TPS7B7702-Q1: soft start time of this LDO

Hi Sam,

For startup, depending on the rising time of the Vin, there will be some overshot. The internal loop will try to stop the pass FET switch when voltage exceeds the set voltage. When you have load, the overshot will be discharged quickly. So if you have no load or light load, the overshot is likely to be worse.

In order to better understand the overshot, will you reattach the waveform with Vin, Venable and Vout? Will you also share me with the capacitors values at input and output?

Regards,
Jason Song

Hi Jason,
Input and output capacitors are 10uF. The startup waveforms were measured by asserting enable pin and VIN is 14V in steady state.

Regards,
Sam

Hi Sam,

You could try to make the output cap bigger that may help with the overshot to a certain extend. Like I mentioned, this device does have built-in soft start as from the startup curve on the datasheet, you can see that Vout ramps up monotonically and the ramp speed is pretty linear. But again, soft-start and overshot are different things.

What's the overshot tolerance in the applications and what is the slew rate of the Vin and Venable?

Regards,
Jason Song