XC9128/XC9129
Series
■TYPICAL
APPLICATION CIRCUIT
<Output Voltage Setting>
Output voltage can be set by adding external split resistors. Output voltage is determined by the following equation,
based on the values of R
FB1
and R
FB2
. The sum of R
FB1
and R
FB2
should normally be 500kΩ or less.
V
OUT
=0.45 × (R
FB1
+ R
FB2
) / R
FB2
The value of C
FB
, speed-up capacitor for phase compensation, should be
f
ZFB
= 1 / (2 x
π
x C
FB1
x R
FB1
)
which is in
the range of 10 kHz to 50 kHz. Adjustments are depending on application, inductance (L), load capacitance (C
L
) and
dropout voltage.
[Example of calculation]
When R
FB1
=270kΩ, R
FB2
=43kΩ,
V
OUT1
=
0.45 × (270k+43k ) / 43k = 3.276V
[Typical example]
V
OUT
(V)
1.8
2.5
3.3
5.0
R
FB1
(k
Ω
)
300
270
270
180
R
FB2
(k
Ω
)
100
59
43
17.8
C
FB
(pF)
10
12
12
15
[External Components]
1.2MHz:
L : 4.7μH (CDRH4D28C SUMIDA)
C
L1
: 22μF (ceramic)
C
L2
: 10μF (ceramic)
CIN: 10μF (ceramic)
* C
L1
should be selected in 10μF or higher.
Capacitance C
L1
+ C
L2
is recommended 30μF or higher. (Ceramic capacitor compatible)
If C
L1
is lower than 10μF, operation may be unstable.
In case of the usage C
L1
+ C
L2
＜30μF,
output ripple may increase so that we recommend that you fully
check actual performance on the board.
* If using Tantalum or Electrolytic capacitors please be aware that ripple voltage will be higher due to the larger
ESR (Equivalent Series Resistance) values of those types of capacitors. Please also note that the IC’s
operation may become unstable with such capacitors so we recommend that you fully check actual
performance.
7/13
TOREX [ TOREX SEMICONDUCTOR ]
