XC9116B02A 查看數據表（PDF） - TOREX SEMICONDUCTOR

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XC9116B02A

Step-Up DC/DC Converter-Backlight LED Driver

TOREX SEMICONDUCTOR 

XC9116 Series

■APPLICATION INFORMATION (Continued)

<Dimming Control (Continued)>

3. Using DC Voltage

If in an application it is necessary to control the LED current by a variable DC voltage, illumination control of LED is

achieved by connecting R1 and R2 and applying a direct-current voltage to R2, as shown below.

When R1>>RLED, ILED which flows into LEDs can be calculated by the following equation;

ILED = (VREF - R1 / R2 (VDC - VREF)) / RLED

VREF = 0.2V (TYP.)

Ex.1) When R1 = 10k Ω, R2 = 100k Ω, RLED = 10 Ω,

In the range of 0.2V to 2.2V DC, ILED

(LED current) varies between 20mA to 0mA.

VDC

ZD ILED

XC9116 ( )

FB

R2

R1

RLED

Ex.2) When R1 = 10k Ω, R2 = 100k Ω, R3 = 10k Ω,

C1 = 0.1μF, RLED = 10Ω, the average LED current will

be 10mA by inputting a PWM signal of CE ‘H’ level:

2.2V, CE ’L’ level: 0V, duty cycle: 50%, oscillation

frequency: 100Hz. As well as the way of dimming

control by applying the PWM signal to the CE pin, the

average LED current increases proportionally with the

positive duty cycle of the PWM signal.

Figure : Circuit using DC voltage

R3

PWM

C1

ZD ILED

XC9116 ( )

FB

R2

R1

RLED

Figure : Circuit inputting a PWM signal to the FB pin

<Prevent Emission Caused by White LEDs Leakage>

When the input voltage (VIN) is high, minimum illumination may occur even if the CE pin is in the disable state. If this

happens, please connect a transistor to between the LED and the FB pin. By driving the CE signal in-phase and cutting

the pass to current, the minimum illumination can be prevented.

VIN

3.6V

(3.2V~6.0V)

L:22uH

VLF3010A

SD

XB0ASB03A1B

CIN

4.7uF

VIN

Lx

CE

FB

GND

XP151A21A2

RLED

10Ω

20mA

CL

0.22uF

(base)

8/23

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