XC9306 Series

Synchronous Buck-Boost DC/DC Converters

XC9306 series is a synchronous buck-boost DC/DC converter IC with buid-in FETs. The circuit topology switches over between buck and boost smoothly based on the relationship of the input voltage and the output voltage which is observed by the internal PWM controller. Due to the internal FETs, the number of external components is reduced. Also high oscillation frequency at 6MHz enables to use smaller external components such as a coil and capacitors. The input voltage range is 2.5V~5.5V and the output voltage is adjustable from 0.8V to 5.0V freely by using external resistors since the reference voltage circuit is embedded internally.

The synchronous topology is adopted so the product has high efficiency feature. The control method is selectable either PWM mode (MODE pin: H) or PFM mode (MODE pin: L). Under the PFM mode, the efficiency at right load current will be improved. When “L” level is fed to CE pin, the product is in stand-by mode and the consumption current is going to be 2.0μA (MAX.) or less. Regarding other functions, the product has UVLO, Thermal shutdown protection, Soft-start function. The soft-start time is approx. 100μs and the output voltage can rise up quickly.

Typical Application Circuit


Input Voltage Range 2.5V~5.5V
Output Voltage Range 0.8V~5.0V(FB=0.5V)
Oscillation Frequency 6.0MHz
Efficiency 92%(VIN=4.2V,VOUT=3.3V/300mA)
Control Methods PWMControl(Mode=High,ILIM=Low)
Protection Circuits Over Current Limit
Thermal Shut Down
Functions Soft-Start
Power Save(Mode=Low)
Capacitor Low ESR Ceramic
Coil Value 0.5(0.47)μH
Environmentally Friendly EU RoHS compliant, Pb free


Package WLP-20-01 Number of Pins 20
Pcs/Reel 6,000 Package Size(mm) 2.15 x 1.94 x 0.625


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.