YB1506 Datasheet, PDF (5/10 Pages) YOBON TECHNOLOGIES,INC. – Step-up DC-DC Converter , White LED Driver

Function Block
YB1506
Step-up DC-DC Converter , White LED Driver
Figure 3jFunction Block
Application Information
The YB1506 features a constant off-time
control scheme. The Housekeeping provides
a bandgap reference used to control the
output voltage. When the voltage at the FB
Inductor Selection
The appropriate inductor for a given
application is calculated using the
following equation:
pin is less than trip point, the input comp
amplifier enables the device and the NMOS
switch is turned on pulling the SW pin to
L
=
⎜⎜⎝⎛ ^VOUT
−
V_{IN, MIN}
I _CL
+
V_D
⎟⎟⎠⎞ ^TOFF
ground. When the NMOS switch is on,
current begins to flow through inductor L
while the load current is supplied by the ^{Where VD is the schottky diode}
output capacitor Cout. Once the current in the ^{voltage, ICL is the switch current limit}
inductor reaches the current limit, the CL ^{found in the Typical Performance}
Comp trips and the timer turns off the NMOS ^{Characteristics section, and TOFF is the}
switch. The inductor current will now begin to ^{switch off time. When using this}
decrease. At the same time, the energy ^{equation be sure to use the minimum}
stored in the inductor transferred to Cout and ^{input voltage for the application, such}
the load. After the 400ns off time the NMOS ^{as for battery-powered application.}
switch is turned on and energy is stored in Choosing inductor with low ESR
the inductor again.
decrease power losses and increase
When FB reaches the trip point, the input ^efficiency.
comp amplifier then disables the device and
turns off the NMOS switch. The SHDN pin
can be used to turn off the device. In the
shutdown mode the output voltage will be a
diode drop lower than the input voltage.
YB1506 MRev1.1
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