STM32F070CB Datasheet, PDF (13/83 Pages) STMicroelectronics – Reset and power management

STM32F070CB/RB/C6/F6
Functional overview
3.4
Cyclic redundancy check calculation unit (CRC)
The CRC (cyclic redundancy check) calculation unit is used to get a CRC code using a
configurable generator polynomial value and size.
Among other applications, CRC-based techniques are used to verify data transmission or
storage integrity. In the scope of the EN/IEC 60335-1 standard, they offer a means of
verifying the Flash memory integrity. The CRC calculation unit helps compute a signature of
the software during runtime, to be compared with a reference signature generated at link-
time and stored at a given memory location.
3.5
3.5.1
3.5.2
3.5.3
Power management
Power supply schemes
• V_DD = 2.4 to 3.6 V: external power supply for I/Os and the internal regulator. Provided
externally through VDD pins.
• V_DDA = from V_DD to 3.6 V: external analog power supply for ADC, Reset blocks, RCs
and PLL. The V_DDA voltage level must be always greater or equal to the V_DD voltage
level and must be provided first.
For more details on how to connect power pins, refer to Figure 9: Power supply scheme.
Power supply supervisors
The device has integrated power-on reset (POR) and power-down reset (PDR) circuits.
They are always active, and ensure proper operation above a threshold of 2 V. The device
remains in reset mode when the monitored supply voltage is below a specified threshold,
V_POR/PDR, without the need for an external reset circuit.
• The POR monitors only the V_DD supply voltage. During the startup phase it is required
that V_DDA should arrive first and be greater than or equal to V_DD.
• The PDR monitors both the V_DD and V_DDA supply voltages, however the V_DDA power
supply supervisor can be disabled (by programming a dedicated Option bit) to reduce
the power consumption if the application design ensures that V_DDA is higher than or
equal to V_DD.
Voltage regulator
The regulator has two operating modes and it is always enabled after reset.
• Main (MR) is used in normal operating mode (Run).
• Low power (LPR) can be used in Stop mode where the power demand is reduced.
In Standby mode, it is put in power down mode. In this mode, the regulator output is in high
impedance and the kernel circuitry is powered down, inducing zero consumption (but the
contents of the registers and SRAM are lost).
DocID027114 Rev 3
13/83
23