According to reference manual RM0377 (page 138 6.1.5 Dynamic voltage scaling configuration) programming voltage regulator is very easy. Unfortunately I'm not able to do this on two Nucleo demo boards with STM32L031 and STM32L053 MCUs. After writing a new value to VOS bits in PWR_CR register, I read always the same value 1.5V (range 2). Is there any other condition, except power supply, that has influence on this? Please help me to solw this problem.