High Current Application

Output Voltage Setting

R1

R2

Feedback Loop Design

Follow Equation A

recommended.

High Voltage Application

leakage, and improper probing to FB pins.

to hundreds K

Ω.

Multi-Output Applications

Referring to application circuits, The selection of R1and

) × 1.25V

R2 based on the trade-off between quiescent current

consumption and interference immunity is stated below:

Higher R reduces the quiescent current (Path current

Referring to application circuits, the output voltage of the

=1.25V/R2), however resistors beyond 5M

Ω are not

Lower R gives better noise immunity, and is less

sensitive to interference, layout parasitics, FB node

A proper value of feed forward capacitor parallel with

suspend modes, the higher values of R1and R2 are

R1 can improve the noise immunity of the feedback

loops, especially in an improper layout. An empirical

suggestion is around 0~33pF for feedback resistors

of M

Ω, and 10nF~0.1µF for feedback resistors of tens

For applications without standby or suspend modes,

lower values of R1 and R2 are preferred. For applications

concerning the current consumption in standby or

feedback needed. Such "high impedance loops" are

sensitive to any interference, which require careful

layout and avoid any interference, e.g. probing to FB pin.

CE

EXT

VDD

GND

FB

LX

L1

3.3--10uH

C2

1uF

C5

100uF

D1

C1

100uF

1N5819

Vin

Q1

NMOS

Vout

3.3V/5V

R1

1.6M/100K

R2

980k/33K

+

+

CE

EXT

VDD

GND

FB

LX

L1

4.7uH 2.5A

R1

R2

C2

C1

C3

CVDD

C4

47uF

D1

RVDD

47

12V / 9V / 8V

1000mA

Vin=3.1V 6.5V Vout=12V

+

1N5819

Vin=2.8V~ 6.5V Vout=9V

+

Q1

NMOS

CVDD=1uF

RM=0.2

C3=NC

R1=860K/620K/210K

R2=100K/100K/39K

C1=47uF

C2=10uF

R2=100

R1=620K

C6=0.1uF

CE

EXT

VDD

GND

FB

LX

L1

3.3--10uH

C3

10uF

C1

1uF

D1

C4

10uF

1N5819

Vin

3.3V/5V

Vout2

+18V 10mA

R1

R3

100

C2

10uF

Q1

NMOS

C5

10uF

R2

C6

C7

1uF

C8

1uF

Vout1

+9V 100mA

Vout3

-9V 10mA

P4 / 5

KB3301

KB3301

KB3301

KB3301

Applications

Application Note

Vin=4.0V 6.5V Vout=8V

XP161A1355PR FDN337N

NMOS=