XCM519 Series

600mA Synchronous Step-Down DC/DC Converter + Low Voltage Input LDO

The XCM519 series is a multi combination module IC which comprises of a 600mA driver transistor built-in synchronous step–down DC/DC converter and a low voltage input LDO regulator. The device is housed in small USP-12B01 package which is ideally suited for space conscious applications. Battery operated portable products require high efficiency so that a dual DC/DC converter is often used. The XCM519 can replace this dual DC/DC to eliminate one inductor and reduce output noise. The DC/DC converter and the LDO regulator blocks are isolated in the package so that noise interference from the DC/DC to the LDO regulator is minimal.

A low output voltage and low On-resistance LDO regulator is added in series to the DC/DC output so that one another low output voltage is created with a high efficiency and low noise. With comparison to the dual DC/DC solution, one inductor can be eliminated which results in parts reduction and board space saving.

Typical Application Circuit


DC/DC Converter Block
Input Voltage Range 2.7V~6.0V
Output Voltage Range 0.8V~4.0V
High Efficiency 92%(TYP.)
Output Current 600mA(MAX.)
Oscillation Frequency 1.2MHz,3.0MHz(Accuracy ±15%)
Maximum Duty Cycle 100%
Protection Circuits Current Limiter Circuit Built-In,(Constant Current & Latching)
Soft-Start Soft-Start Circuit Built-In
Control PWM(XCM519A), PWM/PFM Auto(XCM519B)
Regulator Block
MaximumOutput Current 400mA(500mA limit:TYP.)
Dropout Voltage 35mV@IOUT=100mA(TYP)(VBIAS-VROUT(E)=2.4V)
Bias Voltage Range 2.5V~6.0V(VBIAS-VROUT(E)=0.9V)
Input Voltage Range 1.0V~3.0V(VIN2≦VBIAS)
Output Voltage Range 0.7V~1.8V(0.05V increments)
High Accuracy ±20mV
Quiescent Current IBIAS=25μA,IIN2=1.0μA(TYP.)
Stand-by Current IBIAS=0.01μA,IIN2=0.01μA(TYP.)
Thermal Shut Down Detect 150℃,Release 125℃(TYP.)
Soft-Start Time 240μs@VROUT=1.2V(TYP.)
CL Discharge CL High Speed Auto Discharge
Low ESR Capacitor Low ESR Ceramic
Operating Ambient Temperature -40℃~+85℃



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 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.

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.