Write the STM32U545 DAC register (12-bit, right-justified) = 2048, and the measured output voltage is 2.8V. 1 How many volts is the internal reference output? 2 No external reference input definition is found in the pin definition. How to connect the external reference? thank you.

stm32u5系列DAC的参考电压可以来自外部，也 可能 使用内部的VREFBUF单元提供。


如果从外部引进参考电压，当芯片有VREF脚时就通过该脚过来，如没有该管脚，VDDA就是此时DAC的外部参考电压，即VREF+跟VDDA是硬件绑定在一起的。


如果通过内部VERFBUF引进参考电压，此时芯片有专门的有VERF+脚。VREFBUF的输出可以配置选择：




此时VREFBUF输出与VREF+内部相通，还可以通过VREF+对外提供参考。




当芯片没有专门VREF脚，即VDDA与VREF+内部绑定在一起时，不能通过VREFBUF给DAC提供参考电压。
参考电压只能通过VDDA提供。


VREF+ can be provided either by an external reference of by an internal buffered voltage
reference (VREFBUF). The internal voltage reference can output a configurable voltage:
1.5 V, 1.8 V, 2.048 V or 2.4 V.


VREF- and VREF+ pins are not available on all packages. When not available, they are
bonded to VSSA and VDDA, respectively.


When the VREF+ is double-bonded with VDDA in a package, the internal voltage
reference buffer is not available and must be kept disabled.


VREF- must always be equal to VSSA.