TPS65320-Q1 Buck-Regulator Output Voltage

Makoto-san,
Figure 1 is a typical graph. Also, it is taken to show drop-out voltage, so at a steady (but low) supply voltage. During this condition, the part operates at almost 100% duty-cycle (HS-FET always on, except for recharging the boot-capacitor). During 100% duty-cycle the switching frequency has only minimal impact (only duration of the low-pulse to recharge the boot-strap-capacitor)
The dropout voltage in such conditions is dominated by the RDSon of the HS-FET (127mOhm typical, 250mOhm max) and the DCR or the inductor chosen by the customer. As both are resistances, output load needs to multiplied with it to calculate the voltage drop (Vin to Vout). Allow for additional drops over reverse polarity protection diode, etc.

So Answers to your questions:
①Would it be the same as Figure1 graph of even when used at a Fsw=500kHz?
--> in principle: yes, but needs to be calculated per the above. At any switching frequency, this is just a representation.

②Figure 1 Is data measured at the time of Vin rise?
--> no, Vin is assumed to be stable at the given voltage.
Note, the part features soft-start and the output ramp can be set by the capacitor on the SS-pin. In case of a slow ramp of VIN, the softstart can be slow as well. Alternatively, a resitive divider on the EN-input can be configured tot enable the Buck only after Vin has reached a minimum value...
BR,
Frank

Frank-san,

Thank you for your reply.
If you have Figure1 graph(Fsw=500kHz) , could you please provide it?

Best regards,
Makoto Shiraishi

Makoto-san,
I do have one for 400kHz (default on EVM), Please share your e-Mail with me (f-dehmelt@ti.com) and I will pass it on.
BR,
Frank