Power pins of STM32F103RDT6

Mom.1 · ‎2020-01-16

Hi,

I am using STM32F103RDT6. Kindly suggest me LDO for convert 5 to 3.3V and details regarding decaps values for the all supply line of STM32.

Trevor Jones · ‎2020-01-16

Do you have a 5V input or 8V 12V ?

if you can use 5V in you would use a linear regulator,

maybe 100uF at least on the 5V side, and 47uF on the 3V side of the regulator,

I use the AZ1117-3.3 v style pnp regulators, they work very well but only for 5V input.

like this one

if you have a higher input voltage you should use a switcher, like

Mom.1 · ‎2020-01-16

Hi,

Iam using AZ1117CH-3.3V LDO for convering 5 to 3.3V.

In the datasheet it shows 10nf needed for VDDA pin, is it 10nf or 100nf?

Also for the 8MHz crystal, what is the use of REXT mention on the datasheet.

Is it mandatory?

Trevor Jones · ‎2020-01-16

I would use many caps on a board,

each VDD pin has a 100nF ( also called 0.1uF), sometimes another cap too, like 1uF.

plus you would have a a dump cap like 100uF before the reg and another one after the reg, like 47uF

then the rails would be stable.

some power supplies are very noisy,

so you may need more dump caps and ferrites on the power input to remove the switching spikes(coming from the power supply)