L6756D

Output voltage positioning

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5.2

Current reading and current sharing loop

L6756D embeds a flexible, fully-differential current sense circuitry that is able to read across

inductor parasitic resistance or across a sense resistor placed in series to the inductor ele-

ment. The fully-differential current reading rejects noise and allows placing sensing element

in different locations without affecting the measurement's accuracy. The trans-conductance

the reading points. The current sense circuit always tracks the current information, the pin

CSx is used as a reference keeping the CSxN pin to this voltage. To correctly reproduce the

inductor current an R-C filtering network must be introduced in parallel to the sensing ele-

ment. The current that flows from the CSxN pin is then given by the following equation (See

Figure 7):

Considering now to match the time constant between the inductor and the R-C filter applied

(Time constant mismatches cause the introduction of poles into the current reading network

causing instability. In addition, it is also important for the load transient response and to let

the system show resistive equivalent output impedance) it results:

35

μA at the OC Threshold.

tional to the current delivered by each phase and the information about the average current

that with a proper gain is used to adjust the duty cycle whose dominant value is set by the

voltage error amplifier in order to equalize the current carried by each phase.

Figure 7.

Current reading connections

I

CSx-

DCR

R

G

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

1

s L DCR

⁄

⋅

+

1s R C

⋅⋅

+

-------------------------------------- I

⋅

PHASEx

⋅

=

L

R

L

-------

RC

I

CSxN

R

L

Rg

-------- I

PHASEx

⋅

=

⇒

⋅

I

INFOx

==