Datasheet

DocID024030 Rev 10 29/239
STM32F427xx STM32F429xx Functional overview
44
The over-drive mode allows operating at a higher frequency than the normal mode
for a given voltage scaling.
– In Stop modes
The MR can be configured in two ways during stop mode:
MR operates in normal mode (default mode of MR in stop mode)
MR operates in under-drive mode (reduced leakage mode).
• LPR is used in the Stop modes:
The LP regulator mode is configured by software when entering Stop mode.
Like the MR mode, the LPR can be configured in two ways during stop mode:
– LPR operates in normal mode (default mode when LPR is ON)
– LPR operates in under-drive mode (reduced leakage mode).
• Power-down is used in Standby mode.
The Power-down mode is activated only when entering in Standby mode. The regulator
output is in high impedance and the kernel circuitry is powered down, inducing zero
consumption. The contents of the registers and SRAM are lost.
Refer to Table 3 for a summary of voltage regulator modes versus device operating modes.
Two external ceramic capacitors should be connected on V
CAP_1
and V
CAP_2
pin. Refer to
Figure 22: Power supply scheme and Table 19: VCAP1/VCAP2 operating conditions.
All packages have the regulator ON feature.
3.18.2 Regulator OFF
This feature is available only on packages featuring the BYPASS_REG pin. The regulator is
disabled by holding BYPASS_REG high. The regulator OFF mode allows to supply
externally a V
12
voltage source through V
CAP_1
and V
CAP_2
pins.
Since the internal voltage scaling is not managed internally, the external voltage value must
be aligned with the targeted maximum frequency. Refer to Table 17: General operating
conditions.The two 2.2 µF ceramic capacitors should be replaced by two 100 nF decoupling
capacitors. Refer to Figure 22: Power supply scheme.
When the regulator is OFF, there is no more internal monitoring on V
12
. An external power
supply supervisor should be used to monitor the V
12
of the logic power domain. PA0 pin
should be used for this purpose, and act as power-on reset on V
12
power domain.
Table 3. Voltage regulator configuration mode versus device operating mode
(1)
1. ‘-’ means that the corresponding configuration is not available.
Voltage regulator
configuration
Run mode Sleep mode Stop mode Standby mode
Normal mode MR MR MR or LPR -
Over-drive
mode
(2)
2. The over-drive mode is not available when V
DD
= 1.7 to 2.1 V.
MR MR - -
Under-drive mode - - MR or LPR -
Power-down
mode
---Yes
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