STM1810L datasheet(4/20 Pages) STMICROELECTRONICS

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SUMMARY DESCRIPTION

STM181x devices are low power reset devices

used to monitor power supplies for microcontrol-

lers. They perform a single function: asserting a

reset signal whenever VCC supply voltage drops

below a preset value and keeping it asserted until

VCC has risen above the preset threshold for a

minimum period of time (trec). They provide excel-

lent circuit reliability without additional external

components

when

used

with

+3.0V/+3.3V

(STM1815–STM1818),

and

+5V

(STM1810–

STM1813) power supply systems.

A precision voltage reference and comparator

monitors the VCC input for an out-of-tolerance con-

dition. When an invalid VCC condition occurs, the

reset output (RST) is forced low (or high in the

case of RST) and remains asserted for trec after

VCC rises above the reset threshold. The

STM1813/1818 also keep reset asserted for trec

after the output is momentarily pulled to ground by

an external push-button switch.

The STM1812 and STM1817 have an active-high,

push-pull output. The STM1810 and STM1815

(push-pull) and STM1811, STM1813, STM1816,

and STM1818 (open drain) have an active-low

RST output. The open drain devices (STM1811/

STM1813/STM1816/STM1818) also have an in-

ternal pull-up resistor to VCC. The STM1813 and

STM1818 feature a debounced manual reset fea-

ture that asserts a reset if the RST pin is pulled low

for more than 1.5µs. When used to initiate manual

reset, RST debounces signals from devices such

as mechanical switches. For devices with this fea-

ture, the release of the external switch triggers the

reset period.

The STM181x devices are guaranteed to output

the correct logic state for VCC down to 1.0V (0°C

to +105°C). They also provide a reset comparator

designed to ignore fast transients on VCC.

Reset thresholds are available between +2.55V

and +4.62V These small, low power devices are

ideal for use in portable equipment. All are avail-

able in the space-saving 3-pin SOT23 package,

and are specified from –40°C to +105°C. Figure

4., page 5 shows a typical hardware hookup for

STM181x devices to a Microcontroller.

Figure 2. Logic Diagram

Note: 1. For STM1812, STM1817

Table 2. Signal Names

Note: 1. For STM1812, STM1817

Figure 3. SOT23-3 Connections

Note: RST for STM1812 and STM1817

AI09648

VCC

STM181x

VSS

RST (RST)

(1)

VSS

Ground

RST

Active-low Reset Output

RST(1)

Active-high Reset Output

VCC

Supply Voltage and Input for Reset

Threshold Monitor

AI09649

RST (RST)

VSS

VCC

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