May QN908x VDD power from external DC-DC circuits?

[yuanteliu]

From AN11996 "QN908x Hardware Design Considerations" (Rev.1.3 April, 2018)
It described the way to design QN908x power using its internal DC-DC converter to provide 1.3V VDD power to QN908x core, RF, and Analog block. I have some questions to this

(1) Due to the mechanical dimension limitation, we cannot employ any components higher than 0.8mm, therefore, we cannot use the recommended inductors. Actually, it is very hard to find 10uH inductors with such low profile meeting our requirements.  May I provide VDD power directly from external circuit (eg. external DC-DC controller with higher switching frequency with small inductance)? If it is positive, any cares should be noted?

(2) If the answer of (1) is positive, may you teach me the power (current) to be provided ?

(3) Continued to question (2), If I do not use RF block, how much current may be reduced? May I simply ground (or not connected) the VDD2 pin if I do not use RF ?

Regards  

[estephania_mart]

Hello, 

Using an external DC-DC might work but it should be capable of providing the current limit of the circuit, you could also try with an LDO or another type of solutions. 

The recommendations we provide are the ones in the document you mention for the best performance, and apart from those, we can't guarantee you will have the same performance or the one you want as we might not have that tested.

Regards, 

Estephania