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 RFB1 and RFB2. The sum of RFB1 and RFB2 should normally be 2 MΩor less.
VOUT = 0.9 x (RFB1 + RFB2) / RFB2
The value of CFB1, speed-up capacitor for phase compensation, should result in fzfb = 1/(2π×CFB×RFB1) 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 ]
RFB1 : 120kΩ
RFB2 : 45kΩ
CFB
: 47pF
68pF
(fzfb = 30kHz, L = 10μH)
(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:
*When a NPN Tr. Is used:
XP161A1355PR (N-ch Power MOSFET, TOREX)
Note*: As the breakdown voltage of XP161A1355 is 8V, take care
with the power supply voltage.
2SD1628 (SANYO)
RB : 500Ω(Adjust with Tr's HSE or load)
With output voltages over 6V, use the XP161A1265 with a
breakdown voltage of 12V.
VST1: XP161A1355PR =1.2V (MAX.)
: 2200pF (Ceramic type set so that RB and
pole is less than 70% of FOSC)
CB<1 / (2πx RB x FOSC x 0.7)
CB
XP161A1265PR = 1.5V (MAX.)
:
SD
L, CL
L
MA2Q737 (Schottky type, MATSUSHITA)
:
When Using Ceramic Type
:
22μH (CDRH5D28, SUMIDA, FOSC = 100, 180kHz)
10μH (CDRH5D18, SUMIDA, FOSC = 300, 500kHz)
:
CL
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 (IOUT(mA) / 300mA x VOUT / VIN)
100mΩ (FOSC = 180, 300, 500kHz)
:
RSENSE
50mΩ (FOSC = 100kHz)
:
CL
Tantalum Type
:
L
22μH (CDRH5D28, SUMIDA, FOSC = 300kHz)
47μH (CDRH5D28, SUMIDA, FOSC = 100, 180kHz)
Except when IOUT(mA) / 100mA x VOUT / VIN > 2 → 22μH
10μH (CDRH5D18, SUMIDA, FOSC = 500kHz)
:
CL
16V, 47μF (Tantalum Type 16MCE476MD2, NICHICHEMI)
Use the formula below when step-up ratio and output current is
large.
CL = (CL standard value) x (IOUT(mA) / 300mA x VOUT / VIN)
Not required, but short out the wire.
:
RSENSE
:
CL
AL Electrolytic Type
:
L
22μH (CDRH5D28 SUMIDA, FOSC = 300kHz)
47μH (CDRH5D28 SUMIDA, FOSC = 100, 180kHz)
Except when IOUT(mA) / 100mA x VOUT / VIN > 2 → 22μH
:
CL
16V, 100μF (AL Electrolytic Type) + 10V, 2.2μF (Ceramic Type)
Strengthen appropriately when step-up ratio and output current is
large.
:
:
RSENSE
CFB
Not required, but short out the wire.
Set up so that fzfb = 100kHz.
8/23
TOREX [ Torex Semiconductor ]
