ST7LITE49M datasheet(43/188 Pages) STMICROELECTRONICS

43 / 188 page

ST7LITE49M

Supply, reset and clock management

43/188

Figure 17.

Low Voltage Detector vs Reset

Figure 18.

Reset and supply management block diagram

7.4.2

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 supply voltage (VAVD). The VIT-(AVD)

reference value for falling voltage is lower than the VIT+(AVD) reference value for rising

voltage in order to avoid parasitic detection (hysteresis).

The output of the AVD comparator is directly readable by the application software through a

real time status bit (AVDF) in the SICSR register. This bit is read only.

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 generated 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 microcontroller. See Figure 19.

The interrupt on the rising edge is used to inform the application that the VDD warning state

is over.

VDD

VIT+(LVD)

RESET

VIT-(LVD)

Vhys

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)

AVDIE

AVDF

STATUS FLAG

CR0

CR1

LVDRF

WDGF

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