Difference between AN3216 and stm32L-discovery board schematic

[dhutchison1945]

Posted on May 28, 2012 at 12:29

Hi,

I see on the an3216 ''getting started with the stm32l hardware development'' that there is a strange 10uF (ceramic?? non polarized ??) connected to the vdd. Instead,if I see that on the stm32l discovery schematic the 10uF capacitor is not present. Do I need to mount it or not ?  Also,some one can tell me the value and the vendor code of the

C26 1uF

 and of the

L1  inductor

on the stm32L-discovery board ? regards, Spectre

[Tesla DeLorean]

Posted on May 28, 2012 at 14:31

Well the 100nF parts are there to decouple the supply close to the individual VDD pins to handle CMOS switching noise.

The 1uF and 10uF are there to supply bulk capacitance, to supply instantaneous electrons when higher current is required quicker than the upstream regulators can respond. Ceramics being preferable as tantalum caps have the potential to catch fire or explode. The absence of the bulk capacitance will likely result in more noise/variation in the supply pins, depending on the upstream regulation, and power distribution. This noise would be undesirable for ADC/DAC designs. There may be enough capacitance placed elsewhere on the board, typically at the regulator, most STM32 designs expect there to be some, and ideally close to the chip.

[raptorhal2]

Posted on May 28, 2012 at 22:33

Note that AN3216 and the STM32L schematic illustrate two different pinout count processors with different unit numbers, so something got mixed up. The 10 uF is on the processor with more peripheral connections available.

Is there an empty place to install a capacitor on your discovery board ? Cheers, Hal

[dhutchison1945]

Posted on May 29, 2012 at 08:50

Hi Mr. Baird and Mr.Clive1

thanks for the answers. But I still have a doubt. the following schematic is from the UM1521 STM32L152D-EVAL,the biggest of the series and there isn't the 10uF capacitor mounted. how is the story ? :)

[raptorhal2]

Posted on May 29, 2012 at 14:31

Do I need to mount it or not ?

I don't think we can answer that for you. You have to decide based on the ADC noise levels you are experiencing, and if you can mount it.  Also,some one can tell me the value and the vendor code of the

C26 1uF

 and of the

L1  inductor

on the stm32L-discovery board ? An L1 code is shown on the Discovery Board schematic. Do a Google search and see who can supply it. The capacitor is a standard item. Cheers, Hal

[dhutchison1945]

Posted on May 30, 2012 at 10:04

yes I agree

regards, Spectre