AL1696

Document number: DS38304 Rev. 1 - 2

9 of 14

www.diodes.com

October 2015

© Diodes Incorporated

AL1696

5

REF

PEAK

V

I

R



It automatically provides a cycle-by-cycle protection of maximum current through MOSFET during operation. A propagation delay exists between

over current detection and actual source-switch off, so the actual peak current will be a little higher than the OCP level set by R5.

Output-Short Protection (OSP)

When LED is shorted, the device can

Over-Temperature Protection (OTP)

The AL1696 has OTP protection function. When the junction temperature reaches +170°C typical, it will trigger an over-temperature protection

which makes IC shut down and latched. Once OTP is triggered, the system will only restart after the system

’s power supply powers off and on

again.

Design Parameters based on buck-boost topology

Setting the Current Sense Resistor R5

operation modes will be:

1

sin

1.3

a











Then the output current can be calculated as below:

_

_

_

_

0

_

_

_

2

sin( )

2

sin( )

2

sin( )

( 1.3 sin( )

+

1.3 sin( )

)

25

2

sin( )

2

sin( )

2

sin( )

IN

RMS

IN

RMS

IN

RMS

REF

O MEAN

IN

RMS

O

IN

RMS

O

IN

RMS

O

V

V

V

V

I

dt

dt

dt

R

V

V

V

V

V

V



 





 











































Where,

R5 is the current sense resistor.

Inductance Selection (L2)

The peak current of the MOSFET is calculated as below:

5

REF

PEAK

V

I

R



_

_

2

2

2+

IN

RMS

O

PEAK

IN

RMS

O

MIN

VV

L

I

V

V

f







（

）

According to the Faraday

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