Torex - XC9242/43 Series, 2A Synchronous Step-Down DC/DC Converters

We all know that IC’s using PWM control (such as the XC9242) tend to exhibit a very clean output voltage under all load conditions. However, thanks to a proprietary design from Torex, IC’s that use PWM/PFM control (such as the XC9243) can too maintain a very low output voltage ripple under all loads conditions, while exhibiting other typical advantages of PWM/PFM control such as a high efficiency over a wide range of load conditions.

The XC9242/43 series is available with two different switching frequencies, 1.2MHz for applications where a higher efficiency is critical, and 2.4MHz where space is at a premium and when high speed line and load transient responses are required.

The XC9242/43 series will be forced to stop operating by various protection circuits, such as a thermal shutdown circuit when the chip’s temperature reaches 150ºC and a UVLO (Under Voltage Lock Out) circuit when the input voltage decreases below 2.5V. Both of the above functions are implemented using hysteresis, and will allow the XC9242/43 to resume normal operation when the chip’s temperature drops below 130ºC and when the input voltage increases to 2.68V respectively. In addition to these protections, the XC9242/43 comprises a current limiter that not only stops the IC when the output current is too high, but also permits the IC to automatically resume normal operation (following a soft-start procedure) as soon as the over-current condition disappears.

Others features of the XC9242/43 series include a chip enable pin to turn the IC on and off, a CL discharge function to quickly discharge the output capacitor when the IC is turned off, and the aforementioned high speed soft-start circuit.

Because of the very low on-resistance of its two built-in power transistors, the XC9242/43 chip dissipates less power and can thus be integrated in a small 2.9 x 2.6mm USP-10B package.