Capless Charge Pump for Space-critical Applications
The device is optimized for operation from either a 2.5V or 3.3V input, with user-selectable gain factors of 1.32Vin and 1.5Vin. This makes it suitable for systems that have a 2.5V rail and need a localized 3.3V power supply, or operate from a 3.3V rail and need a localized 5V power supply. It also incorporates an adjust pin so designers can generate other gain factors using a simple resistor divider. Output current is rated at 8 mA minimum.
Charge pumps eliminate the inductor used in switcher-based boost designs, which results in a reduction of total solution size, complexity and cost. EMI associated with inductors is also eliminated, an important factor in the design of wireless applications.
The SC1461 takes cost and size reduction one step further by eliminating the external bucket or flying capacitor typically used in charge pump designs. The high (12 MHz) operating frequency allows the bucket capacitor to be integrated on-chip, and allows smaller input and output capacitors to be used, resulting in an extremely compact, simple and cost-effective solution.
A typical SC1461 application requires only two tiny surface mount ceramic capacitors: 0.22 µF for the input and 47 µF for the output. Other features of the SC1461 include 4% output voltage accuracy, low quiescent current (50 µA typical) and a low-power shut-down control.
Samples of the SC1461 are available now in SOT-23, 5 lead packaging, with full production units available in April 2000. The SC1461 will be available through Semtech's network of direct-sales representatives and distributors, and is priced at $0.67 in lots of 1000.
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