YB1313 Datasheet, PDF (6/9 Pages) YOBON TECHNOLOGIES,INC. – 1x/1.5x/2x Charge Pump for White LED Application

YB1313
1x/1.5x/2x Charge Pump for White LED Application
Applications Information
Soft-Start Circuitry
The YB1313 includes soft-start circuitry to
limit inrush current at turn-on. Once the input
voltage is applied, the output capacitor is
charged directly from the input with a ramped
current source (with no charge-pump action)
until the output voltage approaches the input
voltage. Once this occurs, the charge pump
determines if 1x, 1.5x, 2x mode is required. In
the case of 1x mode, the soft-start is terminated
and normal operation begins. In the case of
1.5x or 2x mode, soft-start operated until the
lowest of LED1-LED4 reaches regulation.
ENABLE (EN1, EN2)
The enable pins EN1 and EN2 are used to
enable the device or set it into shutdown. The
YB1313 is enabled if one of the enable pins is
pulled higher than the enable trip point of 1.2V.
The device starts up by going through the soft
start routine as described in the section Soft
Start. Pulling both pins to GND, after a delay,
programs the device to shutdown. In shutdown,
the charge pump, current sources, voltage
reference, oscillator, and all other functions are
turned off and the supply current is reduced to
0.1μA.
EN1 and EN2 can also be used for dimming.
The logic levels at EN1 and EN2 set the
minimum voltage at the current mirrors and the
voltage at the ISET pin to GND. This sets the
current at the LEDs to be either the full current
or a fraction of the full current. See Table 4 for
further details. The maximum current through
the LEDs is set by a resistor connected between
ISET and GND.
EN1 and EN2 can also be used for PWM
dimming. The PWM signal can either be
applied to EN1 or EN2, or both inputs can be
tied together and the PWM signal can be
applied to both pins. Depending on the
configuration, the current during PWM
dimming is switched between 0 mA and its
maximum (EN1 and EN2 connected to the
PWM signal) or between 0 mA and 1/3 of the
full LED current if EN2= 0 and EN1 is toggled.
When EN1 = 0 and EN2 is toggled, the output
current can be changed between 0 mA and 2/3
of the full range.
Table 4. Enable Levels
Enable Level
EN2 EN1
MODE
0
0
Shutdown
0
1 V_ISET=200mV
1
0 V_ISET=400mV
1
1 V_ISET=620mV
LED
Current
0
1/3
2/3
Full
LED Current Setting
The current of white LED connected to
YB1313 can be set by R_SET. Every current
flows through the white LED is 320 times
greater than the current of R_SET. The white LED
can be estimated by following equation:
I _LED
=
320
×
⎜⎜⎝⎛
V_ISET
R_SET
⎟⎟⎠⎞
YB1313 MRev.1.1
www.yobon.com.tw
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