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器件3D模型￥ 14.846
MAX6818EAP+T 其他数据使用手册 - Maxim Integrated（美信）
制造商:
Maxim Integrated（美信）
分类:
接口芯片
封装:
SSOP-20
描述:
MAXIM INTEGRATED PRODUCTS MAX6818EAP+T 专用接口, 汽车应用, 工业仪器, 电脑板仪器, 便携式仪器, 2.7 V, 5.5 V, SSOP, 20 引脚
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MAX6818EAP+T数据手册
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of 15 Go
若手册格式错乱，请下载阅览PDF原文件
A new debouncing technique employs a switch-debouncer IC to reduce the component count, the power
consumption, and the PC-board space (Figure 2b). U1 is a CMOS switch debouncer connected directly
to a SPST switch. Its input has a 63kΩ pullup resistor for logic-high inputs, which saves PC-board
space. Capacitor C1 decouples the VCC pin. Closing the switch pulls the IN pin low and provides a logic
low at the OUT pin. The OUT pin does not change state until the IN pin is stable for 40ms, which hides
the effect of any contact bounce.
A not-so-obvious advantage of this circuit is resistive loading of the switch by the internal 63kΩ resistor,
ensuring reliability and an indefinite switch life. Disallowed states do not exist in this circuit, because the
input is either low or high. Moreover, the IC's undervoltage-lockout circuitry ensures a condition crucial in
automotive and industrial applications: that the OUT pin be in a known state during power-up. The circuit
improves reliability and lowers system costs by requiring fewer components, a less expensive SPST
switch, and only two wires connected to the switch.
Relay Bounce
Relays are also represented as ideal switching devices in textbooks. Like the switching contacts of an
ideal switch, those of a relay are assumed to have zero resistance and a single switching transition that
occurs immediately on actuation. As with switches, actual relay contacts, of course, have contact
resistance, which increases over time with repeated actuations. Typical contact resistance ranges from
less than 50mΩ to 200mΩ when new.
The actuation of a relay is also mechanical. Unlike the switch, however, a SPST relay has only one
movable contact, which connects electrically by a wire to one of the external-contact terminals. The
stationary contact connects to the other external contact. Relay contacts also make several open-close
cycles of contact bounce before coming to rest in the final state. This contact-bounce interval is in
addition to the relay's operate and release times, which can measure tens of milliseconds.
Figure 3 shows the voltage across a resistive load after actuating an industrial relay that supplies 24V to
the resistor. At least 12 major switching transitions are evident before the contacts come to rest at 24V.
An automotive microcontroller or industrial control system would interpret these transitions as multiple
cycles of the relay contacts.
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