Voltage offset is introduced for 32MHz clock on STM32L4S7ZIT

[Shruthi]

Hi,

Im working on STM32L4 chip. I wanted to work on LTDC with 32MHz clock. I'm using internal 16MHz clock and generating 32MHz using PLL.

When I give output of this clock pin to PA8 MCO pin, Im able to see 32MHz triangle wave with ~1.2V offset. When I give Internal clock 16MHz to MCO pin I see 0.8V offset and when 4MHz is given to MCO there is no offset.

May I know why is this offset as the frequency increases. Is there any other setting to be done? 

[Danish1]

MCO is (notionally) a digital square wave, going between Vss = 0 V to Vdd (often 3.3 V).

But the frequency you are trying to output is very high, and might cause problems like electromagnetic interference. ST allow you to configure pins with reduced slew-rate to minimise the risk of such interference.

What does that mean? That the output tries to rise to Vdd but the slew-rate might be too low and it doesn't get close before the output starts falling towards Vss. So you see a triangle wave.

Or maybe your 'scope (or the 'scope probe) is too slow, giving similar effects.

There is no intended offset on the output.

Hope this helps,

Danish