Buck DC/DC converter for demanding industrial applications

With a maximum output current of 2A the XC9270/71 includes Over Current and Short circuit protection circuits and the designer can select either a Latch or Auto-restart (Hiccup) configuration depending on the application requirements. The XC9270/71 is readily available with a 300 (±8%) or 500kHz (±8%) switching frequency and designers can also opt to synchronise the switching frequency of the DC/DC with an external CLK signal (within ±25% of the nominal frequency).

Using the internal 0.8V reference voltage, the output voltage can be set using two external resistors within a range of 1.2-12V.  To ensure maximum efficiency at higher output loads the designer can select fixed frequency PWM mode using the MODE/SYNC pin or alternatively PFM/PWM automatic switching can be used for improved efficiency during light loads. The converters operate over a temperature range from -40 to +105°C.

The XC9270/71 series will be forced to stop operating by additional protection circuits, such as a thermal shutdown circuit when the chip’s temperature reaches +150˚C and a UVLO (Under Voltage Lock Out) circuit when the input voltage decreases below 4.6V (typical). Both of the above functions are implemented using hysteresis, and will allow the XC9270/71 to resume normal operation when the chip’s temperature drops below +125˚C and when the input voltage increases to 5.3V respectively.

Others features of the XC9270/71 series include a chip enable pin to turn the IC on and off and an integral soft-start circuit to help limit rush current and output voltage overshoot during start-up. The soft start time is fixed internally at 0.7 (at 300KHz) or 1.3ms (at 500KHz) and an external CR can be connected to extend the time as desired. Inexpensive ceramic capacitors can also be used for the output load capacitor.

The XC9270/71 is readily available in a SOP-8FD package measuring 6.0x4.9x1.55mm and the package incorporates an exposed GND tab to maximise heat dissipation.