Regulated charge pump delivers 30 mA at 5V
By Paul Rako, Technical Editor -- EDN, January 15, 2009
IC maker austriamicrosystems has released the AS1302 inductorless dc/dc boost converter, which can deliver output currents as high as 30 mA from a voltage input of 2.9 to 5.12V. The output voltage regulation is 3%. The part operates at a 1.2-MHz switching frequency and provides low-noise operation with low input and output ripple voltages. Under light load conditions, the device operates at 49 kHz for better efficiency. It provides 99% efficiency in the 1-to-1 mode and better than 90% efficiency in 1-to-2 or 2-to-3 boost ratios for the charge-pump section. The linear-output-regular section of the part causes a loss depending on the voltage across it and the current thorough it. In the 1-to-2 boost mode with a 2.9V input, the device delivers 30 mA with 85% efficiency. In 2-to-3 boost mode, the part delivers 30 mA from a 3.8V input, also with 85% efficiency.
To deliver full current, you can use the part with two 220-nF flying capacitors and two 220-nF bypass capacitors. Commensurately smaller capacitors can supply smaller loads. The device’s shutdown quiescent current is 10 nA in a mode in which the output is fully disconnected from the input and 1 μA otherwise. The AS1302 includes built-in undervoltage-lockout, short-circuit, and thermal protection circuitry.
Because the AS1302 provides a regulated output, you can use it to boost the voltage of two AA cells or a single lithium-ion cell to 5V. Because the device uses no inductors, boost conversion generates less EMI (electromagnetic interference). The device’s compact size and thickness make it suitable for use in portable electronics.
The AS1302 comes in 1.2×1.2-mm WL-CSP-8 and 3×3×0.8-mm 10-pin TDFN packages, operates in the −40 to +85°C industrial-temperature-range, and sells for 49 cents (1000).
