Dual push-button Smart Reset with push-button controlled output delay
The Smart Reset™ devices provide a useful feature that ensures inadvertent short reset push-button closures do not cause system resets. This is done by implementing extended Smart Reset™ input delay time (tSRC) and combined push-button inputs, which together ensures a safe reset and eliminates... Read More
The Smart Reset™ devices provide a useful feature that ensures inadvertent short reset push-button closures do not cause system resets. This is done by implementing extended Smart Reset™ input delay time (tSRC) and combined push-button inputs, which together ensures a safe reset and eliminates the need for a specific dedicated reset button.
This reset configuration provides versatility and allows the application to discriminate between a software generated interrupt and a hard system reset. When the input push-buttons are connected to microcontroller interrupt inputs, and are closed for a short time, the processor can only be interrupted. If the system still does not respond properly, continuing to keep the push-buttons closed for the extended setup time tSRCcauses a hard reset of the processor through the reset outputs.
The STM6520 has two combined delayed Smart Reset™ inputs (SR0, SR1) with two user-selectable delayed Smart Reset™ setup time (tSRC) options of 7.5 s and 12.5 s typ., selected by a dual-state Smart Reset™ DSR input pin. When DSR is connected to ground, tSRC= 7.5 s, when connected to VCC, tSRC= 12.5 s (typ.). There are two reset outputs, both going active simultaneously after both of the Smart Reset™ inputs were held active for the selected tSRC delay time. The outputs remain asserted until either or both inputs go to inactive logic level (for this device the output reset pulse duration is fully push-button controlled, meaning neither fixed nor minimum reset pulse width, nor power-on reset pulse is implemented). The first reset output, RST1, is active-low, open-drain; the second reset output, RST2, is active-high, push-pull. The device fully operates over a broad VCC range 1.65 to 5.5 V. Below 1.575 V typ. the inputs are ignored and outputs are deasserted; the deasserted reset output levels are then valid down to 1.0 V.