Zetex dc/dc converter IC provides 3.3V regulated output

The ZXCP330 switch-capacitor dc/dc converter transforms a 2V to 4.4V input into a regulated 3.3V output with a maximum load current of 40mA, making it suitable for Li-ion and alkaline battery backup supplies, smart card readers, and PDAs.

Measuring 8-by-5.3mm, the SOT23-6 device operates with a 220nF flying capacitor and 10?F bypass capacitor at the input and output. It draws an input current of 20?A in normal operation and 1?A during sleep mode. A pin is also provided for logic controlled shutdown of the output.

Based on a standard switched capacitor voltage doubler design, the converter IC achieves regulation by sensing the output and activating a charge pump when sense voltage falls below a set threshold.

The ZXCP is also fully protected against short circuit and thermal overload. With the output short-circuited, the increase in input current causes a rise in chip temperature. At 150°C, on-chip thermal shutdown circuitry disables the charge pump until the device has cooled. The converter then cycles in and out of operation indefinitely until the short circuit is removed.