L6712A L6712

20/29

Figure 16. Main Control Loop Diagram

3.12.1Current Sharing (CS) Control Loop

Active current sharing is implemented using the information from Trans conductance differential amplifier.

read current and this reference is converted to a voltage with a proper gain and it is used to adjust the duty

cycle whose dominant value is set by the error amplifier at COMP pin (See Figure 17).

The current sharing control is a high bandwidth control loop allowing current sharing even during load transients.

The current sharing error is affected by the choice of external components; choose precise Rg resistor

(±1% is necessary) to sense the current. The current sharing error is internally dominated by the voltage

offset of Trans conductance differential amplifier; considering a voltage offset equal to 2mV across the

sense resistor, the current reading error is given by the following equation:

Figure 17. Current Sharing Control Loop.

L1

L2

+

+

PWM1

1/5

+

-

1/5

4/5

PWM2

FB

COMP

ERROR

AMPLIFIER

REFERENCE

PROGRAMMED

BY VID

CURRENT

SHARING

DUTY CYCLE

CORRECTION

D03IN1518

RA_Gain

∆I

READ

I

MAX

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

2mV

R

SENSE

I

MAX

⋅

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

=

L1

L2

+

+

PWM1

1/5

1/5

PWM2

COMP

CURRENT

SHARING

DUTY CYCLE

CORRECTION

D02IN1393