30V 2A step-down DC/DC converter with -40˚C to 105˚C temperature range

Paul Boughton

The new XC9250/51 series from Torex is a step-down (buck) DC/DC converter with integrated 0.3Ω N-ch driver Transistor that utilises a bootstrap configuration.  

The operating input voltage range is 7.0V to 30V and the XC9250/51 can also withstand surge voltages of 46V for up to 400ms. This resilience, coupled with an operating temperature range of -40˚C to 105˚C makes the XC9250/51 an ideal choice for more demanding Industrial applications.

With a maximum output current of 2A the XC9250/51 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 XC9250/51 is readily available with a 300KHz or 500kHz switching frequency and designers can also opt to synchronise the switching frequency of the DC/DC with an external CLK signal (within ±25 per cent 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 1.2V to 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 XC9250/51 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 (TYP). Both of the above functions are implemented using hysteresis, and will allow the XC9250/51 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 XC9250/51 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 0.7ms (300KHz) or 1.3ms (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 (CL).

The XC9250/51 is readily available in a SOP-8FD package measuring 6.0mm x 4.9mm x 1.55mm and the package incorporates an exposed GND tab to maximise heat dissipation.  

For more information, visit www.torex-europe.com