I have a customer that is using TPS3306 and they belive noise is coupling into the WDI input.
This is a weakly driven pin that toggles and looks for transitions. How is this pin sampled during transition? Is there any way to calculate a noise margin for WDI?
The way I read it, the thresholds are VIH (.7 VCC) and VIL (.3 VCC) with a 40K termination that will either be high or low.
The WDI pin is a logic input with Vih => 0.7*Vdd and Vil <= 0.3*Vdd. The input must see an edge from a logic low to logic high in order to reset the watchdog timer. You can think of this input an analogous to the clock pin of a D type flip flop or any other edge triggered signal.
Internally, the WDI pin is driven by a pulse generator so that if the WDI pin is left open, then the watchdog input is automatically provided by the IC. There is a 40kOhm resistor between the pulse generator and the WDI input pin so that you don't have signal conflicts when using an external WDI source. The internal pulse generator stays low until a watchdog pulse is needed, then a high level pulse is generated for a few microseconds to reset the watchdog.
ALL CONTENT AND MATERIALS ON THIS SITE ARE PROVIDED "AS IS". TI AND ITS RESPECTIVE SUPPLIERS MAKE NO REPRESENTATIONS ABOUT THE SUITABILITY OF THESE MATERIALS FOR ANY PURPOSE AND DISCLAIM ALL WARRANTIES AND CONDITIONS WITH REGARD TO THESE MATERIALS, INCLUDING BUT NOT LIMITED TO, ALL IMPLIED WARRANTIES AND CONDITIONS OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT OF ANY THIRD PARTY INTELLECTUAL PROPERTY RIGHT. NO LICENSE, EITHER EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, IS GRANTED BY TI. USE OF THE INFORMATION ON THIS SITE MAY REQUIRE A LICENSE FROM A THIRD PARTY, OR A LICENSE FROM TI.
Content on this site may contain or be subject to specific guidelines or limitations on use. All postings and use of the content on this site are subject to the Terms of Use of the site; third parties using this content agree to abide by any limitations or guidelines and to comply with the Terms of Use of this site. TI and its suppliers reserve the right to make corrections, deletions, modifications, enhancements, improvements and other changes to the content and materials, its products, programs and services at any time or to move or discontinue any content, products, programs, or services without notice.