AN609 MAXIM | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 2
Technical content
www.maxim - ic.com/an609 Page 1 of 2 SUPERVISORY/VOLTAGE MONITOR CIRCUITS Application Note 609: Jun 01, 2001 Tiny IC Debounces Pushbutton Switch When a push-button is used to manually reset a µP, ringing from the switch may cause a false reset output signal when the switch is press and de-pressed. Maxim's microprocessor supervisors have a debounced manual reset input to help ignore this ringing. Though they're not complicated, schemes for debouncing a pushbutton switch usually entail using several logic gates. It's easy to include such circuits in an ASIC. Adding a debouncer as a last - minute design change, however, can be inconvenient. In such cases, the circuit in the figure below can come in handy. The circuit, using only a 4 - pin SO - package IC, squares up and debo unces a pushbutton signal. IC 1 is a reset chip with a reset output that goes high when its supply voltage drops below 2.65V or when its manual - reset input (MR - bar) goes low. MR - bar usually connects to a system - reset input, and reset connects to a µC, but t he connections shown enable the device to debounce any signal. The internal one - shot provides an instant response to the first falling edge on the input and then delays any further response until 140msec after the last rising edge. The MAX812 shown invert s the pushbutton input; a similar device (MAX811) is noninverting. The ICs also incorporate a power - on reset function that asserts the reset output when V CC falls below a preset threshold and also asserts the output for 140msec after each application of po wer. Selecting an R - suffix part sets this threshold at its lowest value (2.63V), preventing false outputs in the debouncer except when the supply voltage fails.
www.maxim - ic.com/an609 Page 2 of 2 Using almost no real estate, this circuit squares up and debounces a pushbutton signal and extends it to at least 140msec. A similar version of this article appeared in the April 1, 2001 issue of EDN. MORE INFORMATION MAX6384: QuickView -- Full (PDF) Data Sheet (208k) -- Free Samp le MAX6385: QuickView -- Full (PDF) Data Sheet (208k) -- Free Sample MAX6386: QuickView -- Full (PDF) Data Sheet (208k) -- Free Sample MAX812: QuickView -- Full (PDF) Data Sheet (128k) -- Free Sample