L3010
Preliminary
LINEAR INTEGRATED CIRCUIT
FUNCTION DESCRIPTION
The UTC L3010 is a current mode and fixed frequency (280kHz) LED driver.
1. Output current setting
The output current is determined by the sampling resistor (RS) and setting voltage (VIN-VSENSE a built-in fixed
88mV).
VIN − VSENSE
IOUT
=
=88mV/Rs
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:
VOUT × (VIN − VOUT
VIN × ΔIL × fOSC
)
L =
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.
The average current through the diode is ID:
ID= (1-D)·ILED
ILED is the current of LED
UNISONIC TECHNOLOGIES CO., LTD
4 of 5
QW-R125-024.a
www.unisonic.com.tw