XC9116B02ADL TOREX [Torex Semiconductor], XC9116B02ADL Datasheet - Page 7

• Manufacturer Part Number: XC9116B02ADL
• Description: Step-Up DC/DC Converter-Backlight LED Driver
• Manufacturer: TOREX [Torex Semiconductor]

■APPLICATION INFORMATION
<Dimming Control>
1. Applying PWM signal to the CE pin
2. Step-Wise Regulation of LED Current
The XC9116 repeats on/off operations by a PWM signal applied to the CE pin. The magnitude of LED current, I
the diode is on, is determined by R
proportional to the positive duty ratio of the PWM signal.
The frequency of the PWM signal can be controlled to the optimum value between 100Hz and 10kHz. With regard to the
amplitude of the PWM signal, the high level should be higher than the "H" voltage of CE, V
than the "L" voltage of CE, V
In some applications, it may be necessary to incorporate step-wise regulation of LED current, I
of LED illumination is achieved by connecting a switch element SW1 in parallel with R
turning SW1 on and off, as shown below. Choose a resistance of R
when switch element SW1 is off. The resistance of R
through the LED is gained when the switch element is on.
Ex.) Current I
R
R
LED
LED1
= 200mV / 5mA = 40
= 200mV / (15mA – 5mA) = 20
LED
200µsec / div
= 5mA and 15mA
20µsec / div
CEL
.
Ω
LED
. The magnitude is zero when the diode is off. The average of LED current is
Ω
VIN
CIN
Figure : Circuit using Step-wise Regulation of LED Current
LED1
should be such that a desired increase of current passed
ON/OFF
LED
VIN
CE
so that the minimum necessary current is gained
VSS
L
FB
Lx
LED
ILED
SD
RLED
200µsec / div
20µsec / div
and in series with R
CEH
LED
, and the low level, lower
. Step-wise regulation
RLED1
signal
SW1
CL
LED
XC9116
LED1
, when
Series
7/22
and