max5440eagt Maxim Integrated Products, Inc., max5440eagt Datasheet - Page 7

• Manufacturer Part Number: max5440eagt
• Description: Max5440 Stereo Volume Control With Rotary Encoder Interface
• Manufacturer: Maxim Integrated Products, Inc.

The MAX5440 dual, 40kΩ logarithmic taper digital
potentiometer features a debounced up/down interface
for use with a simple rotary encoder without using a
microcontroller. Each potentiometer has 32 log-spaced
tap points with a buffered wiper output and replaces
mechanical potentiometers.
The MAX5440 MODE input toggles between volume
and balance modes. Force MODE low to toggle
between volume and balance modes. For example, dri-
ving MODE low once while in volume-control mode
switches the MAX5440 to balance mode. Driving MODE
low again switches the MAX5440 back to volume mode.
MODE is internally pulled high with a 45kΩ resistor to
V
mode. Leave unconnected or connect to V
ance mode is not required.
Figure 1. Rotary Encoder Interface
LOGIC
ENCODER
ROTARY
. The MAX5440 powers up in volume-control
RENCODEA
RENCODEB
_______________________________________________________________________________________
DECREASING GRAY CODE (AB)
INCREASING GRAY CODE (AB)
Detailed Description
Mode Control (
45kΩ
COUNTERCLOCKWISE ROTATION
MAX5440
V
LOGIC
CLOCKWISE ROTATION
45kΩ
GND
A
B
with Rotary Encoder Interface
LOGIC
11, 10, 00, 01, 11, 10, ETC.
11, 01, 00, 10, 11, 01, ETC.
CLOSED CIRCUIT
CLOSED CIRCUIT
MODE )
OPEN CIRCUIT
OPEN CIRCUIT
1/4 CYCLE PER DETENT
CW
if bal-
D
The MAX5440 interfaces with rotary encoder switches.
The rotary encoder is a contact closure type switch with
two outputs that connect to RENCODEA and
RENCODEB on the device. As the shaft is rotated,
RENCODEA and RENCODEB produce a gray code
count. Figure 1 shows a typical rotary encoder interface.
State changes trigger a wiper movement and the direc-
tion of the count dictates the direction of wiper move-
ment. An increasing gray code count moves the wiper
up to a lower attenuation setting in volume mode and
towards a full right channel (CH1) in balance mode. A
decreasing gray code count moves the wiper down to a
higher attenuation in volume mode and towards a full left
channel (CH0) in balance mode. Both switch inputs are
internally pulled up to V
During rapid rotation, the inputs must be stable for at
least 20ms and have separation between state
changes by at least 40ms for the debounce circuitry to
accurately detect the input states.
Stereo Volume Control
D
D
D
D
D
D
CHANNEL A
CHANNEL B
D
LOGIC
Rotary Encoder Interface
D
D
by internal 45kΩ resistors.
D
D
D
D
D
D
D
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