YB1303 Datasheet, PDF (7/8 Pages) YOBON TECHNOLOGIES,INC. – Low Dropout LED Driver

YB1303
Low Dropout LED Driver
Example 3:
Drive white, blue, red, amber LEDs
string
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).
LED Brightness Control
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
solution. To determine the value of R_SET,
use the “I_SET vs. V_CTR” graph under the
“typical characteristics” section.
-V_DROP < 0.3V
-V_{IN_MIN} = N×V_F + V_DROP
- V_{IN_MAX} = N×V_F + 6V
-V_IN (@5mA typical) ~3.3V
Where V_IN = Existing Bus / Boost Voltage
Key advantages:
y No need for current matching resistors
and discrete transistor for brightness
control.
Scenario 1 - Analog
Set V_CONTROL and R_SET for LED current
I_LED=200×(V_CONTROL-V_CTR)/R_SET
Scenario 2 – PWM - 1
I_LED=200×(V_CONTROL-V_CTR)/R_SET
V_CONTROL = PWM
y Amplitude sets maximum LED current
y Pulse width controls between 0 and
maximum
Notes:
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 V_IN (delivered by
boost circuit or existing bus) and avoid from
V_IN > 6V when EN is off.
Scenario 3 – PWM - 2
I_LED ~ 200×I_SET
V_EN = 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