L6713ATR datasheet(59/64 Pages) STMICROELECTRONICS

59 / 64 page

L6713A

Layout guidelines

59/64

24.2

Small signal components and connections

These are small signal components and connections to critical nodes of the application as

well as bypass capacitors for the device supply (See Figure 28). Locate the bypass

capacitor (VCC, VCCDRx and Bootstrap capacitor) close to the device and refer sensible

components such as frequency set-up resistor ROSC, over current resistor ROCP and OVP

resistor ROVP to SGND. Star grounding is suggested: connect SGND to PGND plane in a

single point to avoid that drops due to the high current delivered causes errors in the device

behavior.

Warning:

Boot capacitor extra charge. Systems that do not use

Schottky diodes might show big negative spikes on the

phase pin. This spike can be limited as well as the positive

spike but has an additional consequence: it causes the

bootstrap capacitor to be over-charged. This extra-charge

can cause, in the worst case condition of maximum input

voltage and during particular transients, that boot-to-phase

voltage overcomes the abs. max. ratings also causing device

failures. It is then suggested in this cases to limit this extra-

charge by adding a small resistor in series to the boot diode

(one resistor can be enough for all the three diodes if placed

upstream the diode anode, See Figure 28) and by using

standard and low-capacitive diodes.

Figure 28.

Power connections and related connections layout (same for all phases)

Remote sensing connection must be routed as parallel nets from the FB/VSEN pins to the

load in order to avoid the pick-up of any common mode noise. Connecting these pins in

points far from the load will cause a non-optimum load regulation, increasing output

tolerance.

Locate current reading components close to the device. The PCB traces connecting the

reading point must use dedicated nets, routed as parallel traces in order to avoid the pick-up

of any common mode noise. It's also important to avoid any offset in the measurement and,

to get a better precision, to connect the traces as close as possible to the sensing elements.

Symmetrical layout is also suggested. Small filtering capacitor can be added, near the

controller, between VOUT and SGND, on the CSx- line to allow higher layout flexibility.

CIN

VIN

UGATEx

PHASEx

LGATEx

PGNDx

LOAD

BOOTx

PHASEx

VCC

SGND

+Vcc

CIN

VIN

LOAD

To limit C

BOOT

Extra-Charge

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