AN609 [MAXIM]

Tiny IC Debounces Pushbutton Switch; 微小的IC去抖按钮开关
AN609
元器件型号: AN609
生产厂家: MAXIM INTEGRATED PRODUCTS    MAXIM INTEGRATED PRODUCTS
描述和应用:

Tiny IC Debounces Pushbutton Switch
微小的IC去抖按钮开关

开关按钮开关
PDF文件: 总2页 (文件大小:177K)
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MAX34334CSE前5页PDF页面详情预览
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
debounces 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 the 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
inverts 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 power.
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.
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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:
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MAX6385:
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MAX6386:
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Full (PDF) Data Sheet (208k)
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MAX812:
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Full (PDF) Data Sheet (128k)
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Free Sample
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Page 2 of 2
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