Hi, I've purchased an STM32H723ZG Nucleo Board to evaluate and test the potential of the onboard DAC. The max sampling time for the STM32H72x with the max bus speed at 137.5MHz is 51.1Msps as described in the AN4566 but I can't reach them.

[MZ.NG]

I'm trying to generate a 1.2 MHz sine burst using the DAC, DMA and Timers. Everything works fine but only up to 200-250KHz then increasing the frequency the amplitude begins to decrease.

Moreover I've managed to reach about 25Msps and it seems impossible to reach 51.1Msps without distorting the waveform. I'm using HSI and my clock configuration set the max bus speed at 137.5MHz as indicated in the AN4566 application note. I've disabled the internal buffer that probably has too low GWB to reach 1.2MHz output frequency but it didn't solve the problem anyway. I've also tried to use an external high speed voltage follower opamp but i've obtained the same result. So I think it's an internal problem...maybe I forgot to make some settings? Am I doing something wrong? Are there any capacitance that I'm not considering? Perhaps the evaluation board is not made to achieve that speed and sampling rate? Any suggestions?

Thanks

[S.Ma]

Download the Datasheet, Electrical characteristics, DAC portion You will have some info about the max slew rate with and without built-in buffers. Sample rate does not necessarily mean swing from min to max...