L6756D

System control loop compensation

33/36

Sensitivity of the load transient detector and the gain of the LTB ramp can be programmed in

order to control precisely both the undershoot and the ring-back.

●

which is desired the controller to be sensitive as follow:

●

Gain design. Through the LTBGAIN pin it is possible to modify the slope of the LTB

Ramp in order to modulate the entity of the LTB response once the LT has been

detected. In fact, the response depends on the board design and its parasites requiring

different actions from the controller.

Leaving the LTBGAIN pin floating, the maximum pulse-width is programmed. The slope

of the LTB ramp will be equal to 1/2 of the OSC ramp slope.

(20

μA plus the current coming from the OSC pin).

–

–

higher dV/dt.

–

R

LTB

dV

OUT

25

μA

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

=

C

LTB

1

2

πNR

LTB

F

SW

⋅⋅

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

=

LTBRamp

Slope

OSC

Slope

1

I

LTBGAIN

I

OSC

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

+

⎝⎠

⎛⎞

⋅

=