Rainbow Electronics MAX5457 - Manual (Page 7)

MAX5456/MAX5457
Stereo Audio Taper Potentiometers
with Pushbutton Interface
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Detailed Description
The MAX5456/MAX5457 dual, logarithmic taper digital
potentiometers feature a simple pushbutton interface that
controls volume and balance in audio applications. Each
potentiometer has 32 tap points and replaces mechanical
potentiometers (see the Functional Diagrams).
Up and Down Interface
The MAX5456/MAX5457 interface with momentary con-
tact SPST switches. All switch inputs are internally
debounced and pulled up to V
LOGIC through 50k
Ω
resistors. The wiper setting advances once per button
press up to 1s. Maxim’s SmartWiper control circuitry
allows the wiper to advance at a rate of 4Hz when an
input is held low from 1s up to 4s, and at a rate of 16Hz
if the contact is maintained for greater than 4s (see
Table 2). The SmartWiper control eliminates the need for
a microcomputer to increase the wiper transition rate.
The MAX5456 features independent control inputs for
volume and balance control while the MAX5457 MODE
input toggles between volume and balance control.
Each transition of MODE from high to low toggles the
MAX5457 between volume-control and balance-control
modes. MODE is internally pulled high with a 50k
Ω
resistor to V LOGIC.
Volume Control
In volume-control mode, the MAX5456/MAX5457s’
wipers move simultaneously, maintaining the balance
separation between each wiper (Figure 3a).
When either wiper reaches the maximum tap position
(position closest to H_), further commands to increase
the volume are ignored. Balance separation is main-
tained in the maximum volume configuration (Figure 3b).
When either wiper reaches the minimum tap position
(position closest to L_), further commands to decrease
the volume adjust the other wiper until it also reaches
the minimum tap position (Figure 3c).
Increasing the volume from this minimum position
restores the original balance separation of the wipers
(Figure 3d).
When both wipers are in the 31st tap position (-62dB
attenuation), further commands to VOLDN place the
wipers in the mute position (see Table 1). VOLUP or
MUTE pulses return wipers to position 31.
C H
C L
C W
MAX5456
MAX5457
R W
W_
H_
L_
R
Figure 1. Potentiometer Model (Active)
C H
C
L
C
W
MAX5456
MAX5457
R W
W_
H_
L_
R
Figure 2. Potentiometer Model (Shutdown)