19-0542; Rev 2; 11/08 Stereo Volume Control with Rotary Encoder Interface The MAX5440 dual, 40kΩ logarithmic taper volume control 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 + 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 -40°C to +85°C 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 0.5µA 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 Ordering Information PART MAX5440EAG TEMP RANGE PIN-PACKAGE -40°C to +85°C 24 SSOP Applications Stereo Volume Control Desktop Speakers Typical Operating Circuit Multimedia Docking Stations Set-Top Boxes Automotive Back-Seat Multimedia VLOGIC VDD VLOGIC Pin Configuration SHDN (VDD + VSS) / 2 MAX5440 H1 TOP VIEW VLOGIC 1 24 GND RENCODEB 2 23 MODEIND RENCODEA 3 22 LEDIND4 MUTE 4 MODE 5 20 LEDIND2 SHDN 6 19 LEDIND1 GND 7 18 LEDIND0 H0 8 17 H1 MAX5440 W1 RIGHT INPUT L1 MIDBIAS (VDD + VSS) / 2 21 LEDIND3 LEDIND0 L0 9 16 L1 RENCODEB RENCODEA 13 VDD BIAS MODE 14 VSS BIAS 12 H0 LEDIND4 VSS MUTE 15 W1 LEFT INPUT W0 LEDIND3 GND W0 10 MIDBIAS 11 HEADPHONE DRIVER LEDIND1 LEDIND2 L0 VPEAK MODEIND ROTARY ENCODER SSOP ________________________________________________________________ Maxim Integrated Products 1 For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX5440 General Description Stereo Volume Control with Rotary Encoder Interface MAX5440 ABSOLUTE MAXIMUM RATINGS 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 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 = VGND = 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 = +25°C.) (Note 1) PARAMETER End-to-End Resistance SYMBOL CONDITIONS R MIN 36 TYP MAX UNITS 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 = ∞ to VL_ = VDD / 2, 20Hz to 20kHz 0.004 VH_= (VDD / 2) + 1.5VRMS, 1kHz tap at top, RL = ∞ 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 Interchannel Matching ±0.5 dB SHDN = VDD 90 dB Input referred, 217Hz, 100mVP-P on VDD Mute Attenuation Power-Supply Rejection Ratio PSRR dB -60 dB H Terminal Capacitance CH 5 pF L Terminal Capacitance End-to-End Resistance CL 7 pF 35 ppm/°C 5 ppm/°C CW = 33pF 100 kHz en 20Hz to 20kHz 3.2 µVRMS VO RL = 10kΩ to VMIDBIAS Ratiometric Resistance Bandwidth, -3dB Output Noise fCUTOFF WIPER BUFFER Output Voltage Swing VDD - 0.2 Output Current Output Resistance ROWB DC Offset -14 V 3 mA 1 10 Ω ±2 +14 mV INTEGRATED BIAS GENERATOR Output Voltage 2 ILOAD = 1mA (VDD + VSS) / 2 - 30mV (VDD + VSS) /2 _______________________________________________________________________________________ (VDD + VSS) / 2 + 30mV V Stereo Volume Control with Rotary Encoder Interface (VDD = +2.7V to +5.5V, VSS = VGND = 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 = +25°C.) (Note 1) PARAMETER Power-Supply Rejection Ratio SYMBOL PSRRBR Maximum Load CONDITIONS 1kHz, 100mV on VDD, 1µF on BIAS To VDD or GND Output Resistance MIN TYP MAX 60 dB 3 ROBR UNITS kΩ Ω 6 CONTACT INPUTS (MUTE, MODE, RENCODEA, RENCODEB) Internal Pullup Resistor RPULLUP Single Pulse Input Low Time tCPW Repetitive Input Pulse Separation tIPWS Timeout Period tWS 45 kΩ 22 ms 66 Click/pop suppression inactive ms 32 ms DIGITAL INPUTS (MUTE, MODE, RENCODEA, RENCODEB, SHDN) Input High Voltage (Note 2) VIH Input Low Voltage (Note 2) VIL Input Leakage Current 3.6V < VLOGIC ≤ 5.5V 2.4 2.7V ≤ VLOGIC ≤ 3.6V 2.0 V 3.6V < VLOGIC ≤ 5.5V 0.8 2.7V ≤ VLOGIC ≤ 3.6V 0.6 Inputs unconnected -1 Input Capacitance +1 5 V µA pF POWER SUPPLIES Supply Voltage VDD Negative Power Supply VSS Supply Voltage Difference Active Supply Current Shutdown Supply Current ISHDN tPU Logic Active Supply Current VDD = +2.7V -2.7 5.5 IDD ISTBY Logic Supply Voltage 2.7 VDD - VSS Standby Supply Current (Notes 3, 4) Power-Up Time VSS = 0 VLOGIC IL Logic Standby Supply Current ILSTBY Logic Shutdown Current ILSHDN 0 V 5.5 V 1.4 mA VDD = +5V, VSS = 0 1.3 VDD = +2.7V, VSS = -2.7V 1.3 (Note 3) 1 Click/pop suppression inactive VSS = 0 50 2.7 VRENCODEA = VRENCODEB = 0V (Note 4) V mA µA ms VDD V 320 µA 1 µA 1 µA LED INDICATORS (LEDIND0–LEDIND4, MODEIND) Output Low Voltage VOL Output Leakage Current Output Capacitance Maximum Sink Current VLOGIC = 2.7V, ISINK = 10mA 0.4 VLOGIC = 5.5V, ISINK = 10mA 0.2 0.1 10 V µA 3 pF 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 (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. _______________________________________________________________________________________ 3 MAX5440 ELECTRICAL CHARACTERISTICS (continued) Stereo Volume Control with Rotary Encoder Interface MAX5440 Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) -40 -50 -60 0 -0.05 -0.10 -0.15 -0.20 4 8 12 16 20 24 28 1.44 1.43 1.42 1.41 1.40 -15 10 35 60 -40 85 -15 10 TEMPERATURE (°C) WIPER SWITCHING TRANSIENT WIPER-TO-END TERMINAL VOLTAGE vs. TAP POSITION FREQUENCY RESPONSE VHW 80 0.8 0 70 60 50 40 30 W_ SET TO 0dB -0.4 -0.8 -1.2 -1.6 -2.0 20 VWL 10 -2.4 -2.8 0 0 20ms/div VH_ = 2.5 ±1VRMS, VL_ = 2.5V, CL_ = 33pF 0.4 4 8 12 16 20 24 28 32 0.01 0.1 TAP POSITION FREQUENCY RESPONSE THD+N vs. FREQUENCY W_ SET TO -6dB THD+N (%) -6.8 -7.2 0.01 -7.6 100 1000 THD+N vs. FREQUENCY VDD = 5.0V VSS = GND L_ = VMIDBIAS H_ = VMIDBIAS + 1VRMS THD+N (%) VDD = 2.5V VSS = -2.5V L_ = VMIDBIAS H_ = VMIDBIAS + 1VRMS -6.0 10 0.1 MAX5440 toc08 -5.6 1 FREQUENCY (kHz) 0.1 MAX5440 toc07 VH_ = 2.5 ±1VRMS, VL_ = 2.5V, CL_ = 33pF 85 W_ SET AT -6dB MAX5440 toc09 WIPER TRANSITION FROM -2dB TO -4dB 90 RESPONSE (dB) 51ms NOMINAL END-TO-END VOLTAGE (%VHL) 100 RENCODEB RESPONSE (dB) 60 TEMPERATURE (°C) RENCODEA -6.4 35 TAP POSITION MAX5440 toc04 -5.2 MAX5440 toc03 1.45 1.38 -40 32 MAX5440 toc05 0 1.46 1.39 -0.25 -70 VLOGIC = VDD = 5.5V 1.47 MAX5440 toc06 -30 0.05 1.48 TOTAL SUPPLY CURRENT (mA) -20 MAX5440 toc02 -10 0.10 END-TO-END RESISTANCE CHANGE (%) MAX5440 toc01 0 ATTENUATION (dB) TOTAL SUPPLY CURRENT vs. TEMPERATURE END-TO-END RESISTANCE % CHANGE vs. TEMPERATURE ATTENUATION vs. TAP POSITION W_ SET AT -6dB 0.01 W_ SET AT -2dB -8.0 W_ SET AT -2dB -8.4 -8.8 0.01 0.1 1 10 FREQUENCY (kHz) 4 W_ SET AT 0dB W_ SET AT 0dB 100 1000 0.001 0.001 0.01 0.1 1 FREQUENCY (kHz) 10 100 0.001 0.001 0.01 0.1 1 FREQUENCY (kHz) _______________________________________________________________________________________ 10 100 Stereo Volume Control with Rotary Encoder Interface (VDD = +5V, TA = +25°C, unless otherwise noted.) -45 -50 -55 -60 -65 ACTIVE CURRENT 200 150 100 50 STANDBY CURRENT SHUTDOWN MAX5440 toc12 MAX5440 toc11 250 350 LOGIC SUPPLY CURRENT (µA) -40 VDD = VLOGIC = 5.5V, RENCODEA = RENCODEB = 0 300 250 200 150 100 50 -70 0 0 -75 0.1 1 10 2.5 100 3.0 3.5 4.0 4.5 5.0 ACTIVE SUPPLY CURRENT vs. TEMPERATURE -40 -15 35 60 85 1.1764 1.1762 1.1760 1.1758 1.1756 MAX5440 toc14 1.1766 1000 DIGITAL SUPPLY CURRENT (µA) VDD = VLOGIC = 5.5V, RENCODEA = RENCODEB = 0 10 TEMPERATURE (°C) DIGITAL SUPPLY CURRENT vs. DIGITAL INPUT VOLTAGE MAX5440 toc13 1.1770 1.1768 5.5 LOGIC SUPPLY VOLTAGE (V) FREQUENCY (kHz) 100 1.1754 1.1752 10 -15 10 35 60 85 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 TEMPERATURE (°C) DIGITAL INPUT VOLTAGE (V) SPECTRAL NOISE DENSITY SUPPLY CURRENT vs. INPUT VOLTAGE SWEEP 1200 8 800 600 400 VDD = VLOGIC = 5V, W_ AT 0dB RL = 10kΩ TO VMIDBIAS 7 SUPPLY CURRENT (mA) 1000 MAX5440 toc16 -40 MAX5440 toc15 SUPPLY CURRENT (mA) 0.01 NOISE (nV/√Hz) RESPONSE (dB) -35 LOGIC SUPPLY CURRENT (µA) VDD_ = 5V ±100mVP-P, VH = 5V VL_ = 2.5V, W_ SET TO -6dB -30 300 MAX5440 toc10 -25 ACTIVE LOGIC SUPPLY CURRENT vs. TEMPERATURE LOGIC SUPPLY CURRENT vs. LOGIC SUPPLY VOLTAGE POWER-SUPPLY REJECTION RATIO vs. FREQUENCY 6 5 4 3 2 200 1 0 0 0.01 0.1 1 FREQUENCY (kHz) 10 100 2.5 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE SWEEP (VH_) _______________________________________________________________________________________ 5 MAX5440 Typical Operating Characteristics (continued) Stereo Volume Control with Rotary Encoder Interface MAX5440 Pin Description 6 PIN NAME FUNCTION 1 VLOGIC 2 RENCODEB 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. 3 RENCODEA 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. 4 MUTE 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. 5 MODE 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. 6 SHDN 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. 8 H0 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 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. Digital Logic Power Supply. Bypass VLOGIC to ground with a 0.1µF capacitor as close to the device as possible. Midbias Voltage Output. VMIDBIAS = (VDD + VSS) / 2. _______________________________________________________________________________________ Stereo Volume Control with Rotary Encoder Interface 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. 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. 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. VLOGIC 1/4 CYCLE PER DETENT CW 45kΩ 45kΩ RENCODEA CHANNEL A OPEN CIRCUIT A CLOSED CIRCUIT RENCODEB B OPEN CIRCUIT CLOSED CIRCUIT MAX5440 ROTARY ENCODER D GND 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 _______________________________________________________________________________________ 7 MAX5440 Detailed Description MAX5440 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 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. H_ W0 W1 W1 W0 ROTATE CW TWICE W0 BALANCE SEPARATION MAINTAINED W1 ROTATE CCW ONCE L_ a NO CHANGE W0 W1 W0 W1 W0 W1 W0 W1 H_ ROTATE CW ONCE ROTATE CW L_ H_ b W0 W1 W0 W1 ROTATE CCW ONCE ROTATE CCW TO D L_ c ORIGINAL BALANCE SEPARATION MAINTAINED W0 W1 H_ W0 W1 W0 W1 ROTATE CW ONCE FROM C ROTATE CW ONCE L_ d Figure 2. Volume-Control Operation 8 _______________________________________________________________________________________ Stereo Volume Control with Rotary Encoder Interface POSITION ATTENUATION (dB) 0 0 1 -2 2 -4 … … 6 (POR) -12 … … 30 -60 Click-and-Pop Suppression 31 -62 32 (MUTE) ≥ 90 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 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. 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 H_ W0 W1 W0 ROTATE CW ONCE W1 W0 W1 ROTATE CW ONCE L_ Figure 3. Balance-Control Operation _______________________________________________________________________________________ 9 MAX5440 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). Table 1. Wiper Position and Attenuation MAX5440 Stereo Volume Control with Rotary Encoder Interface USER ROTATES ENCODER SWITCH CONTACT IS BOUNCING SWITCH CONTACT IS STABLE SWITCH CONTACT IS BOUNCING 01 INPUT ACCEPTED 00 tWS tHPW WAIT FOR FIRST ZERO CROSSING, tWS DEBOUNCE BY WAITING FOR STABLE HIGH, tHPW tLPW 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 ______________________________________________________________________________________ Stereo Volume Control with Rotary Encoder Interface MAX5440 SWITCH CONTACT IS STABLE SWITCH CONTACT IS BOUNCING READY TO ACCEPT ANOTHER ENCODER INPUT SIGNAL SWITCH CONTACT IS BOUNCING 01 INPUT ACCEPTED 00 tWS tHPW WAIT FOR FIRST ZERO CROSSING OR TIMEOUT, tWS tLPW DEBOUNCE BY WAITING FOR STABLE HIGH, tHPW DEBOUNCE BY WAITING FOR STABLE LOW, tLPW VH VL WIPER MOVES HERE (tLPW + tWS) 2dB STEPS Figure 4b. Wiper Transition Timing Diagram—Timed Out ______________________________________________________________________________________ 11 MAX5440 Stereo Volume Control with Rotary Encoder Interface Power-On Reset Mode Indicator (MODEIND) The power-on comparators monitor (VDD - 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. 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. 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 45kΩ 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. 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. Table 2. LED Settings in Volume Mode VOLUME POSITION (dB) 12 VOLUME LED OUTPUTS (1 = LED IS ON) LED0 LED1 LED2 LED3 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 0 0 0 -40 to -52 1 0 0 0 0 -54 to mute (-90) 0 0 0 0 0 ______________________________________________________________________________________ LED4 Stereo Volume Control with Rotary Encoder Interface L + 12 L+6 R+6 CCW ROTATION (CH0) LED0 ON R + 12 FULL R CW ROTATION (CH1) CENTERED LED1 ON MAX5440 FULL L LED2 ON LED3 ON LED4 ON Figure 5. LED Setting in Balance Mode VDD VLOGIC VLOGIC SHDN MODEIND VPEAK 0V MAX5440 H1 W1 RIGHT INPUT L1 (VDD + VSS) / 2 HEADPHONE DRIVER MIDBIAS LEDIND0 L0 LEFT INPUT LEDIND1 W0 LEDIND2 LEDIND3 H0 LEDIND4 BIAS RENCODEB RENCODEA MODE MUTE GND VSS = -VDD ROTARY ENCODER Figure 6. Dual-Supply Volume/Balance Control ______________________________________________________________________________________ 13 MAX5440 Stereo Volume Control with Rotary Encoder Interface 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. Chip Information PROCESS: BiCMOS 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 MODEIND VLOGIC LEDIND0 SHDN VDD VSS MIDBIAS BIAS LEDIND2 LEDIND1 LEDIND4 LEDIND3 BIAS GENERATOR MAX5440 H1 H0 CLICK-AND-POP SUPPRESSION CIRCUITRY 0 CLICK-AND-POP SUPPRESSION CIRCUITRY 0 1 1 2 2 3 3 POSITION COUNTER 4 POSITION COUNTER 4 W0 W1 UP/DOWN UP/DOWN 28 28 TIMING AND CONTROL 29 29 30 30 DEBOUNCE DEBOUNCE DEBOUNCE DEBOUNCE 31 31 VLOGIC 45kΩ 45kΩ 45kΩ 45kΩ MUTE MUTE L0 DEBOUNCE 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 MAX5440 Functional Diagram MAX5440 Stereo Volume Control with Rotary Encoder Interface Revision History REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 2 11/08 Fixed pin names and thermal data. Updated two specifications in EC table 1, 2, 3, 6, 13 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.