DAC output in STM32L151RCT6 MCU is not constant.

[MBhir.11]

Hi,

I am using STM32L151RCT6 MCU and creating the project in STM32cube IDE .

i implemented DAC peripheral and kept 1.52 As input and did calculation like:

float value = 1.52; // Dac output

uint32_t var;

 var = (value * 4096)/3.3 ; // From datasheet

 HAL_DAC_SetValue(&hdac, DAC_CHANNEL_1, DAC_ALIGN_12B_R, var);

i am getting output voltage as 1.55V to 1.56V ..

here my requirement is 1.55V but i am getting output varying from 1.55V to 1.56V...why that variation in output of DAC?

How can i make it constant ??

or it will like that or what??

Please help me to clear this

[waclawek.jan]

What hardware are you using? How is DAC loaded? Are there ADC conversions running? Our any other code influencing the analog part of the mcu, or introducing significant supply/ground current? Isn't it the measurement which is imprecise/noisy?

DAC stability among other things depends on VREF+ stability.

JW

[Ozone]

And - 10mV of a 1500mV signal is about 0.5%.

About what measurement device tolerance we are speaking here ?

[MBhir.11]

Hi,

I am using NUCLEO- L152RE - Evaluation board..

used DAC 1 out:

i am not using any ADC..

just DAC1 out pin probing and checking the waveform along with output voltage.

[MBhir.11]

this is configuration image

[MBhir.11]

[Ozone]

What is the tolerance of the device you are measuring the signal with ?

Your expectations sound unrealistic to me.

The DAC output is high-impedance (1 Mohm/15kOhm), the measurement device must have an appropriately high input inpedance.