Rainbow Electronics MAX5457 - Manual (Page 12)

MAX5456/MAX5457
Stereo Audio Taper Potentiometers
with Pushbutton Interface
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Mode Control,
MODE
The MAX5457 MODE input toggles between volume-
and balance-control modes. Force MODE low to toggle
between volume-control and balance-control modes.
For example, driving MODE low once while in volume-
control mode, switches the MAX5457 to balance-con-
trol mode. Driving mode low once again, switches the
MAX5457 back to volume-control mode. MODE is inter-
nally pulled high with a 50k
Ω resistor to V
LOGIC . The
MAX5457 powers up in volume-control mode.
Mode Indicator, MODE_IND
MODE_IND is the volume-control and balance-control
mode indicator with an open-drain output. Connect
MODE_IND to an LED through a pullup resistor to
V
LOGIC . When the LED is on, the MAX5457 is in balance-
control mode. When the LED is off, the MAX5457 is in
volume-control mode. See the Mode Control,
MODE sec-
tion for more detail on switching between modes.
Shutdown does not affect the state of MODE_IND.
Multiple Button Pushes
The MAX5456/MAX5457 do not respond to simultane-
ous button pushes. Pushing more than one button at the
same time stops the wipers in their present states. Only
a single button push configures the device. Additionally,
a 40ms blocking period affects all other inputs when
releasing any input forced low. The MAX5456/MAX5457
do not respond to any logic input until the blocking peri-
od ends. If multiple wiper-control buttons are pressed,
all wiper-control connections must be released before
the part will respond to further commands.
Applications Information
Stereo Volume/Balance Control
Figure 6 shows a volume/balance application using the
MAX5457. The op amp is connected in a follower (non-
inverting gain) configuration to isolate the potentiome-
ter’s wiper impedance from the load and provide drive
capability. Connect the W_ of the MAX5457 to the posi-
tive input of a noninverting gain amp. The pushbutton
potentiometers attenuate the input signals. Use the
MODE input to switch between volume-control and bal-
ance-control modes.