DAC output range when buffer ON

[12144309d]

Posted on April 18, 2015 at 06:47

Hello,

I have read the datasheet of stm32f407 about the DAC output range. When buffer on, the min DAC_OUT is 0.2V and max DAC_OUT is VDDA-0.2V.However, I get 0.069V at 0x000 and 3.272V at 0xfff rather than 0.2V and 3.1V(My reference voltage is 3.3V) when I enable the DAC buffer.Why would be that result? Does anyone have any ideal?RegardsBilly  #stm32 #dac

[AvaTar]

Posted on April 18, 2015 at 14:36

Why would be that result? Does anyone have any ideal?

Learn to read datasheets more carefully. It states a maximum of 200mV offset to the rails in that mode.

[12144309d]

Posted on April 20, 2015 at 04:36

to be migrated, sourceId: 52644:697285D7-A9CA-445D-B16C-F23BF0E3B1A3

[John F.]

Posted on April 20, 2015 at 09:00

Without the buffer you get the DAC output voltage which will range approximately 0V to VRef (but has limited drive capability (output current)).

With the buffer the DAC output voltage is buffered by an internal circuit which is not capable of pulling its output all the way down to 0V so some of the lower DAC settings will result in the same voltage close to but not as low as 0V. The DataSheet is telling you that in the worst case the buffer is guaranteed by design to pull at least as low as 0.2V and at least as high as VddA - 0.2V (within its output current capability). If your load is light or the chip is one of the better ones within the production spread then you may see voltages less than 0.2V or higher than VddA - 0.2V. The DataSheet is telling you that you can't depend on the output except within the stated limits.

[AvaTar]

Posted on April 20, 2015 at 11:26

Where is the statement ''It states a maximum of 200mV offset to the rails in that mode'' from?

Look at the header of the table. The three data columns are named ''minimal'', ''typical'' and ''maximal''. The ''minimal'' and ''maximal'' values are guaranteed by the vendor over the whole temperature and supply voltage range.