19-2859; Rev 0; 4/03 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown Features DirectDrive Eliminates Bulky DC-Blocking Capacitors SmartSense Automatic Short Detection Low 5mA Quiescent Current Fixed Gain Eliminates External Feedback Network MAX9720A: -1V/V MAX9720B: -1.41V/V 50mW per Channel Output Power Ultra-Low 0.003% THD+N High PSRR (92dB at 217Hz) Integrated Click-and-Pop Suppression 1.8V to 3.6V Single-Supply Operation Thermal Overload Protection Available in Space-Saving Packages 16-Bump UCSP (2mm x 2mm x 0.6mm) 16-Pin TSSOP SmartSense automatically detects the presence of a short at either the left or right amplifier output. Under a fault condition, the shorted output is automatically disabled and the stereo input signal is automatically mixed and routed to the remaining active channel. This feature is useful in cell phone and PDA applications where a variety of headphone jacks with unknown loads can be inserted into the headphone jack socket. SmartSense prevents both damage to the amplifier and eliminates battery drain into a shorted load. The MAX9720 delivers up to 50mW per channel into a 16 load and has an ultra-low 0.003% THD+N. A high (92dB at 217kHz) power-supply rejection ratio (PSRR) allows the device to operate from noisy digital supplies without additional power conditioning. The gain of the MAX9720 is set internally, further reducing component count. Two gain options are available (-1V/V, MAX9720A and -1.41V/V, MAX9720B). The headphone outputs include a comprehensive click-and-pop circuitry that eliminates audible glitches on startup and shutdown. A shutdown mode provides a fast 250s turn-on time. Ordering Information PIN/BUMPPACKAGE GAIN (V/V) PART TEMP RANGE MAX9720AEBE-T -40oC to +85oC 16 UCSP-16 -1 MAX9720BEBE-T -40oC to +85oC 16 UCSP-16 -1.41 MAX9720AEUE -40oC to +85oC 16 TSSOP -1 16 TSSOP -1.41 o MAX9720BEUE The MAX9720 operates from a single 1.8V to 3.6V supply and consumes only 5mA of supply current. The MAX9720 also features thermal overload protection, and is specified over the extended -40C to +85C temperature range. The MAX9720 is available in a tiny (2mm x 2mm x 0.6mm) 16-bump chip-scale package (UCSPTM) and a 16-pin TSSOP package. o -40 C to +85 C Simplified Block Diagram 3.6V TO 1.8V SUPPLY Applications MAX9720 RIN PDAs Cellular Phones Smart Phones Tablet PCs MP3 Players Notebook PCs Portable Audio Equipment SmartSense and UCSP are trademarks of Maxim Integrated Products, Inc. ROUT + LIN SmartSense HPS MODE1 MODE2 ALERT LOUT Pin Configuration 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 MAX9720 General Description The MAX9720 stereo headphone amplifier combines Maxim's patented DirectDrive architecture and SmartSenseTM, an automatic mono/stereo detection feature. 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, saving cost, board space, and component height. MAX9720 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown ABSOLUTE MAXIMUM RATINGS PGND to SGND .....................................................-0.3V to +0.3V PVSS to SVSS .........................................................-0.3V to +0.3V VDD to PGND or SGND ............................................-0.3V to +4V PVSS and SVSS to PGND or SGND ..........................-4V to +0.3V IN_, OUT_, and HPS to SGND .......(SVSS - 0.3V) to (VDD + 0.3V) C1P to PGND ...............................(PGND - 0.3V) to (VDD + 0.3V) C1N to PGND .............................(PVSS - 0.3V) to (PGND + 0.3V) ALERT to PGND .......................................................-0.3V to +4V MODE_ to PGND ........................................-0.3V to (VDD + 0.3V) TIME to SGND ............................................-0.3V to (VDD + 0.3V) Output Short Circuit to GND or VDD ...............................Continuous Continuous Power Dissipation (TA = +70C) 16-Bump UCSP (derate 8.2mW/C above +70C) .......659mW 16-Pin TSSOP (derate 9.4mW/C above +70C) .......754.7mW Junction Temperature ......................................................+150C Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Bump Temperature (soldering) Reflow ...........................................................................+235C 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 = VMODE1 = VMODE2 = 3.0V, PGND = SGND = 0V, RL = , C1 = C2 = 2.2F. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 3.6 V Stereo mode 5 8.4 Mono mode (MODE1 = VDD, MODE2 = GND) 3 GENERAL Supply Voltage Range Supply Current Shutdown Supply Current Turn-On/Turn-Off Time VDD IDD ISHDN Inferred from PSRR test 1.8 MODE1 = MODE2 = GND 6 tS 10 250 mA A s CHARGE PUMP Oscillator Frequency fOSC 272 320 368 kHz HEADPHONE AMPLIFIERS Voltage Gain AV Gain Match AV Total Output Offset Voltage (Note 3) VOS Input Resistance RIN MAX9720A -1.02 -1 -0.98 MAX9720B -1.443 -1.415 -1.386 Output Power 2 PSRR POUT % MAX9720A -5 -0.8 +3.6 MAX9720B -6.5 -1 +4.5 10 15 20 76 92 1.8V VDD 3.6V (Note 3) Power-Supply Rejection Ratio 1 Between OUTL and OUTR VDD = 3.0V, 200mVP-P ripple (Note 3) THD+N = 1%, fIN = 1kHz, TA = +25C DC fRIPPLE = 217Hz 92 fRIPPLE = 1kHz 86 fRIPPLE = 20kHz 61 RL = 32 50 RL = 16 32 50 _______________________________________________________________________________________ V/V mV k dB mW 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown (VDD = VMODE1 = VMODE2 = 3.0V, PGND = SGND = 0V, RL = , C1 = C2 = 2.2F. TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Total Harmonic Distortion Plus Noise SYMBOL THD+N Signal-to-Noise Ratio SNR Slew Rate SR Maximum Capacitive Load CL Crosstalk CONDITIONS fIN = 1kHz MIN TYP RL = 32, POUT = 30mW 0.003 RL = 16, POUT = 30mW 0.005 MAX UNITS % fIN = 1kHz, VOUT = 0.5VRMS, RL = 16, BW = 22Hz to 22kHz 97 dB 0.8 V/s No sustained oscillations 150 pF 75 dB RL = 32, POUT = 1mW, fIN = 10kHz Thermal Shutdown Threshold 140 o C Thermal Shutdown Hysteresis 15 o C SmartSense Shorted Load Threshold RSMS Pulse Duration tSMS 2.4 4 5.6 3.1 s DEBOUNCE TIME (TIME) TIME Charging Current ITIME TIME Discharge Switch Resistance RTIME TIME Threshold VTIME 0.7 HPS = GND 1.1 4 1 1.1 1.8 A 10 k 1.2 V HEADPHONE SENSE INPUT (HPS) VIH HPS Threshold 0.9 x VDD V 0.7 x VDD VIL Input Leakage Current Input Capacitance IIL 1 MODE1= MODE2 = GND CIN 10 A pF ALERT Output Current High IOH VALERT = VDD Output Voltage Low VOL IOL = 3mA 1 A 0.4 V MODE_ INPUT VIH MODE_ Thresholds 0.7 x VDD VIL MODE_ Input Leakage Current V 0.3 x VDD 1 A Note 1: All specifications are 100% tested at TA = +25oC; temperature limits are guaranteed by design. Note 2: Inputs are AC-coupled to ground. Note 3: Inputs are connected directly to ground. _______________________________________________________________________________________ 3 MAX9720 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.) VDD = 3V AV = -1V/V RL = 16 VDD = 3V AV = -1V/V RL = 32 1 THD+N (%) POUT = 10mW POUT = 10mW 0.01 VDD = 3V AV = -1.41V/V RL = 16 0.1 THD+N (%) 0.1 THD+N (%) 0.1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9720 toc03 1 MAX9720 toc01 1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX9720 toc02 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY 0.01 POUT = 40mW POUT = 10mW 0.01 POUT = 40mW POUT = 40mW 0.001 1k 10k 100k 0.001 10 100 1k 10k FREQUENCY (Hz) FREQUENCY (Hz) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY VDD = 3V AV = -1.41V/V RL = 32 1 100k 10 VDD = 1.8V AV = -1V/V RL = 16 POUT = 40mW 0.01 VDD = 1.8V AV = -1V/V RL = 32 THD + N (%) POUT = 2mW POUT = 9mW 1k 10k 0.001 10 100k 100 1k 10k TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY 1 VDD = 3V AV = -1.41V/V RL = 32 10 THD+N (%) POUT = 9mW 0.01 1k 10k POUT = 2mW 1 OUTPUTS OUT OF PHASE 0.1 0.01 VDD = 3V AV = -1V/V f = 20Hz RL = 16 0.01 POUT = 9mW 0.001 0.001 10 100 1k FREQUENCY (Hz) 4 10k 100k 100k OUTPUTS IN PHASE 0.1 POUT = 2mW 100 100 THD+N (%) 0.1 10 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX9720 toc08 FREQUENCY (Hz) VDD = 3V AV = -1.41V/V RL = 16 100k POUT = 9mW FREQUENCY (Hz) FREQUENCY (Hz) MAX9720 toc07 1 100 POUT = 2mW 0.01 0.001 10 100k MAX9720 toc06 1 0.01 0.001 10k 0.1 THD+N (%) THD+N (%) POUT = 10mW 1k TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY 0.1 0.1 100 FREQUENCY (Hz) MAX9720 toc05 1 100 MAX9720 toc04 10 MAX9720 toc09 0.001 THD+N (%) MAX9720 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 0 30 60 90 OUTPUT POWER (mW) _______________________________________________________________________________________ 120 150 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER OUTPUTS OUT OF PHASE VDD = 3V AV = -1V/V f = 1kHz RL = 16 0.01 30 60 90 120 150 0.001 0 30 60 90 120 150 0 80 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER OUTPUTS IN PHASE 1 OUTPUTS OUT OF PHASE 0.1 0.01 0.001 40 60 80 100 1 OUTPUTS OUT OF PHASE 0.1 VDD = 3V AV = -1.41V/V f = 20Hz RL = 16 0.01 0.001 20 OUTPUTS IN PHASE 10 THD+N (%) THD+N (%) 10 MAX9720 toc15 VDD = 3V AV = -1V/V f = 10kHz RL = 32 0.001 0 20 40 60 80 100 0 30 60 90 120 OUTPUT POWER (mW) OUTPUT POWER (mW) OUTPUT POWER (mW) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER VDD = 3V AV = -1.41V/V f = 1kHz RL = 16 0.01 0.001 60 90 OUTPUT POWER (mW) 120 150 1 OUTPUTS OUT OF PHASE 0.1 VDD = 3V AV = -1.41V/V f = 10kHz RL = 16 0.01 0.001 0 30 60 90 OUTPUT POWER (mW) 120 150 150 100 OUTPUTS IN PHASE 10 THD+N (%) OUTPUTS OUT OF PHASE OUTPUTS IN PHASE 10 THD+N (%) OUTPUTS IN PHASE 30 100 MAX9720 toc16 100 100 100 MAX9720 toc14 MAX9720 toc13 100 VDD = 3V AV = -1V/V f = 1kHz RL = 32 0.01 0 60 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER OUTPUTS OUT OF PHASE 0.1 40 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 1 1 20 OUTPUT POWER (mW) OUTPUTS IN PHASE 10 VDD = 3V AV = -1V/V f = 20Hz RL = 32 0.01 OUTPUT POWER (mW) 10 0 OUTPUTS OUT OF PHASE 0.1 OUTPUT POWER (mW) 100 0.1 OUTPUTS IN PHASE 1 VDD = 3V AV = -1V/V f = 10kHz RL = 16 0.001 0 THD+N (%) OUTPUTS OUT OF PHASE 0.01 0.001 THD+N (%) 1 0.1 10 MAX9720 toc18 0.1 OUTPUTS IN PHASE THD+N (%) THD+N (%) 1 10 MAX9720 toc11 OUTPUTS IN PHASE 100 MAX9720 toc17 THD+N (%) 10 100 MAX9720 toc10 100 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX9720 toc12 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 1 OUTPUTS OUT OF PHASE 0.1 VDD = 3V AV = -1.41V/V f = 20Hz RL = 32 0.01 0.001 0 20 40 60 80 100 120 OUTPUT POWER (mW) _______________________________________________________________________________________ 5 MAX9720 Typical Operating Characteristics (continued) (VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.) Typical Operating Characteristics (continued) (VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 0.1 VDD = 3V AV = -1.41V/V f = 10kHz RL = 32 20 40 60 80 100 120 VDD = 1.8V AV = -1V/V f = 20Hz RL = 16 0.001 0 20 40 60 80 100 0 120 10 20 30 40 50 OUTPUT POWER (mW) 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 0.1 OUTPUTS OUT OF PHASE 0.001 10 20 30 50 40 0 10 20 30 1 0.1 VDD = 1.8V AV = -1V/V f = 20Hz RL = 32 0.001 0 50 40 OUTPUTS OUT OF PHASE 0.01 0.001 0 OUTPUTS IN PHASE 10 VDD = 1.8V AV = -1V/V f = 10kHz RL = 16 0.01 MAX9720 toc24 1 0.1 VDD = 1.8V AV = -1V/V f = 1kHz RL = 16 0.01 OUTPUTS IN PHASE THD+N (%) THD+N (%) 1 10 100 MAX9720 toc23 100 MAX9720 toc22 10 5 10 15 20 25 30 OUTPUT POWER (mW) OUTPUT POWER (mW) OUTPUT POWER (mW) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER VDD = 1.8V AV = -1V/V f = 1kHz RL = 32 0.01 10 15 20 25 OUTPUT POWER (mW) 30 1 OUTPUTS OUT OF PHASE 0.1 VDD = 1.8V AV = -1V/V f = 10kHz RL = 32 35 MAX9720 toc27 10 1 OUTPUTS OUT OF PHASE 0.1 VDD = 1.8V AV = -1.41V/V f = 20Hz RL = 16 0.01 0.001 35 OUTPUTS IN PHASE OUTPUTS IN PHASE 0.01 0.001 100 THD+N (%) OUTPUTS OUT OF PHASE 5 10 THD+N (%) OUTPUTS IN PHASE 10 100 MAX9720 toc25 100 0 0.1 OUTPUT POWER (mW) OUTPUTS IN PHASE 0.1 OUTPUTS OUT OF PHASE OUTPUT POWER (mW) 100 1 1 0.01 0.001 0 THD+N (%) OUTPUTS OUT OF PHASE 0.01 0.001 6 1 VDD = 3V AV = -1.41V/V f = 1kHz RL = 32 0.01 10 OUTPUTS IN PHASE THD+N (%) THD+N (%) OUTPUTS OUT OF PHASE 0.1 10 OUTPUTS IN PHASE MAX9720 toc26 THD+N (%) 1 100 MAX9720 toc20 OUTPUTS IN PHASE 10 100 MAX9720 toc19 100 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX9720 toc21 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER THD+N (%) MAX9720 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown 0.001 0 5 10 15 20 25 OUTPUT POWER (mW) 30 35 0 10 20 30 OUTPUT POWER (mW) _______________________________________________________________________________________ 40 50 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 0 10 20 30 50 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER THD+N (%) OUTPUTS OUT OF PHASE VDD = 1.8V AV = -1.41V/V f = 1kHz RL = 32 0.01 1 VDD = 1.8V AV = -1.41V/V f = 10kHz RL = 32 0.01 0.001 160 15 20 25 30 35 40 0 5 OUTPUT POWER (mW) OUTPUT POWER vs. SUPPLY VOLTAGE 25 30 35 140 OUTPUT POWER (mW) 80 60 40 20 0 2.1 2.4 2.7 3.0 SUPPLY VOLTAGE (V) STEREO IN PHASE 80 60 0 40 1.8 2.1 fIN = 1kHz RL = 32 THD+N = 1% STEREO OUT OF PHASE 120 100 80 3.3 3.6 2.4 2.7 3.0 3.3 3.6 OUTPUT POWER vs. SUPPLY VOLTAGE STEREO IN PHASE 60 160 140 fIN = 1kHz RL = 32 THD+N = 10% 120 100 STEREO OUT OF PHASE STEREO IN PHASE 80 60 40 40 20 20 0 1.8 100 SUPPLY VOLTAGE (V) 160 MAX9720 toc34 STEREO OUT OF PHASE STEREO IN PHASE 100 20 40 120 OUTPUT POWER vs. SUPPLY VOLTAGE 140 120 15 35 STEREO OUT OF PHASE 140 OUTPUT POWER (mW) 200 fIN = 1kHz RL = 16 THD+N = 10% 10 30 20 OUTPUT POWER (mW) 10 25 40 MAX9720 toc35 5 20 fIN = 1kHz RL = 16 THD+N = 1% 180 0.001 0 15 200 MAX9720 toc32 OUTPUTS OUT OF PHASE 0.1 10 OUTPUT POWER vs. SUPPLY VOLTAGE OUTPUTS IN PHASE 10 5 0 OUTPUT POWER (mW) 100 MAX9720 toc31 OUTPUTS IN PHASE 0.1 OUTPUT POWER (mW) 40 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 1 160 30 OUTPUT POWER (mW) 10 180 20 OUTPUT POWER (mW) 100 THD+N (%) 0.001 10 0 50 40 VDD = 1.8V AV = -1.41V/V f = 20Hz RL = 32 0.01 0.001 0.001 0.1 VDD = 1.8V AV = -1.41V/V f = 10kHz RL = 16 0.01 OUTPUTS OUT OF PHASE MAX9720 toc33 VDD = 1.8V AV = -1.41V/V f = 1kHz RL = 16 0.01 0.1 1 MAX9720 toc36 0.1 THD+N (%) OUTPUTS OUT OF PHASE OUTPUTS OUT OF PHASE 1 OUTPUTS IN PHASE 10 OUTPUT POWER (mW) 1 THD+N (%) 10 OUTPUTS IN PHASE 10 100 MAX9720 toc29 OUTPUTS IN PHASE THD+N (%) 100 MAX9720 toc28 100 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX9720 toc30 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 0 1.8 2.1 2.4 2.7 3.0 SUPPLY VOLTAGE (V) 3.3 3.6 1.8 2.1 2.4 2.7 3.0 3.3 3.6 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 7 MAX9720 Typical Operating Characteristics (continued) (VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.) Typical Operating Characteristics (continued) (VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.) 80 60 40 100 60 INPUTS IN PHASE 100 100 15 INPUTS IN PHASE 10 300 RL = 16 250 200 150 100 RL = 32 VDD = 3V f = 1kHz POUT = POUTL + POUTR 50 5 POWER DISSIPATION (mW) 20 10 100 150 200 OUTPUT POWER (mW) POWER-SUPPLY REJECTION RATIO vs. FREQUENCY POWER-SUPPLY REJECTION RATIO vs. FREQUENCY VDD = 1.8V VRIPPLE = 200mVP-P -10 -20 -40 -50 -60 -80 -90 100 1k FREQUENCY (Hz) 10k 100k 0 -10 -20 10 100 1k FREQUENCY (Hz) 10k 40 60 VDD = 3V RL = 32 VIN = 200mVP-P 80 -30 -40 -50 -60 -70 RIGHT-TO-LEFT CHANNEL -80 -90 -100 LEFT-TO-RIGHT CHANNEL -110 -120 -100 10 20 CROSSTALK vs. FREQUENCY -70 -100 -110 -120 VDD = 1.8V f = 1kHz POUT = POUTL + POUTR 0 CROSSTALK (dB) PSRR (dB) -70 -80 -90 RL = 32 OUTPUT POWER (mW) -30 -40 -50 -60 50 250 MAX9720 toc44 0 MAX9720 toc43 VDD = 3V VRIPPLE = 200mVP-P -10 -20 -30 50 LOAD RESISTANCE () 0 75 0 0 100 RL = 16 100 25 0 0 MAX9720 toc39 POWER DISSIPATION vs. OUTPUT POWER 125 MAX9720 toc41 MAX9720 toc40 VDD = 1.8V f = 1kHz THD+N = 10% 100 LOAD RESISTANCE () 350 POWER DISSIPATION (mW) OUTPUT POWER (mW) 25 INPUTS IN PHASE 10 POWER DISSIPATION vs. OUTPUT POWER OUTPUT POWER vs. LOAD RESISTANCE 30 15 LOAD RESISTANCE () 40 INPUTS OUT OF PHASE INPUTS OUT OF PHASE 20 0 10 LOAD RESISTANCE () 35 25 5 0 10 30 10 20 0 8 MAX9720 toc38 80 40 INPUTS IN PHASE 20 INPUTS OUT OF PHASE 120 VDD = 1.8V f = 1kHz THD+N = 1% 35 MAX9720 toc42 100 f = 1kHz THD+N = 10% 140 OUTPUT POWER vs. LOAD RESISTANCE 40 OUTPUT POWER (mW) 120 f = 1kHz THD+N = 1% MAX9720 toc37 INPUTS OUT OF PHASE OUTPUT POWER (mW) OUTPUT POWER (mW) 140 OUTPUT POWER vs. LOAD RESISTANCE 160 100k MAX9720 toc45 OUTPUT POWER vs. LOAD RESISTANCE 160 PSRR (dB) MAX9720 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown 10 100 1k FREQUENCY (Hz) _______________________________________________________________________________________ 10k 100k 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown 4 AV = -1V/V RIGHT-TO-LEFT CHANNEL 1 0 -1 -2 6 4 2 -4 ILOAD = 10mA -5 1k 10k 0 0.01 100k 0.1 FREQUENCY (Hz) 10 100 1k 10k OUTPUT SPECTRUM vs. FREQUENCY OUTPUT SPECTRUM (dB) 1F 40 30 0.47F 20 fIN = 1kHz THD+N = 1% OUTPUTS IN PHASE VIN = 1VP-P RL = 32 fIN = 1kHz -20 -40 -60 -80 40 1k 10k LOAD RESISTANCE () FREQUENCY (Hz) SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE EXITING SHUTDOWN 8 7 3.6 5 STEREO MODE 4 3 MONO MODE 2 100k 1.8 2.1 2.4 2.7 3.0 3.3 3.6 SUPPLY VOLTAGE (V) POWER-UP/DOWN WAVEFORM MAX9720 toc54 MAX9720 toc53 MAX9720 toc52 9 3.3 0 100 50 3.0 1 -120 30 2.7 SUPPLY CURRENT vs. SUPPLY VOLTAGE -100 0 2.4 6 SUPPLY CURRENT (mA) 2.2F 50 20 2.1 SUPPLY VOLTAGE (V) 0 MAx9720 toc49 60 10 1.8 FREQUENCY (Hz) OUTPUT POWER vs. LOAD RESISTANCE AND CHARGE-PUMP CAPACITOR SIZE 10 1 MAX9720 toc50 100 10 OUTPUT POWER (mW) 8 -3 LEFT-TO-RIGHT CHANNEL -120 SUPPLY CURRENT (A) 10 MAX9720 toc51 -80 -90 -100 -110 12 OUTPUT IMPEDANCE () 3 2 -40 -50 -60 -70 14 MAX9720 toc47 VDD = 1.8V RL = 32 VIN = 200mVP-P GAIN (dB) CROSSTALK (dB) 5 MAX9720 toc46 0 -10 -20 -30 CHARGE-PUMP OUTPUT IMPEDANCE vs. SUPPLY VOLTAGE GAIN FLATNESS vs. FREQUENCY MAx9720 toc48 CROSSTALK vs. FREQUENCY MAX9720 Typical Operating Characteristics (continued) (VDD = 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = VDD.) 3V 3V MODE1 AND MODE2 VDD 0V 6 0V 100dB 5 10mV/div OUT_ 4 OUT_ 3 500mV/div 2 20dB/div OUT_FFT 1 0 1.8 2.1 2.4 2.7 3.0 SUPPLY VOLTAGE (V) 3.3 400s/div 3.6 fIN = 1kHz RL = 32 VIN = GND RL = 32 200ms/div FFT: 25Hz/div _______________________________________________________________________________________ 9 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720 Pin Description PIN BUMP TSSOP UCSP 1 D2 VDD 2 C2 MODE1 3 D1 C1P 4 C1 PGND Power Ground. Connect to SGND. 5 B1 C1N Flying Capacitor Negative Terminal 6 A1 PVSS Charge-Pump Output 7 B2 MODE2 Mode Select 2 Logic Input 8 A2 ALERT Open-Drain Interrupt Logic Output NAME FUNCTION Positive Power Supply Mode Select 1 Logic Input Flying Capacitor Positive Terminal 9 A3 INL 10 B3 TIME Left-Channel Audio Input 11 A4 INR 12 B4 SGND Signal Ground. Connect to PGND. 13 C4 SVSS Amplifier Negative Power Supply. Connect to PVSS. 14 D4 OUTR Right-Channel Output 15 C3 HPS 16 D3 OUTL Debouncing Timer Capacitor Right-Channel Audio Input Headphone Sense Input Left-Channel Output Detailed Description The MAX9720 fixed-gain, stereo headphone amplifier includes Maxim's patented DirectDrive architecture and SmartSense. DirectDrive eliminates the large outputcoupling capacitors required by conventional singlesupply headphone amplifiers. SmartSense automatically detects the presence of a short at either output. Under a fault condition, the shorted output is automatically disabled and the stereo input signal is automatically mixed and routed to the remaining active channel. This prevents damage to the amplifier and optimizes power savings by eliminating battery drain into a shorted load. The device consists of two 50mW Class AB headphone amplifiers, an internal feedback network (MAX9720A: fixed -1V/V gain, MAX9720B: fixed -1.41V/V gain), a mono mixer/attenuator, undervoltage lockout (UVLO)/ shutdown control, SmartSense, a charge pump, and comprehensive click-and-pop suppression circuitry (see Functional Diagram). The charge pump inverts the positive supply (V DD ), creating a negative supply (PVSS). The headphone amplifiers operate from these bipolar supplies with their outputs biased about GND (Figure 1). The amplifiers have almost twice the supply range compared to other single-supply amplifiers, nearly quadrupling the available output power. The benefit of the GND bias is that the amplifier outputs do not have a DC component (typically VDD/2). This elimi10 nates the large DC-blocking capacitors required with conventional headphone amplifiers, conserving board space, system cost, and improving frequency response. The noninvasive SmartSense feature of the MAX9720 detects a short on either output. The SmartSense routine executes when the device is powered up or brought out of shutdown (see the SmartSense section). If a fault is detected, the shorted channel is shut down, the output goes high impedance, and the stereo audio input is mixed/attenuated and fed to the remaining active channel. The device also features an ALERT output that indicates to a host C that SmartSense has detected a short-circuit condition on either amplifier output. Forced stereo and forced mono modes can also be selected through the two MODE_ inputs. In forced operation mode, SmartSense is disabled and the device operates as specified by the MODE_ inputs, regardless of output load conditions. A fast low-power shutdown mode is also selected through the MODE_ inputs (see the Mode_ Selection section). The UVLO prevents operation from an insufficient power supply and click-and-pop suppression, which eliminates audible transients on startup and shutdown. Additionally, the MAX9720 features thermal overload protection and can withstand 4kV ESD strikes on the output. ______________________________________________________________________________________ 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown VDD VOUT VDD/2 GND CONVENTIONAL DRIVER-BIASING SCHEME +VDD VOUT GND -VDD DirectDrive BIASING SCHEME Figure 1. Conventional Amplifier Output Waveform vs. MAX9720 Output Waveform DirectDrive Conventional single-supply headphone amplifiers 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 amplifier. Maxim's patented DirectDrive architecture uses a charge pump to create an internal negative supply voltage. This allows the MAX9720 output 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 capacitors (220F typ), the MAX9720 charge pump requires only two, small ceramic capacitors (1F typ), conserving board space, reducing cost, and improving the frequency response of the headphone amplifier. See the Output Power vs. 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 raised some issues: * The sleeve is typically grounded to the chassis. Using this biasing approach, the sleeve must be isolated from system ground, complicating product design. * During an ESD strike, the amplifier's ESD structures are the only path to system ground. The amplifier must be able to withstand the full ESD strike. * 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 large ground-loop current and possible damage to the amplifiers. * When using a combination microphone and speaker headset (in a cell phone or PDA application), the microphone typically requires a GND return. Any DC bias on the sleeve conflicts with the microphone requirements (Figure 2). Low-Frequency Response In addition to the cost and size disadvantages, the DCblocking capacitors limit the low-frequency response of the amplifier and distort the audio signal: * The impedance of the headphone load and the DCblocking capacitor form a highpass filter with the -3dB point determined by: f-3dB = 1 2RLCOUT where R L is the impedance of the headphone and COUT is the value of the DC-blocking capacitor. The highpass filter is required by conventional singleended, single-supply headphone amplifiers to block the midrail DC component of the audio signal from the headphones. Depending on the -3dB point, the filter can attenuate low-frequency signals within the audio band. Larger values of COUT reduce the attenuation, but are physically larger, more expensive capacitors. Figure 3 shows the relationship between the size of COUT and the resulting low-frequency attenuation. Note that the -3dB point for a 16 headphone with a 100F blocking capacitor is 100Hz, well within the audio band. ______________________________________________________________________________________ 11 MAX9720 Charge-Pump Capacitance and Load Resistance graph in the Typical Operating Characteristics for details of the possible capacitor sizes. The voltage coefficient of the capacitor, the change in capacitance due to a change in the voltage across the capacitor, distorts the audio signal. At frequencies around the -3dB point, the reactance of the capacitor dominates, and the voltage coefficient appears as frequency-dependent distortion. Figure 4 shows the THD+N introduced by two different capacitor dielectrics. Note that around the -3dB point, THD+N increases dramatically. The combination of low-frequency attenuation and frequency-dependent distortion compromises audio reproduction. DirectDrive improves low-frequency reproduction in portable audio equipment that emphasizes low-frequency effects such as multimedia laptops and MP3, CD, and DVD players. Charge Pump The MAX9720 features a low-noise charge pump. The 320kHz switching frequency is well beyond the audio range, and 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. Limiting the switching speed of the charge pump minimizes the di/dt noise caused by the parasitic bond wire and trace inductance. Although not typically required, additional high-frequency ripple attenuation can be achieved by increasing the size of C2 (see Typical Application Circuit). SmartSense The SmartSense feature detects a short on either output and automatically reconfigures the MAX9720 for optimum power savings. If an output short circuit is detected during the SmartSense routine, the shorted channel is disabled, ALERT is asserted, and the device is set to mono mode (assuming the other channel is not shorted). SmartSense works by applying an inaudible 3s test voltage pulse to the load. The resulting current from the test pulse and load is sensed. If the load impedance is less than 4, the output is determined to be a short. LOW-FREQUENCY ROLLOFF (RL = 16) 0 -3 DirectDrive -6 ATTENUATION (dB) * -9 330F -12 220F -15 100F -18 33F -21 -24 -27 -30 0.01 0.1 1 10 100 FREQUENCY (Hz) MICROPHONE BIAS MICROPHONE AMPLIFIER Figure 3. Low-Frequency Attenuation of Common DC-Blocking Capacitor Values MICROPHONE AMPLIFIER OUTPUT ADDITIONAL THD+N DUE TO DC-BLOCKING CAPACITORS 10 AUDIO INPUT AUDIO INPUT 1 MAX9720 THD+N (%) MAX9720 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown 0.1 TANTALUM 0.01 0.001 ALUM/ELEC 0.0001 HEADPHONE DRIVER 10 100 1k 10k 100k FREQUENCY (Hz) Figure 2. Earbud Speaker/Microphone Combination Headset Configuration 12 Figure 4. Distortion Contributed by DC-Blocking Capacitors ______________________________________________________________________________________ 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown any of the following events trigger a SmartSense test sequence: * HPS rises above 0.8 x VDD, indicating a headphone jack has been inserted into the socket. * The 180mA high-side (sourcing) overcurrent threshold is approached, and the output is near GND. * The die temperature exceeds the thermal limit (+140C). * Power or shutdown is cycled. MAX9720 SmartSense MODE1 is also used to execute a host-controlled SmartSense routine and reset the ALERT output. On the rising edge of MODE1, the device invokes a SmartSense routine. The falling edge of MODE1 resets the ALERT output to its idle state. M1 = L M2 = L ? N Y SHDN STATUS CHANGE ? N Automatic Detection Mode A fault condition is defined as a short (under 4) on either amplifier output to ground. SmartSense automatically detects and disables the shorted output. The mixer/attenuator combines the two stereo inputs (INL and INR), attenuates the resultant signal by a factor of 2, and redirects the audio playback to the remaining active channel. This allows for full reproduction of a stereo signal through a single headphone while maintaining optimum headroom. The mixed mono signal is output only on the properly loaded channel. If both outputs are shorted then both outputs go into a highimpedance state and no audio playback occurs. In automatic detection mode (MODE1 = MODE2 = high), M1 = H M2 = L ? N Y FORCED MONO STATUS CHANGE ? N M1 = L M2 = H ? N Y N SHORT DETECTED ? N OPERATING MODE MODE2 SmartSense High High Enabled Automatic detection mode Low Low Disabled Shutdown High Low Disabled Forced left mono Low High Disabled Forced stereo High Enabled Host controlled X -- Y N STATUS CHANGE ? STATUS CHANGE ? Y MONO MODE N STEREO MODE Y FORCED STEREO Table 1. MAX9720 Operating Modes MODE1 Y STATUS CHANGE ? Y Y Reset ALERT Figure 5. SmartSense Flow Diagram ______________________________________________________________________________________ 13 MAX9720 Mode Selection (MODE_) SmartSense is controlled by the two mode select inputs, MODE1 and MODE2. Table 1 shows the operating modes in relation to the status of the MODE_ inputs. When MODE1 = MODE2 = low, the device is in lowpower shutdown mode. When MODE1 = high and MODE2 = low, the device is in forced mono mode. The right channel is disabled, OUTR goes high impedance, and the stereo audio input is mixed, and the audio signal is reproduced on OUTL. SmartSense is disabled in this mode. When MODE1 = low and MODE2 = high, the device is in forced stereo mode, and SmartSense is disabled. When the device detects the presence of a short BEFORE forced stereo mode is selected, the device remains in mono mode (Figure 5). When MODE1 = MODE2 = high, the device is in automatic detection mode; the operating mode of the device is determined by SmartSense. MAX9720 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown For automatic headphone detection, connect HPS to the control pin of a 3-wire headphone jack, as shown in Figure 7. With no headphone present, the output impedance of the amplifier pulls HPS to less than 0.8 x VDD. When a headphone plug is inserted into the jack, the control pin is disconnected from the tip contact, and HPS is pulled to VDD through the internal 100k pullup. A debounce delay controls the time between HPS going high and the initiation of the SmartSense test sequence. This time is controlled by an external capacitor on the TIME pin and allows the user to customize the debounce time (see the TIME Capacitor section). Shutdown Driving MODE1 and MODE2 to GND shuts down the MAX9720, disconnects the internal HPS pullup resistor, disables the charge pump and amplifiers, sets the amplifier output impedance to 1k, and reduces supply current to less than 6A. Forced Mono Mode In forced left mono mode (MODE1 = high, MODE2 = low), the right channel is disabled and OUTR goes high impedance. The stereo signal inputs are combined through the mixer/attenuator and output on the left channel. In forced mono mode, the SmartSense routine is disabled. Forced Stereo Mode In forced stereo mode (MODE1 = low, MODE2 = high), the device operates as a stereo headphone amplifier. In forced stereo mode, the SmartSense routine is disabled. ALERT Output The MAX9720 includes an active-low, open-drain ALERT output that indicates to the master device that SmartSense has detected a fault condition. ALERT triggers when an output short circuit is detected through the SmartSense routine. During normal operation, ALERT idles high. If a fault condition is detected, ALERT pulls the line low. ALERT remains low until MODE1 is toggled from high to low. Click-and-Pop Suppression In conventional single-supply audio amplifiers, the output-coupling capacitor is a major contributor of audible clicks and pops. Upon startup, the amplifier charges the coupling capacitor to its bias voltage, typically half the supply. Likewise, during shutdown, the capacitor is discharged to GND. A DC shift across the capacitor results, which in turn appears as an audible transient at the speaker. Since the MAX9720 does not require output-coupling capacitors, no audible transient occurs. 14 TIP (SIGNAL) SLEEVE (GND) Figure 6. Typical 2-Wire (Mono) Headphone Plug VDD MAX9720 R1 100k HPS OUTL OUTR 15 16 14 Figure 7. HPS Configuration Additionally, the MAX9720 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 and shutdown. In most applications, the preamplifier output driving the MAX9720 has a DC bias of typically half the supply. During startup, the input-coupling capacitor is charged to the preamplifier's DC bias voltage through the input resistor of the MAX9720, resulting in a DC shift across the capacitor and an audible click/pop. Delaying the startup of the MAX9720 by 4 to 5 time constants (80ms to 100ms) based on RIN and CIN, relative to the startup of the preamplifier, eliminates this click/pop caused by the input filter. If the SmartSense routine occurs during normal operation, a low-level audible transient may be heard. To prevent this, a host-controlled SmartSense routine should only be executed when ALERT asserts. ______________________________________________________________________________________ 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER Power Dissipation 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 of the TSSOP package is +106.38C/W. The MAX9720 has two power dissipation sources: the charge pump and the two amplifiers. If the power dissipation for a given application exceeds the maximum allowed for a given package, either reduce VDD, increase load impedance, decrease the ambient temperature, or add heat sinking to the device. Large output traces improve the maximum power dissipation in the package. Thermal overload protection limits total power dissipation in the MAX9720. When the junction temperature exceeds +140C, the thermal protection circuitry disables the amplifier output stage. The amplifiers are enabled once the junction temperature cools by 15C, resulting in a pulsing output under continuous thermal overload conditions. Output Power The MAX9720 is specified for the worst-case condition--when both inputs are in phase. Under this condition, the amplifiers 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 present differences in both magnitude and phase, subsequently leading to an increase in the maximum attainable output power. Figure 8 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 MAX9720 is the internally generated, negative supply voltage (PVSS). PVSS is the negative supply for the MAX9720 headphone amplifiers. PVSS can power other devices within a system. Limit the current drawn from PVSS to 5mA. Exceeding this affects the operation of the headphone amplifiers. A typical application is a negative supply to adjust the contrast of LCD modules. 100 OUTPUTS IN PHASE 10 THD+N (%) 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) = JA MAX9720 Applications Information OUTPUTS OUT OF PHASE 1 SINGLECHANNEL 0.1 VDD = 3V AV = -1V/V f = 1kHz RL = 16 0.01 0.001 0 20 40 60 80 100 120 140 160 OUTPUT POWER (mW) Figure 8. THD+N vs. Output Power with Inputs In-/Out-of-Phase The charge-pump voltage at PVSS is roughly proportional to VDD and is not a regulated voltage. Consider the charge-pump output impedance when powering other devices from PVSS. See the Charge-Pump Output Impedance graph in the Typical Operating Characteristics. Use 2.2F charge-pump capacitors for the highest output power; 1F or lower capacitors can also be used for most applications. See the Output Power vs. Load Resistance and Charge-Pump Capacitance graph for details of the output power vs. capacitor size. Component Selection Input Filtering The input capacitor (C IN ), in conjunction with the MAX9720 input impedance, 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 2RINCIN RIN is the amplifier's internal input impedance value given in the Electrical Characteristics. Chose 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 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. ______________________________________________________________________________________ 15 MAX9720 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown Table 2. Suggested Capacitor Manufacturers PHONE FAX Taiyo Yuden SUPPLIER 800-348-2498 847-925-0899 www.t-yuden.com TDK 847-803-6100 847-390-4405 www.component.tdk.com Charge-Pump Capacitor Selection Use capacitors with an ESR less than 100m 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 2 lists suggested manufacturers. Flying Capacitor (C1) The value of the flying capacitor (C1) affects the charge pump's load regulation and output impedance. 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. In most applications, 1F for both C1 and C2 provides adequate performance. 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 2.2F, the on-resistance of the switches and the ESR of C1 and C2 dominate. Hold Capacitor (C2) The hold capacitor value and ESR directly affect the ripple on PVSS. Increasing the value of C2 reduces output ripple. Likewise, decreasing the ESR of C2 reduces both ripple and output impedance. 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 MAX9720's charge-pump switching transients. Bypass VDD with C3, the same value as C1, and place it physically close to the device. 16 WEBSITE TIME Capacitor The TIME capacitor (CTIME) sets the HPS debounce time. The debounce time is the delay between HPS exceeding 0.8 x V DD and the execution of the SmartSense routine. The delay ensures that any excessive contact bounce caused by the insertion of a headphone plug into the jack does not cause HPS to register an invalid state (Figure 9). The value of the CTIME in nF equals the nominal delay time in ms, i.e., CTIME = 10nF = tDELAY = 10ms. CTIME values in the 200nF to 600nF range are recommended. Adding Volume Control The addition of a digital potentiometer provides simple, digital volume control. Figure 10 shows the MAX9720 with the MAX5408 dual log taper digital potentiometer used as an input attenuator. Connect the high terminal of the MAX5408 to the audio input, the low terminal to GND, and the wiper to CIN. Setting the wiper to the top position passes the audio signal unattenuated. Setting the wiper to the lowest position fully attenuates the input. 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 PVSS and SVSS together at the device. Bypassing of both the positive and negative supplies is accomplished by the charge-pump capacitors, C2 and C3 (see Typical Application Circuit). Place capacitors C1 and C3 as close to the device as possible. Place capacitor C2 as close to PVSS as possible. Route PGND and all traces that carry switching transients away from SGND, traces, and components in the audio signal path. ______________________________________________________________________________________ 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720 LEFT AUDIO 5 H0 INPUT HEADPHONE INSERTED CIN 9 W0A 7 HPS 6 OUTL 16 MAX9720 MAX5408 tDELAY RIGHT AUDIO 12 H1 INPUT 3.1s INL L0 CIN W1A 10 11 INR OUTR 14 11 L1 70mV OUT_ Figure 9. HPS Debouncing Delay Figure 10. MAX9720 and MAX5408 Volume Control Circuit Pin Configurations TOP VIEW VDD 1 16 OUTL MODE1 2 15 HPS 14 OUTR C1P 3 MAX9720 PGND 4 13 SVSS 12 SGND C1N 5 11 INR PVSS 6 10 TIME MODE2 7 9 ALERT 8 UCSP Applications Information For the latest application details on UCSP construction, dimensions, tape carrier information, printed circuit board techniques, bump-pad layout, and the recommended reflow temperature profile, as well as the latest information on reliability testing results, go to Maxim's website at www.maxim-ic.com/ucsp and look up Application Note: UCSP--A Wafer-Level Chip-Scale Package. Chip Information TRANSISTOR COUNT: 4858 PROCESS: BiCMOS INL TSSOP TOP VIEW (BUMP SIDE DOWN) 1 2 3 4 INL INR A PVSS ALERT B C1N MODE2 TIME SGND C PGND MODE1 HPS SVSS D C1P VDD OUTL OUTR UCSP ______________________________________________________________________________________ 17 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown MAX9720 System Diagram VDD VDD 0.1F 0.1F 15k AUX_IN 0.1F 15k IN MAX4063 OUT 2.2k CODEC/ BASEBAND PROCESSOR BIAS OUT+ OUT- VDD 0.1F 15k BIAS MAX4365 1F 2.2k OUT 0.1F SHDN IN+ VDD IN- 100k 0.1F VDD MODE1 MODE2 C HPS 1F VDD 10k 1F INL MAX9720 OUTL INR OUTR ALERT PVSS 1F SVSS TIME 220nF C1P CIN 1F 1F 18 ______________________________________________________________________________________ 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown 1.8V TO 3.8V LOGIC CONTROL R4 10k C3 1F 1 (D2) 2 (C2) VDD MODE1 CIN 1F LEFTCHANNEL AUDIO INPUT 7 (B2) 8 (A2) MODE2 ALERT 9 (A3) INL MAX9720 MIXER ATTENUATOR AND GAIN SETTING VDD OUTL 3 (D1) C1P SVSS SmartSense AND HEADPHONE DETECTION CHARGE PUMP C1 1F VDD SGND UVLO AND SHUTDOWN CONTROL 5 (B1) C1N 16 (D3) R1 100k HPS 15 (C3) OUTR 14 (D4) CLICK-AND-POP SUPPRESSION VDD SGND MIXER ATTENUATOR AND GAIN SETTING PVSS 6 (A1) SVSS 13 (C4) C2 1F PGND 4 (C1) SGND TIME INR 12 (B4) 10 (B3) C4 220nF 11 (A4) RIGHTCHANNEL AUDIO INPUT SVSS CIN 1F ( ) UCSP BUMP. ______________________________________________________________________________________ 19 MAX9720 Typical Application Circuit 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.) 16L,UCSP.EPS MAX9720 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown 20 ______________________________________________________________________________________ 50mW, DirectDrive, Stereo Headphone Amplifier with SmartSense and Shutdown 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 ____________________ 21 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX9720 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.)