Tiny 400mA synchronous step-down DC/DC converters
Available in a tiny 1.3mm x 1.3mm x 0.4mm USPN-6 package, the new XC9244/45 series is a group of step-down synchronous DC/DC converters with a built-in 0.65W P-channel driver transistor and 0.45W N-channel switching transistor. These new DC/DCs provide a high efficiency and a stable power supply with output currents of up to 400mA, all achievable using only a coil and two ceramic capacitors connected externally.The operating voltage range is from 2.3V to 6.0V and output voltage is fixed within a range of 0.8V to 4.0V in 50mV steps (accuracy: ± 2.0 per cent). The XC9244 is PWM control whereas the XC9245 series is automatic PWM/PFM switching control providing fast response, low ripple (<10mVpp) and high efficiency over the full range of load conditions. Switching frequency is 1.2MHz (± 15 per cent).
The XC9244/45 series 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 quickly discharge the output capacitor when the IC is turned off.
Other features include a built-in UVLO (Under Voltage Lock Out) circuit whose threshold is 1.9V(typ): The XC9244/45 will stop operating when the input voltage decreases below this threshold, and will resume normal operation when the input voltage rises above this threshold. In addition, the XC9244/45 features 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.
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