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HWD2182 250mW Audio Power Amplifier with Shutdown Mode
General Description
The HWD2182 is a single-ended audio power amplifier capable of delivering 250mW of continuous average power into an 8 load with 1% THD+N from a 5V power supply.
Key Specifications
j THD+N at 1kHz at 250mW
1.0% (max) audio power amplifiers were designed specifically j Output Power at 1% THD+N to provide high quality output power with a minimal amount at 1kHz into 4 380mW (typ) of external components using surface mount packaging. Since the HWD2182 does not require bootstrap capacitors or j THD+N at 1kHz at 85mW snubber networks, it is optimally suited for low-power porcontinuous average output table systems. power into 32 0.1% (typ) The HWD2182 features an externally controlled, low power j Shutdown Current 0.7A (typ) consumption shutdown mode which is virtually clickless and popless, as well as an internal thermal shutdown protection Features mechanism. n MSOP surface mount packaging The unity-gain stable HWD2182 can be configured by external n "Click and Pop" Suppression Circuitry gain-setting resistors. n Supply voltages from 2.4V-5.5V n Operating Temperature -40C to 85C n Unity-gain stable n External gain configuration capability n No bootstrap capacitors, or snubber circuits are necessary
continuous average output power into 8
Applications
n Personal Computers n Cellular Phones n General Purpose Audio
Typical Application
Connection Diagram
MSOP and SOIC Package
Top View Order Number HWD2182MM or HWD2182M
*Refer to the Application Information Section for information concerning proper selection of the input and output coupling capacitors.
FIGURE 1. Typical Audio Amplifier Application Circuit
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required, please contact the CSMSC Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Storage Temperature Input Voltage Power Dissipation (Note 3) ESD Susceptibility (Note 4) PIn 5 Junction Temperature Soldering Information Small Outline Package Vapor Phase (60 seconds) Infrared (15 seconds) 215C 220C 6.0 V -65C to +150C -0.3V to VDD + 0.3V Internally limited 2000V 1500V 150C
See AN-450 Surface Mounting and their Effects on Product Reliability for other methods of soldering surface mount devices. Thermal Resistance JC (MSOP) JA (MSOP) JC (SOP) JA (SOP) 56C/W 210C/W 35C/W 170C/W
Operating Ratings
Temperature Range TMIN TA TMAX Supply Voltage -40C TA 85C 2.4V VDD 5.5V
Electrical Characteristics (Notes 1, 2) The following specifications apply for VDD = 5V unless otherwise specified. Limits apply for TA = 25C.
HWD2182 Symbol IDD ISD VOS PO Parameter Quiescent Current Shutdown Current Offset Voltage Output Power Conditions VIN = 0V, IO = 0A Vpin1 = VDD VIN = 0V THD + N = 1% (max); f = 1 kHz; RL = 4 RL = 8 RL = 32 THD + N = 10%; f = 1 kHz RL = 4 RL = 8 RL = 32 THD + N Total Harmonic Distortion + Noise RL = 8, P f = 1 kHz PSRR Power Supply Rejection Ratio Vpin3 = 2.5V, V f = 120 Hz
ripple O
Typical (Note 5) 2 0.5 5 380 270 95 480 325 125
Limit (Note 6) 4.0 5 50
Units (Limits) mA (max) A (max) mV (max) mW
250
mW (min) mW mW mW mW % %
= 250 mWrms;
0.5 0.1
RL = 32, PO = 85 mWrms; = 200 mVrms,
50
dB
Electrical Characteristics (Notes 1, 2) The following specifications apply for VDD = 3V unless otherwise specified. Limits apply for TA = 25C.
HWD2182 Symbol IDD ISD VOS PO Parameter Quiescent Current Shutdown Current Offset Voltage Output Power Conditions VIN = 0V, IO = 0A Vpin1 = VDD VIN = 0V THD + N = 1% (max); f = 1 kHz RL = 8 RL = 32 THD + N = 10%; f = 1 kHz RL = 8 RL = 32 105 40 mW mW 80 30 mW mW Typical (Note 5) 1.2 0.3 5 Limit (Note 6) Units (Limits) mA A mV
2
Electrical Characteristics (Notes 1, 2)
(Continued)
The following specifications apply for VDD = 3V unless otherwise specified. Limits apply for TA = 25C. HWD2182 Symbol THD + N Parameter Total Harmonic Distortion + Noise RL = 8, P f = 1 kHz PSRR Power Supply Rejection Ratio Vpin3 = 2.5V, V f = 120 Hz
ripple
Conditions
O
Typical (Note 5) 0.25 0.3
Limit (Note 6)
Units (Limits) % %
= 70 mWrms;
RL = 32, PO = 30 mWrms; = 200 mVrms,
50
dB
Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified. Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device performance. Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, JA, and the ambient temperature TA. The maximum allowable power dissipation is P DMAX = (TJMAX - TA)/JA. For the HWD2182, TJMAX = 150C, and the typical junction-to-ambient thermal resistance, when board mounted, is 210C/W for the MUA08A Package and 170C/W for the M08A Package. Note 4: Human body model, 100 pF discharged through a 1.5 k resistor. Note 5: Typicals are measured at 25C and represent the parametric norm.
External Components Description
(Refer to Figure 1) Components 1. Ri 2. Ci Functional Description Inverting input resistance which sets the closed-loop gain in conjunction with Rf. This resistor also forms a high pass filter with Ci at fc = 1 / (2RiCi). Input coupling capacitor which blocks the DC voltage at the amplifier's input terminals. Also creates a highpass filter with Ri at fc = 1 / (2RiC i). Refer to the section, Proper Selection of External Components, for an explanation of how to determine the values of Ci. Feedback resistance which sets closed-loop gain in conjunction with Ri. Supply bypass capacitor which provides power supply filtering. Refer to the Application Information section for proper placement and selection of the supply bypass capacitor. Bypass pin capacitor which provides half-supply filtering. Refer to the section, Proper Selection of External Components, for information concerning proper placement and selection of CB. Output coupling capacitor which blocks the DC voltage at the amplifier's output. Forms a high pass filter wth RL at fO = 1 / (2RLC O).
3. Rf 4. CS 5. CB 6. CO
Typical Performance Characteristics
THD+N vs Frequency THD+N vs Frequency THD+N vs Frequency
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Typical Performance Characteristics
THD+N vs Frequency
(Continued) THD+N vs Frequency
THD+N vs Frequency
THD+N vs Frequency
THD+N vs Frequency
THD+N vs Output Power
THD+N vs Output Power
THD+N vs Output Power
4
Typical Performance Characteristics
THD+N vs Output Power THD+N vs Output Power
(Continued)
THD+N vs Output Power
THD+N vs Output Power
THD+N vs Output Power
Output Power vs Supply Voltage
Output Power vs Supply Voltage
Output Power vs Supply Voltage
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Typical Performance Characteristics
Dropout Voltage vs Supply Voltage
(Continued)
Dropout Voltage vs Supply Voltage
Power Supply Rejection Ratio
Output Power vs Load Resistance
Power Dissipation vs Output Power
Supply Current vs Supply Voltage
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Typical Performance Characteristics
Open Loop Frequency Response
(Continued)
Output Attenuation in Shutdown Mode
Noise Floor
Frequency Response vs Output Capacitor Size
Frequency Response vs Output Capacitor Size
Frequency Response vs Input Capacitor Size
Typical Application Frequency Response
Typical Application Frequency Response
Power Derating Curve
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Application Information
SHUTDOWN FUNCTION In order to reduce power consumption while not in use, the HWD2182 contains a shutdown pin to externally turn off the amplifier's bias circuitry. This shutdown features turns the amplifier off when a logic high is placed on the shutdown pin. The trigger point between a logic low and logic high level is typically half supply. It is best to switch between ground and supply to provide maximum device performance. By switching the shutdown pin to the VDD, the HWD2182 supply current draw will be minimized in idle mode. While the device will be disabled with shutdown pin voltages less than V DD, the idle current may be greater than the typical value of 0.5 A. In either case, the shutdown pin should be tied to a definite voltage because leaving the pin floating may result in an unwanted shutdown condition. In many applications, a microcontroller or microprocessor output is used to control the shutdown circuitry which provides a quick smooth transition into shutdown. Another solution is to use a single-pole, single-throw switch in conjunction with an external pull-up resistor. When the switch is closed, the shutdown pin is connected to ground and enables the amplifier. If the switch is open, then the external pull-up resistor will disable the HWD2182. This scheme guarantees that the shutdown pin will not float which will prevent unwanted state changes. POWER DISSIPATION Power dissipation is a major concern when using any power amplifier and must be thoroughly understood to ensure a successful design. Equation 1 states the maximum power dissipation point for a single-ended amplifier operating at a given supply voltage and driving a specified output load. PDMAX = (VDD) 2/(22RL) (1) Even with this internal power dissipation, the HWD2182 does not require heat sinking over a large range of ambient temperature. From Equation 1, assuming a 5V power supply and an 4 load, the maximum power dissipation point is 316 mW. The maximum power dissipation point obtained must not be greater than the power dissipation that results from Equation 2: PDMAX = (TJMAX-T A)/JA (2) For the HWD2182 surface mount package, = 210C/W and JA TJMAX = 150C. Depending on the ambient temperature, TA, of the system surroundings, Equation 2 can be used to find the maximum internal power dissipation supported by the IC packaging. If the result of Equation 1 is greater than that of Equation 2, then either the supply voltage must be decreased, the load impedance increased or T A reduced. For the typical application of a 5V power supply, with an 4 load, the maximum ambient temperature possible without violating the maximum junction temperature is approximately 83C provided that device operation is around the maximum power dissipation point. Power dissipation is a function of output power and thus, if typical operation is not around the maximum power dissipation point, the ambient temperature may be increased accordingly. Refer to the Typical Performance Characteristics curves for power dissipation information for lower output powers. POWER SUPPLY BYPASSING As with any power amplifier, proper supply bypassing is critical for low noise performance and high power supply rejection. The capacitor location on both the bypass and power supply pins should be as close to the device as possible. As
displayed in the Typical Performance Characteristics section, the effect of a larger half supply bypass capacitor is improved low frequency PSRR due to increased half-supply stability. Typical applications employ a 5V regulator with 10 F and a 0.1 F bypass capacitors which aid in supply stability, but do not eliminate the need for bypassing the supply nodes of the HWD2182. The selection of bypass capacitors, especially CB, is thus dependent upon desired low frequency PSRR, click and pop performance as explained in the section, Proper Selection of External Components section, system cost, and size constraints. PROPER SELECTION OF EXTERNAL COMPONENTS Selection of external components when using integrated power amplifiers is critical to optimize device and system performance. While the HWD2182 is tolerant of external component combinations, consideration to component values must be used to maximize overall system quality. The HWD2182 is unity gain stable and this gives a designer maximum system flexibility. The HWD2182 should be used in low gain configurations to minimize THD+N values, and maximize the signal to noise ratio. Low gain configuartions require large input signals to obtain a given output power. Input signals equal to or greater than 1 Vrms are available from sources such as audio codecs. Please refer to the section, Audio Power Amplifier Design, for a more complete explanation of proper gain selection. Besides gain, one of the major considerations is the closed loop bandwidth of the amplifier. To a large extent, the bandwidth is dictated by the choice of external components shown in Figure 1. Both the input coupling capacitor, Ci, and the output coupling capacitor, Co, form first order high pass filters which limit low frequency response. These values should be chosen based on needed frequency response for a few distinct reasons. CLICK AND POP CIRCUITRY The HWD2182 contains circuitry to minimize turn-on and turnoff transients or "clicks and pops." In this case, turn-on refers to either power supply turn-on or the device coming out of shutdown mode. When the device is turning on, the amplifiers are internally muted. An internal current source ramps up the voltage of the bypass pin. Both the inputs and outputs track the voltage at the bypass pin. The device will remain muted until the bypass pin has reached its half supply voltage, 1/2 VDD. As soon as the bypass node is stable, the device will become fully operational, where the gain is set by the external resistors. Although the bypass pin current source cannot be modified, the size of CB can be changed to alter the device turn-on time and the level of "clicks and pops." By increasing the value of C B, the level of turn-on pop can be reduced. However, the tradeoff for using a larger bypass capacitor is an increase in turn-on time for the device. There is a linear relationship between the size of CB and the turn-on time. Here are some typical turn-on times for a given CB: CB 0.01 F 0.1 F 0.22 F TON 20 ms 200 ms 420 ms
0.47 F 900 ms In order to eliminate "clicks and pops," all capacitors must be discharged before turn-on. Rapid on/off switching of the de-
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Application Information
(Continued)
vice or the shutdown function may cause the "click and pop" circuitry to not operate fully, resulting in increased "click and pop" noise. The value of Ci will also reflect turn-on pops. Clearly, a certain size for Ci is needed to couple in low frequencies without excessive attenuation. But in many cases, the speakers used in portable systems have little ability to reproduce signals below 100 Hz to 150 Hz. In this case, using a large input and output coupling capacitor may not increase system performance. In most cases, choosing a small value of Ci in the range of 0.1 F to 0.33 F, along with CB equal to 1.0 F should produce a virtually clickless and popless turn-on. In cases where C i is larger than 0.33 F, it may be advantageous to increase the value of CB. Again, it should be understood that increasing the value of CB will reduce the "clicks and pops" at the expense of a longer device turn-on time. AUDIO POWER AMPLIFIER DESIGN Design a 250 mW/8 Audio Amplifier Given: Power Output Load Impedance Input Level Input Impedance Bandwidth 250 mWrms 8 1 Vrms (max) 20 k 100 Hz-20 kHz 0.50 dB
Extra supply voltage creates headroom that allows the HWD2182 to reproduce peaks in excess of 300 mW without clipping the signal. At this time, the designer must make sure that the power supply choice along with the output impedance does not violate the conditions explained in the Power Dissipation section. Once the power dissipation equations have been addressed, the required gain can be determined from Equation 4. (4) AV = Rf / Ri (5) From Equation 4, the minimum gain is: AV = 1.4 Since the desired input impedance was 20 k, and with a gain of 1.4, a value of 28 k is designated for Rf, assuming 5% tolerance resistors. This combination results in a nominal gain of 1.4. The final design step is to address the bandwidth requirements which must be stated as a pair of -3 dB frequency points. Five times away from a -3 dB point is 0.17 dB down from passband response assuming a single pole rolloff. As stated in the External Components section, both Ri in conjunction with C i, and Co with RL, create first order highpass filters. Thus to obtain the desired frequency low response of 100 Hz within 0.5 dB, both poles must be taken into consideration. The combination of two single order filters at the same frequency forms a second order response. This results in a signal which is down 0.34 dB at five times away from the single order filter -3 dB point. Thus, a frequency of 20 Hz is used in the following equations to ensure that the response is better than 0.5 dB down at 100 Hz. Ci 1 / (2 * 20 k * 20 Hz) = 0.397 F; use 0.39 F. Co 1 / (2 * 8 * 20 Hz) = 995 F; use 1000 F. The high frequency pole is determined by the product of the desired high frequency pole, fH, and the closed-loop gain, A V. With a closed-loop gain of 1.4 and fH = 100 kHz, the resulting GBWP = 140 kHz which is much smaller than the HWD2182 GBWP of 12.5Mhz. This figure displays that if a designer has a need to design an amplifier with a higher gain, the HWD2182 can still be used without running into bandwidth limitations.
A designer must first determine the needed supply rail to obtain the specified output power. Calculating the required supply rail involves knowing two parameters, VOPEAK and also the dropout voltage. The latter is typically 530mV and can be found from the graphs in the Typical Performance Characteristics. VOPEAK can be determined from Equation 3. (3) For 250 mW of output power into an 8 load, the required VOPEAK is 2 volts. A minimum supply rail of 4.55V results from adding VOPEAK and VOD. Since 5V is a standard supply voltage in most applications, it is chosen for the supply rail.
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Physical Dimensions
inches (millimeters) unless otherwise noted
Order Number HWD2182
10
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
Order Number HWD2182
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(Http://www.csmsc.com)
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