L3010

Preliminary

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

4 of 5

www.unisonic.com.tw

QW-R125-024.a

FUNCTION DESCRIPTION

The UTC L3010 is a current mode and fixed frequency (280kHz) LED driver.

1. Output current setting

88mV).

S

SENSE

IN

OUT

R

V

V

I

−

=

=88mV/Rs

2. Current limiting

UTC L3010 has internal current limiting function, and the voltage on COMP is clamped at about 2V, the output

current of the power MOSFET is limited at about 2.1A by current comparator.

COMPONENTS SELECTION

1. Input Capacitor Selection

This capacitor should be located close to the IC using short leads. The RMS current rating requirement for the

input capacitor of a buck regulator is approximately 1⁄2 the DC load current. A low ESR input capacitor sized for

maximum RMS current must be used. It is recommend use the MLCC capacitor of 10μF or larger.

2. Output Capacitance Selection

The output capacitor is required to filter the output reduce the ripple current of LED and provide regulator loop

stability. The important capacitor parameters are; The 100KHz Equivalent Series Resistance (ESR), the RMS ripples

current rating, voltage rating, and capacitance value. For the output capacitor, the ESR value is the most important

parameter. It is recommend use the MLCC capacitor of 2.2μF or larger.

3. Inductance Selection

For most designs, the operates with inductors of 47μH to 68μH. Where is inductor Ripple Current. Large value

inductors lower ripple current and small value inductors result in high ripple currents. The DC current rating of the

inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation.

In order to improve the efficiency, the series-wound resistor (DCR) of inductance should be smaller than 0.2Ω.

The inductor value can be derived from the following equation:

OSC

L

IN

OUT

IN

OUT

f

I

V

)

V

V

(

V

L

×

Δ

×

−

×

=

Where: L: Inductance value

F: Oscillator frequency

ΔI is ripple current

4. Diode Selection

UTC L3010 driver LED need a Schottky diode. If output current is 700mA or smaller then SS14 (D1N5819) is ok.