Rainbow Electronics MAX5457 - Manual (Page 10)

MAX5456/MAX5457
Stereo Audio Taper Potentiometers
with Pushbutton Interface
10 ______________________________________________________________________________________
Click/Pop Suppression
The click/pop suppression feature reduces the audible
noise (clicks and pops) that result from wiper transitions.
The MAX5456/MAX5457 minimize this noise by allowing
the wiper position changes only when V
H_ = V L_ . Thus,
the wiper changes position only when the voltage at L_ is
the same as the voltage at the corresponding H_. Each
wiper has its own suppression and timeout circuitry (see
Figure 5a). The MAX5456/MAX5457 change wiper posi-
tion after 32ms or when V
H_
= V
L
, whichever occurs first
(see Figure 5b).
The suppression circuitry monitors left and right chan-
nels separately. In volume-control mode, when the first
wiper changes position, the second wiper has 32ms to
change or it will be forced to change.
Power-On Reset
The power-on comparators monitor V
DD
- V
SS
and
V LOGIC - GND. A power-on reset is initiated when either
of the supplies is brought back to normal operating
voltage. The power-on-reset feature sets both wipers to
-12dB. Power-on reset places the MAX5457 in volume-
control mode.
DN OR UP
1
0
USER PRESSES PUSHBUTTON
SWITCH
CONTACT
IS BOUNCING
SWITCH
CONTACT
IS STABLE
SWITCH
CONTACT
IS BOUNCING
READY TO ACCEPT
ANOTHER KEYPRESS
INPUT ACCEPTED
t IPW
t
WS
t HPW
DEBOUNCE BY
WAITING FOR
STABLE LOW, t IPW
WAIT FOR
FIRST ZERO
CROSSING, t WS
DEBOUNCE BY
WAITING FOR
STABLE HIGH, t HPW
V H
V
L
WIPER MOTION
WIPER MOVES HERE
2dB
STEPS
Figure 5a. Wiper Transition Timing Diagram