Power supplies AN4488
12/44 DocID026304 Rev 3
2.3.4 PDR_ON circuitry example
Note: This example doesn’t apply to STM32F411xx and STM32F446xx, where PDR_ON can be
connected to VSS to permanently disable internal reset circuitry (external voltage supervisor
required on NRST pin). Anyway (thanks to backward compatibility), circuitry built for other
STM32F4xxxx products will work for STM32F411xx and STM32F446xx.
Note: Please contact your local STMicroelectronics representative or visit www.st.com in case you
want to use circuitry different from the one described hereafter.
Restrictions:
• PDR_ON = 0 is mostly intended for V
DD
supply between 1.7 V and 1.9V (i.e. 1.8V +/-
5% supply).
Supply ranges which never go below 1.8V minimum should be better managed with
internal circuitry (no additional component thanks to fully embedded reset controller).
• To ensure safe power down, the external voltage supervisor (or equivalent) is required
to drive PDR_ON=1 during power off sequence.
When the internal reset is OFF, the following integrated features are no longer supported:
• The integrated power-on reset (POR) / power-down reset (PDR) circuitry is disabled.
• The brownout reset (BOR) circuitry must be disabled.
• The embedded programmable voltage detector (PVD) is disabled.
• V
BAT
functionality is no more available and V
BAT
pin should be connected to V
DD
.
Figure 5. PDR_ON simple circuitry example
(not needed for STM32F411xx and STM32F446xx)
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