L5988D datasheet(36/52 Pages) STMICROELECTRONICS

36 / 52 page

Application information

L5988D

36/52

DocID15324 Rev 4

Some measurements of the output regulation during load transient for the examples

provided in Section 6.8 on page 43 are provided at the end of this document.

6.5

R.M.S. current of the embedded power MOSFETs

The L5988D integrates both the power elements (high side and low side) and so the power

dissipation is often the bottleneck for the output current capability (refer to Section 6.6 for

the estimation of the operating temperature).

Nevertheless, as mentioned in Section 1: Description on page 6 the device can manage

a continuous output current of 4 A in most of the application conditions.

However the rated continuous current is 5 A and the rated RMS current of the power

elements is 4.5 A, where:

Equation 40

Equation 41

and the duty cycle D:

Equation 42

Fixing the limit of 4.5 A for IRMS HS and IRMS LS the maximum output current can be derived,

as illustrated in Figure 19.

IRMS HS

ILOAD



IRMS LS

ILOAD

–



VOUT

RDS ON LS DCR

 I

LOAD



VIN

RDS ON LS RDS ON HS

–

 I

LOAD



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