AN2586 Datasheet, PDF (7/28 Pages) STMicroelectronics – Getting started with STM32F10xxx hardware development

AN2586
Power supplies
1.1.2
1.1.3
On packages with 64 pins or less
The V_REF+ and V_REF- pins are not available, they are internally connected to the ADC
voltage supply (V_DDA) and ground (V_SSA).
Battery backup
To retain the content of the Backup registers when V_DD is turned off, the V_BAT pin can be
connected to an optional standby voltage supplied by a battery or another source.
The V_BAT pin also powers the RTC unit, allowing the RTC to operate even when the main
digital supply (V_DD) is turned off. The switch to the V_BAT supply is controlled by the power
down reset (PDR) circuitry embedded in the Reset block.
If no external battery is used in the application, it is highly recommended to connect V_BAT
externally to V_DD.
Voltage regulator
The voltage regulator is always enabled after reset. It works in three different modes
depending on the application modes.
● in Run mode, the regulator supplies full power to the 1.8 V domain (core, memories and
digital peripherals)
● in Stop mode, the regulator supplies low power to the 1.8 V domain, preserving the
contents of the registers and SRAM
● in Standby mode, the regulator is powered off. The contents of the registers and SRAM
are lost except for those concerned with the Standby circuitry and the Backup domain.
1.2
Power supply schemes
The circuit is powered by a stabilized power supply, V_DD.
● Caution:
– If the ADC is used, the V_DD range is limited to 2.4 V to 3.6 V
– If the ADC is not used, the V_DD range is 2.0 V to 3.6 V
● The V_DD pins must be connected to V_DD with external decoupling capacitors (one
100 nF Ceramic capacitor for each V_DD pin + one Tantalum or Ceramic capacitor (min.
4.7 µF typ.10 µF).
● The V_BAT pin can be connected to the external battery (1.8 V < V_BAT < 3.6 V). If no
external battery is used, it is recommended to connect this pin to V_DD with a 100 nF
external ceramic decoupling capacitor.
● The V_DDA pin must be connected to two external decoupling capacitors (100 nF
Ceramic + 1 µF Tantalum or Ceramic).
● The V_REF+ pin can be connected to the V_DDA external power supply. If a separate,
external reference voltage is applied on V_REF+, a 100 nF and a 1 µF capacitors must be
connected on this pin. In all cases, V_REF+ must be kept between 2.4 V and V_DDA.
● Additional precautions can be taken to filter analog noise:
– V_DDA can be connected to V_DD through a ferrite bead.
– The V_REF+ pin can be connected to V_DDA through a resistor (typ. 47 Ω).
Doc ID 13675 Rev 7
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