Document Number: 002-08491 Rev.*C

Page 29 of 51

S6AP111A28

L

OUT

ΔI

ESR

ΔV





12. Application Note

12.1 Setting Operating Conditions

Setting the Output Voltage

You can set the output voltage by adjusting the R1 and R2 resistance ratio. The output voltage is calculated using the following

formula.

2

ΔV

)

R

)

t

10

2.800

-

(1

ΔI

0.0184

0.0100

-

(INTREF

R2

R2

R1

V

OUT

ON_Sync

OFF

7

L

OUT





















OSC

IN

O

O

IN

L

V

V

L

V

-

V

ΔI

f

UT

UT







,

IN

OSC

OUT

IN

OFF

V

f

)

V

-

(V

t





INTREF

: Internal reference voltage (DC threshold) [V]

: Output settings voltage [V]

: Power supply voltage [V]

: Output ripple voltage value [V]

: Off time [s]

: ON resistance of low side FET [

Ω]

: Ripple current peak-to-peak value of inductor [A]

ESR

: Series resistance element of output capacitor [

Ω]

L

: Inductor value [H]

: Switching frequency [Hz]

Select a total resistor value (R1+R2) of up to 100 k

Ω for the setting output resistor.

Figure 12-1. FB Connection

Connecting the Feedback Capacitor

The IC internally generates the output voltage slope during the OFF period to stabilize the switching frequency, but it is also effective

voltage value to the FB terminals is more effective than high output voltage conditions that decrease it based on the R1 and R2 ratio.

When selecting which capacitors to add, use the following formula.

2

1

2

)

2

1

(

10

R

R

f

R

R

C

OSC

FB















: Feedback capacitor capacitance [F]

R1,R2

: Output voltage setting resistance [Ω]

: Switching frequency [Hz]

FBx

R1

R2

VOx

x: Each channel number