YB1303
Low Dropout LED Driver
Application Information
Analog Dimming Control Table
Table 4
V
EN
=3V, V
CONTROL
=3V
voltage. The lower the V
LED
voltage, the
higher the system efficiency. The system
efficiency can be calculated as follows:
Efficiency = (V
IN
-V
CATHODE
) / V
IN
Thermal Considerations
At any given ambient temperature, the
maximum package power dissipation can
be determined by the following equation:
P
D(MAX)
= [T
J(MAX)
-T
A
] /
θ
JA
Constraints for the YB1303 are maximum
junction temperature T
J(MAX)
=125
℃
, and
package thermal resistance,
θ
JA
=300℃/W.
The maximum total LED current for
YB1303 depends on package power
dissipation and the LED cathode voltage at
T
J(MAX)
. At 85℃, P
D(MAX)
=133mW. At T
A
=
25℃, P
D(MAX)
=333mW.
The maximum current is calculated by the
following equation:
I
LED
< (P
D(MAX)
/ V
LED(MAX)
)
For example, if I
LED
= 60mA, and T
A
= 85℃,
V
LED(MAX)
= 2.2V.
If the ambient temperature were to
increase, the internal die temperature
would increase, and the device would be
damaged.
I
LED
(mA)
5
10
15
20
25
R
SET
(kΩ)
75
34
24
17.4
13
Table 5
V
EN
=3V, R
SET
=17.4k
I
LED
(mA)
5
10
15
20
25
V
CONTROL
(V)
1.5
2.1
2.5
3
3.6
Setting the LED Current
The LED current can be set by the control
voltage and the R
SET
resistor from the
following equation.
I
LED
=200×(V
CONTROL
-V
CTR
)/R
SET
The suggested values and relations
between V
CONTROL
and R
SET
can also be
found in the diagram of typical
characteristics and table 4 and table5. The
LED brightness can be controlled by either
the above equation or applying a PWM
signal to the EN pin. The driving signal
frequency should be greater than 100Hz to
avoid flickering, and increased to more
than 1MHz if necessary.
Efficiency Considerations
The YB1303 featured low drop out can
achieve excellent efficiency performance.
The efficiency is mainly dominated by V
LED
YB1303 Rev.1.0
Application Examples
The ultra-low voltage drop across the
YB1303 allows the devices to drive white,
blue and any color LEDs in a wide range of
input voltages. The driver can be used in
many applications presented in this
document, due to their similar operation.
5
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YOBON [ YOBON TECHNOLOGIES,INC. ]
