AL1697

Document number: DS38223 Rev. 6 - 2

8 of 13

www.diodes.com

October 2017

© Diodes Incorporated

AL1697

The AL1697 is a closed loop constant current control with the relationship between output current and current sense voltage follows this equation

0

1

sin( ) R5

OFF

REF

PEAK

ON

OFF

DELAY

t

V

I

d

t

t

t







 











Where,

R5 is the current sense resistor

So we can get the output current equation as below,

_

1

=

25

REF

O MEAN

V

I

R



Inductance Selection (L2)

In buck-boost structure, the peak current of the inductance can be calculated as below

_

0

_

2

sin( )

5

sin( )

2

sin( )

REF

PEAK

IN

RMS

IN

RMS

V

I

V

Rd

V

Vo



























Where,

’s RMS value

The AL1697 controls the system operating at boundary conduction mode which results in its operating frequency not being constant. To set the

_

_

2

2

2+

IN

RMS

O

PEAK

IN

RMS

O

MIN

VV

L

I

V

V

f







According to the Faraday

’s Law, the winding number of the inductance can be calculated by:

2

2

PEAK

L

em

LI

N

AB







Where,

_

_

3.3

+0.5

10 R6

REF

ON MAX

RT

REF

C

t

V

uA







Where

’s reference.