L6995

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be supposed linear function of the time.

Eq 8

so the output voltage is given by:

Eq 9

Eq 10

Eq 11

1.5 Current limit

pares this value with the ILIM pin voltage value. While the current is above the current limit value, the control

inhibits the one-shot start.

To properly set the current limit threshold, it should be noted that this is a valley current limit. Average current

The average output current in current limit is given by:

Eq 12

Thus, to set the current threshold, choose RILIM according to the following equation:

Eq 13

output voltage meets the undervolatge threshold. The system is capable to sink current, but it has not a negative

current limit.

The system accuracy is function of the exactness of the resistance connected to ILIM pin and the low side MOS-

tem linearity.

Figure 6. Current limit schematic

I

()

R

K

C

I

SS

t

⋅⋅

⋅

()

V

SS

C

SS

⋅

∆

()

----------------------------------------------------------------------------

=

V

()

Qt,C

SS

()

C

out

-------------------------

R

K

C

I

SS

t

2

⋅⋅

⋅

()

C

ou t

V

SS

C

SS

2

⋅⋅

∆

⋅

()

-------------------------------------------------------------------------------

==

I

()

V

out

C

ou t

V

SS

C

SS

2

⋅⋅

∆

⋅⋅

()

R

K

C

I

SS

⋅⋅

()

---------------------------------------------------------------------------------------

0.5

=

I

OUT

CL

I

max valley

I

∆

2

-----

+

=

I

max valley

R

ILim

Rds

on

-----------------

K

C

⋅

=

Positive current limit

R

ILIM

5µA

Current

Comparator

To

logic

PGN

D

PHASE

To inductor

LS