XC9119D10A
Series
■OPERATIONAL
EXPLANATION (Continued)
<Lx (Pin No. 1): Switch Pin>
Please connect the anode of an Schottky barrier diode and inductor to the Lx pin.
<FB (Pin No. 3): Voltage Feedback Pin>
The reference voltage is 1.0V (TYP.).
Output voltage is approximated by the following equation according to the value
for two resistors (R
FB1
and R
FB2
). The sum of the two resistors should be 1MΩ or less.
V
OUT
= R
FB1
/ R
FB2
+ 1
Output voltage should be set as to fill
V
OUT
<(Maximum value of V
Lx
) – (V
F
of Schottky diode).
Please adjust the C
FB
value of the speed–up capacitor for phase compensation so that
fzfb=1/(2
π
x C
FB
x R
FB1
)
will be
about 500Hz. According to the usage, adjusting the inductance value, the load capacity value, and so on to the most
suitable operation.
Typical example:
V
OUT
(V)
3.3
5.0
7.0
10.0
15.0
18.0
R
FB1
(kΩ)
300
300
180
270
510
510
R
FB2
(kΩ)
130
75
30
30
36
30
C
FB
(pF)
1000
1000
1800
1200
510
510
<V
DD
(Pin No. 5): Power Supply Pin>
Please connect an input by-pass capacitor (C
IN
).
●Application
Information
<Obtaining V
DD
from other source than V
IN
>
In case that the input voltage V
IN
and power source V
DD
in the step-up circuit are isolated, the circuit starts step-up
operations with the input voltage less than 2.5V when voltage from 2.5V to 6.0V is applied to the power source. Please
connect more than 1uF of C
DD
between the V
DD
pin and the V
SS
pin as close as possible.
Ex.) When V
DD
=3.6V, V
IN
=1.8V, V
OUT
=5.0V (R
FB1
=300kΩ, R
FB2
=75kΩ, C
FB
=1000pF, C
L
=10uF), the IC can operate up to
I
OUT
=40mA.
V
DD
2.5V~6V
C
DD
L
SD
R
SS
C
IN
4.7uF
C
SS
V
DD
Lx
R
FB1
C
FB
C
L
10uF
R
FB2
V
IN
CE/SS
V
SS
FB
■NOTES
ON USE
1. Please do not exceed the value of stated absolute maximum ratings.
2. The DC/DC converter performance is greatly influenced by not only the ICs’ characteristics, but also by those of the
external components. Care must be taken when selecting the external components.
3. Make sure that the PCB GND traces are as thick as possible, as variations in ground potential caused by high ground
currents at the time of switching may result in instability of the IC.
4. Please mount each external component as close to the IC as possible and use thick, short connecting traces to reduce
the circuit impedance.
5. Please set up the output voltage value so that the Lx pin voltage does not exceed 20V.
9
TOREX [ TOREX SEMICONDUCTOR ]
