![](http://datasheet.mmic.net.cn/290000/XC9505_datasheet_16185209/XC9505_8.png)
Functional Settings
< Output Voltage Setting, Ch.1 (Step-up DC/DC Converter Controller) >
Output voltage can be set by adding external split resistors. Output voltage is determined by the following equation, based on the values of
RFB11 and RFB12. The sum of RFB11 and RFB12 should normally be 1 M
or less.
V
OUT
1=0.9
×
(RFB11+RFB12) / RFB12
[Calculation Example]
When RFB11=220k
and RFB12=75k
:
V
OUT
1=0.9
×
(200k+75k) / 75k=3.3V.
[Typical Example]
VOUT
(V)
< Output Voltage Setting, Ch.2 (Inverting DC/DC Converter) >
Output voltage can be set by adding reference voltage and split resistors externally. Output voltage is determined using the following
equation and is based on the values of RFB21 and RFB22. The sum of RFB21 and RFB22 should normally be 500k
or less. The
equation uses Ch 1's (V
OUT1
) output voltage calculation method for the reference voltage.
V
OUT
2 = (0.9 - V
OUT
1) x (RFB21 / RFB22) + 0.9V
[Calculation Example]
When RFB21=17.5k
,
RFB22=10k
,
V
OUT
1=3.3V, V
OUT
2= - 3.3V
The value of speed-up capacitor for phase compensation CFB21 :
[Conditions: Heavy load (when coil current is continous.)]
fzfb2 = 1/2 x
π
x CFB21 x RFB21) = 10kHz
Depending on the application, the inductance value L, and the load capacity value CL, adjustments to this value are suggested so that the
value is somewhere between 1kHz to 50kHz.
[Conditions: Light load (when coil current is discontinous.)]
Less than CFB21=0.1
μ
F
Depending on the application, the inductance value L, and the load capacity value CL, adjustments to this value are suggested.
> Example Circuit 1 : Using voltage of Ch 1 (Step-Down)
> Example Circuit 1 : Using a positive regulator
VOUT2 = (0.9 - VROUT) x (RFB21 / RFB22) + 0.9V
Channel 1 (Step-Down) circuits should be enable by setting EN1 to
High level so that a stable voltage is provided. Inrush current to the
inverter when the supply voltage VDD of the IC is 2.0 V or higher can
be controlled by setting EN 1 and EN 2 to enable (“H” level)
simultaneously.
A stable positive voltage produced by a positive-voltage regulator or
by other means is usable.
2.0
2.2
VOUT
(V)
5.0
3.0
3.3
1.0
1.5
1.8
220
330
220
270
62
39
560
200
240
75
24
62
180
33
33
220
330
62
360
2.7
30
270
430
390
220
2.5
RFB12
(k
)
CFB1
(pF)
2ch. Step-Down / Inverting DC/DC Controller ICs
RFB11
(k
)
RFB12
(k
)
CFB1
(pF)
RFB11
(k
)
XC9505 Series
390
270
33
82
18
160
The speed-up capacitor for phase compensation's (CFB1) value should be adjusted using the formula fzfb=1/(2
×π×
CFB1
×
RFB11) so that it
equals 12kHz. Depending on the application, the inductance value L, and the load capacity value CL, adjustments to this value are
suggested so that the value is somewhere between 1kHz to 50kHz.
SBD2
RFB21
CFB21
VOUT2
CL2
RFB22
VOUT1
FB2
Inside of XC9505 IC
SBD2
RFB21
CFB21
VOUT2
CL2
RFB22
FB2
Inside of
XC9505 IC
VR
To the other
circuit
VR_OUT
8