19-3963; Rev 1; 7/09 KIT ATION EVALU E L B A AVAIL 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown The MAX9728A/MAX9728B stereo headphone amplifiers are designed for display and notebook applications or portable equipment where board space is at a premium. These devices use a unique, patented DirectDrive™ architecture to produce a ground-referenced output from a single supply, eliminating the need for large DC-blocking capacitors, saving cost, board space, and component height. The MAX9728A offers an externally adjustable gain, while the MAX9728B has an internally preset gain of -1.5V/V. The MAX9728A/ MAX9728B deliver up to 60mW per channel into a 32Ω load and have low 0.02% THD+N. An 80dB at 1kHz power-supply rejection ratio (PSRR) allows these devices to operate from noisy digital supplies without an additional linear regulator. Comprehensive clickand-pop circuitry suppresses audible clicks and pops on startup and shutdown. The MAX9728A/MAX9728B operate from a single 4.5V to 5.5V supply, consume only 3.5mA of supply current, feature short-circuit and thermal-overload protection, and are specified over the extended -40°C to +85°C temperature range. The devices are available in tiny 12pin Thin QFN (3mm x 3mm x 0.8mm) and 14-pin TSSOP packages (5mm x 4.4mm x 1.1mm). Applications Features ♦ No Bulky DC-Blocking Capacitors Required ♦ Low-Power Shutdown Mode, < 0.1µA ♦ Adjustable Gain (MAX9728A) or Fixed -1.5V/V Gain (MAX9728B) ♦ Low 0.02% THD+N ♦ High PSRR (80dB at 1kHz) Eliminates LDO ♦ Integrated Click-and-Pop Suppression ♦ 4.5V to 5.5V Single-Supply Operation ♦ Low Quiescent Current (3.5mA) ♦ Available in Space-Saving Packages 12-Pin Thin QFN (3mm x 3mm x 0.8mm) 14-Pin TSSOP (5mm x 4.4mm x 1.1mm) Ordering Information PART GAIN (V/V) PIN-PACKAGE MAX9728AETC+ Adj. 12 TQFN-EP* MAX9728AEUD+ Adj. 14 TSSOP MAX9728BETC+ -1.5 12 TQFN-EP* MAX9728BEUD+ -1.5 14 TSSOP TOP MARK ABC — ABD — Notebook PCs CRT TVs Note: All devices specified over the -40°C to +85°C operating range. DVD Players Multimedia Monitors +Denotes lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. LCD/PDP Displays Pin Configurations appear at end of data sheet. Block Diagrams MAX9728B MAX9728A LEFT AUDIO INPUT SHDN RIGHT AUDIO INPUT DirectDrive OUTPUTS ELIMINATE DC-BLOCKING CAPACITORS LEFT AUDIO INPUT DirectDrive OUTPUTS ELIMINATE DC-BLOCKING CAPACITORS SHDN RIGHT AUDIO INPUT FIXED GAIN ELIMINATES EXTERNAL RESISTOR NETWORK ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX9728A/MAX9728B General Description MAX9728A/MAX9728B 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown ABSOLUTE MAXIMUM RATINGS VDD to GND ..............................................................-0.3V to +6V PVSS to SVSS .........................................................-0.3V to +0.3V PGND to SGND .....................................................-0.3V to +0.3V C1P to PGND..............................................-0.3V to (VDD + 0.3V) C1N to PGND............................................(PVSS - 0.3V) to +0.3V PVSS and SVSS to PGND..........................................-6V to +0.3V IN_ to SGND (MAX9728A)..........................-0.3V to (VDD + 0.3V) IN_ to SGND (MAX9728B) .............(SVSS - 0.3V) to (VDD + 0.3V) OUT_ to SVSS (Note 1) ....-0.3V to Min (VDD - SVSS + 0.3V, +9V) OUT_ to VDD (Note 2) ......+0.3V to Max (SVSS - VDD - 0.3V, -9V) SHDN to _GND.........................................................-0.3V to +6V OUT_ Short Circuit to GND ........................................Continuous Short Circuit between OUTL and OUTR ....................Continuous Continuous Input Current into PVSS ..................................260mA Continuous Input Current (any other pin) .........................±20mA Continuous Power Dissipation (TA = +70°C) 12-Pin TQFN (derate 14.7mW/°C above +70°C) .........1177mW 14-Pin TSSOP (derate 9.1mW/°C above +70°C) ...........727mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Junction Temperature ......................................................+150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: OUTR and OUTL should be limited to no more than 9V above SVSS, or above VDD + 0.3V, whichever limits first. Note 2: OUTR and OUTL should be limited to no more than 9V below VDD, or below SVSS - 0.3V, whichever limits first. 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 = 5V, PGND = SGND, SHDN = 5V, C1 = C2 = 1µF, RL = ∞, resistive load reference to ground; for MAX9728A gain = -1.5V/V (RIN = 20kΩ, RF = 30kΩ); for MAX9728B gain = -1.5V/V (internally set), TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C, unless otherwise noted.) (Note 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 5.5 V 3.5 5.5 mA <0.1 1 µA GENERAL Supply Voltage Range VDD Quiescent Current ICC Shutdown Current ISHDN Shutdown to Full Operation RIN Output Offset Voltage VOS PSRR Output Power POUT Voltage Gain AV Channel-to-Channel Gain Tracking Total Harmonic Distortion Plus Noise 2 SHDN = SGND = PGND tSON Input Impedance Power-Supply Rejection Ratio 4.5 THD+N 180 MAX9728B, measured at IN_ 15 19 25 kΩ ±1.5 ±10 mV VDD = 4.5V to 5.5V 86 f = 1kHz, 100mVP-P 80 f = 20kHz, 100mVP-P 65 RL = 32Ω, THD+N = 1% 30 RL = 16Ω, THD+N = 1% MAX9728B (Note 4) µs dB 63 mW 42 -1.52 -1.5 MAX9728B ±0.15 RL = 1kΩ, VOUT = 2VRMS, fIN = 1kHz 0.003 RL = 32Ω, POUT = 50mW, fIN = 1kHz 0.02 RL = 16Ω, POUT = 35mW, fIN = 1kHz 0.04 _______________________________________________________________________________________ -1.48 V/V % % 60mW, DirectDrive, Stereo Headphone Amplifier with Shutdown (VDD = 5V, PGND = SGND, SHDN = 5V, C1 = C2 = 1µF, RL = ∞, resistive load reference to ground; for MAX9728A gain = -1.5V/V (RIN = 20kΩ, RF = 30kΩ); for MAX9728B gain = -1.5V/V (internally set), TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C, unless otherwise noted.) (Note 3) PARAMETER Signal-to-Noise Ratio SYMBOL SNR Slew Rate SR Capacitive Drive CL Crosstalk Charge-Pump Oscillator Frequency Click-and-Pop Level CONDITIONS TYP RL = 1kΩ, VOUT = 2VRMS BW = 22Hz to 22kHz 102 A-weighted 105 RL = 32Ω, POUT = 50mW BW = 22Hz to 22kHz 98 A-weighted 101 MAX UNITS dB 0.5 V/µs No sustained oscillations 100 pF L to R, R to L, f = 10kHz, RL = 16Ω, POUT = 15mW -70 dB fOSC KCP MIN 190 Into shutdown RL = 32Ω, peak voltage, A-weighted, 32 samples per Out of second (Note 5) shutdown 270 400 kHz -67 dB -64 DIGITAL INPUTS (SHDN) Input Voltage High VINH Input Voltage Low VINL Input Leakage Current 2 V 0.8 V ±1 µA Note 3: All specifications are 100% tested at TA = +25°C; temperature limits are guaranteed by design. Note 4: Gain for the MAX9728A is adjustable. Note 5: Test performed with a 32Ω resistive load connected to GND. Mode transitions are controlled by SHDN. KCP level is calculated as 20log[(peak voltage during mode transition, no input signal)/(peak voltage under normal operation at rated power level)]. Units are expressed in dB. _______________________________________________________________________________________ 3 MAX9728A/MAX9728B ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VDD = 5V, PGND = SGND = 0V, SHDN = VDD, C1 = C2 = 1µF, RL = ∞, gain = -1.5V/V (RIN = 20kΩ, RF = 30kΩ for the MAX9728A), THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, TA = +25°C, unless otherwise noted.) VDD = 5V RL = 16Ω 10 1 MAX9728A/28B toc02 100 MAX9728A/28B toc01 100 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER VDD = 5V RL = 32Ω 10 MAX9728A/28B toc03 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER VDD = 5V RL = 16Ω POUT = 20mW fIN = 1kHz 0.1 THD+N (%) THD+N (%) 1 fIN = 1kHz 0.1 0.01 0.01 fIN = 10kHz fIN = 20Hz fIN = 20Hz 0.001 0.001 0.001 40 60 80 100 0 OUTPUT POWER (mW) 80 POUT = 30mW 0.01 POUT = 50mW THD+N = 10% 60 50 30 100 1k FREQUENCY (Hz) 10k 100k 100 1k 10k 100k FREQUENCY (Hz) OUTPUT POWER vs. SUPPLY VOLTAGE THD+N = 1% 20 fIN = 1kHz RL = 16Ω 120 THD+N = 10% 100 80 60 40 THD+N = 1% 20 0 0.001 10 10 120 40 10 4 100 70 OUTPUT POWER (mW) 0.1 60 OUTPUT POWER vs. SUPPLY VOLTAGE MAX9728A/28B toc04 VDD = 5V RL = 32Ω 40 OUTPUT POWER (mW) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY 1 20 OUTPUT POWER (mW) 20 MAX9728A/28B toc05 0 POUT = 37mW 0.01 fIN = 10kHz MAX9728A/28B toc06 THD+N (%) 0.1 1 THD+N (%) MAX9728A/MAX9728B 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown fIN = 1kHz RL = 32Ω 0 4.5 5.0 SUPPLY VOLTAGE (V) 5.5 4.5 5.0 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 5.5 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown POWER-SUPPLY REJECTION RATIO vs. FREQUENCY THD+N = 10% 70 50 40 -60 -80 30 POUT = 15mW RL = 16Ω -20 CROSSTALK (dB) -40 60 -40 -60 LEFT TO RIGHT -80 THD+N = 1% 20 -100 VDD = 5V fIN = 1kHz 10 10 100 -120 10 1000 RIGHT TO LEFT -100 -120 0 100 1k 10k 100k 10 100 1k 10k FREQUENCY (Hz) FREQUENCY (Hz) OUTPUT POWER vs. LOAD RESISTANCE AND CHARGE-PUMP CAPACITOR SIZE SUPPLY CURRENT vs. SUPPLY VOLTAGE SHUTDOWN CURRENT vs. SUPPLY VOLTAGE 50 C1 = C2 = 0.47μF 40 VDD = 5V fIN = 1kHz THD+N = 1% 30 3.40 3.35 3.30 50 250 100 200 150 LOAD RESISTANCE (Ω) 300 8 7 6 5 4 3 1 NO LOAD INPUTS GROUND 3.20 0 9 2 3.25 20 MAX9728A/28B toc12 3.45 100k 10 SHUTDOWN CURRENT (nA) 60 MAX9728A/28B toc11 C1 = C2 = 1μF 70 3.50 SUPPLY CURRENT (mA) C1 = C2 = 2.2μF MAX9728A/28B toc10 LOAD RESISTANCE (Ω) 80 OUTPUT POWER (mW) RL = 32Ω VDD = 5V -20 PSRR (dB) OUTPUT POWER (mW) 80 CROSSTALK vs. FREQUENCY 0 MAX9728A/28B toc09 90 0 MAX9728A/28B toc07 100 MAX9728A/28B toc08 OUTPUT POWER vs. LOAD RESISTANCE NO LOAD INPUTS GROUND 0 4.5 5.0 SUPPLY VOLTAGE (V) 5.5 4.5 5.0 5.5 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 5 MAX9728A/MAX9728B Typical Operating Characteristics (continued) (VDD = 5V, PGND = SGND = 0V, SHDN = VDD, C1 = C2 = 1µF, RL = ∞, gain = -1.5V/V (RIN = 20kΩ, RF = 30kΩ for the MAX9728A), THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VDD = 5V, PGND = SGND = 0V, SHDN = VDD, C1 = C2 = 1µF, RL = ∞, gain = -1.5V/V (RIN = 20kΩ, RF = 30kΩ for the MAX9728A), THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, TA = +25°C, unless otherwise noted.) ENTERING SHUTDOWN VSHDN 5V/div MAX9728A/28B toc14 EXITING SHUTDOWN MAX9728A/28B toc13 MAX9728A/MAX9728B 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown VSHDN 5V/div VIN_ 1V/div VIN_ 1V/div VOUT_ 500mV/div VOUT_ 500mV/div 40μs/div 20μs/div Pin Description PIN 6 NAME FUNCTION TQFN TSSOP 1 3 C1P 2 4 PGND 3 5 C1N Flying Capacitor Negative Terminal. Connect a 1µF ceramic capacitor from C1P to C1N. 4 7 PVSS Charge-Pump Output. Connect to SVSS and bypass with a 1µF ceramic capacitor to PGND. 5 8 SHDN Active-Low Shutdown Input 6 9 INL 7 10 SGND 8 11 INR Flying Capacitor Positive Terminal. Connect a 1µF ceramic capacitor from C1P to C1N. Power Ground. Connect to SGND. Left-Channel Input Signal Ground. Connect to PGND. Right-Channel Input 9 12 SVSS Amplifier Negative Supply. Connect to PVSS. 10 14 OUTR Right-Channel Output 11 1 OUTL Left-Channel Output 12 2 VDD — 6,13 N.C. EP — EP Positive Power-Supply Input. Bypass with a 1µF capacitor to PGND. No Connection. Not internally connected. Exposed Paddle. Leave this connection floating or connect it to SVSS. _______________________________________________________________________________________ 60mW, DirectDrive, Stereo Headphone Amplifier with Shutdown The MAX9728A/MAX9728B stereo headphone amplifiers feature Maxim’s patented DirectDrive architecture, eliminating the large output-coupling capacitors required by conventional single-supply headphone amplifiers. The device consists of two 60mW Class AB headphone amplifiers, undervoltage lockout (UVLO)/shutdown control, charge pump, and comprehensive click-and-pop suppression circuitry (see the Functional Diagram/Typical Operating Circuits). The charge pump inverts the positive supply (VDD), creating a negative supply (PVSS). The headphone amplifiers operate from these bipolar supplies with their outputs biased about PGND (Figure 1). The benefit of this PGND bias is that the amplifier outputs do not have a DC component. The large DC-blocking capacitors required with conventional headphone amplifiers are unnecessary, conserving board space, reducing system cost, and improving frequency response. The MAX9728A/MAX9728B feature an undervoltage lockout that prevents operation from an insufficient power supply and click-and-pop suppression that eliminates audible transients on startup and shutdown. The MAX9728A/MAX9728B also feature thermal-overload and short-circuit protection. DirectDrive Conventional single-supply headphone amplifiers have their outputs biased about a nominal DC voltage (typically half the supply) for maximum dynamic range. Largecoupling 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 amplifier. Maxim’s patented DirectDrive architecture uses a charge pump to create an internal negative supply voltage, allowing the MAX9728A/MAX9728B outputs to be biased about GND. With no DC component, there is no need for the large DC-blocking capacitors. The MAX9728A/MAX9728B charge pumps require two small ceramic capacitors, conserving board space, reducing cost, and improving the frequency response of the headphone amplifier. See the Output Power vs. Load Resistance and Charge-Pump Capacitor Size graph in the Typical Operating Characteristics for details of the possible capacitor sizes. There is a low DC voltage on the amplifier outputs due to amplifier offset. However, the offsets of the MAX9728A/MAX9728B are typically 1.5mV, which, when combined with a 32Ω load, results in less than 47µA of DC current flow to the headphones. MAX9728A/MAX9728B Detailed Description VOUT VDD VDD VDD/2 GND CONVENTIONAL DRIVER-BIASING SCHEME VOUT VDD GND 2VDD -VDD DirectDrive BIASING SCHEME Figure 1. Conventional Driver Output Waveform vs. MAX9728A/MAX9728B Output Waveform Charge Pump The MAX9728A/MAX9728B feature a low-noise charge pump. The 270kHz switching frequency is well beyond the audio range and does not interfere with audio signals. The switch drivers feature a controlled switching speed that minimizes noise generated by turn-on and turn-off transients. The di/dt noise caused by the parasitic bond wire and trace inductance is minimized by limiting the switching speed of the charge pump. Although not typically required, additional high-frequency noise attenuation can be achieved by increasing the value of C2 (see the Functional Diagram/Typical Operating Circuits). Click-and-Pop Suppression In conventional single-supply audio amplifiers, the output-coupling capacitor contributes significantly to audible clicks and pops. Upon startup, the amplifier charges the coupling capacitor to its bias voltage, typically half the supply. Likewise, on shutdown, the capacitor is discharged. This results in a DC shift across the capacitor, which appears as an audible transient at the speaker. _______________________________________________________________________________________ 7 MAX9728A/MAX9728B 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown Since the MAX9728A/MAX9728B do not require outputcoupling capacitors, this problem does not arise. Additionally, the MAX9728A/MAX9728B feature extensive click-and-pop suppression that eliminates any audible transient sources internal to the device. Typically, the output of the device driving the MAX9728A/MAX9728B has a DC bias of half the supply voltage. At startup, the input-coupling capacitor is charged to the preamplifier’s DC-bias voltage through the input and feedback resistors of the MAX9728A/ MAX9728B, resulting in a DC shift across the capacitor and an audible click/pop. Delay the rise of SHDN 4 to 5 time constants based on RIN and CIN, relative to the startup of the preamplifier, to eliminate clicks-and-pops caused by the input filter. Shutdown The MAX9728A/MAX9728B feature a < 0.1µA, lowpower shutdown mode that reduces quiescent current consumption and extends battery life for portable applications. Drive SHDN low to disable the amplifiers and the charge pump. In shutdown mode, the amplifier output impedance is set to 14kΩ||RF (RF is 30kΩ for the MAX9728B). The amplifiers and charge pump are enabled once SHDN is driven high. 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: PDISSPKG(MAX) = TJ(MAX) − TA 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 Thin QFN package is +68°C/W, and +110°C/W for the TSSOP package. The MAX9728A/MAX9728B have two power dissipation sources; a charge pump and the two output amplifiers. If power dissipation for a given application exceeds the maximum allowed for a particular package, reduce VDD, increase load impedance, decrease the ambient temperature, or add heatsinking to the device. Large 8 output, supply, and ground traces decrease θJA, allowing more heat to be transferred from the package to the surrounding air. Thermal-overload protection limits total power dissipation in the MAX9728A/MAX9728B. When the junction temperature exceeds +150°C, the thermal-protection circuitry disables the amplifier output stage. The amplifiers are enabled once the junction temperature cools by approximately 12°C. This results in a pulsing output under continuous thermal-overload conditions. Output Dynamic Range Dynamic range is the difference between the noise floor of the system and the output level at 1% THD+N. Determine the system’s dynamic range before setting the maximum output gain. Output clipping occurs if the output signal is greater than the dynamic range of the system. The DirectDrive architecture of the MAX9728A/ MAX9728B has increased the dynamic range compared to other single-supply amplifiers. Maximum Output Swing Internal device structures limit the maximum voltage swing of the MAX9728A/MAX9728B. The output must not be driven such that the peak output voltage exceeds the opposite supply voltage by 9V. For example, if VDD = 5V, the charge pump sets PVSS = -5V. Therefore, the peak output swing must be less than ±4V to prevent exceeding the absolute maximum ratings. Component Selection Input-Coupling Capacitor The input capacitor (CIN), in conjunction with the input resistor (RIN), forms a highpass filter that removes the DC bias from an incoming signal (see the Functional Diagram/Typical Operating Circuits). The AC-coupling capacitor allows the device 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 Choose the CIN such that f-3dB is well below the lowest frequency of interest. Setting f-3dB too high affects the device’s low-frequency response. Use capacitors whose dielectrics have low-voltage coefficients, such as tantalum or aluminum electrolytic. Capacitors with high-voltage coefficients, such as ceramics, can result in increased distortion at low frequencies. _______________________________________________________________________________________ 60mW, DirectDrive, Stereo Headphone Amplifier with Shutdown switching transients. Bypass VDD with C3, the same value as C1, and place it physically close to the VDD and PGND pins. Amplifier Gain The gain of the MAX9728B amplifier is internally set to -1.5V/V. All gain-setting resistors are integrated into the device, reducing external component count. The internally set gain, in combination with DirectDrive, results in a headphone amplifier that requires only five small capacitors to complete the amplifier circuit: two for the charge pump, two for audio input coupling, and one for power-supply bypassing (see the Functional Diagram/Typical Operating Circuits). Flying Capacitor (C1) The value of the flying capacitor (see the Functional Diagram/Typical Operating Circuits) affects the charge pump’s load regulation and output resistance. 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. Load Resistance and Charge-Pump Capacitor Size graph in the Typical Operating Characteristics. Above 1µF, the on-resistance of the switches and the ESR of C1 and C2 dominate. The gain of the MAX9728A amplifier is set externally as shown in Figure 2, the gain is: AV = -RF/RIN (V/V) Choose feedback resistor values in the tens of kΩ range. Lower values may cause excessive power dissipation and require impractically small values of RIN for large gain settings. The high-impedance state of the outputs can also be degraded during shutdown mode if an inadequate feedback resistor is used since the equivalent output impedance during shutdown is 14kΩ||RF (RF is equal to 30kΩ for the MAX9728B). The source resistance of the input device may also need to be taken into consideration. Since the effective value of RIN is equal to the sum of the source resistance of the input device and the value of the input resistor connected to the inverting terminal of the headphone amplifier (20kΩ for the MAX9728B), the overall closed-loop gain of the headphone amplifier can be reduced if the input resistor is not significantly larger than the source resistance of the input device. Hold Capacitor (C2) The hold capacitor value (see the Functional Diagram/Typical Operating Circuits) 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. Load Resistance and Charge-Pump Capacitor Size graph in the Typical Operating Characteristics. Power-Supply Bypass Capacitor (C3) The power-supply bypass capacitor (see the Functional Diagram/Typical Operating Circuits) lowers the output impedance of the power supply, and reduces the impact of the MAX9728A/MAX9728Bs’ charge-pump Table 1. Suggested Capacitor Manufacturers SUPPLIER Taiyo Yuden PHONE FAX 800-348-2496 847-925-0899 WEBSITE www.t-yuden.com TDK 847-803-6100 847-390-4405 www.component.tdk.com Murata 770-436-1300 770-436-3030 www.murata.com _______________________________________________________________________________________ 9 MAX9728A/MAX9728B Charge-Pump Capacitor Selection Use ceramic capacitors with a low ESR for optimum performance. For optimal performance over the extended temperature range, select capacitors with an X7R dielectric. Table 1 lists suggested manufacturers. Lineout Amplifier and Filter Block To suppress this noise, and to provide a 2VRMS standard audio output level from a single 5V supply, the MAX9728A can be configured as a line driver and active lowpass filter. Figure 4 shows the MAX9728A connected as 2-pole Rauch/multiple feedback filter with a passband gain of 6dB and a -3dB (below passband) cutoff frequency of approximately 27kHz (see Figure 5 for the Gain vs. Frequency plot). 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 PVSS to SVSS and bypass with a 1µF capacitor. Place the power-supply bypass capacitor and the charge-pump hold capacitor as close to the MAX9728 as possible. Route PGND and all traces that carry switching transients away from SGND and the audio signal path. The thin QFN package features an exposed paddle that improves thermal efficiency. Ensure that the exposed paddle is electrically isolated from PGND, SGND, and VDD. Connect the exposed paddle to SVSS only when the board layout dictates that the exposed paddle cannot be left floating. 10 RF MAX9728A LEFT AUDIO INPUT RIN RIGHT AUDIO INPUT RIN INL OUTL OUTR INR RF Figure 2. Gain Setting for the MAX9728A RMS OUTPUT VOLTAGE vs. SUPPLY VOLTAGE 4.1 MAX9728A/28B fig03 The MAX9728A can be used as an audio line driver capable of providing 2VRMS into 10kΩ loads with a single 5V supply (see Figure 3 for the RMS Output Voltage vs. Supply Voltage plot). 2VRMS is a popular audio line level, first used in CD players, but now common in DVD and set-top box (STB) interfacing standards. A 2VRMS sinusoidal signal equates to approximately 5.7VP-P, which means that the audio system designer cannot simply run the lineout stage from a (typically common) 5V supply—the resulting output swing would be inadequate. A common solution to this problem is to use op amps driven from split supplies (±5V typically), or to use a high-voltage supply rail (9V to 12V). This can mean adding extra cost and complexity to the system power supply to meet this output level requirement. Having the ability to derive 2VRMS from a 5V supply can often simplify power-supply design in some systems. When the MAX9728A is used as a line driver to provide outputs that feed stereo equipment (receivers, STBs, notebooks, and desktops) with a digital-to-analog converter (DAC) used as an audio input source, it is often desirable to eliminate any high-frequency quantization noise produced by the DAC output before it reaches the load. This high-frequency noise can cause the input stages of the line-in equipment to exceed slew-rate limitations or create excessive EMI emissions on the cables between devices. fIN = 1kHz 3.9 RMS OUTPUT VOLTAGE (V) MAX9728A/MAX9728B 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown RL = 10kΩ 1% THD+N 3.7 3.5 RL = 1kΩ 1% THD+N 3.3 3.1 2.9 2.7 2.5 4.5 5.0 SUPPLY VOLTAGE (V) Figure 3. RMS Output Voltage vs. Supply Voltage ______________________________________________________________________________________ 5.5 60mW, DirectDrive, Stereo Headphone Amplifier with Shutdown MAX9728A/MAX9728B 15kΩ 220pF LEFT AUDIO INPUT 1μF 7.5kΩ 7.5kΩ MAX9728A INL OUTL 1.2nF STEREO DAC LINE-IN DEVICE 10kΩ 1.2nF RIGHT AUDIO INPUT 1μF OUTR 7.5kΩ 7.5kΩ INR 10kΩ 220pF 15kΩ Figure 4. MAX9728A Line-Out Amplifier and Filter Block Configuration MAX9728A ACTIVE FILTER GAIN vs. FREQUENCY 10 RL = 10kΩ 5 0 GAIN (dB) -5 -10 -15 -20 -25 -30 -35 1k 10k 100k 1M FREQUENCY (Hz) Figure 5. Frequency Response of Active Filter of Figure 4 ______________________________________________________________________________________ 11 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown MAX9728A/MAX9728B System Diagram VDD 0.1μF 15kΩ 1μF 15kΩ INR VDD PVDD BIAS OUTR+ OUTR- 1μF MAX9710 GND PGND MUTE 0.1μF 15kΩ OUTL- SHDN OUTL+ INL VDD 15kΩ μCONTROLLER 100kΩ 100kΩ 0.1μF STEREO DAC OUTL SHDN O.47μF MAX9728B OUTR INL SGND O.47μF INR PGND VDD PVSS 1μF SVSS C1P C1N VDD 1μF 1μF 12 ______________________________________________________________________________________ 60mW, DirectDrive, Stereo Headphone Amplifier with Shutdown 4.5V TO 5.5V ON C3 1μF OFF CIN R IN* 0.47μF 20kΩ LEFT AUDIO INPUT RF* 30kΩ 12 (2) 5 (8) 6 (9) VDD SHDN INL VDD 11 OUTL (1) HEADPHONE JACK 1 (3) C1P SVSS UVLO/ SHUTDOWN CONTROL CLICK-AND-POP SUPPRESSION CHARGE PUMP C1 1μF SGND VDD 3 (5) C1N OUTR 10 (14) MAX9728A PVSS 4 (7) SVSS PGND 2 9 (12) (4) C2 1μF SVSS SGND 7 (10) RIGHT AUDIO INPUT CIN RIN* 0.47μF 20kΩ INR 8 (11) RF* 30kΩ *RIN AND RF VALUES ARE CHOSEN FOR A GAIN -1.5V/V. ( ) TSSOP PACKAGE ______________________________________________________________________________________ 13 MAX9728A/MAX9728B Functional Diagram/Typical Operating Circuits 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown MAX9728A/MAX9728B Functional Diagram/Typical Operating Circuits (continued) 4.5V TO 5.5V ON C3 1μF OFF LEFT AUDIO INPUT CIN 0.47μF 12 (2) 5 (8) 6 (9) VDD SHDN INL RIN* 20kΩ RF* 30kΩ VDD 11 OUTL (1) HEADPHONE JACK 1 (3) C1P VSS UVLO/ SHUTDOWN CONTROL CLICK-AND-POP SUPPRESSION CHARGE PUMP C1 1μF SGND VDD 3 (5) C1N MAX9728B OUTR RIN 20kΩ 10 (14) SVSS RF 30kΩ PVSS SVSS PGND SGND 4 (7) C2 1μF 9 (12) 2 (4) 7 (10) INR 8 (11) CIN RIGHT 0.47μF AUDIO INPUT ( ) TSSOP PACKAGE 14 ______________________________________________________________________________________ 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown SVSS INR SGND TOP VIEW 9 8 7 TOP VIEW + OUTL 1 OUTR 10 6 MAX9728A MAX9728B OUTL 11 INL 5 SHDN 4 PVSS VDD 2 13 N.C. C1P 3 12 SVSS PGND 4 C1N 5 VDD 12 1 2 3 C1P PGND C1N + 14 OUTR MAX9728A MAX9728B 11 INR 10 SGND N.C. 6 9 INL PVSS 7 8 SHDN TSSOP TQFN Chip Information TRANSISTOR COUNT: 993 PROCESS: BiCMOS ______________________________________________________________________________________ 15 MAX9728A/MAX9728B Pin Configurations Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 12 TQFN-EP T1233-1 21-0136 14 TSSOP U14-1 21-0066 (NE - 1) X e E MARKING 12x16L QFN THIN.EPS MAX9728A/MAX9728B 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown E/2 D2/2 (ND - 1) X e D/2 AAAA e CL D D2 k CL b 0.10 M C A B E2/2 L E2 0.10 C C L C L 0.08 C A A2 A1 L L e e PACKAGE OUTLINE 8, 12, 16L THIN QFN, 3x3x0.8mm 21-0136 16 ______________________________________________________________________________________ I 1 2 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown PKG 8L 3x3 12L 3x3 16L 3x3 REF. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. A 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 b 0.25 0.30 0.35 0.20 0.25 0.30 0.20 0.25 0.30 D 2.90 3.00 3.10 2.90 3.00 3.10 2.90 3.00 3.10 E 2.90 3.00 3.10 2.90 3.00 3.10 2.90 3.00 3.10 e L 0.65 BSC. 0.35 0.55 0.50 BSC. 0.50 BSC. 0.75 0.45 0.55 0.65 0.30 0.40 N 8 12 16 ND 2 3 4 NE 2 3 4 0 A1 A2 k 0.05 0.02 0 - 0.05 0 - 0.25 - 0.02 0.50 0.05 0.20 REF 0.20 REF 0.20 REF 0.25 0.02 EXPOSED PAD VARIATIONS - 0.25 - PKG. CODES TQ833-1 D2 E2 PIN ID JEDEC MIN. NOM. MAX. MIN. NOM. MAX. 0.25 0.70 1.25 0.25 0.70 1.25 0.35 x 45° WEEC WEED-1 T1233-1 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° T1233-3 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° WEED-1 T1233-4 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° WEED-1 T1633-2 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° WEED-2 T1633F-3 0.65 0.80 0.95 0.65 0.80 0.95 0.225 x 45° WEED-2 T1633FH-3 0.65 0.80 0.95 0.65 0.80 0.95 0.225 x 45° WEED-2 T1633-4 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° WEED-2 T1633-5 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° WEED-2 - NOTES: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES. N IS THE TOTAL NUMBER OF TERMINALS. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.20 mm AND 0.25 mm FROM TERMINAL TIP. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS . DRAWING CONFORMS TO JEDEC MO220 REVISION C. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY. NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY. WARPAGE NOT TO EXCEED 0.10mm. PACKAGE OUTLINE 8, 12, 16L THIN QFN, 3x3x0.8mm 21-0136 I 2 2 ______________________________________________________________________________________ 17 MAX9728A/MAX9728B Package Information (continued) For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. Package Information (continued) TSSOP4.40mm.EPS For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. 18 ______________________________________________________________________________________ MAX9728A/MAX9728B MAX9728A/MAX9728B 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 0 1/06 Initial release — 1 7/09 Corrected top mark designations 1 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 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX9728A/MAX9728B Revision History