19-2842; Rev 1; 6/04 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense Features The MAX4409 stereo headphone amplifier combines Maxim’s DirectDrive architecture and a common-mode sense input, which allows the amplifier to reject common-mode noise. Conventional headphone amplifiers require a bulky DC-blocking capacitor between the headphone and the amplifier. DirectDrive produces a ground-referenced output from a single supply, eliminating the need for large DC-blocking capacitors, which saves cost, board space, and component height. The common-mode voltage sensing corrects for any difference between SGND of the amplifier and the headphone return. This feature minimizes ground-loop noise when the HP socket is used as a line out connection to other grounded equipment, for example, a PC connected to a home hi-fi system. ♦ No Bulky DC-Blocking Capacitors Required ♦ Ground-Referenced Outputs Eliminate DC-Bias Voltages on Headphone Ground Pin ♦ Common-Mode Voltage Sensing Eliminates Ground-Loop Noise ♦ 96dB CMRR ♦ No Degradation of Low-Frequency Response Due to Output Capacitors ♦ 80mW per Channel into 16Ω ♦ Low 0.002% THD+N ♦ High 86dB PSRR ♦ Integrated Click-and-Pop Suppression ♦ 1.8V to 3.6V Single-Supply Operation ♦ Low Quiescent Current ♦ Low-Power Shutdown Mode ♦ Short-Circuit and Thermal-Overload Protection ♦ ±8kV ESD-Protected Amplifier Outputs ♦ Available in Space-Saving Packages 14-Pin TSSOP 20-Pin Thin QFN (4mm x 4mm x 0.8mm) The MAX4409 draws only 5mA of supply current, delivers up to 80mW per channel into a 16Ω load, and has a low 0.002% THD+N. A high 86dB power-supply rejection ratio allows this device to operate from noisy digital supplies without additional power-supply conditioning. The MAX4409 includes ±8kV ESD protection on the headphone outputs. Comprehensive click-and-pop circuitry eliminates audible clicks and pops on startup and shutdown. A low-power shutdown mode reduces supply current draw to only 6µA. The MAX4409 operates from a single 1.8V to 3.6V supply, has short-circuit and thermal overload protection, and is specified over the extended -40°C to +85°C temperature range. The MAX4409 is available in tiny 20-pin thin QFN (4mm x 4mm x 0.8mm) and 14-pin TSSOP packages. Ordering Information PART TEMP RANGE PIN-PACKAGE MAX4409ETP MAX4409EUD -40°C to +85°C -40°C to +85°C 20 Thin QFN-EP* 14 TSSOP *EP = Exposed paddle. Functional Diagram Applications Notebooks Desktop PCs Cellular Phones PDAs DirectDrive OUTPUTS ELIMINATE DC-BLOCKING CAPACITORS MAX4409 LEFT AUDIO INPUT MP3 Players Tablet PCs SHDN Portable Audio Equipment COM RIGHT AUDIO INPUT COMMON-MODE SENSE INPUT ELIMINATES GROUND-LOOP NOISE Pin Configurations and Typical Application Circuit appear at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX4409 General Description MAX4409 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense ABSOLUTE MAXIMUM RATINGS PGND to SGND .....................................................-0.3V to +0.3V PVDD to SVDD .................................................................-0.3V to +0.3V PVSS to SVSS .........................................................-0.3V to +0.3V PVDD and SVDD to PGND or SGND .........................-0.3V to +4V PVSS and SVSS to PGND or SGND ..........................-4V to +0.3V IN_ and COM to SGND.................................SVSS to (SVDD - 1V) IN_ to COM .....................................(COM + 2V) to (COM - 0.3V) SHDN_ to SGND........................(SGND - 0.3V) to (SVDD + 0.3V) OUT_ to SGND ............................(SVSS - 0.3V) to (SVDD + 0.3V) C1P to PGND.............................(PGND - 0.3V) to (PVDD + 0.3V) C1N to PGND .............................(PVSS - 0.3V) to (PGND + 0.3V) Output Short Circuit to GND or VDD ...........................Continuous Continuous Power Dissipation (TA = +70°C) 14-Pin TSSOP (derate 9.1mW/°C above +70°C) ..........727mW 20-Pin Thin QFN (derate 16.9mW/°C above +70°C) ..1349mW Junction Temperature ......................................................+150°C Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°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 (PVDD = SVDD = 3V, PGND = SGND = 0V, SHDN = SVDD, C1 = C2 = 2.2µF, RIN = RF = R1 = R2 = 10kΩ, RL = ∞, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL Supply Voltage Range VDD Quiescent Supply Current IDD Shutdown Supply Current I SHDN CONDITIONS Guaranteed by PSRR test MIN TYP MAX 3.6 V 5 8.4 mA 6 10 µA 1.8 SHDN = GND 0.7 x SVDD VIH SHDN Thresholds V 0.3 x SVDD VIL SHDN Input Leakage Current SHDN to Full Operation UNITS -1 tSON +1 175 µA µs CHARGE PUMP Oscillator Frequency fOSC 272 320 368 kHz 0.5 2.4 mV -700 -100 0 nA -1400 -200 0 nA +500 mV AMPLIFIERS Input Offset Voltage VOS Input Bias Current IBIAS COM Bias Current ICOM Equivalent Input Offset Current IOS RL = 32Ω IOS = (IBIAS(INR) + IBIAS(INL) - ICOM) / 2 ±2 COM Input Range VCOM Inferred from CMRR test Common-Mode Rejection Ratio CMRR -500mV ≤ VCOM ≤ +500mV, RSOURCE ≤ 10Ω 75 96 1.8V ≤ VDD ≤ 3.6V DC (Note 2) 75 86 VDD = 3.0V, 200mVP-P ripple fRIPPLE = 1kHz Power-Supply Rejection Ratio Output Power 2 PSRR POUT THD+N = 1%, TA = +25°C -500 76 fRIPPLE = 20kHz 48 RL = 32Ω 65 RL = 16Ω 55 80 _______________________________________________________________________________________ nA dB dB mW 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense (PVDD = SVDD = 3V, PGND = SGND = 0V, SHDN = SVDD, C1 = C2 = 2.2µF, RIN = RF = R1 = R2 = 10kΩ, RL = ∞, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL Total Harmonic Distortion Plus Noise THD+N Signal-to-Noise Ratio SNR Slew Rate SR Maximum Capacitive Load CL CONDITIONS fIN = 1kHz MIN TYP RL = 32Ω, POUT = 50mW 0.002 RL = 16Ω, POUT = 60mW 0.005 95 dB 0.8 V/µs No sustained oscillations 150 pF RL = 16Ω, POUT = 1.6mW, fIN = 10kHz 55 dB 140 °C 15 °C ±8 kV Thermal Shutdown Threshold Thermal Shutdown Hysteresis ESD Protection UNITS % RL = 32Ω, POUT = 20mW, fIN = 1kHz Crosstalk MAX Human Body Model (OUTR, OUTL) Note 1: All specifications are 100% tested at TA = +25°C; temperature limits are guaranteed by design. Note 2: Inputs are connected to ground and COM. Note 3: Inputs are AC-coupled to ground. COM is connected to ground. Typical Operating Characteristics (C1 = C2 = 2.2µF, RIN = RF = R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY VDD = 3V RL = 16Ω 1 MAX4409 toc02 1 MAX4409 toc01 1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY VDD = 3V RL = 32Ω VDD = 1.8V RL = 16Ω 0.1 THD+N (%) THD+N (%) POUT = 60mW POUT = 10mW 0.01 THD+N (%) 0.1 0.1 MAX4409 toc03 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY POUT = 50mW 0.01 POUT = 15mW POUT = 5mW 0.01 POUT = 10mW 0.001 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 10 100 1k 10k 100k FREQUENCY (Hz) _______________________________________________________________________________________ 3 MAX4409 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (C1 = C2 = 2.2µF, RIN = RF = R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) 10 THD+N (%) POUT = 15mW POUT = 5mW 0.01 OUTPUTS IN PHASE 1 0.1 0.01 0.001 100 1k 10k 60 90 150 120 30 60 90 120 150 180 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER OUTPUTS OUT OF PHASE 0.01 10 THD+N (%) OUTPUTS IN PHASE 0.1 OUTPUTS OUT OF PHASE 0.001 0.001 90 120 150 180 1 OUTPUTS IN PHASE 0.1 0.01 OUTPUTS OUT OF PHASE 0.001 0.0001 60 VDD = 3V f = 1kHz RL = 32Ω 1 0.1 30 MAX4409 toc09 VDD = 3V f = 20Hz RL = 32Ω 10 100 MAX4409 toc08 MAX4409 toc07 100 0.01 0 20 40 60 80 100 0 120 20 40 60 80 100 120 OUTPUT POWER (W) OUTPUT POWER (W) OUTPUT POWER (W) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER OUTPUTS OUT OF PHASE 0.01 OUTPUTS IN PHASE 1 0.1 OUTPUTS OUT OF PHASE 0.01 20 40 60 80 OUTPUT POWER (W) 100 120 1 OUTPUTS IN PHASE 0.1 OUTPUTS OUT OF PHASE 0.01 0.001 0.001 VDD = 1.8V f = 1kHz RL = 16Ω 10 THD+N (%) 0.1 THD+N (%) OUTPUTS IN PHASE VDD = 1.8V f = 20Hz RL = 16Ω 10 100 MAX4409 toc11 VDD = 3V f = 10kHz RL = 32Ω 1 100 MAX4409 toc10 100 4 0 180 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER THD+N (%) THD+N (%) 30 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER OUTPUTS IN PHASE 0 OUTPUTS OUT OF PHASE 0.01 OUTPUT POWER (W) 1 10 0.1 OUTPUT POWER (W) VDD = 3V f = 10kHz RL = 16Ω 0 OUTPUTS IN PHASE FREQUENCY (Hz) 100 10 1 0.001 0 100k 10 OUTPUTS OUT OF PHASE 0.001 10 VDD = 3V f = 1kHz RL = 16Ω MAX4409 toc12 THD+N (%) 0.1 100 MAX4409 toc06 VDD = 3V f = 20Hz RL = 16Ω THD+N (%) VDD = 1.8V RL = 32Ω MAX4409 toc05 100 MAX4409 toc04 1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY THD+N (%) MAX4409 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense 0.001 0 10 20 30 40 OUTPUT POWER (W) 50 60 0 10 20 30 40 OUTPUT POWER (W) _______________________________________________________________________________________ 50 60 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense (C1 = C2 = 2.2µF, RIN = RF = R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 0.1 0.01 20 30 40 50 MAX4409 toc14 OUTPUTS OUT OF PHASE 10 20 30 40 0 10 20 30 OUTPUT POWER (W) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER POWER-SUPPLY REJECTION RATIO vs. FREQUENCY POWER-SUPPLY REJECTION RATIO vs. FREQUENCY VDD = 3V VIN = 200mVP-P RL = 16Ω -10 -20 0 -20 0.001 10 20 30 -20 -60 -70 -80 -80 -90 -90 40 10 100 1k 10k POWER-SUPPLY REJECTION RATIO vs. FREQUENCY POWER-SUPPLY REJECTION RATIO vs. FREQUENCY MAX4410 toc19 VDD = 1.8V VIN = 200mVP-P RL = 32Ω -10 -20 100k 0 -40 -50 -40 -70 -70 -80 -80 -80 -90 1k FREQUENCY (Hz) 10k 100k RIGHT TO LEFT -50 -70 100 100k -30 -60 10 10k -20 -60 -90 1k VIN = 200mVP-P -10 CROSSTALK (dB) PSRR (dB) -50 100 CROSSTALK vs. FREQUENCY -30 -40 10 FREQUENCY (Hz) 0 -30 -50 -70 FREQUENCY (Hz) VDD = 1.8V VIN = 200mVP-P RL = 16Ω -40 -60 OUTPUT POWER (W) 0 -10 -50 MAX4410 toc20 0 -40 MAX4410 toc21 OUTPUTS OUT OF PHASE 0.01 -30 PSRR (dB) PSRR (dB) OUTPUTS IN PHASE 0.1 VDD = 3V VIN = 200mVP-P RL = 16Ω -10 40 MAX4410 toc18 0 MAX4409 toc16 VDD = 1.8V f = 10kHz RL = 32Ω -30 THD+N (%) OUTPUTS OUT OF PHASE 0.01 OUTPUT POWER (W) 1 PSRR (dB) OUTPUTS IN PHASE 0.1 0.001 0 60 1 OUTPUT POWER (W) 100 10 0.1 0.001 0.001 10 OUTPUTS IN PHASE 0.01 OUTPUTS OUT OF PHASE 0 1 VDD = 1.8V f = 1kHz RL = 32Ω 10 THD+N (%) OUTPUTS IN PHASE 100 MAX4409 toc17 THD+N (%) 1 VDD = 1.8V f = 20Hz RL = 32Ω 10 THD+N (%) VDD = 1.8V f = 10kHz RL = 16Ω 10 100 MAX4409 toc13 100 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX4409 toc15 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER LEFT TO RIGHT -60 -90 10 100 1k FREQUENCY (Hz) 10k 100k 10 100 1k 10k 100k FREQUENCY (Hz) _______________________________________________________________________________________ 5 MAX4409 Typical Operating Characteristics (continued) Typical Operating Characteristics (continued) (C1 = C2 = 2.2µF, RIN = RF = R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) OUTPUT POWER vs. SUPPLY VOLTAGE -50 -60 -70 140 120 100 80 60 -80 40 -90 20 INPUTS IN PHASE 1k 10k 2.1 MAX4409 toc25 INPUTS 180° OUT OF PHASE 80 60 INPUTS IN PHASE 40 fIN = 1kHz RL = 32Ω THD+N = 10% 160 140 2.7 3.0 3.3 INPUTS 180° OUT OF PHASE 120 100 80 INPUTS IN PHASE 60 3.0 3.3 40 2.4 2.7 3.0 3.3 VDD = 1.8V fIN = 1kHz THD+N = 1% INPUTS 180° OUT OF PHASE 35 OUTPUT POWER (mW) INPUTS 180° OUT OF PHASE MAX4409 toc24 INPUTS 180° OUT OF PHASE 60 INPUTS IN PHASE 10 3.6 INPUTS IN PHASE 20 1k 10k 100k OUTPUT POWER vs. LOAD RESISTANCE 30 25 100 LOAD RESISTANCE (Ω) OUTPUT POWER vs. LOAD RESISTANCE 150 100 80 0 2.1 45 MAX4409 toc28 VDD = 3V fIN = 1kHz THD+N = 10% 200 100 SUPPLY VOLTAGE (V) OUTPUT POWER vs. LOAD RESISTANCE 3.6 120 20 SUPPLY VOLTAGE (V) 250 3.3 40 1.8 3.6 3.0 VDD = 3V fIN = 1kHz THD+N = 1% 140 70 60 OUTPUT POWER (mW) 2.7 2.7 OUTPUT POWER vs. LOAD RESISTANCE MAX4409 toc29 2.4 2.4 160 0 0 2.1 2.1 SUPPLY VOLTAGE (V) 20 1.8 INPUTS IN PHASE 1.8 3.6 40 20 15 VDD = 1.8V fIN = 1kHz THD+N = 10% INPUTS 180° OUT OF PHASE 50 40 INPUTS IN PHASE 30 20 10 50 INPUTS IN PHASE 10 10 5 0 0 100 1k 10k LOAD RESISTANCE (Ω) 6 2.4 180 OUTPUT POWER (mW) OUTPUT POWER (mW) 100 100 OUTPUT POWER vs. SUPPLY VOLTAGE OUTPUT POWER vs. SUPPLY VOLTAGE 140 fIN = 1kHz RL = 32Ω THD+N = 1% 150 SUPPLY VOLTAGE (V) FREQUENCY (Hz) 120 200 0 1.8 100k OUTPUT POWER (mW) 100 MAX4409 toc26 10 INPUTS 180° OUT OF PHASE 50 0 -100 fIN = 1kHz RL = 16Ω THD+N = 10% 250 MAX4409 toc27 -40 INPUTS 180° OUT OF PHASE OUTPUT POWER (mW) -30 CMRR (dB) 160 OUTPUT POWER (mW) -20 fIN = 1kHz RL = 16Ω THD+N = 1% 180 OUTPUT POWER vs. SUPPLY VOLTAGE 300 MAX4409 toc23 VIN = 500mVP-P -10 200 MAX4409 toc22 0 MAX4409 toc30 COMMON-MODE REJECTION RATIO vs. FREQUENCY OUTPUT POWER (mW) MAX4409 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense 100k 0 10 100 1k 10k LOAD RESISTANCE (Ω) 100k 10 100 1k 10k LOAD RESISTANCE (Ω) _______________________________________________________________________________________ 100k 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense (C1 = C2 = 2.2µF, RIN = RF = R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) INPUTS 180° OUT OF PHASE 150 100 INPUTS 180° OUT OF PHASE 120 100 80 60 fIN = 1kHz RL = 32Ω VDD = 3V POUT = POUTL + POUTR 40 50 20 0 120 160 200 40 OUTPUT POWER (mW) GAIN/PHASE (dB/DEGREES) 50 INPUTS 180° OUT OF PHASE 30 fIN = 1kHz RL = 32Ω VDD = 1.8V POUT = POUTL + POUTR 10 0 0 10 20 30 40 50 160 200 80 60 40 20 0 -20 -40 -60 -80 -100 -120 -140 -160 -180 60 GAIN PHASE 10k 1k 100k 1M 10M 2.4 C1 = C2 = 2.2µF 80 C1 = C2 = 1µF 60 50 C1 = C2 = 0.68µF 40 C1 = C2 = 0.47µF 30 3.0 SUPPLY VOLTAGE (V) 3.3 3.6 fIN = 1kHz THD+N = 1% INPUTS IN PHASE 10 20 30 10 100 1k 10k 100k 1M MAX4409 toc33 10M 0 40 LOAD RESISTANCE (Ω) VIN = 1VP-P fIN = 1kHz RL = 32Ω AV = -1V/V -20 OUTPUT SPECTRUM (dB) OUTPUT POWER (mW) 2.7 VDD = 3V AV = -1V/V RL = 16Ω OUTPUT SPECTRUM vs. FREQUENCY -40 -60 -80 -100 0 2.1 -20 FREQUENCY (Hz) 90 10 0 0 -40 20 2 60 50 -50 100 MAX4409 toc37 4 40 10 VDD = 3V AV = 1000V/V RL = 16Ω 70 6 30 -30 OUTPUT POWER vs. CHARGE-PUMP CAPACITANCE AND LOAD RESISTANCE VIN_ = GND IPVSS = 10mA NO LOAD 20 -10 CHARGE-PUMP OUTPUT RESISTANCE vs. SUPPLY VOLTAGE 1.8 10 GAIN FLATNESS vs. FREQUENCY FREQUENCY (Hz) 8 0 OUTPUT POWER (mW) OUTPUT POWER (mW) 10 OUTPUT RESISTANCE (Ω) 120 MAX4409 toc38 POWER DISSIPATION (mW) MAX4409 toc34 INPUTS IN PHASE 20 80 GAIN AND PHASE vs. FREQUENCY 70 40 40 OUTPUT POWER (mW) POWER DISSIPATION vs. OUTPUT POWER 60 60 0 0 MAX4409 toc35 80 GAIN (dB) 40 INPUTS 180° OUT OF PHASE 80 20 0 0 100 MAX4410 toc36 200 140 INPUTS IN PHASE fIN = 1kHz RL = 16Ω VDD = 1.8V POUT = POUTL + POUTR 120 MAX4409 toc39 250 140 POWER DISSIPATION (mW) 300 POWER DISSIPATION vs. OUTPUT POWER INPUTS IN PHASE 160 POWER DISSIPATION (mW) 350 POWER DISSIPATION (mW) INPUTS IN PHASE fIN = 1kHz RL = 16Ω VDD = 3V POUT = POUTL + POUTR 180 MAX4409 toc31 400 POWER DISSIPATION vs. OUTPUT POWER MAX4409 toc32 POWER DISSIPATION vs. OUTPUT POWER 50 -120 100 1k 10k 100k FREQUENCY (Hz) _______________________________________________________________________________________ 7 MAX4409 Typical Operating Characteristics (continued) Typical Operating Characteristics (continued) (C1 = C2 = 2.2µF, RIN = RF = R1 = R2 = 10kΩ, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE SUPPLY CURRENT vs. SUPPLY VOLTAGE 6 4 MAX4409 toc41 SHDN = GND 8 SUPPLY CURRENT (µA) 8 POWER-UP/DOWN WAVEFORM MAX4409 toc42 10 MAX4409 toc40 10 SUPPLY CURRENT (mA) MAX4409 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense VDD 0V 6 OUT_ 10mV/div -100dB 4 2 2 3V 20dB/div OUT_FFT 0 0 0 0.9 1.8 2.7 3.6 0 0.9 1.8 2.7 3.6 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) RL = 32Ω VIN_ = GND 200ms/div FFT: 25Hz/div Pin Description PIN 8 NAME FUNCTION TSSOP THIN QFN 1 18 COM Common-Mode Voltage Sense Input 2 19 PVDD Charge-Pump Power Supply. Powers charge-pump inverter, charge-pump logic, and oscillator. 3 1 C1P Flying Capacitor Positive Terminal 4 2 PGND Power Ground. Connect to SGND. 5 3 C1N Flying Capacitor Negative Terminal 6 5 Charge-Pump Output 7 7 PVSS SVSS 8 9 OUTL Left-Channel Output 9 10 Amplifier Positive Power Supply. Connect to PVDD. 10 13 SVDD INL Left-Channel Audio Input 11 11 OUTR Right-Channel Output 12 14 SHDN Active-Low Shutdown. Connect to VDD for normal operation. 13 15 INR 14 17 SGND — 4, 6, 8, 12, 16, 20 N.C. — — EP Amplifier Negative Power Supply. Connect to PVSS. Right-Channel Audio Input Signal Ground. Connect to PGND. No Connection. Not internally connected. Exposed Paddle. Leave this connection floating. Do not connect to VDD or GND. _______________________________________________________________________________________ 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense The MAX4409 stereo headphone driver features Maxim’s patented DirectDrive architecture, eliminating the large output-coupling capacitors required by traditional singlesupply headphone drivers. The device consists of two 80mW Class AB headphone drivers, undervoltage lockout (UVLO)/shutdown control, charge-pump, and comprehensive click-and-pop suppression circuitry (see Typical Application Circuit). The charge pump inverts the positive supply (PV DD ), creating a negative supply (PVSS). The headphone drivers operate from these bipolar supplies with their outputs biased about GND (Figure 1). The drivers have almost twice the supply range compared to other 3V single-supply drivers, increasing the available output power. The benefit of this GND bias is that the driver outputs do not have a DC component typically VDD/2. Thus, the large DC-blocking capacitors are unnecessary, improving frequency response while conserving board space and system cost. The MAX4409 also features a common-mode voltage sense input that corrects for mismatch between the SGND of the device and the potential at the headphone jack return. A low-power shutdown mode reduces supply current to 6µA. The device features an undervoltage lockout that prevents operation from an insufficient power supply and click-and-pop suppression that eliminates audible transients on startup and shutdown. Additionally, the MAX4409 features thermal overload and short-circuit protection and can withstand ±8kV ESD strikes on the output pins. MAX4409 Detailed Description VDD VDD/2 VOUT GND CONVENTIONAL DRIVER-BIASING SCHEME +VDD VOUT GND -VDD DirectDrive BIASING SCHEME Figure 1. Traditional Driver Output Waveform vs. MAX4409 Output Waveform Common-Mode Sense When the headphone jack is used as a line out to interface between other equipment (notebooks, desktops, and stereo receivers), potential differences between the equipment grounds can create ground loops and excessive ground current flow. The MAX4409 COM input senses and corrects for the difference between the headphone return and device ground. Connect COM through a resistive voltage-divider between the headphone jack return and SGND of the device (see Typical Application Circuit). For optimum commonmode rejection, use the same value resistors for R1 and RIN, and R2 and RF. Improve DC CMRR by adding a capacitor in between with SGND and R2 (see Typical Application Circuit). If ground sensing is not required, connect COM directly to SGND through a 5kΩ resistor. DirectDrive Traditional single-supply headphone drivers have their outputs biased about a nominal DC voltage (typically half the supply) for maximum dynamic range. Large coupling capacitors are needed to block this DC bias from the headphone. Without these capacitors, a significant amount of DC current flows to the headphone, resulting in unnecessary power dissipation and possible damage to both headphone and headphone driver. Maxim’s patented DirectDrive architecture uses a charge pump to create an internal negative supply voltage. This allows the outputs of the MAX4409 to be biased about GND, almost doubling dynamic range while operating from a single supply. With no DC component, there is no need for the large DC-blocking capacitors. Instead of two large (220µF, typ) tantalum capacitors, the MAX4409 charge pump requires two small ceramic capacitors, thereby conserving board space, reducing cost, and improving the frequency response of the headphone driver. See the Output Power vs. Charge-Pump Capacitance and Load Resistance graph in the Typical Operating Characteristics for details of the possible capacitor sizes. There is a low DC voltage on the driver outputs due to amplifier offset. However, the offset of the MAX4409 is _______________________________________________________________________________________ 9 When using the headphone jack as a line out to other equipment, the bias voltage on the sleeve may conflict with the ground potential from other equipment, resulting in possible damage to the drivers. Low-Frequency Response In addition to the cost and size disadvantages of the DCblocking capacitors required by conventional headphone amplifiers, these capacitors limit the amplifier’s low-frequency response and can distort the audio signal: • The impedance of the headphone load and the DCblocking capacitor form a highpass filter with the -3dB point set by: f-3dB = 1 2πRLCOUT where RL is the headphone impedance and COUT is the DC-blocking capacitor value. The highpass filter is required by conventional single-ended, single power-supply headphone drivers to block the midrail DC bias component of the audio signal from the headphones. The drawback to the filter is that it can attenuate low-frequency signals. Larger values of COUT reduce this effect but result in physically larger, more expensive capacitors. Figure 2 shows the relationship between the size of COUT and the resulting low-frequency attenuation. Note that the -3dB point for a 16Ω headphone with a 100µF blocking capacitor is 100Hz, well within the normal audio band, resulting in low-frequency attenuation of the reproduced signal. LF ROLL OFF (16Ω LOAD) 0 -3 -5 MAX4409 fig02 • During an ESD strike, the driver’s ESD structures are the only path to system ground. Thus, the driver must be able to withstand the full ESD strike. 330µF 220µF ATTENUATION (dB) • • The voltage coefficient of the DC-blocking capacitor contributes distortion to the reproduced audio signal as the capacitance value varies as a function of the voltage change across the capacitor. At low frequencies, the reactance of the capacitor dominates at frequencies below the -3dB point and the voltage coefficient appears as frequency-dependent distortion. Figure 3 shows the THD+N introduced by two different capacitor dielectric types. Note that below 100Hz, THD+N increases rapidly. The combination of low-frequency attenuation and frequency-dependent distortion compromises audio reproduction in portable audio equipment that emphasizes low-frequency effects such as multimedia lap- -10 -3dB CORNER FOR 100µF IS 100Hz 100µF -15 33µF -20 -25 -30 -35 10 1k 100 FREQUENCY (Hz) Figure 2. Low-Frequency Attenuation for Common DC-Blocking Capacitor Values ADDITIONAL THD+N DUE TO DC-BLOCKING CAPACITORS 10 MAX4409 fig03 typically 0.5mV, which, when combined with a 32Ω load, results in less than 16µA of DC current flow to the headphones. Previous attempts to eliminate the output-coupling capacitors involved biasing the headphone return (sleeve) to the DC-bias voltage of the headphone amplifiers. This method raises some issues: • When combining a microphone and headphone on a single connector, the microphone bias scheme typically requires a 0V reference. • The sleeve is typically grounded to the chassis. Using this biasing approach, the sleeve must be isolated from system ground, complicating product design. 1 THD+N (%) MAX4409 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense 0.1 TANTALUM 0.01 0.001 ALUM/ELEC 0.0001 10 100 1k 10k 100k FREQUENCY (Hz) Figure 3. Distortion Contributed by DC-Blocking Capacitors 10 ______________________________________________________________________________________ 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense Charge Pump The MAX4409 features a low-noise charge pump. The 320kHz switching frequency is well beyond the audio range, and thus does not interfere with the audio signals. The switch drivers feature a controlled switching speed that minimizes noise generated by turn-on and turn-off transients. By limiting the switching speed of the switches, the di/dt noise caused by the parasitic bond wire and trace inductance is minimized. Although not typically required, additional high-frequency noise attenuation can be achieved by increasing the size of C2 (see Typical Application Circuit). Shutdown The MAX4409 features an active-low SHDN control. Driving SHDN low disables the charge pump and amplifiers, sets the amplifier output impedance to approximately 1kΩ, and reduces supply current draw to less than 6µA. Click-and-Pop Suppression In traditional single-supply audio drivers, the outputcoupling capacitor is a major contributor of audible clicks and pops. Upon startup, the driver charges the coupling capacitor to its bias voltage, typically half the supply. Likewise, on shutdown the capacitor is discharged to GND. This results in a DC shift across the capacitor, which in turn, appears as an audible transient at the speaker. Since the MAX4409 does not require output-coupling capacitors, this does not arise. Additionally, the MAX4409 features extensive click-andpop suppression that eliminates any audible transient sources internal to the device. The Power-Up/Down Waveform in the Typical Operating Characteristics shows that there are minimal spectral components in the audible range at the output upon startup or shutdown. In most applications, the output of the preamplifier driving the MAX4409 has a DC bias of typically half the supply. At startup, the input-coupling capacitor is charged to the preamplifier’s DC-bias voltage through the RF of the MAX4409, resulting in a DC shift across the capacitor and an audible click/pop. Delaying the rise of the SHDN_ signals 4 to 5 time constants (40ms to 50ms) based on RIN and CIN relative to the start of the preamplifier eliminates this click/pop caused by the input filter. Applications Information Power Dissipation Under normal operating conditions, linear power amplifiers can dissipate a significant amount of power. The maximum power dissipation for each package is given in the Absolute Maximum Ratings section under Continuous Power Dissipation or can be calculated by the following equation: TJ(MAX) − TA PDISSPKG(MAX) = θJA where TJ(MAX) is +150°C, TA is the ambient temperature, and θJA is the reciprocal of the derating factor in °C/W as specified in the Absolute Maximum Ratings section. For example, θJA of the TSSOP package is +109.9°C/W. The MAX4409 has two sources of power dissipation, the charge pump and two drivers. If the power dissipation for a given application exceeds the maximum allowed for a given package, either reduce V DD , increase load impedance, decrease the ambient temperature, or add heat sinking to the device. Large output, supply, and ground traces improve the maximum power dissipation in the package. Thermal overload protection limits total power dissipation in the MAX4409. When the junction temperature exceeds +140°C, the thermal-protection circuitry disables the amplifier output stage. The amplifiers are enabled once the junction temperature cools by 15°C. This results in a pulsing output under continuous thermal-overload conditions. Output Power The device has been specified for the worst-case scenario—when both inputs are in phase. Under this condition, the drivers simultaneously draw current from the charge pump, leading to a slight loss in headroom of VSS. In typical stereo audio applications, the left and right signals have differences in both magnitude and phase, subsequently leading to an increase in the maximum attainable output power. Figure 4 shows the two extreme cases for in and out of phase. In reality, the available power lies between these extremes. Powering Other Circuits from a Negative Supply An additional benefit of the MAX4409 is the internally generated, negative supply voltage (PVSS). This voltage is used by the MAX4409 to provide the ground-referenced output level. It can, however, also be used to power other devices within a design. Current draw from this negative supply (PVSS) should be limited to 5mA; exceeding this affects the operation of the headphone ______________________________________________________________________________________ 11 MAX4409 tops, as well as MP3, CD, and DVD players. By eliminating the DC-blocking capacitors through DirectDrive technology, these capacitor-related deficiencies are eliminated. Component Selection Gain-Setting Resistors External feedback components set the gain of the MAX4409. Resistors RF and RIN (see Typical Application Circuit) set the gain of each amplifier as follows: R AV = − F RIN Choose feedback resistor values of 10kΩ. Values other than 10kΩ increase VOS due to the input bias current, which in turn increases the amount of DC current flow to the load. Resistors RIN, R2, RF, and R1 must be of equal value for best results. Use high-tolerance resistors for best matching and CMRR. For example, the worst-case CMRR attributed to a 1% resistor mismatch is -34dB. This is the worst case, and typical resistors do not affect CMRR as drastically. The effect of resistor mismatch is shown in Figure 5. If all resistors match exactly, then any voltage applied to node A should be duplicated on OUT so no net differential voltage appears between node A (normally the HP jack socket GND) and OUT. For resistors with a tolerance of n%, the worst mismatch is found when RIN and R1 are at +n%, and RF and R2 are at -n%. If all four resistors are nominally the same value, then 2n% of the voltage at A appears between A and OUT. Packaged resistor arrays can provide well-matched components for this type of application. Although their absolute tolerance is not well controlled, the internal matching of resistors can be very good. At higher frequencies, the rejection is usually limited by PC board layout; care should be taken to make sure any stray capacitance due to PC board traces on node N1 matches those on node N2. Ultimately, CMRR performance is limited by the amplifier itself (see Electrical Characteristics). Compensation Capacitor The stability of the MAX4409 is affected by the value of the feedback resistor (RF). The combination of RF and the input and parasitic trace capacitance introduces an additional pole. Adding a capacitor in parallel with RF compensates for this pole. Under typical conditions with proper layout, the device is stable without the 12 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 100 MAX4409 fig04 driver. The negative supply voltage appears on the PVSS pin. A typical application is a negative supply to adjust the contrast of LCD modules. When considering the use of PVSS in this manner, note that the charge-pump voltage at PVSS is roughly proportional to -VDD and is not a regulated voltage. The charge-pump output impedance plot appears in the Typical Operating Characteristics. VDD = 3V AV = -1V/V RL = 16Ω fIN = 10kHz 10 THD+N (%) MAX4409 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense 1 OUTPUTS IN PHASE 0.1 OUTPUTS 180° OUT OF PHASE 0.01 ONE CHANNEL 0.001 0 50 100 150 200 OUTPUT POWER (mW) Figure 4. Output Power vs. THD+N with Inputs In/Out of Phase RF RIN N1 MAX4409 R2 N2 OUT R1 A Figure 5. Common-Mode Sense Equivalent Circuit additional capacitor. Input Filtering The input capacitor (CIN), in conjunction with RIN, forms a highpass filter that removes the DC bias from an incoming signal (see Typical Application Circuit). The AC-coupling capacitor allows the amplifier to bias the signal to an optimum DC level. Assuming zero-source impedance, the -3dB point of the highpass filter is given by: f-3dB = 1 2πRINCIN ______________________________________________________________________________________ 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense SUPPLIER PHONE FAX WEBSITE Taiyo Yuden 800-348-2496 847-925-0899 www.t-yuden.com TDK 847-803-6100 847-390-4405 www.component.tdk.com Note: Please indicate you are using the MAX4409 when contacting these component suppliers. Choose RIN according to the Gain-Setting Resistors section. Choose the CIN such that f-3dB is well below the lowest frequency of interest. Setting f-3dB too high affects the low-frequency response of the amplifier. Use capacitors whose dielectrics have low-voltage coefficients, such as tantalum or aluminum electrolytic. Capacitors with high-voltage coefficients, such as ceramics, may result in increased distortion at low frequencies. Charge-Pump Capacitor Selection Use capacitors with an ESR less than 100mΩ for optimum performance. Low-ESR ceramic capacitors minimize the output resistance of the charge pump. For best performance over the extended temperature range, select capacitors with an X7R dielectric. Table 1 lists suggested manufacturers. Flying Capacitor (C1) The value of the flying capacitor (C1) affects the load regulation and output resistance of the charge pump. A C1 value that is too small degrades the device’s ability to provide sufficient current drive, which leads to a loss of output voltage. Increasing the value of C1 improves load regulation and reduces the charge-pump output resistance to an extent. See the Output Power vs. Charge-Pump Capacitance and Load Resistance graph in the Typical Operating Characteristics. Above 2.2µF, the on-resistance of the switches and the ESR of C1 and C2 dominate. Output Capacitor (C2) The output capacitor value and ESR directly affect the ripple at PVSS. Increasing the value of C2 reduces output ripple. Likewise, decreasing the ESR of C2 reduces both ripple and output resistance. Lower capacitance values can be used in systems with low maximum output power levels. See the Output Power vs. ChargePump Capacitance and Load Resistance graph in the Typical Operating Characteristics. Power-Supply Bypass Capacitor The power-supply bypass capacitor (C3) lowers the output impedance of the power supply, and reduces the impact of the MAX4409’s charge-pump switching transients. Bypass PVDD with C3, the same value as C1, and place it physically close to the PVDD and PGND pins. Common-Mode Noise Rejection Figure 6 shows a theoretical connection between two devices, for example, a notebook computer (transmitter, on the left) and an amplifier (receiver, on the right). The application includes the headphone socket used as a line output to a home hi-fi system, for example. In the upper diagram, any difference between the two GND references (represented by VNOISE) causes current to flow through the screen of cable between the two devices. This can cause noise pickup at the receiver due to the potential divider action of the audio screen cable impedance and the GND wiring of the amplifier. Introducing impedance between the jack socket and GND of the notebook helps (as shown in the lower diagram). This has the following effect: • Current flow (from GND potential differences) in the cable screen is reduced, which is a safety issue. • It allows the MAX4409 differential sensing to reduce the GND noise seen by the receiver (amplifier). The other side effect is the differential HP jack sensing corrects the headphone crosstalk (from introducing the resistance on the jack GND return). Only one channel is depicted in Figure 6. Figure 6 has some example numbers for resistance, but the audio designer has control over only one series resistance applied to the headphone jack return. Note that this resistance can be bypassed for ESD purposes at frequencies much higher than audio if required. The upper limit for this added resistance is the amount of output swing the headphone amplifier tolerates when driving low-impedance loads. Any headphone return current appears as a voltage across this resistor. Layout and Grounding Proper layout and grounding are essential for optimum performance. Connect PGND and SGND together at a single point on the PC board. Connect all components associated with the charge pump (C2 and C3) to the PGND plane. Connect PVDD and SVDD together at the device. Connect PV SS and SV SS together at the device. Bypassing of both supplies is accomplished by charge-pump capacitors C2 and C3 (see Typical ______________________________________________________________________________________ 13 MAX4409 Table 1. Suggested Capacitor Manufacturers MAX4409 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense Application Circuit). Place capacitors C2 and C3 as close to the device as possible. Route PGND and all traces that carry switching transients away from SGND and the traces and components in the audio signal path. Ensure that the COM traces have the same trace length and width as the amplifier input and feedback traces. Route COM traces away from noisy signal paths. The thin QFN package features an exposed paddle that improves thermal efficiency of the package. However, the MAX4409 does not require additional heatsinking. Ensure that the exposed paddle is isolated from GND or VDD. Do not connect the exposed paddle to GND or VDD. EXAMPLE CONNECTION: VIN = VAUDIO VAUDIO GND NOISE COMPONENT IN OUTPUT = VNOISE/2 0.1Ω VNOISE VREF_IN = VNOISE/2 0.1Ω • 0.10Ω RESISTANCE FROM CABLE SCREEN • 0.10Ω RESISTANCE DUE TO GND CABLING AT RECEIVER • VNOISE REPRESENTS THE POTENTIAL DIFFERENCE BETWEEN THE TWO GNDS IMPROVEMENT FROM ADDING MAX4409 WITH SERIES RESISTANCE MAX4409 VIN = VAUDIO + (VNOISE x 0.98) VAUDIO GND NOISE COMPONENT IN OUTPUT = VNOISE /100 0.1Ω RESISTOR IS INSERTED BETWEEN THE JACK SLEEVE AND GND = 9.8Ω 9.8Ω VNOISE VREF_IN = (VNOISE x 0.99) 0.1Ω • 9.8Ω RESISTOR ADDS TO HP CROSSTALK, BUT DIFFERENTIAL SENSING AT THE JACK SLEEVE CORRECTS FOR THIS (ONE CHANNEL ONLY SHOWN). • CURRENT FLOW (IN SIGNAL CABLE SCREEN) DUE TO VNOISE IS GREATLY REDUCED. • NOISE COMPONENT IN THE RECEIVER OUTPUT IS REDUCED BY 34dB OVER THE PREVIOUS EXAMPLE WITH THE VALUES SHOWN. Figure 6. Common-Mode Noise Rejection 14 ______________________________________________________________________________________ 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense 1.8V to 3.6V LEFT CHANNEL AUDIO IN C3 1µF CIN 1µF RF 10kΩ RIN 10kΩ 2 9 12 10 PVDD SVDD SHDN INL SVDD OUTL 8 HEADPHONE JACK 3 C1P UVLO/ SHUTDOWN CONTROL SVSS CLICK-AND-POP SUPPRESSION CHARGE PUMP C1 1µF COM 1 R2 10kΩ SVDD 5 C1N OUTR 11 MAX4409 PVSS 6 SVSS PGND SGND 7 4 14 C2 1µF R1 10kΩ INR SVSS 13 RIGHT CHANNEL AUDIO IN CIN 1µF RIN 10kΩ RF 10kΩ *PIN NUMBERS ARE FOR THE TSSOP PACKAGE. ______________________________________________________________________________________ 15 MAX4409 Typical Application Circuit 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense MAX4409 System Diagram VDD 0.1µF 15kΩ 0.1µF 15kΩ INR VDD PVDD OUTR+ OUTR- 0.1µF AUX_IN 1µF BIAS 1µF OUT MAX4060 BIAS MAX9710 0.1µF 15kΩ CODEC SHDN OUTL- INL OUTL+ 15kΩ 2.2kΩ VCC 0.1µF IN+ VCC 10kΩ ININ- Q 0.1µF VCC 10kΩ MAX961 100kΩ 100kΩ Q IN+ 0.1µF 10kΩ VCC 1µF 1µF SHDN PVDD SVDD INL OUTL 10kΩ 10kΩ MAX4409 OUTR INR COM PVSS 10kΩ 10kΩ SVSS 1µF 1µF C1P CIN 1µF 10kΩ 16 ______________________________________________________________________________________ 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense N.C. PVDD COM SGND N.C. 20 19 18 17 16 TOP VIEW COM 1 14 SGND C1P 1 15 INR PGND 2 14 SHDN CIN 3 13 INL N.C. 4 12 N.C. C1N 5 10 INL PVSS 5 11 OUTR PVSS 6 9 SVDD SVSS 7 8 OUTL 6 7 8 9 10 N.C. SVSS N.C. OUTL SVDD MAX4409 PVDD 2 13 INR C1P 3 12 SHDN PGND 4 MAX4409 11 OUTR TSSOP THIN QFN Chip Information TRANSISTOR COUNT: 4295 PROCESS: BiCMOS ______________________________________________________________________________________ 17 MAX4409 Pin Configurations 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. 24L QFN THIN.EPS MAX4409 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense PACKAGE OUTLINE 12, 16, 20, 24L THIN QFN, 4x4x0.8mm 21-0139 C 1 2 PACKAGE OUTLINE 12, 16, 20, 24L THIN QFN, 4x4x0.8mm 21-0139 18 C 2 2 ______________________________________________________________________________________ 80mW, DirectDrive, Stereo Headphone Amplifier with Common-Mode Sense TSSOP4.40mm.EPS 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19 © 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX4409 Package Information (continued) (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.