XC9103/XC9104/XC9105
Series
■
OPERATIONAL EXPLANATION (Continued)
< 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 2 MΩor less.
V
OUT
= 0.9 x (R
FB1
+ R
FB2
) / R
FB2
The value of C
FB1
, speed-up capacitor for phase compensation, should result in fzfb = 1/(2π×C
FB
×R
FB1
) equal to 5 to
30kHz. Adjustments are required depending on the application, value of inductance (L), and value of load capacity (CL).
fzfb = 30kHz (L=10μH)
fzfb = 20kHz (L=22μH)
fzfb = 10kHz (L=47μH)
[ Example of Equation ]
R
FB1
: 120kΩ
R
FB2
: 45kΩ
C
FB
: 47pF
(fzfb = 30kHz, L = 10μH)
68pF
(fzfb = 20kHz, L = 22μH)
130pF (fzfb = 10kHz, L = 47μH)
< The use of ceramic capacitor CL >
The circuit of the XC9103/04/05 series is organized by a specialized circuit, which reenacts negative feedback of both
voltage and current. Also by insertion of approximately 100mΩ of a low and inexpensive sense resistor as current sense,
a high degree of stability is possible even using a ceramic capacitor, a condition which used to be difficult to achieve.
Compared to a tantalum condenser, because the series can be operated in a very small capacity, it is suited to use of the
ceramic capacitor, which is cheap and small.
< External Components >
Tr
:*When a MOSFET is used:
XP161A1355PR (N-ch Power MOSFET, TOREX)
Note*: As the breakdown voltage of XP161A1355 is 8V, take care
with the power supply voltage.
With output voltages over 6V, use the XP161A1265 with a
breakdown voltage of 12V.
VST1: XP161A1355PR =1.2V (MAX.)
XP161A1265PR = 1.5V (MAX.)
:MA2Q737 (Schottky type, MATSUSHITA)
:When Using Ceramic Type
:22μH (CDRH5D28, SUMIDA, FOSC = 100, 180kHz)
10μH (CDRH5D18, SUMIDA, FOSC = 300, 500kHz)
:10V 10μF (Ceramic Type, LMK325BJ106ML, TAIYO YUDEN)
Use the formula below when step-up ratio and output current is
large.
CL = (CL standard value) x (I
OUT
(mA) / 300mA x V
OUT
/ V
IN
)
:100mΩ (FOSC = 180, 300, 500kHz)
50mΩ (FOSC = 100kHz)
:Tantalum Type
:22μH (CDRH5D28, SUMIDA, FOSC = 300kHz)
47μH (CDRH5D28, SUMIDA, FOSC = 100, 180kHz)
Except when IOUT(mA) / 100mA x V
OUT
/ V
IN
> 2
→
22μH
10μH (CDRH5D18, SUMIDA, FOSC = 500kHz)
:16V, 47μF (Tantalum Type 16MCE476MD2, NICHICHEMI)
Use the formula below when step-up ratio and output current is
large.
CL = (CL standard value) x (I
OUT
(mA) / 300mA x V
OUT
/ V
IN
)
:Not required, but short out the wire.
:AL Electrolytic Type
:22μH (CDRH5D28 SUMIDA, FOSC = 300kHz)
47μH (CDRH5D28 SUMIDA, FOSC = 100, 180kHz)
Except when
I
OUT
(mA) / 100mA x V
OUT
/ V
IN
> 2
→
22
μ
H
:16V, 100μF (AL Electrolytic Type) + 10V, 2.2μF (Ceramic Type)
Strengthen appropriately when step-up ratio and output current is
large.
:Not required, but short out the wire.
:Set up so that fzfb = 100kHz.
*When a NPN Tr. Is used:
2SD1628 (SANYO)
R
B
: 500Ω(Adjust with Tr's HSE or load)
C
B
: 2200pF (Ceramic type set so that R
B
and
pole is less than 70% of FOSC)
C
B
<1 / (2
π
x R
B
x FOSC x 0.7)
SD
L, C
L
L
C
L
R
SENSE
C
L
L
C
L
R
SENSE
C
L
L
C
L
R
SENSE
CFB
8/23
TOREX [ TOREX SEMICONDUCTOR ]
