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STM181x devices are low power reset devices used to monitor power supplies for microcontrollers. They perform a single function: asserting a reset signal whenever VCCsupply voltage drops below a preset value and keeping it asserted until VCChas risen above the preset threshold for a minimum period of time (trec). They provide excellent circuit reliability without additional external components when used with +3.0 V / +3.3 V (STM1815–STM1818), and +5 V (STM1810–STM1813) power supply systems.
A precision voltage reference and comparator monitors the VCCinput for an out-of-tolerance condition. When an invalid VCCcondition occurs, the reset output (RST) is forced low (or high in the case of RST) and remains asserted for trecafter VCCrises above the reset threshold. The STM1813/1818 also keep reset asserted for trecafter 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 RSToutput. 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 RSTpin is pulled low for more than 1.5 μs. When used to initiate manual reset, RSTdebounces signals from devices such as mechanical switches. For devices with this feature, the release of the external switch triggers the reset period.
The STM181x devices are guaranteed to output the correct logic state for VCCdown to 1.0 V (0 °C to +105 °C). They also provide a reset comparator designed to ignore fast transients on VCC.
Reset thresholds are available between +2.55 V and +4.62 V. 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.