17

 2004 Semtech Corp.

www.semtech.com

SC4605

POWER MANAGEMENT

Over current protection characteristic of SC4605 for 3.3V to 1.5V @12A application

The over current protection curve below is obtained by applying a gradually increased load while the load current

and the output voltage are monitored and measured. When the load current is increased from 0 to 16.2A (over

current trigger point), the output voltage is 1.5V, corresponding from Point A to Point B. As the load current in-

creases further from 16.2A to 16.3A, the output voltage drops significantly from 1.5V (Point B) to 0.88V (Point C).

Because an over current and a lower output voltage (0.88V<68.75%*1.5V=1.03V) are present at Point C, the

SC4605 enters its HICCUP mode. Then the locus of the output current and the output voltage follows Line CD as

shown in the curve. Due to the over current applied, the HICCUP protection will go back and forth on Line CD. This

prevents excess power dissipation in the TOP MOSFET during a short output condition.

Applications Information (Cont.)

Over current protection

0

0.5

1

1.5

2

2.5

3

0

5

10

15

20

Io (A)

B

C

D

A

Over current protection

0

0.5

1

1.5

2

2.5

3

0

5

10

15

20

Io (A)

B

C

D

A