AN4938 Rev 4 11/46
AN4938 Power supplies
45
2.1.5 SMPS step-down converter
To optimize power consumption, some devices embed a high power-efficient DC/DC non-
linear switched-mode power supply voltage down-converter regulator. It can be enabled via
the SDEN bit of the PWR_CR3 register.
The SMPS can be used to deliver power either in inter
nal or external supply mode.
1. Internal supply mode (Direct mode):
V
CORE
domain direct supply follows the device system operating modes (Run, Stop
and Standby) where the output voltage is set according to the voltage scaling
configured via VOS and SVOS bits.
The SMPS can also supply the internal voltage regulator (LDO) in Normal operating
mode or High-performance mode according to SDEXTHP bit setting in PWR_CR3.
2. External supply mode
In this mode, the SMPS can be used to supply external circuits. It operates in MR mode
(SDEXTHP
bit set to 1 in PWR_CR3) in order to achieve a high performance with an
output voltage of 2.5 V or 1.8 V (configured through SDLEVEL bits of PWR_CR3).
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