L4946B datasheet(6/9 Pages) STMICROELECTRONICS

6 / 9 page

FUNCTIONAL DESCRIPTION

The L4946 includes a monitoring circuit to warn

the microprocessor if a low voltage or no voltage

condition is occurring. Between 7V and 8V on the

STCAP pin, the LVW output will go low. This tells

the microprocessor to stop executing code and

save vital information. The reset output will go low

when V04 drops 0.15V below it’s typical reading.

A reset will occur between a minimum of 4.5 and

a maximum of 5V on V04. The reset output will go

low when V04 drops 0.15 below it’s typical value.

A reset will occur between a minimum of 4.5V

and a maximum of 5V on V04. When the V04

drops between 4.5 and 5V

the RESET output

goes low. It is very important that the RESET out-

put doesn’t go above 0.75V until the V04 output

has gone back above 4.75V (typical). The micro-

processor looks for a rising edge. So, any spike

will tell the microprocessor to start operating.

Once the STCAP line passes 7.5V (typical), the

LVW output will also return to high state.

TIMING DIAGRAM

Graphs of the Output Curves for VO1,2,3 and 4

5.0

7.5

150

µs

100

µs

150

µs100µs

L4946

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L4946B Datasheet(PDF) 6 Page - STMicroelectronics