MAX16997

19-4000; Rev 1; 4/09 High-Voltage Watchdog Timers with Adjustable Timeout Delay General Description The MAX16997/MAX16998 are microprocessor (µP) supervisory circuits for high-input-voltage and low-quiescent-current applications. These devices detect downstream circuit failures and provide switchover to redundant circuitry. See the Selector Guide for the different versions of this product family. The MAX16997/MAX16998 family has four independent inputs for reset and watchdog functions. SWT and SRT inputs independently set the timeout periods of watchdog and reset timers through external capacitors. RESETIN/EN monitor voltages at respective inputs. A resistive voltage-divider sets the reset threshold. The MAX16998A/B/D generate two output signals, RESET and ENABLE . RESET asserts whenever RESETIN drops below its threshold voltage or when the watchdog timer detects a timing fault at WDI. Once asserted, and after all reset conditions are removed, RESET remains low for the reset timeout period, tRESET, and then goes high. The MAX16997A generates one output signal (ENABLE) based on the voltage level at EN and the signal at WDI. The MAX16997A does not have a RESET output. The watchdog is disabled if the voltage at EN is below its threshold. The MAX16997A watchdog timer starts timing when the voltage at EN becomes higher than the preset threshold voltage level. Each time EN rises above the preset threshold voltage, the initial watchdog timeout period is 8 times the normal watchdog ...