7 Output voltage positioning

L6722

18/34

Figure 8.

Offset definition (margin mode)

●

No Offset (M1=1; M2=0)

●

Positive Margin (M1=0; M2=0)

●

Negative Margin (M1=0; M2=1)

Offset resistors may be simply defined as follow

mode.

Offset current is always sourced from REF_IN pin: to avoid having steps during soft-start, the

the soft-start time as well as long enough to smooth the initial step. Typical values are in the

range of few tens / hundreds of nF.

Offset function can be easily disabled by shorting REF_IN and REF_OUT together.

Warning:

Maximum offset must be limited to less than 200mV to avoid setting the OVP protection

resulting in a maximum +25% margin.

7.2

Droop function (optional)

This method "recovers" part of the drop due to the output capacitor ESR in the load transient,

introducing a dependence of the output voltage on the load current: a static error proportional to

the output current causes the output voltage to vary according to the sensed current.

Figure 9 shows the Current Sense Circuit used to implement the Droop Function. The current

Ref

REF_IN

REF_OUT

To Vout

(Remote Sense)

FB

COMP

VSEN

64k

FBR

FBG

64k

M1

M2

V

REFIN

Ref

I

OS

R

OS1

⋅

+

=

V

REFIN

Ref

I

OS

R

OS1

⋅

+

()

R

OS2

R

OS1

R

OS2

+

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

⋅

=

R

OS1

V

TARGET

POS

–

Ref

–

I

OS

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

=

R

OS2

R

OS1

V

TARGET

POS

–

V

TARGET

POS

–

V

TARGET

NEG

–

–

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

⋅

=