LA5759

No.A1683-3/4

Block Diagram

2SWOUT

DRIVE

OCP

RESET

OSC

Comp.

Reg.

Amp.

TSD

4VOS

VREF

0.4V

ON/OFF Comp.

1

VIN

5

SS

3

GND

Constnt

Current

Circuit

Application Circuit Example

VIN

SWOUT

VOS

GND

SS

L1

C1

C2

D1

LA5759

C3

R2

R1

Notes: C3 is for the soft start function. Delete C3 and keep the SS pin open when the soft function is not necessary.

Description of Functional Settings

1. Calculation equation to set the output voltage

This IC controls the switching output so that the VOS pin voltage becomes 1.26V (typ).

The equation to set the output voltage is as follows:

VO = 1+

× 1.26V(typ)

R2

R1

The VOS pin has the inrush current of 1μA (typ). Therefore, the error becomes larger when R1 and R2 resistance

values are large.