DAC output register value not propagating to the output pin at startup

[IIvan.22]

When I write to the DAC register DHR12R2 within less then 1.5 mlsec from enabling DAC, its value is transferred to the DOR2 register as expected, but the voltage on the output pin PA5 remains zero indefinitely. Writing to the DHR12R2 after 1.5 mlsec from enabling becomes visible on the output pin.

Configuration:

STM32L496, VDD=3.1V, VDDA=3.1V, core/bus clocks=64MHz.

DAC: no software/hardware triggers. No calibration requests. MCR=0 (MODE=0: buffered output).

Datasheet says Twakeup <=7.5 microseconds for the DAC. But waiting even 1000 microseconds does not help.

[my possible explanation: VDDA startup curve is different from VDD]

 

[waclawek.jan]

Interesting. Which STM32 exactly do you use?

> [my possible explanation: VDDA startup curve is different from VDD]

Sounds very plausible. Can you please show those curves?

JW