A5974D datasheet(30/46 Pages) STMICROELECTRONICS

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Application information

A5974D

30/46

DocID018774 Rev 2

8.4

R.M.S. current of the embedded Power MOSFET

As the A5974D device embeds the high-side switch and so the internal power dissipation is

sometimes the bottleneck for the output current capability (refer to Section 8.3 on page 24

for the estimation of the operating temperature).

Nevertheless, as mentioned in Description on page 1, the device can manage a continuous

output current of 2.5 A in most of the application conditions.

However the rated maximum RMS current of the power elements is 2 A, where:

Equation 31

and the real duty cycle D:

Equation 32

Fixing the limit of 2 A for IRMS HS the maximum output current can be derived, as illustrated

in Figure 18..

Figure 18. Maximum continuous output current vs. duty cycle

IRMS HS

ILOAD



VOUT

RDS ON LS DCR

 I

LOAD



VIN

RDS ON LS RDS ON HS

–

 I

LOAD



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