UCC2919

UCC3919

SLUS374C − JULY 1999 − REVISED NOVEMBER 2005

10

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APPLICATION INFORMATION

V

IN *

V

OUT w

1.4 V

t

ON +

C

T

DV

I

PL )

35

10−6

,

where

DV + 1V

equation for the average power dissipation during a short is:

P

DISS +

I

MAX

V

IN

1.2

10−6

I

PL )

35

10−6

,or

P

DISS +

I

MAX

V

IN

t

ON

t

ON )

t

OFF

If PL is left unconnected, the power limiting feature will not be exercised. In the retry mode, the duty cycle during

a fault will be nominally 3%, independent of input voltage. The average power dissipation in the external

MOSFET with a shorted output will be proportional to input voltage, as shown by the equation:

P

DISS +

I

MAX

V

IN

0.033

To ensure recovery from an overload when operating in the retry mode, there is a maximum total output

limiting) can be calculated from:

C

T(min) +

V

IN

C

OUT

35

10−6

I

MAX *

I

LOAD

and can be estimated from:

C

T(min) +

−C

OUT

R

L

n 1

*

V

IN

I

MAX

R

L

28

103

Note that in the latch mode (or when first turning on in the retry mode), since the timing capacitor is not recovering

from a previous fault, it is charging from 0 V rather than 0.5 V. This allows up to 50% more load capacitance

without causing a fault.

(8)

(9)

(10)

(11)

(12)

(13)