L6717 datasheet(51/56 Pages) STMICROELECTRONICS

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L6717

LTB Technology®

Doc ID 17326 Rev 1

51/56

LTB Technology®

LTB Technology® further enhances the performances 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 RLTB - CLTB 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.

RLTB - CLTB is designed according to the output voltage deviation dVOUT which is desired the

controller to be sensitive as follow:

LTB Technology® design tips.

–

Decrease RLTB to increase the system sensitivity making the system sensitive to

smaller dVOUT.

–

Increase CLTB to increase the system sensitivity making the system sensitive to

higher dV/dt.

Ref

COMP

VSEN

PWM

L/N

ESR

d VCOMP

VOUT

ZF(s)

ZFB(s)

VID

Monitor

RLTB

CLTB

PWM_BOOST

LTB Ramp

LTB

LT Detect

LTB

OUT

μA

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

LTB

π NR

LTB

⋅⋅

⋅

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

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