Since the use of cellular phones and portable game consoles color LCD screen, the market appeared solid background for high-brightness light source of the large demand for white LED is considered the best available on the market the background light. This article describes the XC9103 and XC6367 series of commonly used two white LED driver IC features and drive circuit design.

     Common drive circuit description

     Figure 1 is commonly used in series LED driver circuit diagram, figure driver IC for the XC9103 Series DC converter, the circuit has the following characteristics:

1. Can be used in tandem white LED, regardless of the number of the number of connections LED, just a resistor can be to provide them with a constant current;

2.The reduction in component count,further reducing the power consumption;

4. With a resistor you can adjust the white LED operating current;

5. Almost without any other changes, you can randomly change the number of white LED connections;

6. The use of ceramic capacitors available to low ripple noise, and extend the life of the circuit;

7. Can greatly saves space: XC9105 and FET + SD have adopted SOT23 package, the maximum coil thickness of only 1.2 mm, the input and output capacitors are used ceramic capacitors.

      When using the XC9103 family of devices, the ceramic capacitors can be used as a CL capacitor to suppress harmful signal radiation.
When using the XC9103 family of devices, the ceramic capacitors can be used as a CL capacitor to suppress harmful signal radiation.

      Diagram of the step-up DC / DC converters for output drive LED constant drive current, LED drive current value is equal to FB control voltage divided by the resistance of the resistor connected. XC9103 of the FB control voltage for the 0.9V, XC6367 of the FB control voltage of 1.0V. Therefore, by changing the resistor values, you can adjust the LED drive current to the desired value. DC / DC converter output voltage is equal to the forward voltage of LED with FB terminal voltage, if the LED quantity greater than 1, the output voltage for the FB terminal voltage plus the forward voltage of a single LED and LED product of the number.

     Figure LED drive current can be calculated by:
ILED=VFB /RFB2

       When using the XC9103 family of devices, the ceramic capacitors can be used as a CL capacitor to suppress harmful signal radiation.

       Diagram of the step-up DC / DC converters for output drive LED constant drive current, LED drive current value is equal to FB control voltage divided by the resistance of the resistor connected. XC9103 of the FB control voltage for the 0.9V, XC6367 of the FB control voltage of 1.0V. Therefore, by changing the resistor values, you can adjust the LED drive current to the desired value. DC / DC converter output voltage is equal to the forward voltage of LED with FB terminal voltage, if the LED quantity greater than 1, the output voltage for the FB terminal voltage plus the forward voltage of a single LED and LED product of the number.

        Figure LED drive current can be calculated by:
VLED×ILED/(VIN×IIN)×100% 
Which VLED voltage drop on the LED.

        When using the XC6367 family of devices is not required RSEN resistance, using 221μF tantalum capacitor as the output capacitor CL.