XCM517 Series

600mA Synchronous Dual Output Step-Down DC/DC Converters

The XCM517 series is a multi combination module IC which comprises of two 600mA driver transistor built-in synchronous step–down DC/DC converter.

The XCM517 series is available in an ultra small package USP-12B01 suited for space conscious applications.

The XCM517 series is a group of synchronous-rectification type DC/DC converters with a built-in 0.42Ω P-channel driver transistor and 0.52Ω N-channel switching transistor, designed to allow the use of ceramic capacitors. The ICs enable a high efficiency, stable power supply with an output current of 600mA to be configured using only a coil and two capacitors connected externally. Operating voltage range is from 2.7V to 6.0V. With the built-in oscillator, either 1.2MHz or 3.0MHz can be selected for suiting to your particular application. As for operation mode, the XCM517xA / XCM517xB series are PWM control, the XCM517xC / XCM517xD series are automatic PWM/PFM switching control, allowing fast response, low ripple and high efficiency over the full range of loads (from light load to heavy load).

The soft start and current control functions are internally optimized. During stand-by, all circuits are shutdown to reduce current consumption to as low as 1.0μA or less. With the built-in UVLO (Under Voltage Lock Out) function, the internal P-channel driver transistor is forced OFF when input voltage becomes 1.4V or lower.

Typical Application Circuit


P-ch Driver Transistor Built-In: 0.42Ω
N-ch Driver Transistor Built-In: 0.52Ω
Input Voltage Range 2.7V~6.0V
High Efficiency 92%(TYP.)
Output Current 600mA
Oscillation Frequency 1.2MHz,3.0MHz(+15%)
Maximum Duty Cycle 100%
Functions Soft-Start
Function Protection CircuitsCurrent Limiter Circuit Built-In,(Constant Current & Latching)
Capacitor Low ESR Ceramic



Quality Reports


QuestionWhat does the standby mode mean in the case of the multi channel IC?

It means the state where the entire IC has been turned off. For Torex products, it means that the pin voltages of EN1 and EN2 are both 0V.

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.

QuestionHow does the CL discharge function work?

The function rapidly releases the charge remained in the CL capacitor to make the VOUT pin voltage zero. The VOUT pin voltage does not reach zero immediately after being turned off by the CE function due to the charge remained in the connected CL capacitor. While the charge in the CL capacitor is gradually reaching zero, the LSI continues operating and does not work with the CE pin signal, which may cause a malfunction. This is why the discharge is required when turning off the CE pin. A larger capacitance of the capacitor needs longer time to be discharged.

QuestionWhat does CL mean?

Load capacitor. Other companies often refer to it as COUT.

QuestionWhat is the standby current?

The current that flows through the IC in the standby mode. The standby mode means the state where the IC has been turned off by the CE function.

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.