Watchdog constant RESETn

Question

Hi, 
 I'm looking for watchdog, open drain, that can reset a FET transistor if it fails to strobe within a preset timeout period- constant '0' as long as the input watchdog stays without toggling . 
 I found the ADM8617 module that has an on-chip watchdog timer. The problem is that I'm not so sure that the "RESETn" stays low as long as the WDI will not toggle (I'm most fear from "RESETn" oscillation regardless to the WDI condition). 
 Can you confirm that if the WDI stays without toggling (after "t WD ")- the "RESETn" will stays constant low? In other words, "RESET TIMEOUT PERIOD" is referring to min only because the max depending only in the WDI toggling and the VCC input voltage. 
 If you have another technical material about the ADM8617/ another WD recommended, please share with me ( Ozanaidan@gmail.com ) 
 Thank You! 
 Idan

Ren · Accepted Answer

Hi Idan, 
 Some parts like ADM705 ADM706 ADM8699 ADM699 etc would have WDO pin which is the dedicated output pin of the watchdog timer. This pin would remain asserted after watchdog timeout until WDI toggle or RESET is generated. 
 Maybe you can make use of it in your application. 
 The current part released with WDO function are all push-pull type with 1.6s watchdog timeout. 
 If you want different output type or different timeout, you can try a different voltage supervisory part with some simple external latching circuitry like this one: 
 http://www.eetimes.com/design/power-management-design/4218752/Power-Tip-38--Simple- latch -circuit-protects-power-supplies - 
 this tool would be useful for finding the right supervisory part from ADI: 
 http://designtools.analog.com/psSupervisorWeb/psSupervisorMain.aspx 
 Ren)