DocID17496 Rev 7

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AN3216

Power supplies

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2.3.1

Power-on reset (POR)/power-down reset (PDR),

brownout reset (BOR)

The monitoring voltage begins at 0.7 V.

During power-on, for devices operating between 1.8 and 3.6 V, the BOR keeps the device

voltage (1.8 V). At power-up this internal reset is maintained during ~1 ms to wait for the

supply to reach its final value and stabilize.

At power-down the reset is activated as soon as the power drops below the lowest limit

(1.65 V).

At power-on, a defined reset should be maintained below 0.7 V. The upper threshold for a

reset release is defined in the electrical characteristics section of the product datasheets.

Figure 5. Power on reset/power down reset waveform

If you want to run the cpu at full speed the threshold should be raised to 2.0 V. For a

programmable threshold above the chip lowest limit, a brownout reset can be configured to

the desired value. The BOR can also be used to detect a power voltage drop earlier. The

threshold values of the BOR can be configured through the FLASH_OBR option byte.

2.3.2

Programmable voltage detector (PVD)

The device features an embedded programmable voltage detector (PVD) that monitors the

can be selected by software between 1.85 V and 3.05 V, with a 200 mV step. An interrupt

message and/or puts the MCU into a safe state. The PVD is enabled by software

configuration. As an example, the service routine can perform emergency shutdown tasks.

Reset

POR

PDR

Temporization