EVALUATION KIT AVAILABLE Low-Cost, Mono, 1.4W BTL Audio Power Amplifiers BIAS MAX9716 BIAS MAX9717B/C/D IN-

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1 9-346; Rev 3; 3/2 EVALUATION KIT AVAILABLE Low-Cost, Mono,.4W BTL Audio General Description The MAX976/MAX977 audio power amplifiers are ideal for portable audio devices with internal speakers. A bridge-tied load (BTL) architecture minimizes external component count, while providing high-quality audio reproduction. Both devices deliver.4w continuous power into a 4Ω load with less than % Total Harmonic Distortion (THD) while operating from a single +5V supply. With an 8Ω load, both devices deliver W continuous power. These devices also deliver 35mW continuous power into an 8Ω load while operating from a single +3.V supply. The devices are available as adjustable gain amplifiers (MAX976/MAX977A) or with internally fixed gains of 6dB, 9dB, and 2dB (MAX977B/ MAX977C/MAX977D), reducing component count. A low-power shutdown mode disables the bias generator and amplifiers, reducing quiescent current consumption to less than na. These devices feature Maxim s industry-leading, comprehensive click-and-pop suppression that reduces audible clicks and pops during startup and shutdown. The MAX977 features a headphone sense input (BTL/SE) that senses when a headphone is connected to the device, disables the BTL slave driver, muting the speaker while driving the headphone as a single-ended load. The MAX976 is pin compatible with the LM489 and is available in 9-bump UCSP, 8-pin TDFN (3mm x 3mm), and 8-pin µmax packages. The MAX977 is available in 9-bump UCSP, 8-pin TDFN, and 8-pin µmax packages. Both devices operate over the -4 C to +85 C extended temperature range. Mobile Phones PDAs Applications Portable Devices Features 2.7V to 5.5V Single-Supply Operation.4W into 4Ω at % THD+N na Low-Power Shutdown Mode 73dB PSRR at khz No Audible Clicks or Pops at Power-Up/Down Internal Fixed Gain to Reduce Component Count (MAX977B/C/D) Adjustable Gain Option (MAX976/MAX977A) BTL /SE Input Senses when Headphones are Connected (MAX977) Pin Compatible with LM489 (MAX976) Pin Compatible with TPA7 (MAX977A) Available in Compact, Thermally Enhanced µmax and TDFN (3mm x 3mm) Packages Ordering Information PART TEMP RANGE P PACKAGE MAX976ETA+T -4 C to +85 C 8 TDFN-EP* Adj. MAX976EBL+TG45-4 C to +85 C 3 x 3 UCSP Adj. MAX976EUA -4 C to +85 C 8 µmax-ep* Adj. MAX976EUA/V+ -4 C to +85 C 8 µmax-ep* Adj. *EP = Exposed pad. +Denotes a lead(pb)-free/rohs-compliant package. G45 indicates protective die coating. /V denotes automotive qualified part. Ordering Information continued at end of data sheet. GAIN (db) Pin Configurations and Selector Guide appear at end of data sheet. Simplified Block Diagrams MAX976/MAX977 SINGLE SUPPLY 2.7V TO 5.5V SINGLE SUPPLY 2.7V TO 5.5V MAX976 MAX977B/C/D BTL/SE UCSP is a trademark of Maxim Integrated Products, Inc. µmax is a registered trademark of Maxim Integrated Products, Inc. Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim's website at

2 Low-Cost, Mono,.4W BTL Audio MAX976/MAX977 ABSOLUTE MAXIMUM RATINGS Supply Voltage ( to )...-.3V to +6V Any Other Pin to...-.3v to ( +.3V) IN_,,, BTL/SE Continuous Current...2mA OUT_ Short-Circuit Duration to or (Note )...Continuous Continuous Power Dissipation (T A = +7 C) 8-Pin TDFN (derate 24.4mW/ C above +7 C)...95mW 8-Pin µmax (derate.3mw/ C above +7 C)...825mW 9-Bump UCSP (derate 5.2mW/ C above 7 C)...42mW 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 5V Supply Operating Temperature Range...-4 C to +85 C Maximum Junction Temperature...+5 C Storage Temperature Range C to +5 C Lead Temperature (soldering, s)...+3 C Soldering Temperature (reflow) Lead(Pb)-Free Packages C Packages Containing Lead(Pb) C ( = 5V, V = V, =, T A = +25 C. C = µf, R IN = R F = (MAX976/MAX977A), IN+ = (MAX976), BTL/SE = (MAX977_), R L = connected between OUT+ and. Typical values are at T A = +25 C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage Inferred by PSRR test V Quiescent Supply Current I CC V = V IN+ = V (Note 3), T A = -4 C to +85 C ma Shutdown Supply Current I =. µa Threshold BTL/SE Threshold V IH.2 V IL.4 V IH V IL Common-Mode Bias Voltage V (Note 4).9 x /2-6% /2.7 x /2 + 6% V V V Output Offset Voltage V OS V = V OUT+, V IN+ = V (Note 5) ±7 ±5 mv = 2.7V to 5.5V DC, V =.5V 6 8 Power-Supply Rejection Ratio PSRR V IN+ = V, f = 27Hz 6 V RIPPLE = 2mV P-P, (Note 6) f = khz 73, THD+N = %, f IN = khz (Note 7).8., THD+N = %, f IN = khz (Note 7).4 Output Power P OUT R L = 6Ω, BTL/SE = (single-ended.55 mode), THD+N = %, f IN = khz Total Harmonic Distortion Plus Noise THD+N,, f IN = khz, P OUT =.5W (Note 8) db W.24 % Output Noise Density e n f IN = khz 6 nv/ Hz Signal-to-Noise Ratio SNR THD+N = % 5 db 2

3 Low-Cost, Mono,.4W BTL Audio ELECTRICAL CHARACTERISTICS 5V Supply (continued) ( = 5V, V = V, =, T A = +25 C. C = µf, R IN = R F = (MAX976/MAX977A), IN+ = (MAX976), BTL/SE = (MAX977_), R L = connected between OUT+ and. Typical values are at T A = +25 C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Output Short-Circuit Current Limit I SC (Note 9). A Thermal Shutdown Threshold +6 C Thermal Shutdown Hysteresis 5 C Power-Up/Enable from Shutdown Time (Note ) t PU C =.µf 25 Shutdown Time t 5 µs Input Resistance R IN MAX977B/C/D kω 25 ms MAX976/MAX977 ELECTRICAL CHARACTERISTICS 3V Supply ( = 3V, V = V, =, T A = +25 C. C = µf, R IN = R F = (MAX976/MAX977A), IN+ = (MAX976), BTL/SE = (MAX977_), R L = connected between OUT+ and. Typical values are at T A = +25 C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Quiescent Supply Current I CC V = V IN+ = V (Note 3), T A = -4 C to +85 C 4 8. ma Shutdown Supply Current I =. µa Threshold BTL/SE Threshold V IH.2 V IL.4 V IH V IL Common-Mode Bias Voltage V (Note 4) Output Offset Voltage V OS V = V OUT+, V IN+ = V (Note 5) ±7 ±5 mv.9 x /2-9% /2.7 x /2 + 9% V V V Power-Supply Rejection Ratio PSRR V IN+ = V, f = 27Hz 6 V RIPPLE = 2mV P-P, (Note 6) f = khz 73, THD+N = %, f IN = khz (Note 7) 35 Output Power P OUT, THD+N = %, f IN = khz (Note 7) 525 db mw Total Harmonic Distortion Plus Noise THD+N,, f IN = khz, P OUT =.5W, = 3V (Note 8).24 % Output-Noise Density e n f IN = khz 6 nv/ Hz Signal-to-Noise Ratio SNR THD+N = % db 3

4 Low-Cost, Mono,.4W BTL Audio MAX976/MAX977 ELECTRICAL CHARACTERISTICS 3V Supply (continued) ( = 3V, V = V, =, T A = +25 C. C = µf, R IN = R F = (MAX976/MAX977A), IN+ = (MAX976), BTL/SE = (MAX977_), R L = connected between OUT+ and. Typical values are at T A = +25 C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Output Short-Circuit Current Limit I SC (Note 9). A Thermal Shutdown Threshold +6 C Thermal Shutdown Hysteresis 5 C Power-Up/Enable from Shutdown Time (Note ) t PU C =.µf 25 Shutdown Time t 5 µs Input Resistance R IN MAX977B/C/D kω Note : Continuous power dissipation must also be observed. Note 2: All specifications are tested at T A = +25 C. Specifications over temperature (T A = T MIN to T MAX ) are not production tested, and guaranteed by design. Note 3: Quiescent power-supply current is specified and tested with no load. Quiescent power-supply current depends on the offset voltage when a practical load is connected to the amplifier. Note 4: Common-mode bias voltage is the voltage on and is nominally /2. Note 5: V OS = V OUT+ - V. Note 6: The amplifier input is AC-coupled to through C IN. Note 7: Output power is specified by a combination of a functional output current test and characterization analysis. Note 8: Measurement bandwidth for THD+N is 22Hz to 22kHz. Note 9: Extended short-circuit conditions result in a pulsed output. Note : Time for V OUT to rise to 5% of final DC value. 25 ms 4

5 Low-Cost, Mono,.4W BTL Audio Typical Operating Characteristics ( = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, BTL mode, T A = +25 C, unless otherwise noted.).. TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY = 5V OUTPUT POWER = 8mW OUTPUT POWER = 3mW. k k k MAX976 toc.. TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY = 5V A V = 2dB OUTPUT POWER = 8mW OUTPUT POWER = 2mW. k k k MAX976 toc2.. TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY = 3V OUTPUT POWER = 25mW OUTPUT POWER = 3mW. k k k MAX976 toc3 MAX976/MAX977 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY = 3V A V = 2dB MAX976 toc4 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY = 5V MAX976 toc5 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY = 5V A V = 2dB MAX976 toc6. OUTPUT POWER = 2mW. OUTPUT POWER = W. OUTPUT POWER = W. OUTPUT POWER = 5mW. OUTPUT POWER = 2mW. OUTPUT POWER = 25mW. k k k. k k k. k k k TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY = 3V MAX976 toc7 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY = 3V A V = 2dB MAX976 toc8 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (SINGLE-ENDED) = 5V R L = 6Ω A V = 2dB MAX976 toc9. OUTPUT POWER = 35mW. OUTPUT POWER = 35mW.. OUTPUT POWER = 25mW. OUTPUT POWER = 5mW. OUTPUT POWER = 5mW. OUTPUT POWER = 25mW. k k k. k k k. k k k 5

6 Low-Cost, Mono,.4W BTL Audio MAX976/MAX977 Typical Operating Characteristics (continued) ( = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, BTL mode, T A = +25 C, unless otherwise noted.).. TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER = 5V f IN = Hz f IN = khz f IN = khz OUTPUT POWER (W) MAX976 toc... TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER = 5V A V = 2dB.2 f IN = khz f IN = khz f IN = Hz OUTPUT POWER (W).2 MAX976 toc.4.. TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER = 3V f IN = Hz f IN = khz f IN = khz OUTPUT POWER (mw) MAX976 toc2 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER = 3V A V = 2dB MAX976 toc3 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER = 5V MAX976 toc4 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER = 5V A V = 2dB MAX976 toc5. f IN = khz. f IN = Hz f IN = khz. f IN = khz. f IN = khz f IN = Hz. f IN = khz. f IN = Hz f IN = khz OUTPUT POWER (mw) OUTPUT POWER (W) OUTPUT POWER (W) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER = 3V MAX976 toc6 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER = 3V A V = 2dB MAX976 toc7 TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (SINGLE-ENDED) = 5V R L = 6Ω f IN = Hz MAX976 toc8. f IN = khz f IN = khz. f IN = khz f IN = khz. f IN = khz f IN = khz. f IN = Hz. f IN = Hz OUTPUT POWER (mw) OUTPUT POWER (mw) OUTPUT POWER (mw) 6

7 Low-Cost, Mono,.4W BTL Audio Typical Operating Characteristics (continued) ( = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, BTL mode, T A = +25 C, unless otherwise noted.) OUTPUT POWER (W) f = khz OUTPUT POWER vs. SUPPLY VOLTAGE THD+N = % THD+N = % SUPPLY VOLTAGE (V) MAX976 toc9 OUTPUT POWER (W) f = khz OUTPUT POWER vs. SUPPLY VOLTAGE THD+N = % THD+N = % SUPPLY VOLTAGE (V) MAX976 toc2 OUTPUT POWER (mw) = 5V f = khz OUTPUT POWER vs. LOAD RESISTANCE THD+N = % THD+N = % LOAD RESISTANCE (Ω) MAX976 toc2 MAX976/MAX977 OUTPUT POWER (mw) OUTPUT POWER vs. LOAD RESISTANCE THD+N = % = 3V f = khz THD+N = % MAX976 toc22 POWER DISSIPATION (W) = 5V f = khz POWER DISSIPATION vs. OUTPUT POWER MAX976 toc23 POWER DISSIPATION (mw) = 3V f = khz POWER DISSIPATION vs. OUTPUT POWER MAX976 toc24 LOAD RESISTANCE (Ω) OUTPUT POWER (W) OUTPUT POWER (mw) POWER DISSIPATION (W) = 5V f = khz POWER DISSIPATION vs. OUTPUT POWER MAX976 toc25 POWER DISSIPATION (mw) = 3V f = khz POWER DISSIPATION vs. OUTPUT POWER MAX976 toc26 OUTPUT-NOISE DENSITY (nv/ Hz) OUTPUT-NOISE DENSITY vs. FREQUENCY MAX976 toc OUTPUT POWER (W) OUTPUT POWER (mw) k k k 7

8 Low-Cost, Mono,.4W BTL Audio MAX976/MAX977 Typical Operating Characteristics (continued) ( = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, BTL mode, T A = +25 C, unless otherwise noted.) GAIN AND PHASE ( /db) GAIN AND PHASE vs. FREQUENCY A V = 6dB -2 k k k M M MAX976 toc28 PSRR (db) POWER-SUPPLY REJECTION RATIO vs. FREQUENCY -9 k k k MAX976 toc29 SUPPLY CURRENT (ma) SUPPLY CURRENT vs (V) MAX976 toc3 SUPPLY CURRENT (ma) SUPPLY CURRENT vs. TEMPERATURE = 5V = 3V TEMPERATURE ( C) SHUTDOWN CURRENT (na) MAX976 toc3 SHUTDOWN CURRENT vs. (V) COMING OUT OF SHUTDOWN MAX976 toc32 MAX976 toc34 ms/div SHUTDOWN CURRENT (na) V/div OUT+ V/div V/div OUT+ - 2mV/div SHUTDOWN CURRENT vs. TEMPERATURE GOING INTO SHUTDOWN MAX976 toc33 = 5V µs/div = 3V TEMPERATURE ( C) MAX976 toc35 2V/div OUT+ V/div V/div OUT+ - 2mV/div 8

9 Low-Cost, Mono,.4W BTL Audio PIN TDFN/µMAX BUMP UCSP MAX976 MAX977 MAX976 MAX977 NAME C3 C3 Active-Low Shutdown Pin/Bump Description FUNCTION 2 2 C C DC Bias Bypass Capacitor Connection. Bypass to ground with a µf capacitor. 3 A3 IN+ Noninverting Input 4 4 A A Inverting Input 5 5 A2 A2 OUT+ Bridge Amplifier Positive Output 6 6 B3 B3 Power Supply. Bypass with a µf capacitor to ground. 7 7 B, B2 B, B2 Ground 8 8 C2 C2 Bridge Amplifier Negative Output. becomes high-impedance when BTL/SE is driven high. 3 A3 BTL/SE BTL/Single-Ended Mode Input. Logic low sets the device in BTL mode. Logic high sets the device in single-ended mode. EP Exposed Pad (TDFN and µmax Only). Connect EP to. MAX976/MAX977 Detailed Description The MAX976/MAX977 are.3w BTL speaker amplifiers. Both devices feature a low-power shutdown mode, and industry-leading click-and-pop suppression. The MAX977 features a headphone sense input that disables the slave BTL amplifier to drive the headphone as a single-ended load. These devices consist of high output-current audio amps configured as BTL amplifiers (see Functional Diagrams). The closed-loop gain of the input op amp sets the single-ended gain of the device. Two external gain resistors set the gain of the MAX976 and MAX977A (see the Gain-Setting Resistor section). The MAX977B/C/D feature internally set gains of 6dB, 9dB, and 2dB, respectively. The output of the first amplifier serves as the input of the second amplifier, which is configured as an inverting unity-gain follower. This results in two outputs, identical in amplitude, but 8 out-of-phase. The MAX976/MAX977 operate from a single 2.7V to 5.5V supply and feature an internally generated, commonmode bias voltage of /2 referenced to ground. provides both click-and-pop suppression and sets the DC bias level for the audio outputs. The MAX976 can be configured as a single-ended or differential input. For single-ended input, connect the noninverting input IN+ to externally. The MAX977 is internally connected to the amplifier noninverting input IN+. The MAX977 can only be used with a single-ended input. Always bypass to ground with a capacitor. Choose the value of the bypass capacitor as described in the Capacitor section. Do not connect external loads to. Any load lowers the voltage, affecting the overall performance of the device. BTL/SE Control Input The MAX977 features a headphone sense input, BTL/SE, that enables headphone jack sensing to control the power amplifier output configuration. Driving BTL/SE low enables the slave amplifier (). Driving BTL/SE high disables the slave amplifier. Shutdown Mode The MAX976/MAX977 feature a low-power shutdown mode that reduces quiescent current consumption to na. Entering shutdown disables the bias circuitry, forces the amplifier outputs to through an internal resistor. Drive low to enter shutdown mode; drive high for normal operation. Click-and-Pop Suppression The MAX976/MAX977 feature Maxim s industry-leading click-and-pop suppression circuitry. During startup, the amplifier common-mode bias voltage ramps to the DC bias. When entering shutdown, the amplifier outputs are pulled to through an internal resistor. This scheme minimizes the energy present in the audio band. 9

10 Low-Cost, Mono,.4W BTL Audio MAX976/MAX977 + V OUT(P-P) - Figure. Bridge-Tied Load Configuration Applications Information BTL Amplifier The MAX976/MAX977 are designed to drive a load differentially, a configuration referred to as bridge-tied load or BTL. The BTL configuration (Figure ) offers advantages over the single-ended configuration, where one side of the load is connected to ground. Driving the load differentially doubles the output voltage compared to a single-ended amplifier under similar conditions. Thus, the differential gain of the device is twice the closed-loop gain of the input amplifier. The effective gain is given by: AV Substituting 2 x V OUT(P-P) for V OUT(P-P) into the following equations yields four times the output power due to doubling of the output voltage: VRMS POUT = 2 = = RF RIN VOUT( P P) VRMS RL 2 x V OUT(P-P) V OUT(P-P) There is no net DC voltage across the load because the differential outputs are each biased at midsupply. This eliminates the need for DC-blocking capacitors required for single-ended amplifiers. These capacitors can be large and expensive, consume board space, and degrade low-frequency performance. Power Dissipation and Heat Sinking Under normal operating conditions, the MAX976/ MAX977 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) θja TA where T J(MAX) is +5 C, T A is the ambient temperature, and θ JA is the reciprocal of the derating factor in C/W as specified in the Absolute Maximum Ratings section. For example, θ JA of the TDFN package is 4 C/W. The increase in power delivered by the BTL configuration directly results in an increase in internal power dissipation over the single-ended configuration. The maximum power dissipation for a given and load is given by the following equation: V P CC DISS( MAX) = π RL If the power dissipation for a given application exceeds the maximum allowed for a given package, reduce power dissipation by increasing the ground plane heatsinking capability and the size of the traces to the device (see the Layout and Grounding section). Other methods for reducing power dissipation are to reduce, increase load impedance, decrease ambient temperature, reduce gain, or reduce input signal. Thermal-overload protection limits total power dissipation in the MAX976/MAX977. Thermal protection circuitry disables the amplifier output stage when the junction temperature exceeds +6 C. The amplifiers are enabled once the junction temperature cools by 5 C. A pulsing output under continuous thermal-overload conditions results as the device heats and cools. Fixed Gain The MAX977B, MAX977C, and MAX977D feature internally fixed gains of 6dB, 9dB, and 2dB, respectively (see the Selector Guide). Fixed gain simplifies designs, reduces pin count, decreases required footprint size, and eliminates external gain-setting resistors. Resistors R IN and R F shown in the MAX977B/C/D Typical Operating Circuit are used to achieve each fixed gain.

11 Low-Cost, Mono,.4W BTL Audio AUDIO INPUT C IN R IN Adjustable Gain Gain-Setting Resistors External feedback resistors set the gain of the MAX976 and MAX977A. Resistors R F and R IN (see Figure 2) set the gain of the amplifier as follows: AV = MAX976 Figure 2. Setting the MAX976/MAX977A Gain IN+ RF 2 R IN OUT+ Where A V is the desired voltage gain. Hence, an R IN of and an R F of yields a gain of 2V/V, or 6dB. R F can be either fixed or variable, allowing the use of a digitally controlled potentiometer to alter the gain under software control. The gain of the MAX977 in a single-ended output configuration is half the gain when configured as BTL output. Choose R F between kω and 5kΩ for the MAX976 and MAX977A. Gains for the MAX977B/C/D are set internally. Input Filter C IN and R IN form a highpass filter that removes the DC bias from an incoming signal. The AC-coupling capacitor allows the amplifier to bias the signal to an optimal DC level. Assuming zero-source impedance, the -3dB point of the highpass filter is: f 3dB = 2πRINCIN Setting f -3dB too high affects the low-frequency response of the amplifier. Use capacitors with dielectrics that have low-voltage coefficients, such as tantalum or aluminum electrolytic. Capacitors with highvoltage coefficients, such as ceramics, can increase distortion at low frequencies. R F Output-Coupling Capacitor The MAX977 require output-coupling capacitors to operate in single-ended (headphone) mode. The output-coupling capacitor blocks the DC component of the amplifier output, preventing DC current from flowing to the load. The output capacitor and the load impedance form a highpass filter with a -3dB point determined by: f 3dB = 2πRLCOUT As with the input capacitor, choose C OUT such that f -3dB is well below the lowest frequency of interest. Setting f -3dB too high affects the amplifier s low-frequency response. Load impedance is a concern when choosing C OUT. Load impedance can vary, changing the -3dB point of the output filter. A lower impedance increases the corner frequency, degrading low-frequency response. Select C OUT such that the worstcase load/c OUT combination yields an adequate response. Select capacitors with low ESR to minimize resistive losses and optimize power transfer to the load. Differential Input The MAX976 can be configured for a differential input. The advantage of differential inputs is that any common-mode noise is attenuated and not passed through the amplifier. This input improves noise rejection and provides common-mode rejection (Figure 3). External components should be closely matched for high CMRR. Figure 4 shows the MAX976 configured for a differential input. CMRR (db) COMMON-MODE REJECTION RATIO vs. FREQUENCY - k k k Figure 3. CMRR with Differential Input V RIPPLE = 2mV P-P C = µf MAX976/MAX977

12 Low-Cost, Mono,.4W BTL Audio MAX976/MAX977 22pF C R F CLICKLESS/POPLESS SHUTDOWN CONTROL OFF ON AUDIO INPUT AUDIO INPUT C IN.33µF C IN.33µF R IN R IN IN+ MAX976 OUT+ R F 22pF VALUES SHOWN FOR db GAIN. Figure 4. MAX976 Differential Input Capacitor is the output of the internally-generated /2 bias voltage. The bypass capacitor, C, improves the power-supply rejection ratio by reducing power supply and other noise sources at the common-mode bias node. C also generates the clickless/popless startup DC bias waveform for the speaker amplifiers. Bypass with a µf capacitor to. Larger C values improve PSRR but slow down t ON time. Do not connect external loads to. Supply Bypassing Proper power-supply bypassing ensures low-noise, low-distortion performance. Connect a µf ceramic capacitor from to. Add additional bulk capacitance as required by the application. Connect the bypass capacitor as close to the device as possible. Layout and Grounding Proper PC board layout and grounding is essential for optimizing performance. Use large traces for the power-supply inputs and amplifier outputs to minimize losses due to parasitic trace resistance. Large traces also aid in moving heat away from the package. Proper grounding improves audio performance and prevents digital switching noise from coupling into the audio signal. The MAX976/MAX977 TDFN and µmax packages feature exposed thermal pads on their undersides. This pad lowers the thermal resistance of the package by providing a direct-heat conduction path from the die to the printed circuit board. Connect the exposed pad to the ground plane using multiple vias, if required. 2

13 Low-Cost, Mono,.4W BTL Audio UCSP Applications Information For the latest application details on UCSP construction, dimensions, tape carrier information, printed circuit board techniques, bump-pad layout, and recommended reflow temperature profile, as well as the latest information on reliability testing results, refer to the application note, UCSP A Wafer-Level Chip-Scale Package available on Maxim s web site at UCSP Marking Information Pin A Bump Indicator AAA: Product ID code XXX: Lot Code AAA XXX Ordering Information (continued) PART TEMP RANGE P PACKAGE Selector Guide PART BTL/SE INPUT GAIN (db) MAX976 Adjustable MAX977A Adjustable MAX977B 6 MAX977C 9 MAX977D 2 GAIN (db) MAX977AEBL+TG45-4 C to +85 C 3 x 3 UCSP Adj. MAX977AETA+T -4 C to +85 C 8 TDFN-EP* Adj. MAX977AEUA -4 C to +85 C 8 µmax-ep* Adj. MAX977BEBL+TG45-4 C to +85 C 3 x 3 UCSP 6 MAX977BETA+T -4 C to +85 C 8 TDFN-EP* 6 MAX977BEUA -4 C to +85 C 8 µmax-ep* 6 MAX977CEBL+TG45-4 C to +85 C 3 x 3 UCSP 9 MAX977CETA+T -4 C to +85 C 8 TDFN-EP* 9 MAX977CEUA -4 C to +85 C 8 µmax-ep* 9 MAX977DEBL+TG45-4 C to +85 C 3 x 3 UCSP 2 MAX977DETA+T -4 C to +85 C 8 TDFN-EP* 2 MAX977DEUA -4 C to +85 C 8 µmax-ep* 2 *EP = Exposed pad. +Denotes a lead(pb)-free/rohs-compliant package. G45 indicates protective die coating. MAX976/MAX977 PROCESS: BiCMOS Chip Information 3

14 Low-Cost, Mono,.4W BTL Audio MAX976/MAX977 TOP VIEW MAX976 µmax IN+ OUT Pin/Bump Configurations BTL/SE 8 7 MAX OUT+ µmax TOP VIEW (BUMPS ON BOTTOM) MAX MAX A OUT+ IN+ A OUT+ BTL/SE B B C C UCSP (.5mm x.5mm) UCSP (.5mm x.5mm) IN+ 3 MAX976 6 BTL/SE 3 MAX OUT+ 4 5 OUT+ TDFN (3mm x 3mm x.8mm) TDFN (3mm x 3mm x.8mm) 4

15 Low-Cost, Mono,.4W BTL Audio C IN.33µF AUDIO INPUT C µf R IN Functional Diagrams/Typical Operating Circuits µf IN+ CLICKLESS/POPLESS SHUTDOWN CONTROL MAX976 OUT+ OFF ON MAX976/MAX977 VALUES SHOWN FOR 2dB GAIN. R F 4kΩ µf CLICKLESS/POPLESS SHUTDOWN CONTROL OFF ON C µf kω C OUT µf C IN.33µF AUDIO INPUT R IN MAX977A BTL/SE OUT+ kω kω VALUES SHOWN FOR BTL 2dB GAIN, HEADPHONE 6dB GAIN. R F 4kΩ 5

16 Low-Cost, Mono,.4W BTL Audio MAX976/MAX977 µf C µf Functional Diagrams/Typical Operating Circuits (continued) CLICKLESS/POPLESS SHUTDOWN CONTROL OFF ON kω IN+ C OUT µf AUDIO INPUT C IN.33µF R IN R F BTL/SE OUT+ kω kω MAX977B MAX977C MAX977D 6

17 Low-Cost, Mono,.4W BTL Audio Package Information For the latest package outline information and land patterns (footprints), go to 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. 8 µmax U8E TDFN-EP T UCSP B MAX976/MAX977 7

18 Low-Cost, Mono,.4W BTL Audio MAX976/MAX977 Package Information (continued) For the latest package outline information and land patterns (footprints), go to 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. 8

19 Low-Cost, Mono,.4W BTL Audio Package Information (continued) For the latest package outline information and land patterns (footprints), go to 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. COMMON DIMENSIONS SYM BOL MIN. M AX. A.7.8 D E A..5 L.2.4 k A2.25 MIN..2 REF. PACKAGE VARIATIONS PKG.CODE N D2 E2 e JEDEC SPEC b [(N/2)-]x e T ±. 2.3±..95 BSC M O 229 /W EEA.4±.5.9 REF T ±. 2.3±..65 BSC M O 229 /W EEC.3±.5.95 REF T ±. 2.3±..65 BSC M O 229 /W EEC.3±.5.95 REF T33- T33M K- T33-2 T433-.5±. 2.3±..5 BSC M O 229 /W EED-3.5±. 2.3±..5 BSC M O 229 /W EED-3 4.5±..7±. 2.3±. T ±. 2.3±. T433-3F 4.7±. 2.3±..4 BSC ±.5.2±.5 2. REF.25±.5 2. REF 2.3±..5 BSC M O 229 /W EED-3.25±.5 2. REF 2.4 REF.4 BSC ± REF.4 BSC ± REF MAX976/MAX977 9

20 Low-Cost, Mono,.4W BTL Audio MAX976/MAX977 Package Information (continued) For the latest package outline information and land patterns (footprints), go to 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. 2

21 Low-Cost, Mono,.4W BTL Audio REVISION NUMBER REVISION DATE DESCRIPTION Revision History PAGES CHANGED 2 3/9 Added lead-free and G45 options to Ordering Information, 3 3 3/2 Add automotive qualified part MAX976/MAX977 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. 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. 2 Maxim Integrated Products, 2 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.