TPS745-Q1: ramp up time

Hi Weixu,

The rise time will be the same regardless of Cout until the inrush current exceeds the current limit of the device.  You can use the capacitor equation to find the inrush:

Inrush = Cout * Vout/dt

Where dt = the turn on time listed in the table.

Thanks,

Stephen

Hi Weixu,

In modern LDO's, the current limit loop has low bandwidth and engages after 20-50us.  The LDO inrush current must exceed the current limit value for at least this amount of time before current limit engages.  When current limit engages during turn on, the output will be charged up in accordance with the capacitor equation, I = C * dV/dt where "I" is the current limit value.  The typical current limit for this LDO is 720 mA so typically I would not expect this LDO to turn on into current limit with the turn on time measured in this oscilloscope plot.

Thanks,

Stephen

Hi Weixu,

You are welcome, let us know if you need anything else.

Thanks,

Stephen