ST7LITEU09 datasheet(35/115 Pages) STMICROELECTRONICS

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SYSTEM INTEGRITY MANAGEMENT (Cont’d)

Figure 20. Reset and Supply Management Block Diagram

8.4.2 Auxiliary Voltage Detector (AVD)

The Voltage Detector function (AVD) is based on

an analog comparison between a VIT-(AVD) and

VIT+(AVD) reference value and the VDD main sup-

ply voltage (VAVD). The VIT-(AVD) reference value

for falling voltage is lower than the VIT+(AVD) refer-

ence value for rising voltage in order to avoid par-

asitic detection (hysteresis).

The output of the AVD comparator is directly read-

able by the application software through a real

time status bit (AVDF) in the SICSR register. This

bit is read only.

8.4.2.1 Monitoring the VDD Main Supply.

The AVD threshold is selected by the AVD[1:0]

bits in the AVDTHCR register.

If the AVD interrupt is enabled, an interrupt is gen-

erated when the voltage crosses the VIT+(AVD) or

VIT-(AVD) threshold (AVDF bit is set).

In the case of a drop in voltage, the AVD interrupt

acts as an early warning, allowing software to shut

down safely before the LVD resets the microcon-

troller. See Figure 21.

The interrupt on the rising edge is used to inform

the application that the VDD warning state is over

Note: Make sure the right combination of LVD and

AVD thresholds is used as LVD and AVD levels

are not correlated. Refer to section 13.3.2 on page

77 and section 13.3.3 on page 77 for more details.

LOW VOLTAGE

DETECTOR

(LVD)

AUXILIARY VOLTAGE

DETECTOR

(AVD)

RESET

VSS

VDD

RESET SEQUENCE

MANAGER

(RSM)

AVD Interrupt Request

SYSTEM INTEGRITY MANAGEMENT

WATCHDOG

SICSR

TIMER (WDG)

AVD

LVD

STATUS FLAG

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