S6BP401A Maximum Output Current During Soft-start – KBA223406

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Question:

Does the S6BP401A maximum output current during soft-start differ from that in normal operation state?

 

Answer:

For the DCDC channels (DD1~DD4), the maximum output current during soft-start is different from that in normal operation state because of the difference in switching frequency between the soft-start period and normal operation state.

For the LDO channels (LD1~LD2), the maximum output current during soft-start is different from that in normal operation state because of the foldback current limit characteristic at low output voltage. (Refer to “Figure 10-3 LDO Foldback Over Current Protection Characteristic” in the datasheet).

The maximum output current of each channel is as follows.

Table 1. S6BP401A Maximum Output Current

 

DD1

DD2

DD3

DD4

LD1

LD2

Maximum output current in normal operation state (min)

2.0 A

3.0 A

2.0 A

1.0 A

0.1 A

0.4 A

Maximum output current during soft-start (min)

1.150 A

2.145 A

1.150 A

0.589 A

0.099 A

0.109 A

 

When applying very large capacitance to the output of power supply or bypass capacitor of the load, the soft-start time will be lengthened if the charge current to the total output capacitance exceeds the maximum output current during soft-start (min). The maximum charge current of each channel (ICHG(Max)) is calculated as:

               ICHG(Max) =

Ctotal(Max)

TCOESS(MIN)

(A)

Where:  Ctotal(Max): Maximum value of total output capacitance of each channel (F)

TCOESS(Min): Minimum value of soft-start time coefficient of each channel (s/V)

When the total output capacitance is largely different from the recommended output capacitor value, the gain-phase characteristic should also be confirmed using the method shown in KBA222529.