XC9503 Series
2ch. Step-down DC/DC Controller ICs
<Setting of Output Voltage>
Output voltage can be set by adding external split resistors. Output voltage is determined by the following equation, based on
the values of RFB11(RFB21) and RFB12(RFB22). The sum of RFB11(RFB21) and RFB12(RFB22) should normally be 1 M
Ω
or
V
OUT
=0.9
×
(RFB11+RFB12) /RFB12
The value of CFB1(CFB2), speed-up capacitor for phase compensation, should be fzfb= 1 / (2
× π ×
CFB1
×
RFB11) which is
equal to 12kHz. Adjustments are required from 1kHz to 50kHz depending on the application, value of inductance (L), and value
of load capacity (CL).
[Example of Calculation]
When RFB11=200kΩ and RFB12=75kΩ, V
OUT1
=0.9
×
(200k+75k) / 75k=3.3V.
[Typical Example]
RFB11
RFB12
RFB11
V
OUT
CFB1
V
OUT
(V)
(pF)
(V)
(kΩ)
(kΩ)
(kΩ)
1.0
1.5
1.8
2.0
2.2
30
220
220
330
390
270
330
220
270
270
430
62
62
39
33
2.5
2.7
3.0
3.3
5.0
390
360
560
200
82
RFB12
(kΩ)
220
180
240
75
18
CFB1
(pF)
33
33
24
62
160
The same method can be adopted for channel two also.
[External Components]
Tr :
* MOSFET
XP162A12A6P
(TOREX P-Channel Power MOSFET)
Note : VGS Breakdown Voltage of this Tr. is 12V
so please be careful with the power supply voltage.
MA2Q737
(Schottky , MATSUSHITA)
CMS02
(Schottky, TOSHIBA)
10µH
(SUMIDA, CDRH5D28, FOSC = 500kHz)
22µH
(SUMIDA, CDRH5D28, FOSC = 300kHz)
22µH
(SUMIDA, CDRH5D28, FOSC = 180kHz)
16V, 47µF
(Tantalum)
Increase capacity according to the equation below
when the step-up voltage ratio is large and output
current is high.
C=(CL standard value)×(IOUT (mA)/500mA×VOUT/VIN
SD :
L:
CL :
Tr :
RB :
* PNP MOSFET
2SA1213 (SANYO)
500Ω
( Adjust in accordance with load & Tr.'s HFE.)
Set according to the equation below.
RB
≤
(VIN-0.7) x hFE / I
C
-R
EXTBH
2200pF (Ceramic)
Set according to the equation below.
CB
≤
(2
π
x RB x FOSC x 0.7)
CB :
The same components can be adopted for both channel 1 and channel 2.
8
TOREX [ TOREX SEMICONDUCTOR ]
