MAX5440EAG+T [MAXIM]
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| 型号： | MAX5440EAG+T |
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MAXIM INTEGRATED PRODUCTS |
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19-0542; Rev 2; 11/08
Stereo Volume Control
with Rotary Encoder Interface
MAX540
General Description
Features
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 microcon-
troller (µC). Each potentiometer has 32 log-spaced tap
points with a buffered wiper output and replaces
mechanical potentiometers. An integrated bias genera-
♦ 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 Supplꢀ
Voltage Operation
tor provides the required ((V
+ V ) / 2) bias voltage,
SS
DD
♦ Low 0.5µA Shutdown Supplꢀ Current
♦ Integrated Bias Voltage Generator
♦ Five-Segment LED Volume/Balance Indicator
♦ Clickless Switching
eliminating the need for costly external op-amp circuits
in unipolar audio applications. A mode-indicator LED
output specifies volume or balance control. Five inte-
grated LED drivers indicate volume level or balance set-
tings, depending on the status of the mode indicator.
The MAX5440 includes debounced pushbutton inputs
for mute and mode. The mute input allows a single
pushbutton 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 gener-
ated by wiper transitions. The MAX5440 provides a
nominal temperature coefficient of 35ppm/°C end-to-
end and 5ppm/°C, ratiometrically. The MAX5440 is
available in a 24-pin SSOP package and is specified for
operation over the -40°C to +85°C extended tempera-
ture range.
♦ 40kΩ End-to-End Fixed Resistance Value
♦ Mute Function Toggles to -90dB (tꢀp)
♦ Power-On Reset to -12dBFS Wiper Position
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX5440EAG
-40°C to +85°C
24 SSOP
Applications
Stereo Volume Control
Desktop Speakers
Typical Operating Circuit
Multimedia Docking Stations
Set-Top Boxes
V
DD
V
LOGIC
Automotive Back-Seat Multimedia
V
LOGIC
V
PEAK
SHDN
MODEIND
Pin Configuration
(V
V ) / 2
+ SS
DD
MAX5440
H1
TOP VIEW
W1
V
1
2
3
4
24
23
22
21
20
19
LOGIC
GND
RIGHT INPUT
MODEIND
LEDIND4
LEDIND3
RENCODEB
RENCODEA
MUTE
L1
HEADPHONE
DRIVER
MIDBIAS
(V
DD
V ) / 2
SS
+
MAX5440
LEDIND0
LEDIND1
LEFT INPUT
LEDIND2
LEDIND1
L0
MODE
SHDN
GND
5
6
W0
LEDIND2
LEDIND3
18 LEDIND0
17 H1
7
8
H0
H0
LEDIND4
BIAS
V
SS
16 L1
9
L0
15 W1
10
11
12
W0
14
13
V
MIDBIAS
BIAS
SS
V
DD
ROTARY
ENCODER
SSOP
________________________________________________________________ Maxim Integrated Products
1
For price, deliverꢀ, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Stereo Volume Control
with Rotary Encoder Interface
ABSOLUTE MAXIMUM RATINGS
SHDN, MUTE, RENCODEA, RENCODEB,
and MODE to GND............................-0.3V to (V
V
to GND...............................................................-3V to +0.3V
SS
Input and Output Latchup Immunity............................... 200mA
Continuous Power Dissipation (T = +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
+ 0.3V)
+ 0.3V)
+ 0.3V)
+ 0.3V)
+ 0.3V)
LOGIC
DD
LOGIC
H_, L_, and W_ to V
...............................-0.3V to (V
A
SS
LEDIND_, MODEIND to GND................-0.3V to (V
MIDBIAS, BIAS to V ......................(V - 0.3V) to (V
SS
SS
DD
DD
V
V
V
to GND...........................................-0.3V to (V
to GND..............................................................-0.3V to +6V
to V ................................................................-0.3V to +6V
LOGIC
DD
DD
SS
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.
MAX540
ELECTRICAL CHARACTERISTICS
(V
= +2.7V to +5.5V, V = V
= 0, 2.7V ≤ (V
- V ) ≤ 5.5V, V
= +2.7V to V , V = V , V = V
/ 2, T = T
to
MIN
GND
DD
SS
DD
SS
LOGIC
DD H_
DD L_
DD
A
T
MAX
, unless otherwise specified. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
kΩ
End-to-End Resistance
Absolute Tolerance
R
36
40
52
0.25
0.1
dB
Tap-to-Tap Tolerance
dB
V
= (V / 2) + 1V
, 1kHz tap at top, R
H_
DD
RMS L
0.004
0.006
= ∞ to V = V / 2, 20Hz to 20kHz
L_
DD
V
H_
= (V / 2) + 1.5V
, 1kHz tap at top,
RMS
DD
R = ∞ to V = V / 2, 20Hz to 20kHz
L
L_
DD
Total Harmonic Distortion Plus
Noise
V
(V
= 5V,V = 0V, V = 1.5V, V
=
DD
SS
L_
H_
THD+N
%
/ 2) + 1V
, 1kHz tap at top, R =
RMS L
0.004
0.006
DD
10kΩ to V
, 20Hz to 20kHz
MIDBIAS
V
= 5V,V = 0V, V = 5V, V = (V
/
DD
SS
L_
H_
DD
2) + 1.5V
1kHz tap at top, R = 10kΩ
RMS,
L
to V
, 20Hz to 20kHz
MIDBIAS
Channel Isolation
100
0.5
90
-60
5
dB
dB
Interchannel Matching
Mute Attenuation
SHDN = V
dB
DD
Power-Supply Rejection Ratio
H Terminal Capacitance
L Terminal Capacitance
End-to-End Resistance
Ratiometric Resistance
PSRR
Input referred, 217Hz, 100mV
on V
dB
P-P
DD
C
pF
H
C
7
pF
L
35
5
ppm/°C
ppm/°C
kHz
Bandwidth, -3dB
Output Noise
f
C
= 33pF
W
100
3.2
CUTOFF
e
20Hz to 20kHz
µV
n
RMS
WIPER BUFFER
Output Voltage Swing
Output Current
V
R = 10kΩ to V
V
- 0.2
DD
V
O
L
MIDBIAS
3
mA
Output Resistance
DC Offset
R
1
10
Ω
OWB
-14
2
+14
mV
INTEGRATED BIAS GENERATOR
(V
DD
+
(V
DD
+
(V
DD
+
V
) / 2
V
SS
/ 2
)
V ) / 2 +
SS
30mV
Output Voltage
I
= 1mA
V
SS
LOAD
- 30mV
2
_______________________________________________________________________________________
Stereo Volume Control
with Rotary Encoder Interface
MAX540
ELECTRICAL CHARACTERISTICS (continued)
(V
= +2.7V to +5.5V, V = V
= 0, 2.7V ≤ (V
- V ) ≤ 5.5V, V
= +2.7V to V , V = V , V = V
/ 2, T = T
to
MIN
GND
DD
SS
DD
SS
LOGIC
DD H_
DD L_
DD
A
T
MAX
, unless otherwise specified. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
PSRR
CONDITIONS
1kHz, 100mV on V , 1µF on BIAS
MIN
TYP
MAX
UNITS
dB
Power-Supply Rejection Ratio
Maximum Load
60
BR
DD
To V or GND
3
kΩ
DD
Output Resistance
R
6
Ω
OBR
CONTACT INPUTS (MUTE, MODE, RENCODEA, RENCODEB)
Internal Pullup Resistor
Single Pulse Input Low Time
Repetitive Input Pulse Separation
Timeout Period
R
45
kΩ
ms
ms
ms
PULLUP
t
22
66
CPW
t
IPWS
t
Click/pop suppression inactive
32
WS
DIGITAL INPUTS (MUTE, MODE, RENCODEA, RENCODEB, SHDN)
3.6V < V
2.7V ≤ V
3.6V < V
2.7V ≤ V
≤ 5.5V
≤ 3.6V
≤ 5.5V
≤ 3.6V
2.4
2.0
LOGIC
LOGIC
LOGIC
LOGIC
Input High Voltage (Note 2)
Input Low Voltage (Note 2)
V
V
V
IH
0.8
0.6
+1
V
IL
Input Leakage Current
Input Capacitance
Inputs unconnected
-1
µA
pF
5
POWER SUPPLIES
Supply Voltage
V
V
V
V
= 0
2.7
5.5
0
V
V
DD
SS
Negative Power Supply
Supply Voltage Difference
Active Supply Current
V
= +2.7V
-2.7
SS
DD
DD
- V
5.5
1.4
1.3
1.3
1
V
SS
I
mA
DD
V
V
= +5V, V = 0
SS
DD
DD
Standby Supply Current (Notes 3, 4)
I
mA
STBY
= +2.7V, V = -2.7V
SS
Shutdown Supply Current
Power-Up Time
I
(Note 3)
µA
ms
V
SHDN
t
Click/pop suppression inactive
50
PU
Logic Supply Voltage
V
V
V
= 0
2.7
V
DD
LOGIC
SS
RENCODEA = RENCODEB
Logic Active Supply Current
Logic Standby Supply Current
Logic Shutdown Current
I
V
= 0V
320
1
µA
µA
µA
L
I
(Note 4)
LSTBY
I
1
LSHDN
LED INDICATORS (LEDIND0–LEDIND4, MODEIND)
V
V
= 2.7V, I
= 5.5V, I
= 10mA
0.4
0.2
10
LOGIC
LOGIC
SINK
Output Low Voltage
V
V
OL
= 10mA
SINK
Output Leakage Current
Output Capacitance
0.1
3
µA
pF
Maximum Sink Current
150
mA
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
(V - 0.5V) and (GND + 0.5V). See Digital Supply Current vs. Digital Input Voltage in the Typical Operating Characteristics.
DD
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.
_______________________________________________________________________________________
3
Stereo Volume Control
with Rotary Encoder Interface
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
END-TO-END RESISTANCE % CHANGE
vs. TEMPERATURE
TOTAL SUPPLY CURRENT
vs. TEMPERATURE
ATTENUATION vs. TAP POSITION
1.48
1.47
1.46
1.45
1.44
1.43
1.42
1.41
1.40
1.39
1.38
0
0.10
0.05
0
V
= V = 5.5V
DD
LOGIC
-10
-20
-30
-40
-50
-60
-70
MAX540
-0.05
-0.10
-0.15
-0.20
-0.25
0
4
8
12 16 20 24 28 32
TAP POSITION
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
WIPER-TO-END TERMINAL VOLTAGE
vs. TAP POSITION
WIPER SWITCHING TRANSIENT
FREQUENCY RESPONSE
MAX5440 toc04
100
90
80
70
60
50
40
30
20
10
0
V
= 2.5 ±1V , V = 2.5V, C = 33pF
RMS L_ L_
0.8
0.4
0
H_
RENCODEA
RENCODEB
V
HW
W_ SET TO 0dB
-0.4
-0.8
-1.2
51ms
WIPER
-1.6
-2.0
-2.4
TRANSITION
FROM -2dB
TO -4dB
V
WL
-2.8
0
4
8
12 16 20 24 28 32
TAP POSITION
20ms/div
0.01
0.1
1
10
100
1000
FREQUENCY (kHz)
FREQUENCY RESPONSE
THD+N vs. FREQUENCY
THD+N vs. FREQUENCY
0.1
0.1
V
= 2.5 ±1V , V = 2.5V, C = 33pF
-5.2
-5.6
-6.0
-6.4
-6.8
-7.2
-7.6
-8.0
-8.4
-8.8
H_
RMS L_
L_
V
V
= 2.5V
= -2.5V
MIDBIAS
MIDBIAS
DD
SS
V
V
= 5.0V
= GND
DD
SS
L_ = V
H_ = V
L_ = V
H_ = V
MIDBIAS
MIDBIAS
+ 1V
RMS
+ 1V
RMS
W_ SET AT -6dB
W_ SET TO -6dB
0.01
0.01
W_ SET AT -6dB
W_ SET AT -2dB
W_ SET AT -2dB
W_ SET AT 0dB
W_ SET AT 0dB
10 100
0.001
0.001
0.01
0.1
1
10
100
1000
0.001
0.01
0.1
1
0.001
0.01
0.1
1
10
100
FREQUENCY (kHz)
FREQUENCY (kHz)
FREQUENCY (kHz)
4
_______________________________________________________________________________________
Stereo Volume Control
with Rotary Encoder Interface
MAX540
Typical Operating Characteristics (continued)
(V = +5V, T = +25°C, unless otherwise noted.)
DD
A
LOGIC SUPPLY CURRENT
vs. LOGIC SUPPLY VOLTAGE
ACTIVE LOGIC SUPPLY CURRENT
vs. TEMPERATURE
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
350
300
250
200
150
100
50
300
250
200
150
100
50
-25
V
V
= 5V ±100mV , V = 5V
P-P H
= 2.5V, W_ SET TO -6dB
V
= V
= 5.5V,
LOGIC
DD_
L_
DD
-30
RENCODEA = RENCODEB = 0
-35
-40
ACTIVE CURRENT
-45
-50
-55
-60
-65
-70
-75
STANDBY CURRENT
SHUTDOWN
0
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
-40
-15
10
35
60
85
0.01
0.1
1
10
100
LOGIC SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
FREQUENCY (kHz)
ACTIVE SUPPLY CURRENT
vs. TEMPERATURE
DIGITAL SUPPLY CURRENT
vs. DIGITAL INPUT VOLTAGE
1.1770
1000
V
= V
= 5.5V,
LOGIC
DD
1.1768
1.1766
1.1764
1.1762
1.1760
1.1758
1.1756
1.1754
1.1752
RENCODEA = RENCODEB = 0
100
10
0
-40
-15
10
35
60
85
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
DIGITAL INPUT VOLTAGE (V)
TEMPERATURE (°C)
SUPPLY CURRENT
vs. INPUT VOLTAGE SWEEP
SPECTRAL NOISE DENSITY
8
7
6
5
4
3
2
1
0
1200
1000
800
V
= V
= 5V, W_ AT 0dB
LOGIC
DD
L
R = 10kΩ TO V
MIDBIAS
600
400
200
0
2.5
3.0
3.5
4.0
4.5
5.0
0.01
0.1
1
10
100
INPUT VOLTAGE SWEEP (V
)
FREQUENCY (kHz)
H_
_______________________________________________________________________________________
5
Stereo Volume Control
with Rotary Encoder Interface
Pin Description
PIN
NAME
FUNCTION
to ground with a 0.1µF capacitor as close to the device
Digital Logic Power Supply. Bypass V
as possible.
LOGIC
1
V
LOGIC
RENCODEB
RENCODEA
MUTE
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 V with a 45kΩ resistor.
2
3
4
LOGIC
MAX540
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 V with a 45kΩ resistor.
LOGIC
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 V with an internal 45kΩ resistor.
LOGIC
Volume/Balance Control Input. Each high-to-low transition on MODE toggles between the volume and
5
6
MODE
SHDN
balance modes. MODE is pulled high internally with a 45kΩ resistor to V
MAX5440 is in volume-control mode.
. On power-up, the
LOGIC
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
8
GND
H0
Ground. Connect pins 7 and 24 together.
Potentiometer 0 High Terminal. H0 and L0 terminals can be reversed.
Potentiometer 0 Low Terminal. L0 and H0 terminals can be reversed.
Potentiometer 0 Wiper Buffered Output
9
L0
10
11
12
W0
MIDBIAS
BIAS
Midbias Voltage Output. V
= (V
+ V ) / 2.
DD SS
MIDBIAS
Bias Generator Input. Bypass with a 1µF capacitor to system ground.
Analog Power Supply. Bypass V
possible.
to ground with a 0.1µF capacitor as close to the device as
DD
13
14
V
DD
Negative Power Supply. Bypass V to ground with a 0.1µF capacitor as close to the device as
SS
possible. Connect to GND for single-supply operation.
V
SS
15
16
17
W1
L1
Potentiometer 1 Wiper Buffered Output
Potentiometer 1 Low Terminal. L1 and H1 terminals can be reversed.
Potentiometer 1 High Terminal. H1 and L1 terminals can be reversed.
H1
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.
LEDIND0–
LEDIND4
18–22
23
Volume-Control/Balance-Control Mode Indicator Open-Drain Output. Connect to an LED through a
resistor to V
. When the LED is on, the MAX5440 is in balance-control mode. When the LED is
MODEIND
LOGIC
off, the MAX5440 is in volume-control mode.
6
_______________________________________________________________________________________
Stereo Volume Control
with Rotary Encoder Interface
MAX540
Rotary Encoder Interface
Detailed Description
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.
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.
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
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, 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
internally pulled up to V
by internal 45kΩ resistors.
LOGIC
V
. The MAX5440 powers up in volume-control
LOGIC
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.
mode. Leave unconnected or connect to V
ance mode is not required.
if bal-
LOGIC
V
LOGIC
1/4 CYCLE PER DETENT
CW
CHANNEL A
45kΩ
45kΩ
OPEN CIRCUIT
RENCODEA
RENCODEB
A
CLOSED CIRCUIT
OPEN CIRCUIT
B
CLOSED CIRCUIT
MAX5440
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
ROTARY
ENCODER
GND
CHANNEL B
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.
Figure 1. Rotary Encoder Interface
_______________________________________________________________________________________
7
Stereo Volume Control
with Rotary Encoder Interface
Volume Control
In volume-control mode, the MAX5440’s wipers move
simultaneously, maintaining the balance separation
between each wiper (Figure 2a).
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 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 2b).
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.
5
When either wiper reaches the minimum tap position
(position closest to L_), further commands to decrease
BALANCE SEPARATION
MAINTAINED
H_
W0
W1
W0
W1
W0
W1
ROTATE CW
TWICE
ROTATE CCW
ONCE
L_
a
NO CHANGE
W0
W1
W0
W1
W0
W1
H_
ROTATE CW
ONCE
ROTATE CW
L_
b
H_
W0
W1
W0
W1
W0
W1
ROTATE CCW
ONCE
ROTATE CCW
TO D
L_
c
ORIGINAL BALANCE SEPARATION
MAINTAINED
H_
W0
W1
W0
W1
W0
W1
ROTATE CW
ONCE
ROTATE CW
ONCE
FROM C
L_
d
Figure 2. Volume-Control Operation
8
_______________________________________________________________________________________
Stereo Volume Control
with Rotary Encoder Interface
MAX540
Balance Control
Table 1. Wiper Position and Attenuation
In balance-control mode, the MAX5440 adjusts the bal-
ance between channel 0 and channel 1 while maintain-
ing 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 attenu-
ation than channel 0, adjusting the balance to channel
1 moves channel 1’s wiper up to the same wiper posi-
tion as channel 0 before it was attenuated (Figure 3b).
POSITION
ATTENUATION (dB)
0
0
-2
1
2
…
-4
…
6 (POR)
…
-12
…
30
-60
-62
≥ 90
Click-and-Pop Suppression
The click-and-pop suppression feature reduces the
audible noise (clicks and pops) that results from wiper
transitions. The MAX5440 minimizes this noise by allow-
31
32 (MUTE)
ing the wiper to change position only when V = V .
H
L
Each wiper has its own suppression and timeout cir-
cuitry. The MAX5440 changes wiper position when V
H
= V , or after 32ms, whichever occurs first (see Figures
L
4a and 4b).
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.
VOLUME LEVEL IS SET
VOLUME LEVEL MAINTAINED
BALANCE SHIFTS TO W1
H_
W0
W1
W0
W1
W0
W1
ROTATE CW
ONCE
ROTATE CW
ONCE
L_
VOLUME LEVEL MAINTAINED
BALANCE SHIFTS TO W1
VOLUME LEVEL IS SET BY W0
W0 W1
H_
W0
W1
W0
W1
ROTATE CW
ONCE
ROTATE CW
ONCE
L_
Figure 3. Balance-Control Operation
_______________________________________________________________________________________
9
Stereo Volume Control
with Rotary Encoder Interface
USER ROTATES ENCODER
SWITCH
CONTACT
IS BOUNCING
SWITCH
CONTACT
IS STABLE
SWITCH CONTACT
IS BOUNCING
01
MAX540
INPUT ACCEPTED
00
t
WS
t
HPW
WAIT FOR FIRST
ZERO CROSSING, t
DEBOUNCE BY WAITING
FOR STABLE HIGH, t
WS
HPW
t
LPW
DEBOUNCE BY WAITING
FOR STABLE LOW, t
LPW
V
V
H_
L_
WIPER MOVES HERE
2dB STEPS
WIPER MOTION
Figure 4a. Wiper Transition Timing Diagram—Suppression Circuitry Active
10 ______________________________________________________________________________________
Stereo Volume Control
with Rotary Encoder Interface
MAX540
SWITCH
CONTACT
IS STABLE
SWITCH CONTACT
IS BOUNCING
SWITCH CONTACT
IS BOUNCING
READY TO ACCEPT ANOTHER
ENCODER INPUT SIGNAL
01
INPUT ACCEPTED
00
t
WS
t
HPW
WAIT FOR FIRST
ZERO CROSSING OR
TIMEOUT, t
WS
t
LPW
DEBOUNCE BY WAITING
FOR STABLE HIGH, t
HPW
DEBOUNCE BY WAITING
FOR STABLE LOW, t
LPW
V
V
H
L
WIPER MOVES HERE
(t
+ t
LPW WS)
2dB STEPS
Figure 4b. Wiper Transition Timing Diagram—Timed Out
______________________________________________________________________________________ 11
Stereo Volume Control
with Rotary Encoder Interface
Power-On Reset
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
The power-on comparators monitor (V
LOGIC
- V ) and
SS
DD
(V
- 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
V
. When the LED is on, the MAX5440 is in balance-
LOGIC
control 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.
mode (-90dB) and move to the -12dB position when V
H
= V to eliminate clicks and pops during power-up.
L
With DC inputs at V and V , the wipers move after
H
L
MAX540
Level Indicator LEDs
The MAX5440 includes five indicator LED drivers to dis-
play the current wiper settings in either volume or bal-
ance mode. Connect the LEDIND_ outputs to the LEDs
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
and to V
through a series resistor as shown in the
LOGIC
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.
resistor string when V = V to eliminate clicks and pops
H
L
during shutdown. With DC inputs at V and V , the
H
L
wipers move after exceeding the timeout period. Exiting
shutdown 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 maxi-
mum attenuation (-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
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 balanced position, turning the
encoder counterclockwise (a decreasing gray code
count) turns on LED1, and then LED0 to indicate a bal-
ance shift towards channel 0.
45kΩ resistor to V
. When both wipers are in the
LOGIC
tap 31 position (-62dB attenuation) 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.
Table 2. LED Settings in Volume Mode
VOLUME LED OUTPUTS (1 = LED IS ON)
VOLUME POSITION (dB)
LED0
LED1
LED2
LED3
LED4
0 to -8
-10 to -18
1
1
1
1
1
0
1
1
1
1
0
0
1
1
1
0
0
0
1
1
0
0
0
0
1
0
0
0
0
0
-20 to -28
-30 to -38
-40 to -52
-54 to mute (-90)
12 ______________________________________________________________________________________
Stereo Volume Control
with Rotary Encoder Interface
MAX540
FULL L
L + 12
L + 6
R + 6
R + 12
FULL R
CCW ROTATION (CH0)
CW ROTATION (CH1)
CENTERED
LED2 ON
LED0 ON
LED1 ON
LED3 ON
LED4 ON
Figure 5. LED Setting in Balance Mode
V
DD
V
LOGIC
V
LOGIC
SHDN
MODEIND
V
PEAK
0V
MAX5440
H1
W1
RIGHT INPUT
L1
HEADPHONE
DRIVER
MIDBIAS
(V V ) / 2
DD + SS
LEDIND0
LEDIND1
LEFT INPUT
L0
W0
LEDIND2
LEDIND3
H0
LEDIND4
BIAS
V
SS
= -V
DD
ROTARY
ENCODER
Figure 6. Dual-Supply Volume/Balance Control
______________________________________________________________________________________ 13
Stereo Volume Control
with Rotary Encoder Interface
Multiple Button Pushes (MODE, MUTE)
Chip Information
The MAX5440 does not respond to simultaneous button
PROCESS: BiCMOS
pushes. Pushing more than one button at the same
time stops the wipers in their present states. Only a sin-
gle button 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-sup-
ply configuration. Figure 6 shows a typical volume/bal-
ance application circuit using the MAX5440 in a
dual-supply configuration. The MAX5440 does not
require external op amps because the bias is generat-
ed internally, and the wipers have internal low-power
buffers for low distortion. 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.
MAX540
14 ______________________________________________________________________________________
Stereo Volume Control
with Rotary Encoder Interface
MAX540
Functional Diagram
MODEIND
LEDIND0
LEDIND2
LEDIND4
V
SHDN
LOGIC
V
DD
V
SS
LEDIND1
LEDIND3
BIAS
MIDBIAS
BIAS GENERATOR
MAX5440
H1
H0
CLICK-AND-POP
SUPPRESSION
CIRCUITRY
CLICK-AND-POP
SUPPRESSION
CIRCUITRY
0
1
0
1
2
2
3
4
3
4
POSITION COUNTER
POSITION COUNTER
W0
W1
UP/DOWN
UP/DOWN
28
29
30
31
28
29
30
31
TIMING AND CONTROL
DEBOUNCE
DEBOUNCE
DEBOUNCE
DEBOUNCE
DEBOUNCE
LOGIC
V
45kΩ
45kΩ
45kΩ
45kΩ
MUTE
MUTE
L0
L1
GND
RENCODEA
RENCODEB
MODE
MUTE
Package Information
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
24 SSOP
A24-1
21-0056
______________________________________________________________________________________ 15
Stereo Volume Control
with Rotary Encoder Interface
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
Fixed pin names and thermal data. Updated two specifications in EC table
2
11/08
1, 2, 3, 6, 13
MAX540
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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