YB1303
Low Dropout LED Driver
Example 3:
LED Brightness Control
Drive white, blue, red, amber LEDs
string
The YB1303 LED drivers feature analog
and PWM controls to give designers
flexible brightness control. These control
methods can be applied to the circuit in two
different ways which provide flexible
Assuming boost circuit, or existing voltage
bus, the YB1303 can be used to drive a
whole string of LEDs and flexible
brightness control – whether using analog
or PWM (Notes).
solution. To determine the value of RSET
,
use the “ISET vs. VCTR” graph under the
“typical characteristics” section.
Scenario 1 - Analog
Set VCONTROL and RSET for LED current
-VDROP < 0.3V
ILED=200×(VCONTROL-VCTR)/RSET
-VIN_MIN = N×VF + VDROP
- VIN_MAX = N×VF + 6V
Scenario 2 – PWM - 1
-VIN (@5mA typical) ~3.3V
Where VIN = Existing Bus / Boost Voltage
ILED=200×(VCONTROL-VCTR)/RSET
Key advantages:
VCONTROL = PWM
y No need for current matching resistors
and discrete transistor for brightness
control.
y Amplitude sets maximum LED current
y Pulse width controls between 0 and
maximum
Notes:
Scenario 3 – PWM - 2
1. Whether using analog or PWM signal, please
notice to avoid from exceeding the absolute
maximum rating claimed in this document.
2. EN must be turned on prior to VIN (delivered by
boost circuit or existing bus) and avoid from
VIN > 6V when EN is off.
ILED ~ 200×ISET
VEN = PWM
y Amplitude has no effect on current
y Pulse width controls between 0 and
maximum
YB1303 Rev.1.0
www.yobon.com.tw
7
YOBON [ YOBON TECHNOLOGIES,INC. ]
