PTN3356 reference design

[masahirokiniwa]

Hi,

I checked PTN3356 reference design in data sheet and application note(AN11590).

And I have two questions about their reference design as below.

1. In Fig4 of the data sheet, VDD_3V3 and GND are connected by FB. But they are not used in Fig5.

- Are they OPTION DESIGN as ESD protection and PI filter?

- Are they necessary only for DC to DC converter mode?  

2. In Fig4 and 5, VBUCK_1V5 is connected to GND by 4.7uF capacitor.

    I think that it is smoothing capacitor for SWOUT.

    Is it necessary for LDO mode? If it's necessary to both mode, could you tell me the purpose of it?

Best regards,

M.Kiniwa

[guoweisun · Accepted solution]

Hi,

For your question1:

The FB is optional for both modes.

For your question2:

4.7uF is the output capacitor which can stabilize the output voltage.