A6984 datasheet(27/47 Pages) STMICROELECTRONICS

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A6984

Device description

The eDesignSuite on-line simulation tool (see

http://www.st.com/content/st_com/en/support/resources/edesign.html) supports the design

based on the A6984 device by inserting the required electrical specifications of the final

application. The interface is based on a fully annotated and interactive schematic and the

output provides a complete set of the analysis diagram to estimate the electrical, thermal

and efficiency performance.

Moreover, it is possible to design the optional virtual ESR network based on the output

voltage specification in terms of accuracy over the input voltage range.

4.4

Soft-start

The soft-start feature minimizes the inrush current and decreases the stress of the power

components during the power-up phase. The A6984 implements the soft-start, clamping the

device current limitation in four different steps in 2 msec time.

During normal operation, a new soft-start cycle takes place in case of:



Thermal shutdown event



UVLO event



EN pin rising

Figure 18 shows the soft-start feature. The green trace represents the inductor current

which shows different current protection thresholds.

Figure 18. Soft-start feature with resistive load

4.5

Light load operation

The LNM pinstrapping during the power-up phase determines the light load operation.

A6984 데이터시트(PDF) 27 Page - STMicroelectronics