Functional Settings

< Output Voltage Setting, Ch.1 (Step-up DC/DC Converter Controller) >

× (RFB11+RFB12) / RFB12

[Calculation Example]

When RFB11=220k

[Typical Example]

< Output Voltage Setting, Ch.2 (Inverting DC/DC Converter) >

[Calculation Example]

When RFB21=17.5k

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

[Conditions: Light load (when coil current is discontinous.)]

Less than CFB21=0.1

µF

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.

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.

2.0

2.2

VOUT

(V)

5.0

3.0

3.3

VOUT

(V)

1.0

1.5

1.8

220

220

62

560

240

24

180

33

33

220

330

62

360

2.7

30

270

430

390

220

2.5

RFB12

(k

Ω)

CFB1

(pF)

2ch. Step-Down / Inverting DC/DC Controller ICs

RFB11

(k

Ω)

RFB12

(k

Ω)

CFB1

(pF)

RFB11

(k

Ω)

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

XC9505 Series

390

270

33

82

18

160

200

75

62

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.

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

330

270

39

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