19-4341; Rev 1; 4/09 Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics The MAX13330/MAX13331 stereo headphone amplifiers are designed for automotive applications requiring output short-circuit and ESD protection to battery/ground with diagnostics. These devices use Maxim’s unique, patented † DirectDrive ® architecture to produce a ground-referenced output from a single supply, eliminating the need for large DC-blocking capacitors, saving board space and component height. The gain of the amplifier is set internally (-1.5V/V) on the MAX13330 or adjusted externally with resistors on the MAX13331. The MAX13330/MAX13331 deliver 120mW per channel into a 16Ω load or 135mW into a 32Ω load and have a low 0.01% THD+N. Low output impedance and the efficient integrated charge pump allows the device to drive loads as low as 8Ω, enabling the use of small loudspeakers. An 80dB at 217Hz PSRR allows these devices to operate from noisy digital supplies without an additional linear regulator. These devices include ±15kV Human Body Model ESD protection and shortcircuit protection up to +45V at the headphone outputs. Comprehensive click-and-pop circuitry suppresses audible clicks and pops on startup and shutdown. A low-power shutdown mode reduces the supply current to 3µA (typ). The MAX13330/MAX13331 are specified from -40°C to +105°C AEC-Q100 Level 2 automotive temperature range and are available in a 16-pin QSOP package. Applications Features ♦ 4V to 5.5V Single-Supply Operation ♦ 2MHz Charge Pump Prevents AM Radio Interference ♦ Ground-Referenced Outputs Eliminate Bulky DCBlocking Capacitors ♦ Short-to-Ground and Battery (VBAT up to +45V) Output Protection, Load Dump Protection ♦ Short-Circuit Diagnostic Output ♦ Adjustable Gain (MAX13331) or Fixed -1.5V/V Gain (MAX13330) ♦ 125mW per Channel into 32Ω at 0.01% THD+N ♦ Integrated Click-and-Pop Suppression ♦ High PSRR Eliminates LDO ♦ No Degradation of Low-Frequency Response Due to Output Capacitors ♦ ±15kV Human Body Model ESD Protection for Output Pins Ordering Information PART GAIN TEMP RANGE PINPACKAGE MAX13330GEE/V+T -1.5V/V -40°C to +105°C 16 QSOP Externally -40°C to +105°C 16 QSOP Set +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape-and-reel. /V denotes an automotive qualified part. Typical Application Circuits appear at end of data sheet. MAX13331GEE/V+T Automotive Entertainment Systems Automotive Rear Seat Entertainment Systems DirectDrive is a registered trademark of Maxim Integrated Products, Inc. †U.S. Patent #7,061,327 Simplified Block Diagram MAX13330 SHDN RIGHT-CHANNEL AUDIO IN CLICK-AND-POP SUPPRESSION OUTPUT PROTECTION & DIAGNOSTICS LEFT-CHANNEL AUDIO IN DIAGNOSTICS OUTPUT Pin Configuration + INL 1 16 OUTL SGND 2 15 PGND INR 3 14 VSS SGND 4 13 OUTR MAX13330 MAX13331 VDD 5 12 DIAG SHDN 6 11 CPVSS CPVDD 7 10 C1N C1P 8 9 PGND QSOP ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX13330/MAX13331 General Description MAX13330/MAX13331 Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics ABSOLUTE MAXIMUM RATINGS VDD, CPVDD to SGND..............................................-0.3V to +6V VSS, CPVSS to SGND ...............................................+0.3V to -6V VDD, CPVDD..........................................................-0.3V to +0.3V VSS, CPVSS ...........................................................-0.3V to +0.3V SHDN, DIAG to SGND................................-0.3V to (VDD + 0.3V) OUT_ to PGND.......................................(VCPVSS - 0.3V) to +45V IN_ to SGND (MAX13330)................(VSS - 0.3V) to (VDD + 0.3V) IN_ to SGND (MAX13331) ..........................-0.3V to (VDD + 0.3V) C1P to PGND........................................-0.3V to (VCPVDD + 0.3V) C1N to PGND..............................................(VSS - 0.3V) to +0.3V Output Short-Circuit Duration.....................................Continuous Continuous Power Dissipation (TA = +70°C) 16-Pin QSOP (derate 8.3mW/°C above +70°C)) ......666.7mW Junction-to-Case Thermal Resistance (θJC) (Note 1) θJC ............................................................................... 37°C/W Junction-to-Ambient Thermal Resistance (θJA) (Note 1) θJA ............................................................................. 120°C/W Operating Temperature Range .........................-40°C to +105°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to http://www.maxim-ic.com/thermal-tutorial. 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 = VCPVDD = +5V, VSGND = VPGND = 0, SHDN = VDD, C1 = C2 = 1µF, RL = ∞, resistive load referenced to ground, for MAX13330 gain = -1.5V/V (internally set), for MAX13331 gain = -1.5V/V (RIN = 30kΩ, RFB = 45kΩ), TA = TJ = -40°C to +105°C, unless otherwise noted. Typical values are at TA = +25°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS GENERAL Amplifier Supply Voltage Range VDD 4.0 5.5 V Charge-Pump Supply Voltage Range VCPVDD 4.0 5.5 V Charge-Pump Output Voltage VCPVSS Quiescent Supply Current IDD Shutdown Supply Current I SHDN SHDN Input-Logic High VIH SHDN Input-Logic Low VIL RL = V 10 mA 10 2 SHDN Input Leakage Current SHDN to Full Operation Time -VDD V -1 t SON μA 0.8 V +1 μA 100 μs DIAGNOSTICS 0.02 x VDD No fault Diagnostic Output Voltage VDIAG RDIAG = , TA = +25°C OUTR short to SGND 0.22 x VDD 0.25 x VDD 0.28 x VDD OUTL short to SGND 0.47 x VDD 0.50 x VDD 0.53 x VDD OUTR short to VBAT 0.72 x VDD 0.75 x VDD 0.78 x VDD OUTL short to VBAT 0.97 x VDD V Short-to-SGND Threshold 130 mA Short-to-VBAT Threshold 130 mA 2 _______________________________________________________________________________________ Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics (VDD = VCPVDD = +5V, VSGND = VPGND = 0, SHDN = VDD, C1 = C2 = 1µF, RL = ∞, resistive load referenced to ground, for MAX13330 gain = -1.5V/V (internally set), for MAX13331 gain = -1.5V/V (RIN = 30kΩ, RFB = 45kΩ), TA = TJ = -40°C to +105°C, unless otherwise noted. Typical values are at TA = +25°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS -1.5 -1.52 V/V AMPLIFIERS Voltage Gain AV Gain Matching MAX13330 -1.48 MAX13330 ±0.2 Input Offset Voltage ±1 Input Bias Current VIN_ = 0 Input Impedance RIN Power-Supply Rejection Ratio Output Power Per Channel Output Voltage PSRR POUT_ VOUT_ MAX13330 20 Total Harmonic Distortion Plus Noise Signal-to-Noise Ratio THD+N SNR Noise Vn Slew Rate SR Maximum Capacitive Load CL Click-and-Pop Level Charge-Pump Oscillator Frequency Crosstalk KCP -86 RL = 8 75 RL = 16 120 RL = 32 135 dB mW 2 VRMS 14 k RL = 16, P OUT = 100mW, f = 1kHz 0.03 % RL = 32, P OUT = 125mW, f = 1kHz RL = 32, POUT = 135mW, f = 22Hz to 22kHz 0.01 % 100 dB 6 μVRMS f = 22Hz to 22kHz bandwidth; inputs AC-coupled to grounded 0.3 No sustained oscillation Peak voltage, TA = +25°C, A-weighted, 32 samples per second; Inputs ACcoupled to ground V/μs 3000 Into shutdown pF -80 V Out of shutdown -60 1.9 f OSC RL = 32, VIN = 200mVP-P, f = 10kHz Thermal-Shutdown Temperature Thermal-Shutdown Hysteresis ESD Protection nA k -80 Output Impedance in Shutdown mV 30 f =1kHz, VRIPPLE = 100mVP-P RL = 1k ±6 50 DC, VDD = 4.0V to 5.5V, input referred THD+N = 1%; VDD = VCPVDD = 5V; f IN = 1kHz % Human Body Model (OUTR and OUTL) 2.2 2.5 MHz -75 dB +155 °C 10 °C ±15 kV Note 2: All devices are 100% tested at TA = +25°C; specifications over temperature limits are guaranteed by design and QA sampling. _______________________________________________________________________________________ 3 MAX13330/MAX13331 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VDD = VCPVDD = 5V, VSGND = VPGND = 0, C1 = C2 = 1µF, RL = ∞, gain = -1.5V/V, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) VDD = 4V RL = 8Ω VDD = 5V RL = 8Ω POUT = 25mW 0.1 POUT = 60mW 0.01 0.001 0.01 0.1 1 10 100 0.01 0.1 1 10 0.01 100 0.1 1 10 FREQUENCY (kHz) FREQUENCY (kHz) FREQUENCY (kHz) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY THD+N (%) POUT = 25mW 0.01 POUT = 125mW 0.001 0.001 1 10 POUT = 50mW POUT = 70mW 0.001 0.1 MAX13330/31 toc06 VDD = 5V RL = 32Ω 0.01 POUT = 100mW 100 0.01 0.1 1 10 0.01 100 0.1 1 10 FREQUENCY (kHz) FREQUENCY (kHz) FREQUENCY (kHz) 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 = 5V RL = 8Ω VDD = 4V RL = 16Ω 1 fIN = 10kHz fIN = 10kHz fIN = 1kHz 0.1 fIN = 1kHz THD+N (%) 1 THD+N (%) 1 10 100 MAX13330/31 toc09 VDD = 4V RL = 8Ω MAX13330/31 toc08 10 MAX13330/31 toc07 10 100 0.1 THD+N (%) THD+N (%) VDD = 4V RL = 32Ω 0.1 POUT = 50mW 0.01 1 MAX13330/31 toc05 VDD = 5V RL = 16Ω 0.1 1 MAX13330/31 toc04 1 0.01 POUT = 75mW 0.001 0.001 0.01 POUT = 25mW THD+N (%) THD+N (%) POUT = 45mW 0.01 VDD = 4V RL = 16Ω POUT = 25mW 0.1 THD+N (%) 0.1 1 MAX13330/31 toc02 1 MAX13330/31 toc01 1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY MAX13330/31 toc03 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY THD+N (%) MAX13330/MAX13331 Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics fIN = 10kHz fIN = 1kHz 0.1 0.1 0.01 fIN = 100Hz fIN = 100Hz 0.01 0.001 0.01 0 25 50 OUTPUT POWER (mW) 4 fIN = 100Hz 75 0 25 50 75 OUTPUT POWER (mW) 100 125 0 25 50 75 OUTPUT POWER (mW) _______________________________________________________________________________________ 100 125 Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 1 fIN = 1kHz 0.1 0.01 fIN = 100Hz 0.001 50 75 100 125 150 0 175 25 50 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY 125 0 VOUT_ = 2VRMS VOUT_ = 1VRMS fIN = 1kHz 1% THD+N 160 140 120 RL = 8Ω 4.25 4.50 4.75 5.00 5.25 100 80 60 1% THD+N VDD = 4V 5.50 700 RL = 16Ω 500 400 300 200 RL = 32Ω 1200 VDD = 5V fIN = 1kHz 1000 POWER DISSIPATION (mW) VDD = 4V fIN = 1kHz 10 0 100 1000 POWER DISSIPATION vs. OUTPUT POWER PER CHANNEL MAX13330/31 toc16 800 RL = 8Ω 10% THD+N VDD = 4V LOAD RESISTANCE (Ω) POWER DISSIPATION vs. OUTPUT POWER PER CHANNEL POWER DISSIPATION (mW) 1% THD+N VDD = 5V 120 SUPPLY VOLTAGE (V) FREQUENCY (kHz) 600 175 0 4.00 100 140 20 0 10 150 10% THD+N VDD = 5V 40 20 1 125 160 60 0.0001 100 fIN = 1kHz 180 RL = 16Ω 80 75 OUTPUT POWER vs. LOAD RESISTANCE RL = 32Ω 40 0.1 50 200 100 0.001 0.01 25 OUTPUT POWER (mW) 180 OUTPUT POWER (mW) MAX13330/31 toc13 VDD = 5V RL = 1kΩ 0.01 100 OUTPUT POWER vs. SUPPLY VOLTAGE 1 0.1 75 OUTPUT POWER (mW) OUTPUT POWER (mW) OUTPUT POWER (mW) 25 fIN = 100Hz 0.001 MAX13330/31 toc14 0 fIN = 1kHz 0.1 0.01 fIN = 100Hz 0.001 fIN = 10kHz MAX13330/31 toc15 0.01 THD+N (%) 1 fIN = 10kHz RL = 8Ω RL = 16Ω 800 600 400 RL = 32Ω 200 100 MAX13330/31 toc17 fIN = 1kHz VDD = 5V RL = 32Ω THD+N (%) fIN = 10kHz VDD = 4V RL = 32Ω THD+N (%) THD+N (%) 1 10 MAX13330/31 toc11 VDD = 5V RL = 16Ω 0.1 10 MAX13330/31 toc10 10 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER MAX13330/31 toc12 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER 0 0 0 20 40 60 80 100 OUTPUT POWER PER CHANNEL (mW) 120 0 20 40 60 80 100 120 140 160 180 OUTPUT POWER PER CHANNEL (mW) _______________________________________________________________________________________ 5 MAX13330/MAX13331 Typical Operating Characteristics (continued) (VDD = VCPVDD = 5V, VSGND = VPGND = 0, C1 = C2 = 1µF, RL = ∞, gain = -1.5V/V, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VDD = VCPVDD = 5V, VSGND = VPGND = 0, C1 = C2 = 1µF, RL = ∞, gain = -1.5V/V, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) POWER-SUPPLY REJECTION RATIO vs. FREQUENCY VDD = 5V OUTR VDD = 5V OUTL -110 0.01 0.1 1 10 MAX13330/31 toc20 OUTR GAIN (dB) -70 RIGHT TO LEFT OUTL 3.3 3.2 -80 3.1 LEFT TO RIGHT 0.1 0.01 100 MAX13330 VIN = 100mVP-P 3.0 -100 -120 1 10 0.01 100 0.1 1 OUTPUT FFT -40 -60 -80 -100 MAX13330/31 toc22 10 9 8 SUPPLY CURRENT (mA) MAX13330/31 toc21 RL = 32Ω -20 7 6 5 4 3 2 -120 1000 12 10 8 6 4 2 1 -140 0 0 0 5 10 20 15 4.00 4.25 FREQUENCY (kHz) SHUTDOWN CURRENT vs. TEMPERATURE 3.0 2.5 2.0 1.5 1.0 4.75 5.00 5.25 5.50 -50 -25 0 25 50 SHUTDOWN CURRENT vs. SUPPLY VOLTAGE EXITING SHUTDOWN TRANSIENT 4 SHDN 5V/div 3 OUTL 1V/div 2 OUTR 1V/div 0 -25 0 25 50 75 TEMPERATURE (°C) 100 125 125 MAX13330/31 toc26 0.5 -50 100 TEMPERATURE (°C) 1 0 75 SUPPLY VOLTAGE (V) MAX13330/31 toc25 3.5 4.50 5 SHUTDOWN CURRENT (μA) MAX13330/31 toc24 4.0 6 100 SUPPLY CURRENT vs. TEMPERATURE SUPPLY CURRENT vs. SUPPLY VOLTAGE 0 10 FREQUENCY (kHz) FREQUENCY (kHz) FREQUENCY (kHz) AMPLITUDE (dBV) 3.4 -60 -90 VRIPPLE = 100mVP-P RL = 32Ω MAX13330/31 toc19 VIN = 200mVP-P RL = 32Ω MAX13330/31 toc23 -100 3.5 SUPPLY CURRENT (mA) PSRR (dB) -80 -90 -50 CROSSTALK (dB) VDD = 4V OUTR VDD = 4V OUTL -70 -40 MAX13330/31 toc18 -50 -60 GAIN FLATNESS vs. FREQUENCY CROSSTALK vs. FREQUENCY -40 SHUTDOWN CURRENT (μA) MAX13330/MAX13331 Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics 4.00 4.25 4.50 4.75 5.00 5.25 5.50 200μs/div SUPPLY VOLTAGE (V) _______________________________________________________________________________________ Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics ENTERING SHUTDOWN TRANSIENT POWER-UP/-DOWN TRANSIENT MAX13330/31 toc27 MAX13330/31 toc28 SHDN 5V/div SHDN 5V/div OUTL 1V/div OUTL 1V/div OUTR 1V/div OUTR 1V/div 200μs/div 10ms/div Pin Description PIN NAME 1 INL 2, 4 SGND 3 INR Inverting Right-Channel Audio Input 5 VDD Amplifier Positive-Power Supply. Connect to positive supply. Bypass with a 1µF capacitor to SGND as close to the pin as possible. 6 SHDN Active-Low Shutdown Input 7 CPVDD Charge-Pump Power Supply. Powers charge-pump inverter, charge-pump logic, and oscillator. Connect to positive supply. Bypass with a 1µF capacitor to PGND as close to the pin as possible. 8 C1P 9, 15 PGND 10 C1N 11 CPVSS 12 DIAG Diagnostic Voltage Output 13 OUTR Right-Channel Output 14 VSS 16 OUTL FUNCTION Inverting Left-Channel Audio Input Amplifier Signal Ground. The noninverting inputs of the amplifiers are connected to the amplifier signal ground. Connect both to the signal ground plane. Flying-Capacitor Positive Terminal. Connect a 1µF capacitor between C1P and C1N. Power Ground. Connect both to the power ground plane. Flying-Capacitor Negative Terminal. Connect a 1µF capacitor between C1P and C1N. Charge-Pump Output. Connect to VSS and bypass with a 1µF capacitor to PGND. Amplifier Negative Power Supply. Connect to CPVSS. Left-Channel Output _______________________________________________________________________________________ 7 MAX13330/MAX13331 Typical Operating Characteristics (continued) (VDD = VCPVDD = 5V, VSGND = VPGND = 0, C1 = C2 = 1µF, RL = ∞, gain = -1.5V/V, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.) MAX13330/MAX13331 Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics Detailed Description The MAX13330/MAX13331 headphone amplifiers feature Maxim’s patented DirectDrive architecture, eliminating the large output-coupling capacitors required by conventional single-supply headphone amplifiers. The devices consists of two Class AB headphone amplifiers, undervoltage lockout (UVLO), lowpower shutdown control, comprehensive click-and-pop suppression, output short-circuit/ESD protection and output short-circuit diagnostics. These devices can drive loads as low as 8Ω, and deliver up to 120mW per channel into 16Ω and 135mW into 32Ω. The MAX13330 features a fixed gain of -1.5V/V, and the MAX13331 features a programmable gain configured with external resistors. The headphone outputs feature ±15kV Human Body Model ESD protection, and enhanced short-circuit protection to ground or battery (VBAT up to +45V). An integrated short-circuit diagnostic output provides the status of the MAX13330/ MAX13331 during operation as a fraction of the analog supply voltage. VDD VOUT VDD/2 GND CONVENTIONAL DRIVER-BIASING SCHEME VDD 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 the headphone and the headphone amplifier. Maxim’s patented DirectDrive architecture uses a charge pump to create an internal negative-supply voltage, allowing the MAX13330/MAX13331 outputs to be biased about SGND (Figure 1). With no DC component, there is no need for the large DC-blocking capacitors. Instead of two large (220µF, typ) tantalum capacitors, the MAX13330/MAX13331 charge pump requires two small ceramic capacitors, conserving board space, reducing cost, and improving the frequency response of the headphone amplifier. See the Output Power vs. Load Resistance graph in the Typical Operating Characteristics for details of the possible capacitor sizes. There is a low DC voltage on the amplifier outputs due to amplifier offset. However, the output offset of the MAX13330 is typically ±2.5mV which, when combined with a 32Ω load, results in less than ±78µA of DC current flow to the headphones. Previous attempts to eliminate the output-coupling capacitors involved biasing the headphone return (sleeve) to the DC-bias voltage of the headphone amplifiers. 8 VOUT GND VSS DirectDrive BIASING SCHEME Figure 1. Conventional Driver Output Waveform vs. MAX13330/ MAX13331 Output Waveform This method raises 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. Thus, 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 possible damage to the amplifiers. _______________________________________________________________________________________ Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics 1 (Hz) 2π × RL × COUT 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 power-supply headphone amplifiers to block the midrail DC-bias component of the audio signal from the headphones. The drawback to the filter is that it can attenuate low-frequency signals. Larger values of COUT reduce this effect but result in physically larger, more expensive capacitors. Figure 2 shows the relationship between the size of COUT and the resulting low-frequency attenuation. Note that the -3dB point for a 16Ω headphone with a 100µF blocking capacitor is 100Hz, well within the normal audio band, resulting in low-frequency attenuation of the reproduced signal. LOW-FREQUENCY ROLLOFF (RL = 16Ω) ADDITIONAL THD+N DUE TO DC-BLOCKING CAPACITORS 10 1 THD+N (%) f−3dB = 2) The voltage coefficient of the DC-blocking capacitor contributes distortion to the reproduced audio signal as the capacitance value varies and the function of the voltage across the capacitor changes. The reactance of the capacitor dominates at frequencies below the -3dB point and the voltage coefficient appears as frequency-dependent distortion. Figure 3 shows the THD+N introduced by two different capacitor dielectric types. Note that below 100Hz, THD+N increases rapidly. The combination of low-frequency attenuation and frequency-dependent distortion compromises audio reproduction in portable audio equipment that emphasizes low-frequency effects such as in multimedia laptops, MP3, CD, and DVD players. By eliminating the DC-blocking capacitors through DirectDrive technology, these capacitor-related deficiencies are eliminated. 0.1 TANTALUM 0.01 0.001 ALUM/ELEC 0 0.0001 -3 -6 ATTENUATION (dB) 10 DirectDrive -9 100 1k 10k 100k FREQUENCY (Hz) 330μF -12 Figure 3. Distortion Contributed by DC-Blocking Capacitors 220μF -15 100μF -18 33μF -21 -24 -27 -30 10 100 1k 10k 100k FREQUENCY (Hz) Figure 2. Low-Frequency Attenuation for Common DC-Blocking Capacitor Values Charge Pump The MAX13330/MAX13331 feature a low-noise charge pump. The 2.2MHz (typ) switching frequency is well beyond the audio range. It does not interfere with the audio signals and avoids AM band interference. The switch drivers feature a controlled switching speed that minimizes noise generated by turn-on and turn-off transients. By limiting the switching speed of the charge pump, the di/dt noise caused by the parasitic bond wire and trace inductance is minimized. Although not typically required, additional high-frequency noise attenuation can be achieved by increasing the value of C2 (see the Typical Application Circuits). _______________________________________________________________________________________ 9 MAX13330/MAX13331 Low-Frequency Response In addition to the cost and size disadvantages of the DCblocking capacitors required by conventional headphone amplifiers, these capacitors limit the amplifier’s low-frequency response and can distort the audio signal: 1) The impedance of the headphone load and the DCblocking capacitor form a highpass filter with the -3dB point set by: MAX13330/MAX13331 Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics Diagnostic Output The MAX13330/MAX13331 provides an analog diagnostic output as a fraction of the analog supply voltage VDD. The voltage at DIAG will correspond to the fault condition with the highest priority that is present in the system, as shown in Table 1. When simultaneous fault conditions occur on both headphone outputs, the diagnostic output will only report the fault condition at OUTR until it is cleared or removed. Only then will the fault condition at OUTL be reported at DIAG. Connect DIAG to a high-impedance input. Table 1. MAX13330/MAX13331 Diagnostic Priority VDIAG STATE PRIORITY VDD OUTL Short to VBAT 3/4 VDD OUTR Short to VBAT 1 Shutdown 1/2 VDD OUTL Short to SGND 4 1/4 VDD OUTR Short to SGND 2 No Fault 5 Shutdown — The MAX13330/MAX13331 feature shutdown control allowing audio signals to be shut down or muted. Driving SHDN low disables the amplifiers and the charge pump, sets the amplifier output impedance to 14kΩ (typ), and reduces the supply current. In shutdown mode, the supply current is reduced to 2µA. The charge pump is enabled once SHDN is driven high. 0 Three State 3 For both headphone outputs, short circuits to VBAT are dynamic and VDIAG will be automatically cleared as soon as the fault condition is removed. Short circuits to GND occurring when a positive output voltage is present on OUTL or OUTR, will result in V DIAG being latched until the fault condition is cleared. When VDIAG is latched, it can be cleared by either toggling SHDN low for less than 5µs or initiating a full reset of the MAX13330/MAX13331. Toggling SHDN low for less than 5µs will cause the fault to ground to be cleared without shutting down the device or interrupting the output state of the amplifiers. A full reset requires SHDN to be pulled low for more than 50µs. The amplifier outputs will enter high impedance and remain in that state until the device exits shutdown. 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, on shutdown, the capacitor is discharged to SGND. This results in a DC shift across the capacitor which appears as an audible transient at the speaker. Since the MAX13330/MAX13331 does not require output-coupling capacitors, this problem does not arise. 10 Additionally, the MAX13330/MAX13331 feature extensive click-and-pop suppression that eliminates any audible transient sources internal to the device. The power-up/-down transient graph in the Typical Operating Characteristics shows that there is minimal DC shift and no spurious transients at the output upon startup or shutdown. In most applications, the output of the preamplifier driving the MAX13330/MAX13331 has a DC bias of typically half the supply. At startup, the input-coupling capacitor is charged to the preamplifier’s DC-bias voltage through the feedback resistor of the MAX13330/ MAX13331, resulting in a DC shift across the capacitor and an audible click/pop. Delaying the rise of SHDN 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. Applications Information Power Dissipation Under normal operating conditions, linear power amplifiers can dissipate a significant amount of power. The maximum power dissipation for each package is given in the Absolute Maximum Ratings section under continuous power dissipation or can be calculated by the following equation: PDISSPKG(MAX) = (TJ(MAX) − TA ) θJA where TJ(MAX) is +145°C, TA is the ambient temperature, and θJA is the reciprocal of the derating factor in °C/W as specified in the Absolute Maximum Ratings section. The thermal resistance θJA of the QSOP package is 120°C/W. The MAX13330/MAX13331 have two power dissipation sources: the charge pump and two amplifiers. If power dissipation for a given application exceeds the maximum allowed for a particular package, either reduce VDD, increase load impedance, decrease the ambient temperature, or add heatsinking to the device. Large output, supply, and ground traces improve the maximum power dissipation in the package. ______________________________________________________________________________________ Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics Output Power The device has been specified for the worst-case scenario, when both inputs are in-phase. Under this condition, the amplifiers simultaneously draw current from the charge pump, leading to a proportional reduction in VSS headroom. In typical stereo audio applications, the left and right signals have differences in both magnitude and phase, subsequently leading to an increase in the maximum attainable output power. Figure 4 shows the two extreme cases for in- and out-of-phase. In reality, the available power lies between these extremes. OUTPUT POWER (mW) 200 fIN = 1kHz RL = 32Ω THD+N = 10% Gain-Setting Resistors (MAX13331 Only) The gain of the MAX13330 is internally set at -1.5V/V. All gain-setting resistors are integrated into the device, reducing external component count. The internally set gain, in combination with DirectDrive, results in a headphone amplifier that requires only five tiny 1µF capacitors to complete the amplifier circuit: two for the charge-pump, two for audio input coupling, and one for power-supply bypassing (see the Typical Application Circuits). The gain of the MAX13331 amplifier is set externally as shown in the Typical Application Circuits, the gain is: R A V = − F (V / V ) RIN Choose feedback resistor values of 10kΩ. Values other than 10kΩ increase output offset voltage due to the input bias current, which in turn, increases the amount of DC current flow to the load. OUTPUT POWER vs. SUPPLY VOLTAGE 250 Component Selection INPUTS 180° OUT OF PHASE Input Filtering The input capacitor (CIN), in conjunction with the input resistor (RIN), forms a highpass filter that removes the DC bias from an incoming signal (see the Typical Application Circuits). The AC-coupling capacitor allows the device to bias the signal to an optimum DC level. Assuming zero source impedance, the -3dB point of the highpass filter is given by: 150 INPUTS IN PHASE 100 50 f−3dB = 0 4.00 4.25 4.50 4.75 5.00 5.25 1 (Hz) 2π × RIN × CIN 5.50 SUPPLY VOLTAGE (V) Figure 4. Output Power vs. Supply Voltage UVLO The MAX13330/MAX13331 feature a UVLO function that prevents the device from operating if the supply voltage is less than 3.6V (typ). This feature ensures proper operation during brownout conditions and prevents deep battery discharge. Once the supply voltage reaches the UVLO threshold, the charge-pump is turned on and the amplifiers are powered. Choose CIN so f-3dB is well below the lowest frequency of interest. For the MAX13330, use the value of RIN as given in the Electrical Characteristics table. Setting f -3dB too high affects the device’s low-frequency response. Use capacitors whose dielectrics have lowvoltage coefficients, such as tantalum or aluminum electrolytic. Capacitors with high-voltage coefficients, such as ceramics, can result in increased distortion at low frequencies. Charge-Pump Capacitor Selection Use capacitors with an ESR less than 100mΩ for optimum performance. Low-ESR ceramic capacitors minimize the output resistance of the charge pump. For best performance over the extended temperature range, select capacitors with an X7R dielectric. ______________________________________________________________________________________ 11 MAX13330/MAX13331 Thermal-overload protection limits total power dissipation in the MAX13330/MAX13331. When the junction temperature exceeds +145°C (typ), the thermal-protection circuitry disables the amplifier output stage. The amplifiers are enabled once the junction temperature cools by 5°C. This results in a pulsing output under continuous thermal-overload conditions. MAX13330/MAX13331 Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics Flying Capacitor (C1) The value of the flying capacitor (C1) affects the charge pump’s load regulation and output resistance. A C1 value that is too small degrades the device’s ability to provide sufficient current drive, which leads to a loss of output voltage. Increasing the value of C1 improves load regulation and reduces the charge-pump output resistance to an extent. See the Output Power vs. Load Resistance graph in the Typical Operating Characteristics. Above 1µF, the on-resistance of the switches and the ESR of C1 and C2 dominate. Holding Capacitor (C2) The hold capacitor value and ESR directly affect the ripple at CPVSS. Increasing the value of C2 reduces output ripple. Likewise, decreasing the ESR of C2 reduces both ripple and output resistance. Lower capacitance values can be used in systems with low maximum output power levels. See the Output Power vs. Load Resistance graph in the Typical Operating Characteristics. 12 Power-Supply Bypass Capacitor (C3) The power-supply bypass capacitor (C3) lowers the output impedance of the power supply and reduces the impact of the MAX13330/MAX13331 charge-pump switching transients. Bypass CPVDD with C3, the same value as C1, and place it physically close to the CPVDD and PGND pins. Layout and Grounding Proper layout and grounding are essential for optimum performance. Connect CPVDD and VDD together at the device. Connect CPVSS and V SS together at the device. Bypassing of both supplies is accomplished by charge-pump capacitors C2 and C3 (see the Typical Application Circuits). Place capacitors C2 and C3 as close to the device as possible and bypass them to the PGND plane. Keep PGND and all traces that carry switching transients as short as possible to minimize EMI. Route them away from SGND, the audio signal path, and the external feedback components (MAX13331). Connect the PGND plane and the SGND plane together at a single point on the PCB. Refer to the MAX13330/MAX13331 Evaluation Kit for layout guidelines. ______________________________________________________________________________________ Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics 4V to 5.5V 0.33μF C3 1μF LEFT CHANNEL AUDIO IN SHDN UVLO/ SHUTDOWN CONTROL INL 45kΩ VDD 30kΩ C1P VSS C1 1μF CHARGE PUMP CLICK-AND-POP SUPPRESSION VSS C1N 30kΩ MAX13330 VDD VSS C2 1μF CPVSS PGND SGND INR 0.33μF OUTPUT PROTECTION AND DIAGNOSTICS VDD CPVDD OUTL 1nF DIAG 10nF OUTR 1nF 45kΩ RIGHT CHANNEL AUDIO IN ______________________________________________________________________________________ 13 MAX13330/MAX13331 Typical Application Circuits Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics MAX13330/MAX13331 Typical Application Circuits (continued) CIN 0.33μF RIN 30kΩ LEFT CHANNEL AUDIO IN 4V to 5.5V RF 45kΩ C3 1μF SHDN INL VDD UVLO/ SHUTDOWN CONTROL C1P OUTPUT PROTECTION AND DIAGNOSTICS VDD CPVDD VSS C1 1μF CHARGE PUMP CLICK-AND-POP SUPPRESSION VSS C1N OUTL 1nF DIAG 10nF OUTR MAX13331 VDD VSS CPVSS PGND SGND 1nF INR C2 1μF RIN 30kΩ RF 45kΩ CIN 0.33μF RIGHT CHANNEL AUDIO IN Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. 14 PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 16-QSOP E16-4 21-0055 ______________________________________________________________________________________ Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics REVISION NUMBER REVISION DATE 0 10/08 1 4/09 DESCRIPTION Initial release. PAGES CHANGED — Correct Features for THD+N, style edits 1, 2, 3, 15 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 ____________________ 15 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX13330/MAX13331 Revision History