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19-0542; Rev 1; 5/06
Stereo Volume Control with Rotary Encoder Interface
General Description
The MAX5440 dual, 40k logarithmic taper volume control features a debounced up/down interface for use with a simple rotary encoder without using a microcontroller (C). 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 + VSS) / 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 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 generated by wiper transitions. The MAX5440 provides a nominal temperature coefficient of 35ppm/C end-toend and 5ppm/C, ratiometrically. The MAX5440 is available in a 24-pin SSOP package and is specified for operation over the -40C to +85C extended temperature range.
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 0.5A Shutdown Supply Current Integrated Bias Voltage Generator Five-Segment LED Volume/Balance Indicator Clickless Switching 40k End-to-End Fixed Resistance Value Mute Function Toggles to -90dB (typ) Power-On Reset to -12dBFS Wiper Position
MAX5440
Ordering Information
PART MAX5440EAG TEMP RANGE -40C to +85C PIN-PACKAGE 24 SSOP PKG CODE A24-1
Applications
Stereo Volume Control Desktop Speakers Multimedia Docking Stations Set-Top Boxes Automotive Back-Seat Multimedia
Typical Operating Circuit
VDD VLOGIC
VLOGIC
Pin Configuration
TOP VIEW
VLOGIC RENCODEA RENCODEB MUTE MODE SHDN GND H0 L0 1 2 3 4 5 6 7 8 9 24 GND 23 MODEIND 22 LEDIND4
SHDN
MODEIND
VPEAK (VDD + VSS) / 2
MAX5440
H1 W1
RIGHT INPUT
L1
MIDBIAS HEADPHONE DRIVER
MAX5440
21 LEDIND3 20 LEDIND2 19 LEDIND1 18 LEDIND0 17 H1
VSS LEDIND0 LEDIND1 LEDIND2 LEDIND3
(VDD + VSS) / 2
L0 W0
LEFT INPUT
H0 LEDIND4 BIAS
16 L1
GND MUTE MODE RENCODEA RENCODEA
W0 10 MIDBIAS 11 BIAS 12
15 W1 14 VSS 13 VDD
ROTARY ENCODER
SSOP
________________________________________________________________ Maxim Integrated Products
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Stereo Volume Control with Rotary Encoder Interface
ABSOLUTE MAXIMUM RATINGS
MAX5440
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 = +70C) 24-Pin SSOP (derate 8mW/C above +70C) ..............640mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-60C to +150C Lead Temperature (soldering, 10s) .................................+300C
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 = GND = 0, 2.7V (VDD - VSS) 5.5V, VLOGIC = +2.7V to VDD, VH_ = VDD, VL_ = VDD / 2, TA = TMIN to TMAX, unless otherwise specified. Typical values are at TA = +25C.) (Note 1)
PARAMETER End-to-End Resistance Absolute Tolerance Tap-to-Tap Tolerance VH_= (VDD / 2) + 1VRMS, 1kHz tap at top, RL = to VL_ = VDD / 2, 20Hz to 20kHz VH_= (VDD / 2) + 1.5VRMS, 1kHz tap at top, RL = to VL_ = VDD / 2, 20Hz to 20kHz Total Harmonic Distortion Plus Noise THD+N VDD = 5V,VSS = 0V, VL_ = 1.5V, VH_ = (VDD / 2) + 1VRMS, 1kHz tap at top, RL = 10k to VMIDBIAS, 20Hz to 20kHz VDD = 5V,VSS = 0V, VL_ = 5V, VH_= (VDD / 2) + 1.5VRMS, 1kHz tap at top, RL = 10k to VMIDBIAS, 20Hz to 20kHz Channel Isolation Interchannel Matching Mute Attenuation Power-Supply Rejection Ratio H Terminal Capacitance L Terminal Capacitance End-to-End Resistance Ratiometric Resistance Bandwidth, -3dB Output Noise WIPER BUFFER Output Voltage Swing Output Current Output Resistance DC Offset INTEGRATED BIAS GENERATOR Output Voltage ILOAD = 1mA (VDD + VSS) / 2 - 10mV (VDD + VSS) /2 (VDD + VSS) / 2 + 10mV V ROWB -5 1 2 VO RL = 10k to VMIDBIAS VDD - 0.2 3 10 +5 V mA mV fCUTOFF en CW = 33pF 20Hz to 20kHz PSRR CH CL SHDN = VDD Input referred, 217Hz, 100mVP-P on VDD SYMBOL R CONDITIONS MIN 36 TYP 40 0.25 0.1 0.004 0.006 % 0.004 MAX 52 UNITS k dB dB
0.006 100 0.5 90 -60 5 7 35 5 100 3.2 dB dB dB dB pF pF ppm/C ppm/C kHz VRMS
2
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Stereo Volume Control with Rotary Encoder Interface
ELECTRICAL CHARACTERISTICS (continued)
(VDD = +2.7V to +5.5V, VSS = GND = 0, 2.7V (VDD - VSS) 5.5V, VLOGIC = +2.7V to VDD, VH_ = VDD, VL_ = VDD / 2, TA = TMIN to TMAX, unless otherwise specified. Typical values are at TA = +25C.) (Note 1)
PARAMETER Power-Supply Rejection Ratio Maximum Load Output Resistance Internal Pullup Resistor Single Pulse Input Low Time Repetitive Input Pulse Separation Timeout Period ROBR RPULLUP tCPW tIPWS tWS Click/pop suppression inactive 3.6V < VLOGIC 5.5V 2.7V VLOGIC 3.6V 3.6V < VLOGIC 5.5V 2.7V VLOGIC 3.6V Inputs unconnected -1 5 VDD VSS IDD ISTBY ISHDN tPU VLOGIC IL ILSTBY ILSHDN VLOGIC = 2.7V, ISINK = 10mA VLOGIC = 5.5V, ISINK = 10mA 0.1 3 150 VDD = +5V, VSS = 0 VDD = +2.7V, VSS = -2.7V (Note 3) Click/pop suppression inactive VSS = 0 VRENCODEA = VRENCODEB = 0V (Note 4) 2.7 50 VDD 320 1 1 0.4 0.2 10 VSS = 0 VDD = +2.7V VDD - VSS 2.7 -2.7 5.5 0 5.5 1.4 1.3 1.3 1 2.4 2.0 0.8 0.6 +1 22 50 32 SYMBOL PSRRBR CONDITIONS 1kHz, 100mV on VDD, 1F on BIAS To VDD or GND 3 6 45 MIN TYP 60 MAX UNITS dB k k ms ms ms
MAX5440
CONTACT INPUTS (MUTE, MODE, RENCODEA, RENCODEB)
DIGITAL INPUTS (MUTE, MODE, RENCODEA, RENCODEB, SHDN) Input High Voltage (Note 2) Input Low Voltage (Note 2) Input Leakage Current Input Capacitance POWER SUPPLIES Supply Voltage Negative Power Supply Supply Voltage Difference Active Supply Current Standby Supply Current (Notes 3, 4) Shutdown Supply Current Power-Up Time Logic Supply Voltage Logic Active Supply Current Logic Standby Supply Current Logic Shutdown Current V V V mA mA A ms V A A A VIH VIL V V A pF
LED INDICATORS (LEDIND0-LEDIND4, MODEIND) Output Low Voltage Output Leakage Current Output Capacitance Maximum Sink Current VOL V A pF mA
Note 1: Parameters are 100% production tested at +85C 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.
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Stereo Volume Control with Rotary Encoder Interface MAX5440
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
END-TO-END RESISTANCE % CHANGE vs. TEMPERATURE
MAX5440 toc02 MAX5440 toc01
ATTENUATION vs. TAP POSITION
0 -10 ATTENUATION (dB) -20 -30 -40 -50 -60 -70 0 4 8 12 16 20 24 28 32 TAP POSITION 0.10 END-TO-END RESISTANCE CHANGE (%) 0.05 0 -0.05 -0.10 -0.15 -0.20 -0.25
TOTAL SUPPLY CURRENT vs. TEMPERATURE
1.47 TOTAL SUPPLY CURRENT (mA) 1.46 1.45 1.44 1.43 1.42 1.41 1.40 1.39 1.38 VLOGIC = VDD = 5.5V
MAX5440 toc03
1.48
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (C)
TEMPERATURE (C)
WIPER SWITCHING TRANSIENT
MAX5440 toc04
WIPER-TO-END TERMINAL VOLTAGE vs. TAP POSITION
MAX5440 toc05
FREQUENCY RESPONSE
0.8 0.4 0 RESPONSE (dB) -0.4 -0.8 -1.2 -1.6 -2.0 W_ SET TO 0dB VH_ = 2.5 1VRMS, VL_ = 2.5V, CL_ = 33pF
MAX5440 toc06
100 NOMINAL END-TO-END VOLTAGE (%VHL) RENCODEA RENCODEB 90 80 70 60 50 40 30 20 10 0 0 4 8 VWL VHW
51ms
WIPER TRANSITION FROM -2dB TO -4dB
-2.4 -2.8
20ms/div
12
16
20
24
28
32
0.01
0.1
1
10
100
1000
TAP POSITION
FREQUENCY (kHz)
FREQUENCY RESPONSE
MAX5440 toc07
THD+N vs. FREQUENCY
MAX5440 toc08
THD+N vs. FREQUENCY
VDD = 5.0V VSS = GND L_ = VMIDBIAS H_ = VMIDBIAS + 1VRMS THD+N (%)
MAX5440 toc09
-5.2 -5.6 -6.0 RESPONSE (dB)
VH_ = 2.5 1VRMS, VL_ = 2.5V, CL_ = 33pF
0.1 VDD = 2.5V VSS = -2.5V L_ = VMIDBIAS H_ = VMIDBIAS + 1VRMS THD+N (%)
0.1
-6.4 -6.8 -7.2 -7.6 -8.0 -8.4 -8.8 0.01
W_ SET TO -6dB 0.01
W_ SET AT -6dB
0.01
W_ SET AT -6dB W_ SET AT -2dB
W_ SET AT -2dB W_ SET AT 0dB 0.1 1 10 100 1000 0.001 0.001 0.01 0.1 1 10 100 0.001 0.001 0.01 0.1
W_ SET AT 0dB
1
10
100
FREQUENCY (kHz)
FREQUENCY (kHz)
FREQUENCY (kHz)
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Stereo Volume Control with Rotary Encoder Interface MAX5440
Typical Operating Characteristics (continued)
(VDD = +5V, TA = +25C, unless otherwise noted.)
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
-30 -35 RESPONSE (dB) -40 -45 -50 -55 -60 -65 -70 -75 0.01 0.1 1 FREQUENCY (kHz) 10 100 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 LOGIC SUPPLY VOLTAGE (V) 0 -40 -15 10 35 60 85 TEMPERATURE (C) VDD_ = 5V 100mVP-P, VH = 5V VL_ = 2.5V, W_ SET TO -6dB
MAX5440 toc10
LOGIC SUPPLY CURRENT vs. LOGIC SUPPLY VOLTAGE
MAX5440 toc11
ACTIVE LOGIC SUPPLY CURRENT vs. TEMPERATURE
VDD = VLOGIC = 5.5V, RENCODEA = RENCODEB = 0
MAX5440 toc12
-25
300 LOGIC SUPPLY CURRENT (A) 250 ACTIVE CURRENT 200 150 100 50 SHUTDOWN STANDBY CURRENT
350 300 250 200 150 100 50
ACTIVE SUPPLY CURRENT vs. TEMPERATURE
MAX5440 toc13
DIGITAL SUPPLY CURRENT vs. DIGITAL INPUT VOLTAGE
MAX5440 toc14
1.1770 1.1768 SUPPLY CURRENT (mA) 1.1766 1.1764 1.1762 1.1760 1.1758 1.1756 1.1754 1.1752 -40 -15 10 35 60 VDD = VLOGIC = 5.5V, RENCODEA = RENCODEB = 0
1000 DIGITAL SUPPLY CURRENT (A)
100
10 85 0 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)
SPECTRAL NOISE DENSITY
MAX5440 toc15
SUPPLY CURRENT vs. INPUT VOLTAGE SWEEP
7 SUPPLY CURRENT (mA) 6 5 4 3 2 VDD = VLOGIC = 5V, W_ AT 0dB RL = 10k TO VMIDBIAS
MAX5440 toc16
1200 1000 NOISE (nV/Hz) 800 600 400 200 0 0.01 0.1 1 FREQUENCY (kHz) 10
8
1 0 100 2.5 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE SWEEP (VH_)
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LOGIC SUPPLY CURRENT (A)
5
Stereo Volume Control with Rotary Encoder Interface MAX5440
Pin Description
PIN 1 2 3 4 NAME VLOGIC RENCODEA RENCODEB MUTE FUNCTION Digital Logic Power Supply. Bypass VLOGIC to ground with a 0.1F capacitor as close to the device as possible. 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 45k resistor. 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 45k resistor. 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 45k resistor. 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 45k resistor to VLOGIC. On power-up, the MAX5440 is in volume-control mode. 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. 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 Midbias Voltage Output. VMIDBIAS = (VDD + VSS) / 2. Bias Generator Input. Bypass with a 1F capacitor to system ground. Analog Power Supply. Bypass VDD to ground with a 0.1F capacitor as close to the device as possible. Negative Power Supply. Bypass VSS to ground with a 0.1F capacitor as close to the device as possible. Connect to GND for single-supply operation. 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. 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. 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.
5
MODE
6 7, 24 8 9 10 11 12 13 14 15 16 17 18-22
SHDN GND H0 L0 W0 MIDBIAS BIAS VDD VSS W1 L1 H1 LEDIND0- LEDIND4
23
MODEIND
6
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Stereo Volume Control with Rotary Encoder Interface
Detailed Description
The MAX5440 dual, 40k 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.
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 45k 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.
MAX5440
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 45k resistor to VLOGIC. The MAX5440 powers up in volume-control mode. Leave unconnected or connect to VLOGIC if balance mode is not required.
VLOGIC 1/4 CYCLE PER DETENT CW
CHANNEL A
45k
45k
OPEN CIRCUIT CLOSED CIRCUIT
RENCODEA RENCODEB
A B OPEN CIRCUIT CLOSED CIRCUIT
MAX5440
ROTARY ENCODER GND
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
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
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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). 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
MAX5440
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.
BALANCE SEPARATION MAINTAINED W0 W1 ROTATE CCW ONCE
H_ W0 W1 ROTATE CW TWICE W0 W1
L_
a
NO CHANGE W0 H_ ROTATE CW ONCE ROTATE CW W1 W0 W1 W0 W1
L_
b
H_
W0
W1 ROTATE CCW ONCE
W0
W1 ROTATE CCW
W0
W1
TO D
L_ c
H_ W0 W1 ROTATE CW ONCE W0 W1 ROTATE CW ONCE
ORIGINAL BALANCE SEPARATION MAINTAINED W0 W1
FROM C
L_ d
Figure 2. Volume-Control Operation
8
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Stereo Volume Control with Rotary Encoder Interface
Table 1. Wiper Position and Attenuation
POSITION 0 1 2 ... 6 (POR) ... 30 31 32 (MUTE) ATTENUATION (dB) 0 -2 -4 ... -12 ... -60 -62 90
Balance Control In balance-control mode, the MAX5440 adjusts the balance 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 channel 0 before it was attenuated (Figure 3b).
MAX5440
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 allowing the wiper to change position only when V H = 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.
VOLUME LEVEL MAINTAINED BALANCE SHIFTS TO W1
VOLUME LEVEL IS SET H_ W0 W1 ROTATE CW ONCE W0 W1 ROTATE CW ONCE
W0
W1
L_ VOLUME LEVEL MAINTAINED BALANCE SHIFTS TO W1 W0 ROTATE CW ONCE W1 ROTATE CW ONCE W0 W1
VOLUME LEVEL IS SET BY W0 H_ W0 W1
L_
Figure 3. Balance-Control Operation
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Stereo Volume Control with Rotary Encoder Interface MAX5440
USER ROTATES ENCODER SWITCH CONTACT IS BOUNCING 01 SWITCH CONTACT IS STABLE SWITCH CONTACT IS BOUNCING
INPUT ACCEPTED
00 tWS WAIT FOR FIRST ZERO CROSSING, tWS tLPW tHPW
DEBOUNCE BY WAITING FOR STABLE HIGH, tHPW
DEBOUNCE BY WAITING FOR STABLE LOW, tLPW
VH_
VL_
WIPER MOVES HERE
2dB STEPS WIPER MOTION
Figure 4a. Wiper Transition Timing Diagram--Suppression Circuitry Active
10
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Stereo Volume Control with Rotary Encoder Interface MAX5440
SWITCH CONTACT IS BOUNCING 01 SWITCH CONTACT IS STABLE SWITCH CONTACT IS BOUNCING READY TO ACCEPT ANOTHER ENCODER INPUT SIGNAL
INPUT ACCEPTED
00 tWS WAIT FOR FIRST ZERO CROSSING OR TIMEOUT, tWS tHPW
tLPW
DEBOUNCE BY WAITING FOR STABLE LOW, tLPW
DEBOUNCE BY WAITING FOR STABLE HIGH, tHPW
VH
VL
WIPER MOVES HERE
(tLPW + tWS) 2dB STEPS
Figure 4b. Wiper Transition Timing Diagram--Timed Out
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Stereo Volume Control with Rotary Encoder Interface MAX5440
Power-On Reset
The power-on comparators monitor (V DD - VSS) 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 eliminate 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.
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 display 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 balanced position, turning the encoder counterclockwise (a decreasing gray code count) turns on LED1, and then LED0 to indicate a balance shift towards channel 0.
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 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 maximum 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 45k resistor to VLOGIC. When both wipers are in the 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 POSITION (dB) 0 to -8 -10 to -18 -20 to -28 -30 to -38 -40 to -52 -54 to mute (-90) VOLUME LED OUTPUTS (1 = LED IS ON) LED0 1 1 1 1 1 0 LED1 1 1 1 1 0 0 LED2 1 1 1 0 0 0 LED3 1 1 0 0 0 0 LED4 1 0 0 0 0 0
12
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Stereo Volume Control with Rotary Encoder Interface MAX5440
FULL L
L + 12
CCW ROTATION (CH0) LED0 ON LED1 ON
L+6
R+6
R + 12 CW ROTATION (CH1) LED3 ON LED4 ON
FULL R
CENTERED
LED2 ON
Figure 5. LED Setting in Balance Mode
VDD
VLOGIC
VLOGIC SHDN MODEIND VPEAK 0V
MAX5440
H1 W1
RIGHT INPUT
L1
MIDBIAS HEADPHONE DRIVER
(VDD + VSS) / 2 LEDIND0 LEDIND1 LEDIND2 LEDIND3
L0 W0
LEFT INPUT
H0 LEDIND4 BIAS VSS = -VDD
Figure 6. Dual-Supply Volume/Balance Control
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GND
MUTE
MODE
RENCODEA ROTARY ENCODER
RENCODEA
13
Stereo Volume Control with Rotary Encoder Interface MAX5440
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 button push configures the device. PROCESS: BiCMOS
Chip Information
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 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.
14
______________________________________________________________________________________
Stereo Volume Control with Rotary Encoder Interface MAX5440
Functional Diagram
MODEIND VLOGIC SHDN BIAS VDD VSS MIDBIAS LEDIND0 LEDIND1 LEDIND2 LEDIND3 LEDIND4
MAX5440
H0
0
BIAS GENERATOR
H1 CLICK-AND-POP SUPPRESSION CIRCUITRY CLICK-AND-POP SUPPRESSION CIRCUITRY
0
1
1
2
2
3
3
4
POSITION COUNTER
POSITION COUNTER
4
W0
UP/DOWN 28 UP/DOWN 28
W1
29
TIMING AND CONTROL
29
30 DEBOUNCE 31 DEBOUNCE DEBOUNCE DEBOUNCE DEBOUNCE
30
VLOGIC
31
45k L0
MUTE
45k
45k
45k
MUTE
L1
GND
RENCODEA
RENCODEB
MODE
MUTE
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15
Stereo Volume Control with Rotary Encoder Interface MAX5440
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
2
1
INCHES DIM A A1 B C E H D E e H L MIN 0.068 0.002 0.010 MAX 0.078 0.008 0.015
MILLIMETERS MIN 1.73 0.05 0.25 MAX 1.99 0.21 0.38 D D D D D INCHES MIN 0.239 0.239 0.278 0.317 0.397 MAX 0.249 0.249 0.289 0.328 0.407 MILLIMETERS MIN 6.07 6.07 7.07 8.07 10.07 MAX 6.33 6.33 7.33 8.33 10.33 N 14L 16L 20L 24L 28L
0.20 0.09 0.004 0.008 SEE VARIATIONS 0.205 0.301 0.025 0 0.212 0.311 0.037 8 5.20 7.65 0.63 0 5.38 7.90 0.95 8 0.0256 BSC 0.65 BSC
N
A C B e D A1 L
NOTES: 1. D&E DO NOT INCLUDE MOLD FLASH. 2. MOLD FLASH OR PROTRUSIONS NOT TO EXCEED .15 MM (.006"). 3. CONTROLLING DIMENSION: MILLIMETERS. 4. MEETS JEDEC MO150. 5. LEADS TO BE COPLANAR WITHIN 0.10 MM.
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, SSOP, 5.3 MM
APPROVAL DOCUMENT CONTROL NO. REV.
21-0056
1 1
C
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 (c) 2006 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.

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