STM6905TWEDS6F Ver la hoja de datos (PDF) - STMicroelectronics

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STM6905TWEDS6F

Quintuple, ultralow voltage supervisor with push-button reset

STMicroelectronics 

STM6905

3

Operation

Operation

The STM6905 can monitor critical voltages such as power-supply and battery voltage

levels, while interfacing easily with the system controllers/microprocessors.

Figure 4 shows the typical hardware hookup for monitoring five voltages: two fixed

thresholds (customer-selectable, factory-programmed) and three adjustable monitor inputs.

The RST output is open drain and requires a 10 kΩ pull-up resistor tied to VCC.

3.1

Setting the adjustable voltage levels for V3IN, V4IN, and V5IN

inputs

The user can customize the minimum voltage levels for the three adjustable voltage inputs

by connecting an external resistor divider network to the V3IN, V4IN and V5IN pins in order

to set the trip point at some voltage above the 600 mv (VREF) according to the following

formula.

VTRIP = 0.6 V × R-----1---R--+--2---R-----2-

During normal operation, the STM6905 monitors the voltage levels at all five pins (Vcc,

V2IN, V3IN, V4IN, and V5IN).

3.2

Power on reset (tREC)

On power up, the STM6905 activates a power-on reset circuit which asserts the reset pin

(i.e. RST goes low). The RST signal remains active until VCC (and V2IN, V3IN, V4IN, V5IN,

and MR) rises above the minimum voltage level for the time period tREC thereby ensuring

that the supply voltage has stabilized to sufficient operating levels.

DocID14290 Rev 4

9/19

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