In DS12923 (Rev 1), it is stated that VOS0 is only available with LDO, but it is not clear if LDO-Only mode is required or SMPS-LDO cascaded mode is okay.
First,
3.5.3 Voltage regulator (SMPS step-down converter and LDO) says
• Run mode (VOS0 to VOS3)
– Scale 0: boosted performance (available only with LDO regulator)
And
Table 24. Supply voltage and maximum frequency configuration
Note 1 says
VOS0 (power scale 0) is not available when the SMPS step-down converter directly supplies VCORE.
which suggests SMPS-LDO cascaded mode can be used.
However,
3.5.4 SMPS step-down converter says
1. When the SDEXTHP bit is equal to 1 in PWR_CR3, the SMPS step-down converter is forced to High-performance mode ...
which suggest that SMPS is not suit for boosted performance (480MHz with VOS0) at all (all it can do is to supply up to high-performance mode --- 400MHz with VOS1).
Thoughts?
Btw, Nucleo-H745ZI-Q is configured for Direct-SMPS mode, so it seems that 480MHz applications/examples (if any) are out of spec without mangling with the power supply configuration.
@TDK May be related with
https://community.st.com/s/question/0D50X0000BVpWdpSQF
A note. The Nucleo-H745ZI-Q with default direct-SMPS can be run time configured and execute at 480MHz with VOS0 when CM4 is not clocked (BOOT_CM4 turned off), so the configuration is not checked software-wise, and can be set hardware-wise.
