EVALUATION KIT AVAILABLE MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C General Description The MAX9723 stereo DirectDrive(R) headphone amplifier with BassMax and volume control is ideal for portable audio applications where space is at a premium and performance is essential. The MAX9723 operates from a single 1.8V to 3.6V power supply and includes features that reduce external component count, system cost, board space, and improves audio reproduction. The headphone amplifier uses Maxim's DirectDrive architecture that produces a ground-referenced output from a single supply, eliminating the need for large DCblocking capacitors. The headphone amplifiers deliver 62mW into a 16 load, feature low 0.006% THD+N, and high 90dB PSRR. The MAX9723 features Maxim's industry-leading click-and-pop suppression. The BassMax feature boosts the bass response of the amplifier, improving audio reproduction when using inexpensive headphones. The integrated volume control features 32 discrete volume levels, eliminating the need for an external potentiometer. BassMax and the volume control are enabled through the I2C/SMBusTM-compatible interface. Shutdown is controlled through either the hardware or software interfaces. The MAX9723 consumes only 3.7mA of supply current at 1.8V, provides short-circuit and thermal-overload protection, and is fully specified over the extended -40C to +85C temperature range. The MAX9723 is available in a tiny (2mm x 2mm x 0.62mm) 16-bump chip-scale package (UCSPTM) or 16-pin thin QFN (4mm x 4mm x 0.8mm) package. Applications PDA Audio Portable CD Players Mini Disc Players MP3-Enabled Cellular Phones MP3 Players Selector Guide 62mW, DirectDrive Headphone Amplifier Eliminates Bulky DC-Blocking Capacitors 1.8V to 3.6V Single-Supply Operation Integrated 32-Level Volume Control High 90dB PSRR at 1kHz Low 0.006% THD+N Industry-Leading Click-and-Pop Suppression 8kV HBM ESD-Protected Headphone Outputs Short-Circuit and Thermal-Overload Protection Low-Power Shutdown Mode (5A) Software-Enabled Bass Boost (BassMax) I2C/SMBus-Compatible Interface Available in Space-Saving, Thermally Efficient Packages: * 16-Bump UCSP (2mm x 2mm x 0.62mm) * 16-Pin Thin QFN (4mm x 4mm x 0.8mm) Ordering Information PART** TEMP RANGE MAX9723_EBE-T* -40C to +85C PINPKG PACKAGE CODE 16 UCSP-16 B16-1 MAX9723_ETE+ -40C to +85C 16 TQFN T1644-4 **Replace the `_' with the one-letter code that denotes the slave address and maximum programmable gain. See the Selector Guide. +Denotes a lead-free/RoHS-compliant package. *Future product--contact factory for availability. Pin Configurations appears at end of data sheet. Block Diagram 1.8V TO 3.6V SUPPLY SCL SDA PART SLAVE ADDRESS MAXIMUM GAIN (dB) MAX9723A 1001100 0 MAX9723B 1001101 0 MAX9723C 1001100 +6 MAX9723D 1001101 +6 DirectDrive is a registered trademark of Maxim Integrated Products, Inc. SMBus is a trademark of Intel Corp. UCSP is a trademark of Maxim Integrated Products, Inc. 19-3509; Rev 3; 7/14 Features I2C INTERFACE BBL OUTL INL INR VOLUME CONTROL MAX9723 BassMax OUTR BBR BassMax MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Absolute Maximum Ratings SGND to PGND .....................................................-0.3V to +0.3V VDD to PGND...........................................................-0.3V to +4V PVSS to SVSS.......................................................-0.3V to +0.3V C1P to PGND.............................................-0.3V to (VDD + 0.3V) C1N to PGND...........................................(PVSS - 0.3V) to +0.3V PVSS, SVSS to PGND..............................................+0.3V to -4V IN_ to SGND.................................(SVSS - 0.3V) to (VDD + 0.3V) SDA, SCL to PGND..................................................-0.3V to +4V SHDN to PGND..........................................-0.3V to (VDD + 0.3V) OUT_ to SGND............................................................-3V to +3V BB_ to SGND...............................................................-2V to +2V Duration of OUT_ Short Circuit to _GND ....................Continuous Continuous Current Into/Out of: VDD, C1P, PGND, C1N, PVSS, SVSS, or OUT_...........0.85A Any Other Pin................................................................20mA Continuous Power Dissipation (TA = +70C) 4 x 4 UCSP (derate 8.2mW/C above +70C)..........659.2mW 16-Pin Thin QFN (derate 16.9mW/C above +70C)....1349mW Operating Temperature Range.............................-40C to +85C Junction Temperature.......................................................+150C Storage Temperature Range .............................-65C to +150C Bump Temperature (soldering) Reflow ..........................................................................+230C Lead Temperature (soldering, 10s) .................................+300C Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Electrical Characteristics (VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1F, BB_ = 0V. gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where specified. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS GENERAL Supply Voltage Range VDD Quiescent Supply Current IDD Shutdown Supply Current IDD_SHDN 1.8 No load 4 VSHDN = 0V 5 3.6 V 6.5 mA 8.5 A Turn-On Time tON 200 s Turn-Off Time tOFF 35 s Thermal Shutdown Threshold TTHRES +143 C Thermal Shutdown Hysteresis THYST 12 C HEADPHONE AMPLIFIER Output Offset Voltage Input Resistance BBR, BBL Input Bias Current VOS RIN Measured between OUT_ and SGND (Note 2) Gain = 0dB, MAX9723A/ MAX9723B 0.7 Gain = +6dB, MAX9723C/ MAX9723D 0.8 5 17 27 k 10 100 nA All volume levels Power-Supply Rejection Ratio www.maximintegrated.com mV 10 IBIAS_BB DC, VDD = 1.8V to 3.6V PSRR (Note 2) 4.5 73 90 f = 217Hz, 100mVP-P ripple, VDD = 3.0V 87 f = 1kHz, 100mVP-P ripple, VDD = 3.0V 86 f = 20kHz, 100mVP-P ripple, VDD = 3.0V 61 dB Maxim Integrated 2 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Electrical Characteristics (continued) (VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1F, BB_ = 0V. gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where specified. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL Output Power Total Harmonic Distortion Plus Noise Maximum Gain POUT THD+N AMAX Signal-to-Noise Ratio SNR Slew Rate TYP MAX 59 RL = 16 (Note 5) 38 mW 60 RL = 16, POUT = 35mW, fIN = 1kHz 0.006 RL = 32, POUT = 45mW, fIN = 1kHz 0.004 MAX9723A/ MAX9723B Gain range bit 5 = 1 0 Gain range bit 5 = 0 -5 MAX9723C/ MAX9723D Gain range bit 5 = 1 +6 Gain range bit 5 = 0 +1 RL = 32, VOUT = 1VRMS BW = 22Hz to 22kHz 99 A-weighted 100 UNITS % dB dB dB 0.35 V/s No sustained oscillations 300 pF V = 0V, measured from OUT_ to ROUT_SHDN SHDN SGND 20 k VSHDN = 0V, measured from OUT_ to SGND 60 pF Output Capacitance in Shutdown COUT_SHDN Click/Pop Level KCP Charge-Pump Switching Frequency Crosstalk THD+N = 1%, fIN = 1kHz MIN RL = 32 SR Capacitive Drive Output Resistance in Shutdown CONDITIONS RL = 32, peak voltage, A-weighted, 32 samples per second (Notes 2, 4) MAX9723A/ MAX9723B MAX9723C/ MAX9723D Into shutdown -69 Out of shutdown -71 Into shutdown -70 Out of shutdown -69 fCP XTALK dB 505 L to or to L, f = 10kHz, VOUT = 1VP-P, RL = 32, both channels loaded 600 700 80 kHz dB DIGITAL INPUTS (SHDN, SDA, SCL) Input High Voltage VIH Input Low Voltage VIL 0.7 x VDD Input Leakage Current V 0.3 x VDD V P1 A 0.4 V 1 A DIGITAL OUTPUTS (SDA) Output Low Voltage VOL IOL = 3mA Output High Current IOH VSDA = VDD www.maximintegrated.com Maxim Integrated 3 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Timing Characteristics (VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1F, BB_ = 0V. gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where specified. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C, see Timing Diagram.) (Notes 1, 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 400 kHz Serial Clock Frequency fSCL 0 Bus Free Time Between a STOP and a START Condition tBUF 1.3 s START Condition Hold Time tHD:STA 0.6 s Low Period of the SCL Clock tLOW 1.3 s High Period of the SCL Clock tHIGH 0.6 s Setup Time for a Repeated START Condition tSU:STA 0.6 s Data Hold Time tHD:DAT 0 Data Setup Time tSU:DAT 100 0.9 s ns Maximum Rise Time of SDA and SCL Signals tr 300 ns Maximum Fall Time of SDA and SCL Signals tf 300 ns Setup Time for STOP Condition tSU:STO Pulse Width of Suppressed Spike Maximum Capacitive Load for Each Bus Line Note Note Note Note 0.6 s tSP 100 ns CL_BUS 400 pF 1: 2: 3: 4: All specifications are 100% tested at TA = +25C. Temperature limits are guaranteed by design. Inputs AC-coupled to SGND. Guaranteed by design. Headphone mode testing performed with a 32 resistive load connected to GND. Mode transitions are controlled by SHDN. The KCP level is calculated as: 20 x log [(level peak voltage during mode transition, no input signal)/(peak voltage under normal operation at rated power)]. Units are expressed in dB. Note 5: Output power MIN is specified at TA = +25C. www.maximintegrated.com Maxim Integrated 4 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Typical Operating Characteristics (VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1F, BB_ = 0V, gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where specified. Outputs in phase, both channels loaded. TA = +25C, unless otherwise noted.) (See Functional Diagram/Typical Operating Circuit) POUT = 10mW 0.01 0.1 POUT = 10mW 0.01 100 1k 0.1 POUT = 20mW POUT = 37mW POUT = 23mW 10k 100k 0.001 10 100 1k 10k 100k 0.001 10 100 1k 10k 100k FREQUENCY (Hz) FREQUENCY (Hz) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER POUT = 10mW 0.01 1 fIN = 20Hz 0.1 fIN = 1kHz fIN = 10kHz 0.01 VDD = 2.4V RL = 32 10 1 THD+N (%) 0.1 VDD = 2.4V RL = 16 10 100 MAX9723 toc05 100 MAX9723 toc04 VDD = 3V RL = 32 MAX9723 toc06 FREQUENCY (Hz) THD+N (%) THD+N (%) 1 10 VDD = 3V RL = 16 0.01 POUT = 25mW 0.001 1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9723 toc03 VDD = 2.4V RL = 32 THD+N (%) 0.1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9723 toc02 1 MAX9723 toc01 VDD = 2.4V RL = 16 THD+N (%) THD+N (%) 1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY fIN = 1kHz fIN = 20Hz 0.1 fIN = 10kHz 0.01 POUT = 30mW 1k 10k 100k 0.001 20 0 40 60 0.001 20 0 40 60 OUTPUT POWER (mW) OUTPUT POWER (mW) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER POWER DISSIPATION vs. OUTPUT POWER 1 fIN = 1kHz 0.1 fIN = 10kHz VDD = 3V RL = 32 10 1 fIN = 1kHz 0.1 fIN = 20Hz 0.01 fIN = 10kHz fIN = 20Hz 0.01 180 VDD = 2.4V fIN = 1kHz POUT = POUTL + POUTR OUTPUTS IN PHASE 160 POWER DISSIPATION (mW) 10 100 THD+N (%) VDD = 3V RL = 16 MAX9723 toc08 FREQUENCY (Hz) 100 THD+N (%) 100 140 RL = 16 MAX9723 toc09 10 MAX9723 toc07 0.001 120 100 RL = 32 80 60 40 20 0.001 0 20 40 60 OUTPUT POWER (mW) www.maximintegrated.com 80 100 0.001 0 20 40 60 OUTPUT POWER (mW) 80 100 0 0 20 40 60 80 OUTPUT POWER (mW) Maxim Integrated 5 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Typical Operating Characteristics (continued) (VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1F, BB_ = 0V, gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where specified. Outputs in phase, both channels loaded. TA = +25C, unless otherwise noted.) (See Functional Diagram/Typical Operating Circuit) 250 RL = 16 200 RL = 32 150 80 100 50 40 60 80 100 30 THD+N = 10% 60 THD+N = 1% 40 30 90 80 60 50 30 10 100 0 1k THD+N = 1% 40 20 10 THD+N = 10% 70 10 fIN = 1kHz RL = 16 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 LOAD RESISTANCE () SUPPLY VOLTAGE (V) OUTPUT POWER vs. SUPPLY VOLTAGE POWER-SUPPLY REJECTION RATIO vs. FREQUENCY 0 MAX9723 toc14 120 RL = 32 -10 -20 100 -30 PSRR (dB) THD+N = 10% 60 THD+N = 1% 40 fIN = 1kHz RL = 32 20 0 1k MAX9723 toc13 100 20 140 100 10 OUTPUT POWER vs. SUPPLY VOLTAGE VDD = 3V fIN = 1kHz 50 0 120 OUTPUT POWER vs. LOAD RESISTANCE 70 80 THD+N = 1% 20 LOAD RESISTANCE (W) 80 0 THD+N = 10% 40 OUTPUT POWER (mW) 90 OUTPUT POWER (mW) 50 MAX9723 toc15 20 OUTPUT POWER (mW) 0 100 OUTPUT POWER (mW) 60 10 MAX9723 toc12 0 VDD = 2.4V fIN = 1kHz 70 OUTPUT POWER (mW) VDD = 3V fIN = 1kHz POUT = POUTL + POUTR OUTPUTS IN PHASE MAX9723 toc10 POWER DISSIPATION (mW) 300 OUTPUT POWER vs. LOAD RESISTANCE MAX9723 toc11 POWER DISSIPATION vs. OUTPUT POWER 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 SUPPLY VOLTAGE (V) www.maximintegrated.com -40 -50 -60 -70 -80 -90 -100 10 100 1k 10k 100k FREQUENCY (Hz) Maxim Integrated 6 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Typical Operating Characteristics (continued) (VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1F, BB_ = 0V, gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where specified. Outputs in phase, both channels loaded. TA = +25C, unless otherwise noted.) (See Functional Diagram/Typical Operating Circuit) RIGHT TO LEFT A = 0dB -60 -80 10 1k 10 100 1k BASS BOOST FREQUENCY RESPONSE GAIN FLATNESS vs. FREQUENCY 10 R2 = 22k C3 = 0.1F NO LOAD R1 = 47k 1 10k 100k 10k 100k 0 AMPLITUDE (dB) -1 R2 = 10k C3 = 0.22F 5 0 -2 -3 -4 -5 BassMax DISABLED -6 100 1k 10k -7 100k 10 100 1k FREQUENCY (Hz) FREQUENCY (Hz) OUTPUT SPECTRUM vs. FREQUENCY CHARGE-PUMP OUTPUT VOLTAGE vs. OUTPUT CURRENT RL = 32 VDD = 3V fIN = 1kHz -50 -60 0 -70 -80 -90 -100 -110 -120 NO HEADPHONE LOAD CHARGE-PUMP LOAD CONNECTED BETWEEN PVSS AND PGND -0.5 -1.0 MAX9723 toc21 10 -40 -1.5 -2.0 -2.5 -3.0 -130 -140 -120 100k LEFT TO RIGHT A = -10dB FREQUENCY (Hz) 15 -10 -80 FREQUENCY (Hz) R2 = 36k C3 = 0.068F -5 AMPLITUDE (dBV) 10k OUTPUT VOLTAGE (V) AMPLITUDE (dB) 20 100 RIGHT TO LEFT A = -10dB -60 -100 LEFT TO RIGHT A = 0dB MAX9723 toc18 -120 -40 MAX9723 toc19 -100 MAX9723 toc20 CROSSTALK (dB) -40 VIN = 1VP-P RL = 32 A = -10dB -20 CROSSTALK (dB) VIN = 1VP-P RL = 32 A = 0dB -20 0 MAX9723 toc16 0 CROSSTALK vs. FREQUENCY MAX9723 toc17 CROSSTALK vs. FREQUENCY 0 5 10 FREQUENCY (kHz) www.maximintegrated.com 15 20 -3.5 0 25 50 75 100 125 150 175 200 OUTPUT CURRENT (mA) Maxim Integrated 7 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Typical Operating Characteristics (continued) (VDD = SHDN = 3V, PGND = SGND = 0V, C1 = C2 = 1F, BB_ = 0V, gain = 0dB, maximum volume, BassMax disabled. Load connected between OUT_ and SGND where specified. Outputs in phase, both channels loaded. TA = +25C, unless otherwise noted.) (See Functional Diagram/Typical Operating Circuit) C1 = C2 = 2.2F OUTPUT POWER (mW) 70 C1 = C2 = 1F 65 POWER-UP/POWER-DOWN WAVEFORM MAX9723 toc23 MAX9723 toc22 75 OUTPUT POWER vs. CHARGE-PUMP CAPACITANCE AND LOAD RESISTANCE VDD 2V/div 60 55 C1 = C2 = 0.68F 50 45 40 35 VOUT 10mV/div VDD = 3V fIN = 1kHz THD+N = 1% 20 10 30 40 50 20ms/div LOAD RESISTANCE () EXITING SHUTDOWN ENTERING SHUTDOWN MAX9723 toc25 MAX9723 toc24 VSHDN 2V/div VSHDN 2V/div VOUT_ 200mV/div SUPPLY CURRENT vs. SUPPLY VOLTAGE SHUTDOWN CURRENT vs. SUPPLY VOLTAGE 4.0 3.5 3.0 2.5 2.0 NO LOAD INPUTS GROUNDED 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 SUPPLY VOLTAGE (V) www.maximintegrated.com 8 MAX9723 toc27 20s/div MAX9723 toc26 40s/div 7 SHUTDOWN CURRENT (A) SUPPLY CURRENT (mA) 4.5 VOUT_ 200mV/div 6 5 4 3 2 1 0 NO LOAD INPUTS GROUNDED 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 SUPPLY VOLTAGE (V) Maxim Integrated 8 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Pin Description PIN BUMP THIN QFN UCSP 1 D1 2 3 NAME FUNCTION VDD Power-Supply Input. Bypass VDD to PGND with a 1F capacitor. C1 C1P Charge-Pump Flying Capacitor Positive Terminal B1 PGND 4 A1 C1N Charge-Pump Flying Capacitor Negative Terminal 5 B2 SCL Serial Clock Input. Connect a 10kI pullup resistor from SCL to VDD. 6 A2 PVSS Charge-Pump Output. Connect to SVSS. Bypass PVSS with a 1F capacitor to PGND. 7 A3 SDA Serial-Data Input. Connect a 10k pullup resistor from SDA to VDD. 8 B3 SHDN Shutdown. Drive SHDN low to disable the MAX9723. Connect SHDN to VDD while bit 7 is high for normal operation (see the Command Register section). Signal Ground. Connect to PGND. Power Ground. Connect to SGND. 9 A4 SGND 10 B4 INL Left-Channel Input 11 C4 INR Right-Channel Input 12 D4 SVSS Headphone Amplifier Negative Power-Supply Input. Connect to PVSS. 13 C3 BBR Right BassMax Input. Connect an external lowpass filter between OUTR and BBR to apply bass boost to the right-channel output. Connect BBR to SGND if BassMax is not used (see the BassMax (Bass Boost) section). 14 D3 OUTR Right Headphone Output 15 D2 OUTL Left Headphone Output 16 C2 BBL Left BassMax Input. Connect an external lowpass filter between OUTL and BBL to apply bass boost to the left-channel output. Connect BBL to SGND if BassMax is not used (see the BassMax (Bass Boost) section). EP -- EP Exposed Paddle. Connect EP to SVSS or leave unconnected. Detailed Description The MAX9723 stereo headphone amplifier features Maxim's DirectDrive architecture, eliminating the large output-coupling capacitors required by conventional single-supply headphone amplifiers. The MAX9723 consists of two 62mW Class AB headphone amplifiers, hardware/ software shutdown control, inverting charge pump, integrated 32-level volume control, BassMax circuitry, comprehensive click-and-pop suppression circuitry, and an I2C-compatible interface (see the Functional Diagram/ Typical Operating Circuit). A negative power supply (PVSS) is created internally by inverting the positive supply (VDD). Powering the amplifiers from VDD and PVSS increases the dynamic range of the amplifiers to almost twice that of other single-supply amplifiers, increasing the total available output power. www.maximintegrated.com The MAX9723 DirectDrive outputs are biased at SGND (see Figure 1). The benefit of this 0V bias is that the amplifier outputs do not have a DC component, eliminating the need for large DC-blocking capacitors. Eliminating the DC-blocking capacitors on the output saves board space, system cost, and improves low-frequency response. An I2C-compatible interface allows serial communication between the MAX9723 and a microcontroller. The MAX9723 is available with two different I2C addresses allowing two MAX9723 ICs to share the same bus (see Table 1). The internal command register controls the shutdown status of the MAX9723, enables the BassMax circuitry, sets the maximum gain of the amplifier, and sets the volume level (see Table 2). The MAX9723's BassMax circuitry improves audio reproduction by boosting the bass response of the amplifier, compensating for any lowfrequency attenuation introduced by the headphone. The Maxim Integrated 9 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C VDD VDD/2 GND CONVENTIONAL AMPLIFIER BIASING SCHEME +VDD SGND -VDD DirectDrive BIASING SCHEME Figure 1. Traditional Amplifier Output vs. MAX9723 DirectDrive Output MAX9723A and MAX9723B have a maximum amplifier gain of 0dB while the MAX9723C and MAX9723D have a maximum gain of +6dB. Amplifier volume is digitally programmable to any one of 32 levels. DirectDrive Traditional single-supply headphone amplifiers have their outputs biased at 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 amplifier. Maxim's DirectDrive architecture uses a charge pump to create an internal negative supply voltage. This allows the MAX9723 headphone amplifier outputs to be biased at 0V, almost doubling the 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 (typically 220F) tantalum capacitors, the MAX9723 charge pump requires only two small 1F ceramic capacitors, thereby conserving board space, reducing cost, and improving the low-frequency response of the headphone amplifier. See the Output Power vs. Charge-Pump Capacitance and Load Resistance graph in the Typical Operating Characteristics for details of the possible capacitor sizes. In addition to the cost and size disadvantages, the Cblocking capacitors required by conventional head- www.maximintegrated.com phone amplifiers limit low-frequency response and can distort the audio signal. Previous attempts at eliminating the output-coupling capacitors involved biasing the headphone return (sleeve) to the DC bias voltage of the headphone amplifiers. This method raises some issues: 1) The sleeve is typically grounded to the chassis. Using the midrail biasing approach, the sleeve must be isolated from system ground, complicating product design. The DirectDrive output biasing scheme allows the sleeve to be grounded. 2) During an ESD strike, the amplifier's ESD structure is the only path to system ground. The amplifier must be able to withstand the full ESD strike. The MAX9723 headphone outputs can withstand an 8kV ESD strike (HBM). 3) 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 amplifiers. The DirectDrive outputs of the MAX9723 can be directly coupled to other ground-biased equipment. Charge Pump The MAX9723 features a low-noise charge pump. The 600kHz switching frequency is well beyond the audio range, and does not interfere with the audio signals. This enables the MAX9723 to achieve a 99dB SNR. The switch drivers feature a controlled switching speed that minimizes noise generated by turn-on and turn-off transients. Limiting the switching speed of the charge pump minimizes di/dt noise caused by the parasitic bond wire and trace inductance. Although not typically required, additional high-frequency noise attenuation can be achieved by increasing the size of C2 (see the Functional Diagram/Typical Operating Circuit). Shutdown The MAX9723 features a 5A, low-power shutdown mode that reduces quiescent current consumption and extends battery life. Shutdown is controlled by a hardware or software interface. Driving SHDN low disables the drive amplifiers, bias circuitry, charge pump, and sets the headphone amplifier output impedance to 20k. Similarly, the MAX9723 enters shutdown when bit seven (B7) in the control register is reset. SHDN and B7 must be high to enable the MAX9723. The I2C interface is active and the contents of the command register are not affected when in shutdown. This allows the master to write to the MAX9723 while in shutdown. Maxim Integrated 10 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Click-and-Pop Suppression The output-coupling capacitor is a major contributor of audible clicks and pops in conventional single-supply headphone amplifiers. The amplifier charges the coupling capacitor to its output bias voltage at startup. During shutdown the capacitor is discharged. This charging and discharging results in a DC shift across the capacitor, which appears as an audible transient at the speaker. Since the MAX9723 headphone amplifier does not require outputcoupling capacitors, no audible transients occur. Additionally, the MAX9723 features extensive click-andpop suppression that eliminates any audible transient sources internal to the device. The Power-Up/PowerDown Waveform in the Typical Operating Characteristics shows that there are minimal transients at the output upon startup or shutdown. In most applications, the preamplifier driving the MAX9723 has a DC bias of typically half the supply. The input-coupling capacitor is charged to the preamplifier's bias voltage through the MAX9723's input impedance (RIN) during startup. The resulting voltage shift across the capacitor creates an audible click/pop. To avoid clicks/pops caused by the input filter, delay the rise of SHDN by at least 4 time constants, 4 x RIN x CIN, relative to the start of the preamplifier. BassMax (Bass Boost) Typical headphones do not have a flat-frequency response. The small physical size of the diaphragm does not allow the headphone speaker to efficiently reproduce low frequencies. This physical limitation results in attenuated bass response. The MAX9723 includes a bass boost feature that compensates for the headphone's poor bass response by increasing the amplifier gain at low frequencies. The DirectDrive output of the MAX9723 has more headroom than typical single-supply headphone amplifiers. This additional headroom allows boosting the bass frequencies without the output-signal clipping. Program the BassMax gain and cutoff frequency with external components connected between OUT_ and BB_ (see the Functional Diagram/Typical Operating Circuit). Use the I2C-compatible interface to program the command register to enable/disable the BassMax circuit. BB_ is connected to the noninverting input of the output amplifier when BassMax is enabled. BB_ is pulled to SGND when BassMax is disabled. The typical application of the BassMax circuit involves feeding a lowpass version of the output signal back to the amplifier. This is realized www.maximintegrated.com MAX9723 AUDIO INPUT R R OUT_ R1 BB_ BassMax ENABLE R2 C3 Figure 2. BassMax External Connections using positive feedback from OUT_ to BB_. Figure 2 shows the connections needed to implement BassMax. Maximum Gain Control The MAX9723A and MAX9723B have selectable maximum gains of -5dB or 0dB (see Table 5) while the MAX9723C and MAX9723D have selectable maximum gains of +1dB or +6dB (see Table 6). Bit 5 in the command register selects between the two maximum gain settings. Volume Control The MAX9723 includes a 32-level volume control that adjusts the gain of the output amplifiers according to the code contained in the command register. Volume is programmed through the command register bits [4:0]. Tables 7-10 show all of the available gain settings for the MAX9723A-MAX9723D. The mute attenuation is typically better than 100dB when driving a 32 load. Serial Interface The MAX9723 features an I2C/SMBus-compatible, 2-wire serial interface consisting of a serial data line (SDA) and a serial clock line (SCL). SDA and SCL facilitate communication between the MAX9723 and the master at clock rates up to 400kHz. Figure 3 shows the 2-wire interface timing diagram. The MAX9723 is a receive-only slave device relying on the master to generate the SCL signal. The MAX9723 cannot write to the SDA bus except to acknowledge the receipt of data from the master. The Maxim Integrated 11 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C SDA tBUF tSU, STA tSU, DAT tHD, STA tHD, DAT tLOW tSP tSU, STO SCL tHIGH tHD, STA tR tF START CONDITION REPEATED START CONDITION STOP CONDITION START CONDITION Figure 3. 2-Wire Serial-Interface Timing Diagram master, typically a microcontroller, generates SCL and initiates data transfer on the bus. A master device communicates to the MAX9723 by transmitting the proper address followed by the data word. Each transmit sequence is framed by a START (S) or REPEATED START (Sr) condition and a STOP (P) condition. Each word transmitted over the bus is 8 bits long and is always followed by an acknowledge clock pulse. The MAX9723 SDA line operates as both an input and an open-drain output. A pullup resistor, greater than 500, is required on the SDA bus. The MAX9723 SCL line operates as an input only. A pullup resistor, greater than 500, is required on SCL if there are multiple masters on the bus, or if the master in a single-master system has an opendrain SCL output. Series resistors in line with SDA and SCL are optional. Series resistors protect the digital inputs of the MAX9723 from highvoltage spikes on the bus lines, and minimize crosstalk and undershoot of the bus signals. Bit Transfer One data bit is transferred during each SCL cycle. The data on SDA must remain stable during the high period of the SCL pulse. Changes in SDA while SCL is high are control signals (see the START and STOP Conditions section). SDA and SCL idle high when the I2C bus is not busy. Start and Stop Conditions SDA and SCL idle high when the bus is not in use. A master device initiates communication by issuing a START condition. A START condition is a high-to-low transition www.maximintegrated.com on SDA with SCL high. A STOP condition is a low-to-high transition on SDA while SCL is high (Figure 4). A START condition from the master signals the beginning of transmission to the MAX9723. The master terminates transmission and frees the bus by issuing a STOP condition. The bus remains active if a REPEATED START condition is generated instead of a STOP condition. Early STOP Conditions The MAX9723 recognizes a STOP condition at any point during data transmission except if the STOP condition occurs in the same high pulse as a START condition. Slave Address The MAX9723 is available with one of two preset slave addresses (see Table 1). The address is defined as the seven most significant bits (MSBs) followed by the Read/ Write (R/W) bit. The address is the first byte of information sent to the MAX9723 after the START condition. The MAX9723 is a slave device only capable of being written to. The sent R/W bit must always be a zero when configuring the MAX9723. The MAX9723 acknowledges the receipt of its address even if R/W is set to 1. However, the MAX9723 will not drive SDA. Addressing the MAX9723 with R/W set to 1 causes the master to receive all 1's regardless of the contents of the command register. Acknowledge The acknowledge bit (ACK) is a clocked 9th bit that the MAX9723 uses to handshake receipt of each byte of Maxim Integrated 12 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C S Sr P CLOCK PULSE FOR ACKNOWLEDGMENT START CONDITION SCL SCL 1 2 8 9 NOT ACKNOWLEDGE SDA SDA ACKNOWLEDGE Figure 4. START, STOP, and REPEATED START Conditions Figure 5. Acknowledge Table 1. MAX9723 Address Map Table 3. Shutdown Control, SHDN = 1 PART MAX9723 SLAVE ADDRESS MODE B7 0 1 A6 A5 A4 A3 A2 A1 A0 R/W MAX9723 Disabled MAX9723A 1 0 0 1 1 0 0 0 MAX9723 Enabled MAX9723B 1 0 0 1 1 0 1 0 MAX9723C 1 0 0 1 1 0 0 0 MAX9723D 1 0 0 1 1 0 1 0 Table 2. MAX9723 Command Register B7 SHUTDOWN B6 B5 BassMax MAXIMUM ENABLE GAIN B4 B3 B2 B1 B0 MODE B6 BassMax Disabled 0 BassMax Enabled 1 VOLUME data (see Figure 5). The MAX9723 pulls down SDA during the master-generated 9th clock pulse. The SDA line must remain stable and low during the high period of the acknowledge clock pulse. Monitoring ACK allows for detection of unsuccessful data transfers. An unsuccessful data transfer occurs if a receiving device is busy or if a system fault has occurred. In the event of an unsuccessful data transfer, the bus master may reattempt communication. Write Data Format A write to the MAX9723 includes transmission of a START condition, the slave address with the R/W bit reset to 0 (see Table 1), one byte of data to configure the command register, and a STOP condition. Figure 6 illustrates the proper format for one frame. The MAX9723 only accepts write data, but it acknowledges the receipt of its address byte with the R/W bit set high. The MAX9723 does not write to the SDA bus in the event that the R/W bit is set high. Subsequently, the mas- www.maximintegrated.com Table 4. BassMax Control ter reads all 1's from the MAX9723. Always reset the R/W bit to 0 to avoid this situation. Command Register The MAX9723 has one command register that is used to enable/disable shutdown, enable/disable BassMax, and set the maximum gain and volume. Table 2 describes the function of the bits contained in the command register. Reset B7 to 0 to shut down the MAX9723. The MAX9723 wakes up from shutdown when B7 is set to 1 provided SHDN is high. SHDN must be high and B7 must be set to 1 for the MAX9723 to operate normally (see Table 3). Set B6 to 1 to enable BassMax (see Table 4). The output signal's low-frequency response will be boosted according to the external components connected between OUT_ and BB_. See the BassMax Gain-Setting Components section in the Applications Information section for details on choosing the external components. Maxim Integrated 13 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Table 5. MAX9723A and MAX9723B Maximum Gain Control COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION B7 B6 B5 B4 B3 B2 B1 B0 ACKNOWLEDGE FROM MAX9723 S SLAVE ADDRESS 0 ACK COMMAND BYTE ACK P ACKNOWLEDGE FROM MAX9723 R/W Figure 6. Write Data Format Example The MAX9723A and MAX9723B have a maximum gain setting of -5dB or 0dB, while the MAX9723C and MAX9723D have a maximum gain setting of +1dB or +6dB. B5 in the command register programs the maximum gain (see Tables 5 and 6). Adjust the MAX9723's amplifier gain with the volume control bits [4:0]. The gain is adjustable to one of 32 steps ranging from full mute to the maximum gain programmed by B5. Tables 7-10 list all the possible gain settings for the MAX9723. Figures 7-10 show the volume control transfer functions for the MAX9723. Power-On Reset The contents of the MAX9723's command register at power-on are shown in Table 11. Applications Information Power Dissipation and Heat Sinking Linear power amplifiers can dissipate a significant amount of power under normal operating conditions. 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: PD(MAX) = TJ(MAX) - T A JA where TJ(MAX) is +150C, TA is the ambient temperature, and JA is the reciprocal of the derating factor in C/W as specified in the Absolute Maximum Ratings section. For example, JA for the thin QFN package is +59C/W. The MAX9723 has two power dissipation sources, the charge pump and the two output amplifiers. If the power dissipation exceeds the rated package dissipation, reduce VDD, increase load impedance, decrease the ambient www.maximintegrated.com MAXIMUM GAIN (dB) B5 -5 0 0 1 Table 6. MAX9723C and MAX9723D Maximum Gain Control MAXIMUM GAIN (dB) B5 +1 0 +6 1 temperature, or add heatsinking. Large output, supply, and ground traces decrease JA, allowing more heat to be transferred from the package to surrounding air. Output Dynamic Range Dynamic range is the difference between the noise floor of the system and the output level at 1% THD+N. It is essential that a system's dynamic range be known before setting the maximum output gain. Output clipping will occur if the output signal is greater than the dynamic range of the system. The DirectDrive architecture of the MAX9723 has increased dynamic range compared to other single-supply amplifiers. Use the THD+N vs. Output Power in the Typical Operating Characteristics to identify the system's dynamic range. Find the output power that causes 1% THD+N for a given load. This point will indicate what output power causes the output to begin to clip. Use the following equation to determine the peak output voltage that causes 1% THD+N for a given load. = VOUT_(P-P) 2 2(POUT_1% xR L ) where POUT_1% is the output power that causes 1% THD+N, RL is the load resistance, and VOUT_(P-P) is the peak output voltage. After VOUT_(P-P) is identified, determine the peak input voltage that can be amplified without clipping: VIN_(P-P) = VOUT_(P-P) 10 AV 20 where VIN_(P-P) is the largest peak voltage that can be amplified without clipping, and AV is the voltage gain Maxim Integrated 14 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Table 7. MAX9723A and MAX9723B Gain Settings (B5 = 1, Max Gain = 0dB) Table 8. MAX9723A and MAX9723B Gain Settings (B5 = 0, Max Gain = -5dB) B4 B3 B2 B1 B0 (LSB) GAIN (dB) B4 B3 B2 B1 B0 (LSB) GAIN (dB) 1 1 1 1 1 0 1 1 1 1 1 -5 1 1 1 1 0 -0.5 1 1 1 1 0 -6 1 1 1 0 1 -1 1 1 1 0 1 -7 1 1 1 0 0 -1.5 1 1 1 0 0 -9 1 1 0 1 1 -2 1 1 0 1 1 -11 1 1 0 1 0 -2.5 1 1 0 1 0 -13 1 1 0 0 1 -3 1 1 0 0 1 -15 1 1 0 0 0 -4 1 1 0 0 0 -17 1 0 1 1 1 -5 1 0 1 1 1 -19 1 0 1 1 0 -6 1 0 1 1 0 -21 1 0 1 0 1 -7 1 0 1 0 1 -23 1 0 1 0 0 -9 1 0 1 0 0 -25 1 0 0 1 1 -11 1 0 0 1 1 -27 1 0 0 1 0 -13 1 0 0 1 0 -29 1 0 0 0 1 -15 1 0 0 0 1 -31 1 0 0 0 0 -17 1 0 0 0 0 -33 0 1 1 1 1 -19 0 1 1 1 1 -35 0 1 1 1 0 -21 0 1 1 1 0 -37 0 1 1 0 1 -23 0 1 1 0 1 -39 0 1 1 0 0 -25 0 1 1 0 0 -41 0 1 0 1 1 -27 0 1 0 1 1 -43 0 1 0 1 0 -29 0 1 0 1 0 -45 0 1 0 0 1 -31 0 1 0 0 1 -47 0 1 0 0 0 -33 0 1 0 0 0 -51 0 0 1 1 1 -35 0 0 1 1 1 -55 0 0 1 1 0 -37 0 0 1 1 0 -59 0 0 1 0 1 -39 0 0 1 0 1 -63 0 0 1 0 0 -41 0 0 1 0 0 -67 0 0 0 1 1 -43 0 0 0 1 1 -71 0 0 0 1 0 -45 0 0 0 1 0 -75 0 0 0 0 1 -47 0 0 0 0 1 -79 0 0 0 0 0 MUTE 0 0 0 0 0 MUTE of the amplifier in dB determined by the maximum gain setting (Bit 5) or the combination of the maximum gain setting plus bass boost (see the BassMax Gain-Setting Components section). www.maximintegrated.com Component Selection Input-Coupling Capacitor The AC-coupling capacitor (CIN) and internal gain-setting resistor form a highpass filter that removes any DC bias from an input signal (see the Functional Diagram/ Typical Operating Circuit). CIN allows the MAX9723 to bias the Maxim Integrated 15 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Table 9. MAX9723C and MAX9723D Gain Settings (B5 = 1, Max Gain = +6dB) Table 10. MAX9723C and MAX9723D Gain Settings (B5 = 0, Max Gain = +1dB) B4 B3 B2 B1 B0 (LSB) GAIN (dB) B4 B3 B2 B1 B0 (LSB) GAIN (dB) 1 1 1 1 1 6 1 1 1 1 1 1 1 1 1 1 0 5.5 1 1 1 1 0 0 1 1 1 0 1 5 1 1 1 0 1 -1 1 1 1 0 0 4.5 1 1 1 0 0 -3 1 1 0 1 1 4 1 1 0 1 1 -5 1 1 0 1 0 3.5 1 1 0 1 0 -7 1 1 0 0 1 3 1 1 0 0 1 -9 1 1 0 0 0 2 1 1 0 0 0 -11 1 0 1 1 1 1 1 0 1 1 1 -13 1 0 1 1 0 0 1 0 1 1 0 -15 1 0 1 0 1 -1 1 0 1 0 1 -17 1 0 1 0 0 -3 1 0 1 0 0 -19 1 0 0 1 1 -5 1 0 0 1 1 -21 1 0 0 1 0 -7 1 0 0 1 0 -23 1 0 0 0 1 -9 1 0 0 0 1 -25 1 0 0 0 0 -11 1 0 0 0 0 -27 0 1 1 1 1 -13 0 1 1 1 1 -29 0 1 1 1 0 -15 0 1 1 1 0 -31 0 1 1 0 1 -17 0 1 1 0 1 -33 0 1 1 0 0 -19 0 1 1 0 0 -35 0 1 0 1 1 -21 0 1 0 1 1 -37 0 1 0 1 0 -23 0 1 0 1 0 -39 0 1 0 0 1 -25 0 1 0 0 1 -41 0 1 0 0 0 -27 0 1 0 0 0 -45 0 0 1 1 1 -29 0 0 1 1 1 -49 0 0 1 1 0 -31 0 0 1 1 0 -53 0 0 1 0 1 -33 0 0 1 0 1 -57 0 0 1 0 0 -35 0 0 1 0 0 -61 0 0 0 1 1 -37 0 0 0 1 1 -65 0 0 0 1 0 -39 0 0 0 1 0 -69 0 0 0 0 1 -41 0 0 0 0 1 -73 0 0 0 0 0 MUTE 0 0 0 0 0 MUTE signal to an optimum DC level. The -3dB point of the highpass filter, assuming zero-source impedance, is given by: f -3dB = www.maximintegrated.com 1 2 x R IN x C IN Table 11. Initial Power-Up Command Register Status MODE B7 B6 B5 B4 B3 B2 B1 B0 Power-On Reset 1 1 1 1 1 1 1 1 Maxim Integrated 16 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C MAX9723A AND MAX9723B TRANSFER FUNCTION (B5 = 1) 10 10 6 AV (dB) -20 -30 2 0 -2 -6 -8 0 6 12 18 24 -10 30 10 1 CODE -20 -10 -30 -20 GAIN (dB) 0 -40 -50 -30 -40 -60 -50 -70 -60 -80 -70 6 12 18 10k 24 MAX9723C AND MAX9723D TRANSFER FUNCTION (B5 = 0) 10 -10 0 1k Figure 9. MAX9723C/MAX9723D Transfer Function with B5 = 1 MAX9723A AND MAX9723B TRANSFER FUNCTION (B5 = 0) 0 100 FREQUENCY (Hz) Figure 7. MAX9723A/MAX9723B Transfer Function with B5 = 1 GAIN (dB) MAX9723A CMD REGISTER CODE = 0xFF R1 = 47k R2 = 22k C3 = 0.1mF WITHOUT BassMax -4 -40 -90 fZERO WITH BassMax 4 -10 GAIN (dB) fPOLE 8 0 -50 GAIN PROFILE WITH AND WITHOUT BassMax 30 CODE -80 0 6 12 18 24 30 CODE Figure 8. MAX9723A/MAX9723B Transfer Function with B5 = 0 Figure 10. MAX9723C/MAX9723D Transfer Function with B5 = 0 where RIN is a minimum of 10k. Choose CIN such that f-3dB is well below the lowest frequency of interest. Setting f-3dB too high affects the amplifier's low-frequency response. Use capacitors with low-voltage coefficient dielectrics. Film or C0G dielectric capacitors are good choices for AC-coupling capacitors. Capacitors with highvoltage coefficients, such as ceramics, can result in increased distortion at low frequencies. Charge-Pump Flying Capacitor www.maximintegrated.com The charge-pump flying capacitor connected between C1N and C1P affects the charge pump's load regulation and output impedance. Choosing a flying capacitor that is too small degrades the MAX9723's ability to provide sufficient current drive and leads to a loss of output voltage. Increasing the value of the flying capacitor improves load regulation and reduces the chargepump output impedance. See the Output Power vs. Charge-Pump Capacitance and Load Resistance graph in the Typical Operating Characteristics. Maxim Integrated 17 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C GAIN PROFILE WITH AND WITHOUT BassMax 10 fPOLE 8 6 fZERO WITH BassMax 4 AV (dB) is disabled, can have an on-resistance as high as 300. Choose a value for R1 that is greater than 40k to ensure that positive feedback is negligible when BassMax is disabled. Table 12 contains a list of R2 values, with R1 = 47k, and the corresponding lowfrequency gain. 2 0 -2 MAX9723A CMD REGISTER CODE = 0xFF R1 = 47k R2 = 22k C3 = 0.1mF WITHOUT BassMax -4 -6 -8 -10 10 1 100 1k 10k FREQUENCY (Hz) Figure 11. BassMax, Gain Profile Example Charge-Pump Hold Capacitor The hold capacitor's value and ESR directly affect the ripple at PVSS. Ripple is reduced by increasing the value of the hold capacitor. Choosing a capacitor with lower ESR reduces ripple and output impedance. Lower capacitance values can be used in systems with low maximum output power levels. See the Output Power vs. Charge-Pump Capacitance and Load Resistance graph in the Typical Operating Characteristics. BassMax Gain-Setting Components The bass-boost low-frequency response, when BassMax is enabled, is set by the ratio of R1 to R2 by the following equation (see Figure 2): = 20 x log A V _BOOST R1 + R2 R1 - R2 where AV_BOOST is the voltage gain boost in dB at low frequencies. AV_BOOST is added to the gain realized by the volume setting. The absolute gain at low frequencies is equal to: A V= _TOTAL A V _VOL + A V _BOOST where AV_VOL is the gain due to the volume setting, and AV_TOTAL is the absolute gain at low frequencies. To maintain circuit stability, the ratio: R2/(R1 + R2) The low-frequency boost attained by the BassMax circuit is added to the gain realized by the volume setting. Select the BassMax gain so that the output signal will remain within the dynamic range of the MAX9723. Output signal clipping will occur at low frequencies if the BassMax gain boost is excessively large (see the Output Dynamic Range section). Capacitor C3 forms a pole and a zero according to the following equations: R1 - R2 2 x C3 x R1x R2 R1 + R2 f ZERO = 2 x C3 x R1x R2 f POLE = fPOLE is the frequency at which the gain boost begins to roll off. fZERO is the frequency at which the bassboost gain no longer affects the transfer function and the volume-control gain dominates. Table 13 contains a list of capacitor values and the corresponding poles and zeros for a given DC gain. See Figure 11 for an example of a gain profile using BassMax. Custom Maximum Gain Setting Using BassMax The circuit in Figure 12 uses the BassMax function to increase the maximum gain of the MAX9723. The gain boost created with the circuit in Figure 12 is added to the maximum gain selected by Bit 5 in the command register. Set the maximum gain with RA and RB using the following equation: RA + RB A V _TOTAL = A V _VOL + 20 x log RA - RB where AV_VOL is the gain due to the volume setting, and AV_TOTAL is the absolute passband gain in dB. Capacitor CA blocks any DC offset from being gained, but allows higher frequencies to pass. CA creates a pole that indicates the low-frequency point of the pass band. Choose CA so that the lowest frequencies of interest are not attenuated. For a typical application, set fPOLE equal to or below 20Hz. must not exceed 1/2. A ratio equaling 1/3 is recommended. The switch that shorts BB_ to SGND, when BassMax www.maximintegrated.com Maxim Integrated 18 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C MAX9723 10 R 9 8 R 7 OUT_ CA RA BassMax ENABLE AV (dB) AUDIO INPUT FREQUENCY RESPONSE OF FIGURE 12 6 5 MAX9723A CMD REGISTER CODE = 0xFF RA = 47k RB = 22k CA = 0.33mF 4 3 2 BB_ 1 RB 0 0.1 1 10 100 1k 10k FREQUENCY (Hz) Figure 12. Using BassMax to Increase MAX9723's Maximum Gain Table 12. BassMax Gain Examples (R1 = 47k) Figure 13. Increasing the Maximum Gain Using BassMax CA = 1 2 f POLE x (RA - RB) R2 (k) AV GAIN (dB) 39 20.6 33 15.1 Figure 13 shows the frequency response of the circuit in Figure 12. With RA = 47k, RB = 22k, and CA = 0.33F, the passband gain is set to 8.8dB. 27 11.3 Layout and Grounding 22 8.8 15 5.7 10 3.7 Table 13. BassMax Pole and Zero Examples for a Gain Boost of 8.8dB (R1 = 47k, R2 = 22k) C3 (nF) fPOLE (Hz) fZERO (Hz) 100 38 106 82 47 130 68 56 156 56 68 190 47 81 230 22 174 490 10 384 1060 www.maximintegrated.com 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 1F capacitor to PGND. Bypass VDD to PGND with a 1F capacitor. Place the power-supply bypass capacitor and the charge-pump capacitors as close to the MAX9723 as possible. Route PGND and all traces that carry switching transients away from SGND and the audio signal path. Route digital signal traces away from the audio signal path. Make traces perpendicular to each other when routing digital signals over or under audio signals. 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 when the board layout dictates that the exposed paddle cannot be left floating. Maxim Integrated 19 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Functional Diagram/Typical Operating Circuit 1.8V TO 3.6V ANALOG INPUT R5 10k C5 1F VDD SCL R6 10k SDA CIN 0.47F INR R VDD I2C INTERFACE R SHDN VDD OUTR R3 47k SVSS SVSS MAX9723 VDD BBR R4 22k VDD VDD BBL C1P C1 1F C1N CHARGE PUMP SGND PGND SVSS PVSS SVSS C2 1F INL CIN 0.47F R SVSS R2 22k C4 0.1F C3 0.1F R1 47k OUTL R BASS BOOST CIRCUIT TUNED FOR +8.8dB AT 106Hz. ANALOG INPUT UCSP Applications Information For the latest application details on UCSP construction, dimensions, tape carrier information, PC board techniques, bumppad layout, and recommended reflow temperature profile, as well as the latest information on reliability testing results, go to Maxim's website at www.maximintegrated.com/ucsp and look up Application Note 1891: Understanding the Basics of the Wafer-Level Chip-Scale Package (WL-CSP). www.maximintegrated.com Chip Information TRANSISTOR COUNT: 7165 PROCESS: BiCMOS Maxim Integrated 20 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C System Diagram 1.8V TO 3.6V R6 10k R5 10k C5 1F VDD SDA I2C MASTER SCL CIN 0.47F CIN 0.47F CODEC OUTL INL BBL MAX9723 R4 22k INR C4 0.1F OUTR C1P C1 1F R3 47k C1N BBR C2 1F PVSS SVSS PGND SGND R1 47k C3 0.1F R2 22k A B C1N PGND PVSS SCL SDA SHDN SGND INL MAX9723_ C C1P BBL BBR VDD 1 C1P 2 PGND 3 C1N 4 BBR 16 15 14 13 12 SVSS MAX9723_ 5 INR 11 INR 10 INL 9 6 7 8 SHDN + OUTR 4 SDA 3 BBL TOP VIEW 2 SCL 1 PVSS TOP VIEW (BUMP SIDE DOWN) OUTL Pin Configurations SGND THIN QFN D VDD OUTL OUTR SVSS UCSP www.maximintegrated.com Maxim Integrated 21 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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 OUTLINE NO. LAND PATTERN NO. 16 TQFN T1644-4 21-0139 90-0070 16 UCSP B16-1 21-0101 Refer to Application Note 1891 www.maximintegrated.com Maxim Integrated 22 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Package Information (continued) For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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. www.maximintegrated.com Maxim Integrated 23 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Package Information (continued) For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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. www.maximintegrated.com Maxim Integrated 24 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Package Information (continued) For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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. www.maximintegrated.com Maxim Integrated 25 MAX9723 Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C Revision History REVISION REVISION NUMBER DATE PAGES CHANGED DESCRIPTION 2 8/08 Updated TQFN pin configuration, and corrected Typical Operating Circuit and System Diagram pin names 3 7/14 Removed automotive reference in Applications section 20, 21 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated's website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. (c) 2008 Maxim Integrated Products, Inc. 26 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX9723AEBE+T MAX9723AETE+ MAX9723AETE+T MAX9723BEBE+T MAX9723BETE+ MAX9723BETE+T MAX9723CEBE+T MAX9723CETE+ MAX9723CETE+T MAX9723DEBE+T MAX9723DETE+T MAX9723DETE+CJ6