L5101(2009) Просмотр технического описания (PDF) - Unisonic Technologies
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L5101 Datasheet PDF : 10 Pages
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L5101
LINEAR INTEGRATED CIRCUIT
APPLICATION INFORMATION
Recommended Component Selection
* Inductor Selection: A 10μH inductor is recommended for most applications.
* Capacitor Selection: The small size of ceramic capacitor makes it ideal for UTC L5101 applications, X5R and X7R
types are recommended because of their stable characteristics, 1μF input capacitor with 1μF
output capacitor is sufficient for most UTC L5101 applications.
* Diode Selection: Schottky diode, for its low forward voltage drop and fast reverse recovery, is an ideal choice for
the UTC L5101 diode. A Schottky diode rated 100mA to 200mA is sufficient for most UTC L5101
applications, and the higher current rating usually have larger diode capacitance which can
cause significant switching losses at the 1.2MHz switching frequency.
LED Current Control
A feedback resistor (precision 1% recommended) as feedback resistor control the LED current. (RFB in Figure 1)
* Feedback reference voltage: 95mV.
* LED current is 95mV/RFB.
* The formula for RFB selection: RFB=95mV/ILED
Open-Circuit Protection
The OVP(Over Voltage Protection) protects the voltage lower than its maximum level under the open circuit
condition, which is caused by the failure or disconnection of the LEDs. The above undesired fault conditions will
cause the feedback voltage falling to 0V, then the UTC L5101 increases duty circle resulting in a high voltage in SW
pin.
Dimming Control
There are three different ways of dimming control circuits as follows:
1. Using a PWM signal
L1
10µH
D1
VIN
SW OVP
VIN
C2
C1
UTC L5101
1µF
1µF
SHDN GND
FB
R2 R1
PWM
51K 1K
RFB
4.7Ω
Fig. 2 Dimming Control Using a PWM Signal
Fig. 3 Dimming Control with a PWM Signal
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
6 of 10
QW-R103-026.B
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