Power supplies

AN4467

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DocID026156 Rev 2

1.3.1

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 (i.e.

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

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.

1.3.2

Programmable voltage detector (PVD)

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

can be selected by software between 1.85 and 3.05 V, with 200 mV steps.

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.