MB39C031 datasheet(23/69 Pages) CYPRESS

23 / 69 page

Document Number: 002-08407 Rev. *B

Page 23 of 69

MB39C031

15.

Protection Operation Sequence

DD channel

The DD channel monitors the FET current peak value at any time during the operation. When the DD output becomes the over

current state, the output voltage is decreased. Afterward, the timer operation is performed and the output stops after about 1ms

progress.

LDO channel

It contains the fold-back type over current protection circuit in order to prevent destroy because of the over load and the output

over current. It limits the output current and the output voltage from the peak around the over current protection value for LDO

(ILIMIT) to the over current current (Is).

At this time, if the output voltage Vo gets lower than the detection voltage Vd (Vd: Vo×0.5), the timer operation starts and the output

stops after about 1ms progress. Moreover, because the over current protection circuit does not operate at the soft-start (0V to Vo ×

0.7), neither the output stops nor the error signal outputs. However, the fold-back type over current protection characteristic

functions. The following shows the fold-back type over current protection characteristic.

Thermal shutdown protection

If the temperature at the junction part reaches +150 °C, the thermal shutdown protection circuit turns all channels off.

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