XC9220/XC9221
Series
■OPERATIONAL
EXPLANATION (Continued)
●
Output Voltage Setting
Output voltage can be set by adding 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 1MΩ or less.
V
OUT
= 0.9 x (R
FB1
+ R
FB2
) / R
FB2
The value of C
FB
, speed-up capacitor for phase compensation, should be adjusted by the following equation. Fzfb
should usually be 5kHz. Adjustments are required from 1kHz to 20kHz depending on the application, value of
inductance (L), and value of load capacity (CL).
C
FB
= 1 / (2 x
π
x R
FB1
x fzfb)
[Sample
calculation: Setting 3.3V V
OUT
]
R
FB1
= 200k
Ω
, R
FB2
=75k
Ω
, V
OUT
= 0.9 x (200k + 75k) / 75k = 3.300V
C
FB
= 1 / (2 x
π
x 200k x 5k) =150pF
[Typical examples]
V
OUT
(V)
1.2
1.5
1.8
R
FB1
(kΩ)
100
180
220
R
FB2
(kΩ)
300
270
220
C
FB
(pF)
330
180
150
V
OUT
(V)
3.3
5.0
12.0
R
FB1
(kΩ)
200
150
160
R
FB2
(kΩ)
75
33
13
C
FB
(pF)
150
220
180
●
Recommended MOSFET and SBD (Examples)
I
OUT
P-ch MOSFET (*1)
Schottky Barrier Diode
(SBD) (*2)
*1:
*2:
UP TO 500mA
CPH3308
(SANYO)
XB01SB04A2BR
(TOREX)
UP TO 1A
UP TO 2A
2SJ616
(SANYO)
UP TO 3A
2SJ646
(SANYO)
DE5PC3
(SHINDENGEN)
D1FH3 (SHINDENGEN)
CMS02 (TOSHIBA)
Recommended to use P-ch MOSFET with Ciss less than 1500pF.
SBD should be used with high-toned reverse characteristics.
●
Ceramic Capacitor
With the XC9220/9221 series, a ceramic capacitor can be used as an output capacitor (CL). RSENSE resistor
is required for using the ceramic capacitor. The value of RSENSE resistor is determined depending on the
setting output voltage as the chart below.
OUTPUT VOLTAGE
V
OUT
≦2.5V
V
OUT
>2.5V
RSENSE (mΩ)
100
50
＜External
Components＞
P-ch MOSFET: 2SJ646 (SANYO)
SBD: DE5PC3 (SHINDENGEN)
L: CDRH8D28-4R7 (4.7μH, SUMIDA / Fosc=1.0MHz)
CDRH8D43-100 (10μH, SUMIDA / Fosc=500kHz)
CDRH127-220 (22μH, SUMIDA / Fosc=300kHz)
CIN: 22μF (ceramic)
CL: 22μF (ceramic / Fosc=1.0MHz, 500kHz)
47μF (ceramic / Fosc=300kHz)
RSENSE: 100mΩ (V
OUT
≦2.5V)
50mΩ (V
OUT
＞2.5V)
9/22
TOREX [ TOREX SEMICONDUCTOR ]
