Power sequence required for nRF5340 Soc

[shahid Sultan]

I have been reviewing the datasheet of the BLE audio nRF5340. It lists multiple power rails in power section.

Is any power-on sequence required for the SOC.

Also, can we use an LDO or buck converter instead of a PMIC IC (nPM1300)?

[shahid Sultan]

Thank you for your response, 

I have one more query regarding the power supplies, as given below.

Can we use the internal DC/DC converter for an Audio BLE application?   

What is the efficiency of the internal DC/DC converter? 

[Ressa]

You mean enabling internal DC/DC converter in an audio application ? Yes you can do that. 
Regarding the efficiency of nRF5340 internal DCDC converters there is no official numbers available for that but you can check the below post for a comparison between internal DCDC and external PMIC:
(+) Extend battery life and add USB-C charging with the nPM1300 - Blogs - Nordic Blog - Nordic DevZone