YB1313
1x/1.5x/2x Charge Pump for White LED Application
Thermal Protection
The regulator has thermal shutdown circuitry
that protects it from damage caused by high
temperature conditions. The thermal protection
circuitry shut down the device when the
junction temperature reached approximately
160℃, allowing the device to cool. When the
junction temperature cools to approximately
140℃, the device is automatically reenabled.
Continuously running the regulator into thermal
shutdown can degrade reliability.
Undervoltage Lockout
The undervoltage lockout circuit shuts down
the device when the voltage at VIN drops
below a typical threshold of 2.2V. The prevents
damage to the devices.
Termination of Unused Current Source
Outputs
If any outputs (D1 to D5) are not used, the
LEDs pin should be connected to V
DD
or
floating. Figure 4 shows the connection for
4LEDs application, D5 pin is connection to
V
DD
directly.
Power Efficiency
The battery current and efficiency of the
YB1313 are mostly dependent on the chare
pump mode of operation. To get the best
performance form the YB1313 it is better to use
LEDs with consistently lower V
F
voltage.
Lower V
F
will keep the charge pump in 1x
mode longer and will uses less battery current,
extending the run time of the battery. The
power conversion efficiency of the YB1313 can
be calculated by adding up the products of each
LED current and voltage and dividing it by the
product of the input voltage and current. With a
fully charged battery where the input voltage is
typically above the LED forward voltage, the
charge pump operates in the 1x mode and
efficiency is high. As the battery discharges,
there is a point where the current sources no
longer have enough voltage overhead to
maintain a constant current regulation. At that
point, the charge pump switches into the 1.5x
mode. The conversion efficiency is lowest at
the crossover. When in 1x mode the voltage
conversion efficiency is defined as output
power divided by input power:
η
=
P
OUT
V
OUT
×
I
OUT
=
×
100%
P
IN
V
IN
×
I
IN
P
OUT
V
OUT
×
I
OUT
=
×
100%
P
IN
V
IN
×
(
I
OUT
+
I
Q
)
I
IN
=
I
OUT
+
I
Q
η
=
Figure 4. Application for 4 LEDs.
YB1313 MRev.1.1
When in 1.5x or 2x mode the voltage
conversion efficiency is as output power
divided by input power:
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YOBON [ YOBON TECHNOLOGIES,INC. ]
