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.
Scenario 1 - Analog
-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:
No need for current matching resistors
and discrete transistor for brightness
control.
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.
YB1303 Rev.1.0
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
Amplitude sets maximum LED current
Pulse width controls between 0 and
maximum
Scenario 3 – PWM - 2
I
LED
~ 200×I
SET
V
EN
= PWM
Amplitude has no effect on current
Pulse width controls between 0 and
maximum
7
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YOBON [ YOBON TECHNOLOGIES,INC. ]
