Solved
The STM32L0x3 Reference manual (RM0367) indicates that Vdda can be calculated (page 325): VDDA = 3 V x VREFINT_CAL / VREFINT_DATA. Where can I get VREFINT_CAL?
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It's listed in the product datasheet.
For example, here it is for the STM32L073:

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