantalum capacitors. The IC also boasts a switched multicapacitor topology. Thanks to these components, the SP6680 is packaged in a 10-pin plastic MSOP that measures just 0.118 by 0.116 by 0.040 in.

Designed by Sipex Corp. for appliances with limited space requirements, the SP6680 suits next-generation cellular phones, PDAs, MP3 players, and digital cameras. It's ideal for converting a 3.6-V Li-ion battery input to a 5.0-V regulated output. It can accept an input voltage ranging from 2.7 to 6.5 V and convert it to a pre-regulated output of 5.4 to 6.0 V. Its maximum power dissipation is 720 mW, derated at 8.84 mW/°C above a temperature of 70°C.

"The SP6680 can provide the same efficiency as coil-based circuits, but in less space and at a reduced cost," claims Tim Goodrow, Sipex's director of marketing for power management products. It supplies a regulated 5-V output at 60 mA. Rated for a quiescent current of 100 µA, it consumes only 4 µA in the shutdown mode.

This IC consists of seven major functional circuits: a voltage reference, a clock manager, a pump-switch configuration-control circuit, clock-phase control circuitry, output-voltage control, clock-phase drivers, and charge-pump switches. It operates at three different switching frequencies corresponding to three different output resistances and load-current ranges.

An external 32.768-kHz nominal clock signal is necessary to drive this device. The SP6680 also requires only two external capacitors. Typical applications use 3.3-µF capacitors. Its operating temperature ranges from −40°C to 85°C. Two control inputs can adjust the internal pump frequency on-the-fly. This can be set to the nominal frequency, or to one quarter or eight times the nominal frequency.

The SP6680 is available from stock. It starts at $1.07 each in 10,000-piece quantities. Samples also are available.

Sipex Corp., 22 Linnell Circle, Billerica, MA 01821; (978) 671-1907; fax (978) 670-9001; www.sipex.com.

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