YB1300S
Switched Capacitor Boost Converter 5V/4.5V
Functional Block
Cpump
C
N
V
IN
5
Short-Circuit
Protection
4
6
C
P
Soft-Start
Circuit
1
BOOST DRIVER
V
OUT
C
OUT
C
IN
Current Bias
Generator
Boost Feedback &
Timing Control Block
EN
3
Chip
Enable
1MHz
Oscillator
Thermal
Protection
VREF
2
GND
Figure 3. Block Diagram
Functional Description
The YB1300S regulated charge pump
provides a regulated 5V output voltage for
input voltages between 2.7V and 5V. This is
accomplished by a step-up or boost mode
of operation. A conversion clock of 50%
duty cycle is generated. During the first half
cycle, the pumping capacitor C
PUMP
charges to V
IN
. During the second half
cycle, the voltage on C
PUMP
is added to V
IN
,
then deliver to V
OUT
. The output voltage is
regulated by skipping clock cycles as
necessary.
Soft-Start and Short-Circuit Protection
Circuitry
The YB1300S includes soft-start circuitry to
YB1300S MRev.1.0
limit inrush current at turn-on. When
starting up, the output capacitor is charged
through the charge-pump capacitor with a
limited current source. When the output
voltage approached to its design value, the
soft-start is terminated and normal
operation begins. If an overload condition
occurs, for example, the output is shorted
to ground, the output current is limited by
the YB1300S switching technique.
Thermal Protection
The regulator has thermal shutdown
circuitry that protects it from damage
caused by high temperature conditions.
The thermal protection circuitry shut down
6
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YOBON [ YOBON TECHNOLOGIES,INC. ]
