STM32f7 - ripples on 5.0V supply

[reza]

Posted on September 18, 2017 at 18:20

I have noticed that STM32F7 microcontroller generates a digital noise (see the figures. It is not from transmission lines and bursts are repeating every 16ms) on the 5.0V supply voltage. 

I have observed this using both Discovery and Nucleo boards.

I have seen this using external power supply and the power over USB.

I have also tried different sample codes. It actually does not matter what code you run, because even before I start the code in my debugger, the ripples can be observed. The only time, I do not see the ripples, is when the microcontroller is kept in reset, or when I remove a jumper to power it down.

I have also noticed that, after couple of resets, the noise sometimes disappear. It comes back if I reset again.

Anyone else who has observed this issue?  Any thoughts?

#ripples #noise #stm32f7 #power-supply

[T J]

Posted on November 29, 2017 at 00:00

SDRAM specs

Alliance :- AS4C8M16SA

128M - 8M x 16 bit Synchronous DRAM (SDRAM)

ï‚· Auto Refresh and Self Refresh

ï‚· 4096 refresh cycles/64ms

Micron:

• PC100- and PC133-compliant

• Auto precharge, includes concurrent auto prechargeand auto refresh modes• Self refresh mode (not available on AT devices)• Auto refresh– 64ms, 8192-cycle (commercial and industrial)– 16ms, 8192-cycle (automotive)• LVTTL-compatible inputs and outputs• Single +3.3V ±0.3V power supply

there is your 16mS noise...

[Eugene Solo]

Posted on November 29, 2017 at 02:03

looks like bad decoupling on memory chips