Available in a 1.3x1.3x0.4mm USPN-6 package, the XC9244 and the XC9245 from Torex Semiconductor are step-down synchronous DC/DC converters with a built-in 0.65Ω P-channel driver transistor and 0.45Ω N-channel switching transistor. These DC/DC converters are claimed to provide a stable power supply with output currents of up to 400mA, using a coil and two ceramic capacitors connected externally. The operating voltage range is 2.3 to 6V and output voltage range is 0.8 to 4V, in 50mV steps with an accuracy of ±2%. The XC9244 is for PWM control whereas the XC9245 is for automatic PWM or PFM switching control, providing fast response, low ripple of less than 10mVpp over a range of load conditions. Switching frequency is 1.2MHz. The converters include a 0.25ms high-speed, soft-start for quick turn-on, a chip enable pin to turn the IC on and off, and a CL discharge function to discharge the output capacitor when the IC is turned off. Other features include a built-in under voltage lock-out circuit whose threshold is 1.9V(typical). The converters feature a current limiter that stops the IC when the output current is too high and also permits the IC to automatically resume normal operation as soon as the over-current condition disappears, claims the company.
