DAC parasitic pull-up?

[igor]

Posted on June 03, 2014 at 20:52

I have working code for DAC testing, and it works fine on STM8L152C6 (Discovery board), but meet some problems with STM8L152K6. It works about as expected, excepting output has permanent additional value 0.88V. I tried PB4..PB6 pins with same result. And output volatge doesn't depend from switching on/off output DAC buffer (I suppose it should be changed a little bit). 

All pins input mode without pull-up. Testing code is very easy:1. initialize RI (alllow comparators)2. map DAC to pin3. write exact value to DAC in loopnothing unusual. Tried different MCU on different PCB. Nothing connected to output pins excepting voltmeter. But error still there.Some ideas? #dac

[igor]

Posted on June 04, 2014 at 09:39

I suppose it's a STM8L152K6T6 DAC issue! Same PCB with STM8L151K6T6 and same programm works fine.  

PS: I tested 3 MCU 152K6T6, always have an error DAC value with additional 0.85..0.91V