L6918 L6918A

22/35

Figure 13. Current Sharing Control Loop.

The current sharing between devices uses the droop function. Each device can be modeled with its Thevenin

equivalent circuit (that is an ideal voltage source equal to the programmed voltage by VIDs and its related output

Considering this modelization reported in figure 14, it can be seen that the recirculating current between devices

depends on the accuracy of the regulation.

The accuracy of the voltage source is given by the offset of the master error amplifier Vos (6mV typ) and de-

between the regulated voltages causes a converter to source a current that is sunk by the other one. The accu-

The current sharing error (CSE) results:

Considering the external resistors tolerance of 1%, the typical current feedback accuracy of 2.5

µA/50µA (5%),

Figure 14. Equivalent Circuit for current sharing error calculation

L1

L2

+

+

PWM1

1/5

1/5

PWM2

COMP

CURRENT

SHARING

DUTY CYCLE

CORRECTION

D02IN1393

CSE

∆I

OU T

I

OU T

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

1

2

---

Vos

R

OU T

I

OU T

⋅

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



2

---

∆I

FB

I

FB

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





2

1

2

---

∆R

FB

R

FB

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





2

2

2

---

∆R

SEN SE

R

SE N SE

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





2

4

2

---

∆R

g

R

g

-----------





2

++

+

+

≡

=

CSE

1

2

---

0.006V

1.5m

Ω 60A

⋅

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





2

1

2

---

2.5

µA

50

µA

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





2

1

2

---

0.01

()

2

2

2

---

0.01

()

2

4

2

---

0.01

()

2

+

+++

0.062 6.2%

()

==

VID

L6918

Recirculating Current