L6717ATR datasheet(52/57 Pages) STMICROELECTRONICS

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LTB Technology®

L6717A

52/57

DocID024465 Rev 1

LTB Technology®

LTB Technology

further enhances the performance of dual-edge asynchronous systems by

reducing the system latencies and immediately turning ON all the phases to provide the

correct amount of energy to the load. By properly designing the LTB network as well as the

LTB gain, the undershoot and the ring-back can be minimized also optimizing the output

capacitors count. LTB Technology

applies only to the CORE Section.

LTB Technology

monitors the output voltage through a dedicated pin detecting load-

transients with selected dV/dt, it cancels the interleaved phase-shift, turning-on

simultaneously all phases. it then implements a parallel, independent loop that reacts to

load-transients bypassing E/A latencies.

LTB Technology

control loop is reported in

Figure 19.

Figure 19. LTB Technology® control loop (CORE section)

The LTB detector is able to detect output load transients by coupling the output voltage

through an R

LTB

- C

LTB

network. After detecting a load transient, the LTB Ramp is reset and

then compared with the COMP pin level. The resulting duty-cycle programmed is then OR-

ed with the PWMx signal of each phase by-passing the main control loop. All the phases will

then be turned-on together and the EA latencies results bypassed as well.

Sensitivity of the load transient detector can be programmed in order to control precisely

both the undershoot and the ring-back.

LTB

- C

LTB

is designed according to the output voltage deviation dV

OUT

which is desired

the controller to be sensitive as follow:

LTB technology® design tips.

–

Decrease R

LTB

to increase the system sensitivity making the system sensitive to

smaller dV

OUT

–

Increase C

LTB

to increase the system sensitivity making the system sensitive to

higher dV/dt.

Ref

COMP

VSEN

PWM

L/N

ESR

d V

COMP

OUT

F(s)

FB(s)

VID

Monitor

LTB

PWM_BOOST

LTB Ramp

LTB

LT Detect

LTB

dVOUT

μA

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

LTB

π NR

LTB

⋅⋅

⋅

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

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