DAC noise problem with SPI

[erazedfx]

Hi every one, it’s my first time posting here.

Recently I’ve been learning about DAC and ran into some noise problems. I’m using a STM32F303K8 board to drive a LTC1660CN DAC via SPI. The DAC is outputting a ramping waveform.

The problem is, every time SPI_CS pin is pulled down by the controller,  it creates a voltage spike on the DAC output as well. (As you can see in the picture below)

What i’ve tried :
1 Configuring the SPI_CS pin on the controller to Pulled Up/Pulled Down/No PUPD
2 Add capacitors between ground and VCC/Data In/SPI_CLK near the DAC chip

So far I discovered that putting a 10uF capacitor between the DAC output and ground does help to reduce the noise, but I doubt that this is the correct method. Other than that nothing seems to help.

My question is, is this a problem can be solved?

Thank you for your time and help.

 (In this picture, yellow = SPI_CS Pin, blue = DAC out A)

[radiolistener]

it looks like power line filtering or power supply issue. Try to use separate power line and separate ground for analog circuits. Add ferrite bead and low pass filter with uF capacitors on analog power line. Also add nF caps as close as possible to the chip for analog power/ground lines. Place analog wires as far as possible from digital wires.

[ggchab]

You can try to slow down the rise and fall times of the signals on the bus by adding resistors between the processor and the bus lines. The processor may have an option that has the same effect.

[erazedfx]

Thank you guys, I found the cause (and the solution) of the problem.

I tried to replace the mcu with arduino and suddenly everything works fine. After some checking it turned out that it's the SPI settings on stm32 that I messed up. After I set 'Clock Polarity' to 'Low' then everything works great!

Hope this can help someone on the Internet who runs into the same problem.