General Description
The MAX5440 dual, 40kΩ logarithmic taper volume con-
trol features a debounced up/down interface for use with
a simple rotary encoder without using a microcontroller
(μC). Each potentiometer has 32 log-spaced tap points
with a buffered wiper output and replaces mechanical
potentiometers. An integrated bias generator provides
the required ((VDD + V
SS)/2) bias voltage, eliminating
the need for costly external op-amp circuits in unipolar
audio applications. A mode-indicator LED output specifies
volume or balance control. Five integrated LED drivers
indicate volume level or balance settings, depending on
the status of the mode indicator.
The MAX5440 includes debounced pushbutton inputs for
mute and mode. The mute input allows a single pushbut-
ton to change between volume control and the -90dB (typ)
mute setting. The mode input toggles between volume
and balance control. A click-and-pop suppression feature
minimizes the audible noise generated by wiper transi-
tions. The MAX5440 provides a nominal temperature
coefficient of 35ppm/°C end-toend and 5ppm/°C, ratio-
metrically. The MAX5440 is available in a 24-pin SSOP
package and is specified for operation over the -40°C to
+85°C extended temperature range.
Applications
● Stereo Volume Control
● Desktop Speakers
● Multimedia Docking Stations
● Set-Top Boxes
Features
● Logarithmic Taper Volume Control with (31) 2dB
Steps
● Low-Power Wiper Buffers Provide 0.003% THD
● Single +2.7V to +5.5V or Dual ±2.7V Supply Voltage
Operation
● Low 0.5μA Shutdown Supply Current
● Integrated Bias Voltage Generator
● Five-Segment LED Volume/Balance Indicator
● Clickless Switching
● 40kΩ End-to-End Fixed Resistance Value
● Mute Function Toggles to -90dB (typ)
● Power-On Reset to -12dBFS Wiper Position
19-0542; Rev 3; 4/14
PART TEMP RANGE PIN-PACKAGE
MAX5440EAG+ -40°C to +85°C 24 SSOP
+Denotes a lead(Pb)-free/RoHS-compliant package.
Note: For leaded version, contact factory.
VDD
VSS
(VDD + VSS) / 2
(VDD + VSS) / 2
VLOGIC
VPEAK
H1
L1
W1
SHDN
LEFT INPUT
RIGHT INPUT
MODEIND
HEADPHONE
DRIVER
L0
H0
W0
VLOGIC
LEDIND4
LEDIND3
LEDIND0
GND
MUTE
MODE
RENCODEA
RENCODEB
LEDIND1
LEDIND2
ROTARY
ENCODER
MIDBIAS
BIAS
MAX5440
24
23
22
21
20
19
17
1
2
3
4
5
6
8
GND
MODEIND
LEDIND4
LEDIND3
VLOGIC
VSS
VDD
MUTE
RENCODEA
RENCODEB
TOP VIEW
LEDIND2
LEDIND1
H1
H0
SHDN
18
7LEDIND0
GND
15
10 W1
W0
16
9L1
L0
13
12
BIAS
14
11
MIDBIAS
MODE
SSOP
MAX5440
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
Pin Conguration
Typical Operating Circuit
Ordering Information
SHDN, MUTE, RENCODEA, RENCODEB,
and MODE to GND ..........................-0.3V to (VLOGIC + 0.3V)
H_, L_, and W_ to VSS ............................ -0.3V to (VDD + 0.3V)
LEDIND_, MODEIND to GND .............-0.3V to (VLOGIC + 0.3V)
MIDBIAS, BIAS to VSS ..................(VSS - 0.3V) to (VDD + 0.3V)
VLOGIC to GND ........................................ -0.3V to (VDD + 0.3V)
VDD to GND ............................................................-0.3V to +6V
VDD to VSS ..............................................................-0.3V to +6V
VSS to GND .............................................................-3V to +0.3V
Input and Output Latchup Immunity ...............................±200mA
Continuous Power Dissipation (TA = +70°C)
24-Pin SSOP (derate 12.3mW/°C above +70°C) .....987.7mW
Operating Temperature Range ........................... -40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range ............................ -60°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
(VDD = +2.7V to +5.5V, VSS = V
GND = 0, 2.7V ≤ (VDD - V
SS) ≤ 5.5V, VLOGIC = +2.7V to VDD, VH_ = V
DD, VL_ = V
DD/2,
TA = TMIN to TMAX, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
End-to-End Resistance R 36 40 52 kΩ
Absolute Tolerance ±0.25 dB
Tap-to-Tap Tolerance ±0.1 dB
Total Harmonic Distortion Plus
Noise THD+N
VH_ = (VDD / 2) + 1VRMS, 1kHz tap at top,
RL = J to VL_ = VDD / 2, 20Hz to 20kHz 0.004
%
VH_= (VDD / 2) + 1.5VRMS, 1kHz tap at top,
RL = J to VL_ = VDD / 2, 20Hz to 20kHz 0.006
VDD = 5V,VSS = 0V, VL_ = 1.5V,
VH_ = (VDD / 2) + 1VRMS, 1kHz tap at top,
RL = 10kΩ to VMIDBIAS, 20Hz to 20kHz
0.004
VDD = 5V,VSS = 0V, VL_ = 5V,
VH_ = (VDD / 2) + 1.5VRMS, 1kHz tap at top,
RL = 10kΩ to VMIDBIAS, 20Hz to 20kHz
0.006
Channel Isolation 100 dB
Interchannel Matching ±0.5 dB
Mute Attenuation SHDN = VDD 90 dB
Power-Supply Rejection Ratio PSRR Input referred, 217Hz, 100mVP-P on VDD -60 dB
H Terminal Capacitance CH5pF
L Terminal Capacitance CL7 pF
End-to-End Resistance 35 ppm/°C
Ratiometric Resistance 5ppm/°C
Bandwidth, -3dB fCUTOFF CW = 33pF 100 kHz
Output Noise en20Hz to 20kHz 3.2 µVRMS
WIPER BUFFER
Output Voltage Swing VORL = 10kΩ to VMIDBIAS VDD - 0.2 V
Output Current 3 mA
Output Resistance ROWB 1 10 Ω
DC Offset -14 ±2 +14 mV
INTEGRATED BIAS GENERATOR
Output Voltage ILOAD = 1mA
(VDD +
VSS) / 2
- 30mV
(VDD +
VSS)
/ 2
(VDD +
VSS) / 2
+ 30mV
V
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Electrical Characteristics
(VDD = +2.7V to +5.5V, VSS = V
GND = 0, 2.7V ≤ (VDD - V
SS) ≤ 5.5V, VLOGIC = +2.7V to VDD, VH_ = V
DD, VL_ = V
DD/2,
TA = TMIN to TMAX, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1)
Note 1: Parameters are 100% production tested at +85°C and limits through temperature are guaranteed by design.
Note 2:
The device draws current in excess of the specified supply current when the digital inputs are driven with voltages between
(VDD - 0.5V) and (GND + 0.5V). See Digital Supply Current vs. Digital Input Voltage in the Typical Operating Characteristics.
Note 3: Shutdown refers to the SHDN input being asserted low. Standby refers to SHDN not being asserted and all I/O inactive.
Note 4: Supply current measured with the wiper position fixed.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Power-Supply Rejection Ratio PSRRBR 1kHz, 100mV on VDD, 1µF on BIAS 60 dB
Maximum Load To VDD or GND 3 kΩ
Output Resistance ROBR 6 Ω
CONTACT INPUTS (MUTE, MODE, RENCODEA, RENCODEB)
Internal Pullup Resistor RPULLUP 45 kΩ
Single Pulse Input Low Time tCPW 22 ms
Repetitive Input Pulse Separation tIPWS 66 ms
Timeout Period tWS Click/pop suppression inactive 32 ms
DIGITAL INPUTS (MUTE, MODE, RENCODEA, RENCODEB, SHDN)
Input High Voltage (Note 2) VIH 3.6V < VLOGIC ≤ 5.5V 2.4 V
2.7V ≤ VLOGIC ≤ 3.6V 2.0
Input Low Voltage (Note 2) VIL 3.6V < VLOGIC ≤ 5.5V 0.8 V
2.7V ≤ VLOGIC ≤ 3.6V 0.6
Input Leakage Current Inputs unconnected -1 +1 µA
Input Capacitance 5pF
POWER SUPPLIES
Supply Voltage VDD VSS = 0 2.7 5.5 V
Negative Power Supply VSS VDD = +2.7V -2.7 0V
Supply Voltage Difference VDD - VSS 5.5 V
Active Supply Current IDD 1.4 mA
Standby Supply Current
(Notes 3, 4) ISTBY VDD = +5V, VSS = 0 1.3 mA
VDD = +2.7V, VSS = -2.7V 1.3
Shutdown Supply Current ISHDN (Note 3) 1 µA
Power-Up Time tPU Click/pop suppression inactive 50 ms
Logic Supply Voltage VLOGIC VSS = 0 2.7 VDD V
Logic Active Supply Current ILVRENCODEA = VRENCODEB = 0V 320 µA
Logic Standby Supply Current ILSTBY (Note 4) 1 µA
Logic Shutdown Current ILSHDN 1µA
LED INDICATORS (LEDIND0–LEDIND4, MODEIND)
Output Low Voltage VOL VLOGIC = 2.7V, ISINK = 10mA 0.4 V
VLOGIC = 5.5V, ISINK = 10mA 0.2
Output Leakage Current 0.1 10 µA
Output Capacitance 3 pF
Maximum Sink Current 150 mA
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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│
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Electrical Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
-0.25
-0.15
-0.20
-0.05
-0.10
0.05
0
0.10
-40 10-15 35 60 85
END-TO-END RESISTANCE % CHANGE
vs. TEMPERATURE
MAX5440 toc02
TEMPERATURE (°C)
END-TO-END RESISTANCE CHANGE (%)
1.38
1.41
1.40
1.39
1.42
1.43
1.44
1.45
1.46
1.47
1.48
-40 10-15 35 60 85
TOTAL SUPPLY CURRENT
vs. TEMPERATURE
MAX5440 toc03
TEMPERATURE (°C)
TOTAL SUPPLY CURRENT (mA)
VLOGIC = VDD = 5.5V
WIPER
TRANSITION
FROM -2dB
TO -4dB
20ms/div
WIPER SWITCHING TRANSIENT
MAX5440 toc04
RENCODEA
RENCODEB
51ms
0
20
10
40
30
60
50
70
90
80
100
0 8 124 16 20 24 28 32
WIPER-TO-END TERMINAL VOLTAGE
vs. TAP POSITION
MAX5440 toc05
TAP POSITION
NOMINAL END-TO-END VOLTAGE (%VHL)
VHW
VWL
-2.8
-2.0
-2.4
-0.4
-0.8
-1.2
-1.6
0.8
0.4
0
0.01 10.1 10 100 1000
FREQUENCY RESPONSE
MAX5440 toc06
FREQUENCY (kHz)
RESPONSE (dB)
VH_ = 2.5 1VRMS, VL_ = 2.5V, CL_ = 33pF
W_ SET TO 0dB
-8.8
-8.0
-8.4
-6.4
-6.8
-7.6
-7.2
-5.6
-6.0
-5.2
0.01 10.1 10 100 1000
FREQUENCY RESPONSE
MAX5440 toc07
FREQUENCY (kHz)
RESPONSE (dB)
W_ SET TO -6dB
VH_ = 2.5 1VRMS, VL_ = 2.5V, CL_ = 33pF
-70
-60
-40
-50
-20
-10
-30
0
0 8 124 16 20 24 28 32
ATTENUATION vs. TAP POSITION
MAX5440 toc01
TAP POSITION
ATTENUATION (dB)
0.001
0.01
0.1
0.001 0.10.01 1 10 100
THD+N vs. FREQUENCY
MAX5440 toc08
FREQUENCY (kHz)
W_ SET AT -2dB
THD+N (%)
VDD = 2.5V
VSS = -2.5V
L_ = VMIDBIAS
H_ = VMIDBIAS + 1VRMS
W_ SET AT -6dB
W_ SET AT 0dB
0.001
0.01
0.1
0.001 0.10.01 1 10 100
THD+N vs. FREQUENCY
MAX5440 toc09
FREQUENCY (kHz)
THD+N (%)
VDD = 5.0V
VSS = GND
L_ = VMIDBIAS
H_ = VMIDBIAS + 1VRMS
W_ SET AT -2dB
W_ SET AT -6dB
W_ SET AT 0dB
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
Maxim Integrated
│
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Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
-75
-65
-70
-45
-50
-55
-60
-35
-40
-25
-30
0.01 10.1 10 100
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX5440 toc10
FREQUENCY (kHz)
RESPONSE (dB)
VDD_ = 5V 100mVP-P, VH = 5V
VL_ = 2.5V, W_ SET TO -6dB
0
100
50
200
150
250
300
LOGIC SUPPLY CURRENT
vs. LOGIC SUPPLY VOLTAGE
MAX5440 toc11
LOGIC SUPPLY VOLTAGE (V)
LOGIC SUPPLY CURRENT (µA)
2.5 3.5 4.03.0 4.5 5.0 5.5
ACTIVE CURRENT
STANDBY CURRENT
SHUTDOWN
0
100
50
200
150
300
250
350
-40 10-15 35 60 85
ACTIVE LOGIC SUPPLY CURRENT
vs. TEMPERATURE
MAX5440 toc12
TEMPERATURE (°C)
LOGIC SUPPLY CURRENT (µA)
VDD = VLOGIC = 5.5V,
RENCODEA = RENCODEB = 0
1.1752
1.1756
1.1754
1.1762
1.1760
1.1758
1.1768
1.1766
1.1764
1.1770
-40 10-15 35 60 85
ACTIVE SUPPLY CURRENT
vs. TEMPERATURE
MAX5440 toc13
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
VDD = VLOGIC = 5.5V,
RENCODEA = RENCODEB = 0
10
100
1000
0 0.5 2.0 2.51.0 1.5 3.0 3.5 4.0 4.5 5.0
DIGITAL SUPPLY CURRENT
vs. DIGITAL INPUT VOLTAGE
MAX5440 toc14
DIGITAL INPUT VOLTAGE (V)
DIGITAL SUPPLY CURRENT (µA)
200
0
400
800
600
1000
1200
0.01 10.1 10 100
SPECTRAL NOISE DENSITY
MAX5440 toc15
FREQUENCY (kHz)
NOISE (nV/√Hz)
0
1
2
3
4
5
6
7
8
2.5 3.0 3.5 4.0 4.5 5.0
SUPPLY CURRENT
vs. INPUT VOLTAGE SWEEP
MAX5440 toc16
INPUT VOLTAGE SWEEP (V
H_
)
SUPPLY CURRENT (mA)
VDD = VLOGIC = 5V, W_ AT 0dB
RL = 10kΩ TO VMIDBIAS
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
Maxim Integrated
│
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Typical Operating Characteristics (continued)
PIN NAME FUNCTION
1 VLOGIC Digital Logic Power Supply. Bypass VLOGIC to ground with a 0.1µF capacitor as close to the device as
possible.
2RENCODEB Rotary Encoder Input B. With RENCODEA, this input provides the rotary encoder control for the
potentiometer (see Figure 1). RENCODEB is internally pulled up to VLOGIC with a 45kΩ resistor.
3RENCODEA Rotary Encoder Input A. With RENCODEB, this input provides the rotary encoder control for the
potentiometer (see Figure 1). RENCODEA is internally pulled up to VLOGIC with a 45kΩ resistor.
4MUTE Mute Input. Pull MUTE low to toggle the wiper between the mute setting (see Table 1) and the current
setting. MUTE is pulled up to VLOGIC with an internal 45kΩ resistor.
5MODE
Volume/Balance Control Input. Each high-to-low transition on MODE toggles between the volume
and balance modes. MODE is pulled high internally with a 45kΩ resistor to VLOGIC. On power-up, the
MAX5440 is in volume-control mode.
6SHDN
Active-Low Shutdown Input. Drive SHDN low to place the device in shutdown mode. In shutdown mode,
the MAX5440 stores the last wipers settings. The wipers move to the L_ end of the resistor string.
Terminating shutdown mode restores the wipers to their previous settings.
7, 24 GND Ground. Connect pins 7 and 24 together.
8H0 Potentiometer 0 High Terminal. H0 and L0 terminals can be reversed.
9 L0 Potentiometer 0 Low Terminal. L0 and H0 terminals can be reversed.
10 W0 Potentiometer 0 Wiper Buffered Output
11 MIDBIAS Midbias Voltage Output. VMIDBIAS = (VDD + VSS) / 2.
12 BIAS Bias Generator Input. Bypass with a 1µF capacitor to system ground.
13 VDD Analog Power Supply. Bypass VDD to ground with a 0.1µF capacitor as close to the device as possible.
14 VSS Negative Power Supply. Bypass VSS to ground with a 0.1µF capacitor as close to the device as possible.
Connect to GND for single-supply operation.
15 W1 Potentiometer 1 Wiper Buffered Output
16 L1 Potentiometer 1 Low Terminal. L1 and H1 terminals can be reversed.
17 H1 Potentiometer 1 High Terminal. H1 and L1 terminals can be reversed.
18–22 LEDIND0–
LEDIND4
LED Indicator Open-Drain Output 0 through LED Indicator Open-Drain Output 4. LEDIND0–LEDIND4 form
a bar graph indication of the current volume or balance. In volume mode, all LEDs off indicates mute and
all LEDs on indicates maximum volume. In balanced mode, LED2 on indicates centered or balanced.
23 MODEIND
Volume-Control/Balance-Control Mode Indicator Open-Drain Output. Connect to an LED through a resistor
to VLOGIC. When the LED is on, the MAX5440 is in balance-control mode. When the LED is off, the
MAX5440 is in volume-control mode.
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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Pin Description
Detailed Description
The MAX5440 dual, 40kΩ logarithmic taper digital poten-
tiometer features a debounced up/down interface for use
with a simple rotary encoder without using a microcon-
troller. Each potentiometer has 32 log-spaced tap points
with a buffered wiper output and replaces mechanical
potentiometers.
Mode Control (MODE)
The MAX5440 MODE input toggles between volume
and balance modes. Force MODE low to toggle between
volume and balance modes. For example, driving 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 VLOGIC.
The MAX5440 powers up in volume-control mode. Leave
unconnected or connect to VLOGIC if balance mode is not
required.
Rotary Encoder Interface
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 direction
of the count dictates the direction of wiper movement. 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 VLOGIC by internal 45kΩ resistors.
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.
Figure 1. Rotary Encoder Interface
MAX5440
B
RENCODEA
RENCODEB
ROTARY
ENCODER
A
GND
V
LOGIC
45kΩ45kΩ
CLOCKWISE ROTATION
INCREASING GRAY CODE (AB) 11, 10, 00, 01, 11, 10, ETC.
COUNTERCLOCKWISE ROTATION
DECREASING GRAY CODE (AB) 11, 01, 00, 10, 11, 01, ETC.
CW
CLOSED CIRCUIT
OPEN CIRCUIT
OPEN CIRCUIT
CLOSED CIRCUIT
CHANNEL A
CHANNEL B
1/4 CYCLE PER DETENT
D D D D D D D D D D D D D D D D D
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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Volume Control
In volume-control mode, the MAX5440’s wipers move
simultaneously, maintaining the balance separation
between each wiper (Figure 2a).
When either wiper reaches the maximum tap position
(position closest to H_), further commands to increase the
volume are ignored. Balance separation is maintained in
the maximum volume configuration (Figure 2b).
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 2c).
Increasing the volume from this minimum position restores
the original balance separation of the wipers (Figure 2d).
When both wipers are in the tap 31 position (-62dB
attenuation), further decreasing rotations place the wipers
in the mute position (see Table 1). Rotating the encoder to
a lower attenuation or a pulse to MUTE returns the wipers
to tap 31.
Figure 2. Volume-Control Operation
W0
H_
L_
H_
L_
H_
L_
H_
L_
W1 W0
ROTATE CW
TWICE
ROTATE CCW
ONCE
BALANCE SEPARATION
MAINTAINED
NO CHANGE
ORIGINAL BALANCE SEPARATION
MAINTAINED
ROTATE CW
ROTATE CCW
ROTATE CW
ONCE
ROTATE CW
ONCE
ROTATE CCW
ONCE
ROTATE CW
ONCE
FROM C
TO D
W1 W0 W1
W0 W1 W0 W1 W0 W1
W0 W1 W0 W1 W0 W1
W0 W1 W0 W1 W0 W1
a
b
c
d
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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Balance Control
In balance-control mode, the MAX5440 adjusts the bal-
ance between channel 0 and channel 1 while maintaining
the set volume. For example, if the volume of channel
0 equals the volume of channel 1, forcing the balance
towards channel 1 increases the attenuation of channel
0 (Figure 3a). If channel 1 is at a higher attenuation than
channel 0, adjusting the balance to channel 1 moves
channel 1’s wiper up to the same wiper position as chan-
nel 0 before it was attenuated (Figure 3b).
Click-and-Pop Suppression
The click-and-pop suppression feature reduces the audi-
ble noise (clicks and pops) that results from wiper transi-
tions. The MAX5440 minimizes this noise by allowing
the wiper to change position only when VH = VL. Each
wiper has its own suppression and timeout circuitry. The
MAX5440 changes wiper position when VH = VL, or after
32ms, whichever occurs first (see Figures 4a and 4b).
The suppression circuitry monitors left and right channels
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.
Figure 3. Balance-Control Operation
Table 1. Wiper Position and Attenuation
POSITION ATTENUATION (dB)
0 0
1 -2
2-4
… …
6 (POR) -12
… …
30 -60
31 -62
32 (MUTE) ≥ 90
W0 W1 W0 W1 W0 W1
H_
L_
W0 W1 W0 W1 W0 W1
H_
L_
ROTATE CW
ONCE
ROTATE CW
ONCE
ROTATE CW
ONCE
ROTATE CW
ONCE
VOLUME LEVEL IS SET
VOLUME LEVEL IS SET BY W0
VOLUME LEVEL MAINTAINED
BALANCE SHIFTS TO W1
VOLUME LEVEL MAINTAINED
BALANCE SHIFTS TO W1
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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Figure 4a. Wiper Transition Timing Diagram—Suppression Circuitry Active
01
00
USER ROTATES ENCODER
t
WS
t
HPW
t
LPW
V
H_
V
L_
SWITCH
CONTACT
IS BOUNCING
SWITCH CONTACT
IS BOUNCING
SWITCH
CONTACT
IS STABLE
INPUT ACCEPTED
WAIT FOR FIRST
ZERO CROSSING,
t
WS
DEBOUNCE BY WAITING
FOR STABLE LOW,
t
LPW
DEBOUNCE BY WAITING
FOR STABLE HIGH,
t
HPW
WIPER MOVES HERE
WIPER MOTION
2dB STEPS
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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Figure 4b. Wiper Transition Timing Diagram—Timed Out
t
HPW
INPUT ACCEPTED
WAIT FOR FIRST
ZERO CROSSING OR
TIMEOUT,
t
WS
2dB STEPS
t
WS
t
LPW
(t
LPW
+
t
WS)
V
H
V
L
DEBOUNCE BY WAITING
FOR STABLE LOW,
t
LPW
DEBOUNCE BY WAITING
FOR STABLE HIGH,
t
HPW
01
00
SWITCH CONTACT
IS BOUNCING
SWITCH
CONTACT
IS STABLE
SWITCH CONTACT
IS BOUNCING
WIPER MOVES HERE
READY TO ACCEPT
ANOTHER ENCODER
INPUT SIGNAL
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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11
Power-On Reset
The power-on comparators monitor (VDD - V
SS) and
(VLOGIC - GND). A power-on reset is initiated when either
of the supplies is brought back to the normal operating
voltage. The power-on reset feature sets both wipers to
-12dB. The wipers initially wake up in mute mode (-90dB)
and move to the -12dB position when VH = VL to elimi-
nate clicks and pops during power-up. With DC inputs at
VH and VL, the wipers move after exceeding the timeout
period. A power-on reset places the MAX5440 in volume-
control mode.
Shutdown (SHDN)
Upon entering shutdown, the MAX5440 stores the last
wiper settings. The wipers move to the L_ end of the
resistor string. The wipers move to the L_ end of the
resistor string when VH = VL to eliminate clicks and pops
during shutdown. With DC inputs at VH and VL, the wipers
move after exceeding the timeout period. Exiting shut-
down restores the wipers to their previous settings.
Mute Function (MUTE)
The MAX5440 features a mute function input, MUTE.
Successive low pulses on MUTE toggle its setting. Activating
the mute function forces both wipers to maximum attenua-
tion (-90dB typ). Deactivating the mute function returns
the wipers to their previous settings. Rotating the encoder
clockwise (increasing gray code count) also deactivates
mute, setting the wipers to their previous positions. MUTE
is internally pulled high with a 45kΩ resistor to VLOGIC.
When both wipers are in the tap 31 position (-62dB attenu-
ation) further commands to lower the volume (decreasing
gray code count) place the wipers in the mute position (see
Table 1). Rotating the encoder to a lower attenuation or a
pulse to MUTE returns the wipers to tap 31.
Mode Indicator (MODEIND)
The open-drain MODEIND indicates volume-control
mode or balance-control mode for the MAX5440. Connect
MODEIND to an LED with a series resistor to VLOGIC.
When the LED is on, the MAX5440 is in balancecontrol
mode. When the LED is off, the MAX5440 is in volume-
control mode. See the Mode Control (MODE) section for
more detail on switching between modes.
Level Indicator LEDs
The MAX5440 includes five indicator LED drivers to dis-
play the current wiper settings in either volume or balance
mode. Connect the LEDIND_ outputs to the LEDs and to
VLOGIC through a series resistor as shown in the typical
application circuits.
In volume-control mode, all LEDs are off when the wipers
reach the highest attenuation levels (mute). All LEDs are
on at the lowest attenuation levels (0dB). Table 2 shows
the LED display as the wipers transition through various
attenuation levels.
In balance-control mode, only one LED is on at a time to
indicate the current balance setting. Figure 5 shows the
LEDs display for the current balance setting. When LED2
is on, the display indicates that the channels are centered
or balanced at a set volume level. Turning the encoder
clockwise (an increasing gray code count) turns LED3
on to represent a balance shift towards channel 1. When
LED4 turns on, the balance shifts completely toward
channel 1 and channel 0 is fully attenuated. From a bal-
anced position, turning the encoder counterclockwise (a
decreasing gray code count) turns on LED1, and then
LED0 to indicate a balance shift towards channel 0.
Table 2. LED Settings in Volume Mode
VOLUME POSITION (dB) VOLUME LED OUTPUTS (1 = LED IS ON)
LED0 LED1 LED2 LED3 LED4
0 to -8 1 1 1 1 1
-10 to -18 1 1 1 1 0
-20 to -28 1 1 1 0 0
-30 to -38 1 1 000
-40 to -52 1 0000
-54 to mute (-90) 00000
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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Figure 5. LED Setting in Balance Mode
Figure 6. Dual-Supply Volume/Balance Control
FULL L L + 12 L + 6 R + 6 R + 12 FULL R
CENTERED CW ROTATION (CH1) CCW ROTATION (CH0)
LED0 ON LED1 ON LED2 ON LED3 ON LED4 ON
VDD
VSS = -VDD
VLOGIC
VPEAK
H1
L1
W1
SHDN
LEFT INPUT
RIGHT INPUT
MODEIND
HEADPHONE
DRIVER
L0
H0
W0
VLOGIC
LEDIND4
LEDIND3
LEDIND0
GND
MUTE
MODE
RENCODEA
RENCODEB
LEDIND1
LEDIND2
ROTARY
ENCODER
MIDBIAS
BIAS
0V
(VDD + VSS) / 2
MAX5440
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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Multiple Button Pushes (MODE, MUTE)
The MAX5440 does not respond to simultaneous button
pushes. Pushing more than one button at the same time
stops the wipers in their present states. Only a single but-
ton push configures the device.
Applications Information
Typical Application Circuit
The Typical Operating Circuit shows the MAX5440 in a
typical volume/balance application using a single-supply
configuration. Figure 6 shows a typical volume/balance
application circuit using the MAX5440 in a dual-supply
configuration. The MAX5440 does not require external
op amps because the bias is generated internally, and
the wipers have internal low-power buffers for low distor-
tion. Connect the W_ outputs of the MAX5440 to the left
and right inputs of a stereo audio amplifier, such as the
MAX9761. The rotary encoder controls the potentiometer
attenuation levels without using a microcontroller. Use
the MODE input to switch between volume-control and
balance-control modes.
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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Chip Information
PROCESS: BiCMOS
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
24 SSOP A24-1 21-0056
TIMING AND CONTROL
DEBOUNCE DEBOUNCE DEBOUNCE DEBOUNCE DEBOUNCE
POSITION COUNTER POSITION COUNTER
UP/DOWN UP/DOWN
MODEINDSHDN
V
LOGIC
V
DD
V
SS
H0
W0
L0
GND RENCODEA RENCODEB MUTE
L1
W1
H1
MODE
V
LOGIC
0
1
2
3
4
28
30
31
29
0
1
2
3
4
28
29
30
31
MUTE MUTE
BIAS GENERATOR
MIDBIAS LEDIND0 LEDIND1 LEDIND2 LEDIND3 LEDIND4
45kΩ45kΩ45kΩ45kΩ
CLICK-AND-POP
SUPPRESSION
CIRCUITRY
CLICK-AND-POP
SUPPRESSION
CIRCUITRY
BIAS
MAX5440
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
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Revision History
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
2 11/08 Fixed pin names and thermal data. Updated two specications in EC table 1, 2, 3, 6, 13
3 4/14 Updated Applications 1
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAX5440 Stereo Volume Control
with Rotary Encoder Interface
© 2014 Maxim Integrated Products, Inc.
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Revision History
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