XC9303 Series

High Efficiency, Synchronous Step-Up & Down DC/DC Controller Ics

The XC9303 series is highly efficient, synchronous PWM, PWM/PFM switchable step-up / down DC/DC controller ICs. A versatile, large output current and high efficiency, step-up/down DC/DC controller can be realized using only basic external components - transistors, coil, diode, capacitors, and resistors for detecting voltages. High efficiency is obtained through the use of a synchronous rectification topology. The operation of the XC9303 series can be switched between PWM and PWM/PFM (automatic switching control) externally using the PWM pin. In PWM/PFM mode, the XC9303 automatically switches from PWM to PFM during light loads and high efficiencies can be achieved over a wide range of output loads conditions.

Output noise can be easily reduced with PWM control since the frequency is fixed.

The XC9303 has a 0.9V (±2.0%) internal voltage supply and using externally connected components, output voltage can be set freely between 2.0V to 6.0V. With an internal 300kHz switching frequency smaller external components can be used. Soft-start time is internally set to 10ms and offers protection against in-rush currents when the power is switched on and prevents voltage overshoot.

Typical Application Circuit


Power Supply Voltage Range 2.0V~10.0V
Output Voltage Range 2.0V~6.0V,Can be set freely with 0.9V (±2.0%) of reference voltage supply and external components.
Oscillation Frequency 300kHz,±15%
Output Current 800mA(VIN=4.2V,VOUT=3.3V)
Stand-by Current 3.0μA(MAX.)
Soft-Start 10ms(internally set)



Technical Document

Quality Reports


QuestionHow does the GO function of DC/DC converters work? Does it work just like a regulator?

Torex regard the PWM/PFM automatic switch control function as Green Operation (GO) in the case of DC/DC. The GO function is defined as the switching operation between the PFM mode for a small output current and the PWM mode for a large output current. The PFM control method controls the output current by increasing and decreasing the fall time according to the output current while keeping a pulse width. The PWM control method controls the output current by adjusting the pulse width of the rise time, which keeps the rise/fall time interval constant and increases the efficiency at a heavy load. By switching between the PFM control for a small output current and the PWM control for a large output current, the quiescent current can be controlled for both of heavy and light loads.

QuestionWhat is the soft-start function?

The function to soften the rise to prevent the inrush current.

QuestionWhat does the FB product mean?

An IC for which any output voltage can be set by the reference voltage of the FB pins and the external dividing resistor. The output voltage is determined by the RFB1 and RFB2 values, using the following formula: VOUT = Vref × (RFB1 + RFB2)/RFB2

QuestionHow does UVLO (under voltage lockout) work?

This circuit forcibly turns off the driver transistor when VIN drops below the UVLO voltage. If the input voltage recovers to the value which is equal to the specified value or more, UVLO will be released to resume the switching operation. It is resumed by the soft-start function. The paused state by UVLO is not the shutdown. The pulse output is stopped, but the internal circuit is operating.