STM6904SFEDS6F datasheet(10/21 Pages) STMICROELECTRONICS

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Operation

STM6904

10/21

Operation

The STM6904 provides the ability to monitor critical voltages such as power-supply and

battery voltage levels, while interfacing easily to the system controllers/microprocessors.

Figure 4 shows typical hardware hookup for monitoring four voltages; two fixed thresholds

(customer-selectable, factory-programmed ) and two adjustable monitor inputs. RST output

is open drain and requires a 10k ohms pull-up resistor tied to VCC.

3.1

Setting the adjustable voltage levels for V3IN and V4IN inputs

The user can customize the minimum voltage levels for the two adjustable voltage inputs by

connecting an external resistor divider network to the V3IN and V4IN pins in order to set the

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

During normal operation, the STM6904 monitors the voltage levels at all four pins (VCC,

V2IN, V3IN, and V4IN).

3.2

Power on reset (tREC)

On power up, the STM6904 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 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.

VTRIP

STM6904SFEDS6F Datasheet(PDF) 10 Page - STMicroelectronics