STM1818

STM1818 devices are low power reset devices used to monitor power supplies for microcontrollers.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 excellent circuit reliability without additional external components when used with +3.0V/+3.3V (STM1815STM1818), and +5V (STM1810STM1813) power supply systems.

A precision voltage reference and comparator monitors the VCC input for an out-of-tolerance condition.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/STM1818 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 internal pull-up resistor to VCC. The STM1813 and STM1818 feature a debounced manual reset feature that asserts a reset if the RST pin is pulled low for more than 1.5s. When used to initiate manual reset, RST debounces signals from devices such as mechanical switches. For devices with this feature,the release of the external switch triggers the reset period.

The STM1818 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 available 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 STM1818 devices to a Microcontroller.