On/Off Controller with Debounce and
15ꢀk ꢁED ꢂrotection
Functional Diagram
OUT
OUT
D
Q
Q
V
CC
D
Q
T
COUNTER
R
OSC
R
CLR
0
CLR
V
CC
R
PU
IN
UNDERVOLTAGE
LOCKOUT
XNOR
CLEAR
ESD
PROTECTION
MAX16054
output does not change state from high-to-low or low-
to-high until the input is stable for at least 50ms (typ).
Detailed Description
Theory of Operation
The Functional Eiagram shows the functional blocꢂs
consisting of an on-chip oscillator, counter, exclusiꢁe-
NOR gate, a E flip-flop, and a T (toggle) flip-flop. When
the pushbutton input does not equal the internal
debounced button state (the Q output of the E flip-
flop), the XNOR gate issues a counter reset. When the
switch input state is stable for the full qualification peri-
od, the counter clocꢂs the E flip-flop, changing the
internal pushbutton state. The Q output of the E flip-flop
is connected to a toggle flip-flop that toggles when the
internal pushbutton state goes through a high-to-low
transition. Figure 1 shows the typical opening and clos-
ing switch debounce operation.
The MAX16054 creates a push-on, push-off function
using a momentary-contact normally open ꢃPꢃT
switch. The high-to-low transition that occurs when
closing the switch causes OUT to go high and OUT to
go low. The output state remains latched after the
switch is released/opened. Closing the switch again
causes OUT to go low and OUT to go high.
Eebounce circuitry eliminates the extraneous leꢁel
changes that result from interfacing with mechanical
switches (switch bounce). ꢀirtually all mechanical
switches bounce upon opening and closing. The
bounce when a switch opens or closes is eliminated by
requiring that the sequentially clocꢂed input remains in
the same state for a number of sampling periods. The
A rising pulse at CLVAR resets the T flip-flop and pulls
OUT low and OUT high.
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MAXIM [ MAXIM INTEGRATED PRODUCTS ]
