AN3147 datasheet(7/25 Pages) STMICROELECTRONICS

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AN3147

Power supply

The STM8L/STM8AL families embed two regulators which provide a supply voltage

(VCORE) for the core and internal peripherals.

Figure 1. Power supply overview

1. If VDD is lower than 1.8 V, the 1.8 V domain is supplied by the voltage on the VDD input. For low power

modes where the LPVR is used, this domain is supplied by a 1.55 V voltage.

2. VDD between 1.8 V to 3.6 V for STM8L05xxx.

The main voltage regulator (MVR) provides a 1.8 V supply voltage. It has a high current

capability, as it can deliver up to 25 mA. However, the consumption of this regulator is higher

than the consumption of the low power regulator (LPVR). Consequently, the MVR is used

during a standard operation only.

The consumption of the LPVR is very low, as required for low power modes. The LPVR can

deliver up to 200 µA, providing 1.55 V to the digital part of the MCU.

After reset, the MVR provides a supply voltage (VCORE) to the internal digital parts of the

microcontroller. Depending on the functional mode, the MVR can be switched off. In this

case, the LPVR continues to provide the VCORE voltage.

The power supply is monitored by the POR/PDR (power-on reset/power-down reset) and

BOR (brown-out reset) system. This system ensures a proper startup and reset of the MCU,

while VDD is rising above the POR/BOR threshold. It resets the MCU when VDD is falling

below the PDR/BOR threshold. Correct device reset during power-on sequence is

guaranteed when tVDD[max] is respected. Use of internal BOR is recommended to ensure

correct device reset during power-down, when VPDR < VDD < VDD[min].

Note:

Analog peripherals require a power supply voltage above the PDR threshold (VDD > 1.8 V,

while VPDR = 1.5 V). In this case, it is recommended to use the BOR (Brownout reset) to

guarantee a proper functionality.

The BOR is not available in STM8L101xx devices. If needed, external circuitry shall be used

instead.

For better power monitoring, the STM8L15xxx, STM8L162xx, STM8AL31xx, and

STM8AL3Lxx provide a brown-out reset (BOR) and programmable power voltage detection

(PVD) for an earlier detection of voltage drop.

MS32164V1

Main voltage regulator

(MVR)

Low power voltage regulator

(LPVR)

I/Os

1.65 V - 3.6 V

(2)

1.8 V domain

(1)

STM8 MCU core

CPU

RAM

Flash

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