L6986ITR datasheet(18/60 Pages) STMICROELECTRONICS

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4.8

Output voltage load regulation

Primary output load regulation

Figure below shows negligible primary output voltage variation (normalized to the value measured at IOUT = 0 A)

over the entire output current range for the L6986I with VOUT = 5.3 V.

Figure 19. Load regulation of the not isolated output

-0.6%

-0.5%

-0.4%

-0.3%

-0.2%

-0.1%

0.0%

0.1%

0.2%

0.3%

0.4%

0.5%

0.6%

0.2

0.4

0.6

0.8

1.2

1.4

1.6

1.8

IOUT_prim [A]

Secondary output load regulation

Since there is not a regulation loop involving the secondary output, its load regulation depends to some extent

on the primary load regulation and is affected by the leakage inductance (see figure below) of the transformer,

the voltage drops across to the Schottky diode (diode forward voltage) and the DCR of the secondary coil, as

indicated by the equation (1) (where only the last two contribution are considered). Minimizing all the mentioned

parameters leads to a better load regulation.

Figure 20. Effect of the transformer leakage inductance on the isolated output load regulation

-15%

-10%

-5%

10%

15%

100

IOUT [mA]

Lleak = 240nH

Lleak = 700nH

The input voltage also plays a role in the isolated output regulation. The figure below further proves the slight

dependency of the isolated output voltage on the input voltage.

L6986I

Output voltage load regulation

DS13647 - Rev 1

page 18/60

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