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MP7731
5W - 30W Class D Mono Bridged Audio Amplifier
The Future of Analog IC Technology
DESCRIPTION
The MP7731 is a mono, 5W - 30W Class D Audio Amplifier. It is one of MPS' second generation of fully integrated audio amplifiers which dramatically reduces solution size by integrating the following: Start Up / Shut Down Pop Elimination Short Circuit Protection Circuits 180m Power MOSFETs Mute / Standby Mode The MP7731 utilizes a full bridge output structure capable of delivering 5W - 30W into 4 speakers. As in all other MPS Class D Audio Amplifiers, this device exhibits the high fidelity of a Class AB amplifier with an efficiency of 90%. The circuit is based on the MPS' proprietary variable frequency topology Analog Adaptive Modulation (AAMTM, Patent No. 6,420,930; other patents pending) that delivers excellent PSRR, fast response time and operates on a single power supply.
FEATURES
30W into 4 with VDD = 16.5V 90% Efficiency at 5W Amplifies Full Audio Range with Low THD+N Typical = 0.1% 9.5V to 18V Supply Voltage Operation Full Bridge Output Drive 4 Integrated 180m Switches Turn On / Turn Off Click and Pop Suppression Integrated Short Circuit Protection Integrated Thermal shutdown Mute / Standby Mode
APPLICATIONS
* * * * * * * Flat Panel LCD and PDP Displays Notebook and Multimedia Computers Televisions Home Stereos DVD and VCD Players Game Devices and Systems Monitors
EVALUATION BOARD REFERENCE
Board Number EV0045 Dimensions 4.8cm x 3.0cm x 1.5cm
"MPS" and "The Future of Analog IC Technology" are Registered Trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
THD+N vs Output Power
VCC
20 19 18 17 16 15 14 13 12 11
MP7731
1 2 NC PIN1 NIN1 AGND1 NC EN1 NIN2 PIN2 AGND2 EN2 PGND1 SW1 VDD1 BS1 NC PGND2 SW2 VDD2 BS2 NC
+
VCC
AUDIO IN+
3 4 5 6
VCC VCC +
AUDIO IN-
7 8 9
EN
10
VCC
50 f=1kHz 20 10 5 2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M 1
THD+N (%)
10
50
OUTPUT POWER (W)
MP7731 Rev. 1.8 9/25/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
1
MP7731 - 5W - 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
PACKAGE REFERENCE
ABSOLUTE MAXIMUM RATINGS (1)
Supply Voltage VDD ............................................. 26V BS Voltage ............................ VSW-0.3V to VSW+6.5V Enable Voltage VEN ................................. -0.3V to 6V VSW, VPIN, VNIN..................................... -1V to VDD+1V AGND to PGND................................... -0.3V to 0.3V Junction Temperature......................................150C Lead Temperature ...........................................260C Storage Temperature ....................... -65C to 150C
NC PIN1 NIN1 AGND1 NC EN1 NIN2 PIN2 AGND2 EN2
1 2 3 4 5 6 7 8 9 10
20 19 18 17
PGND1 SW1 VDD1 BS1 NC PGND2 SW2 VDD2 BS2 NC
MP7731
16 15 14 13 12 11
Recommended Operating Conditions
(2)
Supply Voltage VDD ................................ 9.5V to 18V Operating Temperature TA ................. -40C to 85C
Thermal Resistance
(3)
TSSOP20 ............................... 40 ....... 6.... C/W
Notes: 1) Exceeding these ratings may damage the device. 2) The device is not guaranteed to function outside of its operating conditions. 3) Measured on approximately 1" square of 1 oz copper.
JA
JC
EXPOSED PAD
Part Number* MP7731DF *
Package TSSOP20
Temperature -40C to +85C
For Tape & Reel, add suffix -Z (eg. MP7731DF-Z) For RoHS compliant packaging, add suffix -LF (eg. MP7731DF-LF-Z)
ELECTRICAL CHARACTERISTICS (4)
VDD = 16.5V, VEN = 5V, RL = 4, TA = +25C, unless otherwise noted.
Parameter Standby Current Quiescent Current SW On Resistance Short Circuit Current PIN, NIN Input Common Mode Voltage Range PIN, NIN Input Current EN Enable Threshold Voltage EN Enable Input Current Thermal Shutdown Trip Point Thermal Shutdown Hysteresis Sourcing and Sinking Sourcing and Sinking 0 VPIN=VNIN=8V VEN Rising VEN Falling VEN = 5V TJ Rising 0.4 Symbol Condition VEN = 0V Min Typ 2 3 0.18 5.0 VDD/2 1 1.4 1.2 1 150 30 VDD-1.5 5 2.0 Max 10 6 Units A mA A V A V V A C C
MP7731 Rev. 1.8 9/25/2006
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2
MP7731 - 5W - 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
OPERATING SPECIFICATIONS
Circuit of Figure 1, VDD = 16.5V, VEN = 5V, RL = 4, TA = +25C, unless otherwise noted.
Parameter Standby Current Quiescent Current Power Output f=1KHz, THD+N=10% f=1KHz, THD+N=10%, RL=8 POUT=1W, f=1KHz POUT=1W, f=1KHz, RL=8 f=1KHz, POUT=10W f=1KHz, POUT=10W, RL=8 Symbol Condition VEN = 0V Min Typ 700 28 30 17 0.2 0.1 85 88 20 90 370 60 Max Units A mA W W % % % % KHz dB V dB
THD+ Noise Efficiency Maximum Power Bandwidth Dynamic Range Noise Floor Power Supply Rejection
A-Weighted f=1KHz
Note: 4) The device is not guaranteed to function outside its operating rating.
MP7731 Rev. 1.8 9/25/2006
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3
MP7731 - 5W - 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
TYPICAL PERFORMANCE CHARACTERISTICS
Circuit of Figure 1, VDD=16.5V, TA=25C, unless otherwise noted.
THD+N vs Output Power
50 20 10 5 50 20 10 5
THD+N vs Output Power
50 20 10 5
THD+N vs Output Power
THD+N (%)
THD+N (%)
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
THD+N (%)
1 10 OUTPUT POWER (W) 50
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
1 10 OUTPUT POWER (W)
50
1 10 OUTPUT POWER (W)
50
THD+N vs Output Power
50 20 10 5 50 20 10 5
THD+N vs Output Power
50 20 10 5
THD+N vs Output Power
THD+N (%)
THD+N (%)
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
1 10 OUTPUT POWER (W)
50
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
THD+N (%)
1 10 OUTPUT POWER (W) 50
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
1 10 OUTPUT POWER (W)
50
FFT Noise Floor
0 -10 16K FFT -20 A-wtd -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 -140 20 100 1K FREQUENCY (Hz) 100 90 80
Efficiency vs Output Power
40 VDD=12V 35
Output Power vs Supply Voltage
THD=10%
OUTPUT POWER (W)
0 5 10 15 20 OUTPUT POWER (W) 25
AMPLITUDE (dBV)
EFFICIENCY (%)
70 60 50 40 30 20 10 0
30 25 20 15 10 5 0 5 10 15 SUPPLY VOLTAGE (VDD) 20
10K20K
MP7731 Rev. 1.8 9/25/2006
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MP7731 - 5W - 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
PIN FUNCTIONS
Pin # 1, 5, 11, 16 2 3 4 6 7 8 9 10 12 Name NC PIN1 NIN1 AGND1 EN1 NIN2 PIN2 AGND2 EN2 BS2 Description No Connect - Not internally connected Amplifier 1 Positive Input. PIN1 is the positive side of the differential input to Amplifier 1. Use a resistive voltage divider to set the voltage at PIN1 to VDD/2. See Figure 1. Amplifier 1 Negative Input. NIN1 is the negative side of the differential input to Amplifier 1. See Figure 1. Analog Ground 1. Connect AGND1 to AGND2. Enable Input 1. EN1 must be connected to EN2. Drive high to enable MP7731, drive low to disable. Amplifier 2 Negative Input. NIN2 is the negative side of the differential input to Amplifier 2. See Figure 1. Amplifier 2 Positive Input. PIN2 is the positive side of the differential input to Amplifier 2. Use a resistive voltage divider to set the voltage at PIN2 to VDD/2. See Figure 1. Analog Ground 2. Connect AGND2 to AGND1. Enable Input 2. EN2 must be connected to EN1. Drive high to enable MP7731, drive low to disable. High-Side MOSFET Bootstrap Input for Amplifier 2. A capacitor from BS2 to SW2 supplies the gate drive current to the internal high-side MOSFET. Connect a 1F capacitor from SW2 to BS2. See Figure 1. Power Supply Input. Bypass VDD2 to PGND2 with a 1F X7R capacitor (in addition to the main bulk capacitor), placed close to the IC PIN13 and PIN15. Switched Power Output. SW2 is the output of Amplifier 2. Connect the LC filter to this pin. See Figure 1. Power Ground for Amplifier 2. Connect PGND2 to PGND1. See Figure 1. High-Side MOSFET Bootstrap Input for Amplifier 1. A capacitor from BS1 to SW1 supplies the gate drive current to the internal high-side MOSFET. Connect a 1F capacitor from SW1 to BS1. See Figure 1. Power Supply Input. Bypass VDD1 to PGND1 with a 1F X7R capacitor (in addition to the main bulk capacitor), placed close to the IC PIN18 and PIN20. Switched Power Output. SW1 is the output of Amplifier 1. Connect the LC filter to this pin. See Figure 1. Power Ground for Amplifier 1. Connect PGND1 to PGND2. See Figure 1.
13 14 15 17
VDD2 SW2 PGND2 BS1
18 19 20
VDD1 SW1 PGND1
MP7731 Rev. 1.8 9/25/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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MP7731 - 5W - 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
APPLICATION INFORMATION
COMPONENT SELECTION
The MP7731 uses a minimum number of external components to complete a fully bridged Class D audio amplifier. The circuit in Figure 1 shows a typical application. Use the following sections to customize the amplifier for your particular application. Typical values for the LC filters are shown in Figure 1. The characteristic frequency of the LC filter needs to be high enough to allow high frequency audio to reach the output, yet needs to be low enough to filter out high frequency contents of the pulses from SW. The characteristic frequency of the LC filter is:
Setting the Voltage Gain
The voltage gain sets the output voltage swing for a given input voltage swing and is set by the following equation:
R AV = 2 1 R 4
f0 = Where:
1 2 LC
L = L1 + L2, L1 = L2
C2 x C17 C = C9 + , C2 = C17 C2 + C17
Where: R1 = R8 R4 = R6 The maximum output voltage swing is limited by the power supply. The MP7731 is a bridged amplifier and the output load is driven differentially. Each side of the load is limited to a maximum peak-to-peak voltage swing of approximately VDD. To achieve the maximum output power of the MP7731 amplifier, set the amplifier gain such that the maximum peak-to-peak input signal results in at least the maximum peak-topeak output voltage swing.
The quality factor (Q) of the LC filter is important. If this is too low, output noise will increase. If the Q factor is too high, then peaking may occur at high signal frequencies reducing the pass-band flatness. The Q is calculated as:
Q=
R L C
Where R is the load (speaker) resistance. Use an LC filter with a Q between 0.7 and 2.0. The actual output ripple and noise is greatly affected by the type of inductor and capacitor used in the LC filter. Use a film capacitor and an inductor with sufficient power handling capability to supply the output current to the load. The inductor should exhibit soft saturation characteristics. If the inductor exhibits hard saturation, it should operate well below the saturation current. Gapped ferrite, MPP, Powdered Iron, or similar type toroidal cores are recommended. If open or shielded bobbin
Setting the Switching Frequency
The idle switching frequency (the switching frequency with no audio input signal) is a function of the supply voltage, VDD, the capacitors C4, C6 and C10 and resistors R1 and R8. Lower switching frequencies result in more inductor ripple, causing more quiescent output voltage ripple, increasing the output noise.. Higher switching frequencies result in more power loss. The optimum quiescent switching frequency is approximately 400KHz-600KHz. C6 and C14 are typically 1pF to 2.2pF. C10 is used to program the idle switching frequency.
Choosing the LC Filter
Two identical LC filters are required in the typical application. The inductor-capacitor (LC) filter is a second order filter that converts the pulse train at SW (Pins 14, 19) to the output differential signal that drives the speaker.
MP7731 Rev. 1.8 9/25/2006 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
6
MP7731 - 5W - 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
ferrite cores are used, make sure that the start windings of each inductor line up (all starts going toward SW pin, or all starts going toward the output) to prevent crosstalk or other channel-to-channel interference.
Circuit Layout
Proper circuit layout is critical for optimum performance and low output distortion and noise. Place the following components as close to the MP7731 as possible: 1. Power Supply Bypass, C5, C11. C5 and C11 carry the transient current for the switching power stage. Place a 1uF power supply bypass capacitor as close to Pin 18 (VDD1) and Pin 20 (PGND1) as possible. Also place a 1uF power supply bypass capacitor as close to Pin 13 (VDD2) and Pin 15 (PGND2) as possible. 2. Output Catch Diodes, D2, D3, D5, and D6. These diodes carry the current over the dead-time while both MOSFET switches are off. Place D3 between Pin 19 (SW1) and Pin 20 (PGND1) to prevent the voltage at SW1 from swinging excessively below ground, and place D2 between SW1 and pin 18 (VDD1) to prevent the voltage at SW1 from swinging excessively about VDD. Place D6 and D5 similarly to minimize the undershoot and over-shoot of SW2 node. 3. Input Modulator Capacitor, C10. C10 is used to set the amplifier switching frequency. Place C10 as close to the differential inputs, Pin 2 and Pin 3, as possible to reduce distortion and noise.
Input Coupling Capacitor
The input coupling capacitors, C7 and C12, are used to pass only the AC audio signal to the input of the amplifier. In a typical system application, the source input signal is typically centered around the circuit ground, while the MP7731 input is at half the power supply voltage (VDD/2). The input coupling capacitor transmits the AC signal from the source to the MP7731 while blocking the DC voltage. This input coupling capacitor creates a low-pass filter with the input resistor of the MP7731. Choose an input coupling capacitor such that the corner frequency (fIN) is less than the desired passband frequency. The formula for the corner frequency is:
fIN = 1
(2LC)
Where: L = L1 = L2 C = C2 = C17 Where fIN is the -3db cutoff frequency, R4 and R6 are the input resistors and C7 and C12 are the input AC coupling capacitors.
Electro-Magnetic Interference (EMI)
Due to the switching nature of the Class-D amplifier, care must be taken to minimize the effects of electromagnetic interference from the amplifier. However, with proper component selection and careful attention to circuit layout, the effects of the EMI due to the amplifier switching can be minimized. The power inductors are a potential source of radiated emissions. For the best EMI performance, use shielded inductors, since the magnetic field is well contained inside the core. On the system printed circuit board, trace loops that carry rapidly changing currents need to be minimized. VDD bypass capacitors (C5 and C11) must be placed as close to the MP7731 as possible. Nodes that carry rapidly changing voltage, such as SW1 and SW2, must be made as small as possible. If sensitive traces run near SW1 or SW2, place a ground shield between the traces.
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Power Source
For maximum output power, the amplifier circuit requires a regulated external power source to supply the power to the amplifier. The higher the power supply voltage, the more power can be delivered to a given load resistance. However, if the power source voltage exceeds the maximum operating voltage of 18V, the MP7731 may sustain damage. The power supply rejection of the MP7731 is excellent. However, noise at the power supply can get to the output, so care must be taken to minimize power supply noise within the passband frequencies. Bypass the power supply pins with a large electrolytic capacitor (typically aluminum electrolytic) along with smaller 1F ceramic capacitors at the MP7731 VDD supply pins.
MP7731 Rev. 1.8 9/25/2006
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MP7731 - 5W - 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
TYPICAL APPLICATION CIRCUIT
C4 15pF
C14 2pF
MP7731
1 2 NC PIN1 NIN1 AGND1 NC EN1 NIN2 PIN2 AGND2 EN2 PGND1 SW1 VDD1 BS1 NC PGND2 SW2 VDD2 BS2 NC 20 19 18 17 16 15 14 13 12 11
VCC
+
VCC D2 1N5819 D4 6.2V
AUDIO IN+
C10 1nF
3 4 5 6
D3 MBRS130LTR VCC VCC
C36 3.9nF
+
D1 1N4148
AUDIO IN-
7 8 9
D5 1N5819
D7 6.2V D6 MBRS130LTR VCC D8 1N4148 C6 2pF
C37 3.9nF
EN
10
C15 15pF
Figure 1-- Mono Full Bridged Circuit
MP7731 Rev. 1.8 9/25/2006
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MP7731 - 5W - 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
PACKAGE INFORMATION
TSSOP20F (Exposed Paddle)
4.40 TYP 6.40 6.60 20 11 1.60 TYP 0.40 TYP 0.65 BSC
PIN 1 ID
4.30 4.50
6.20 6.60
3.20 TYP
5.80 TYP
1
10
TOP VIEW
RECOMMENDED LAND PATTERN
0.80 1.05 0.19 0.30 0.65 BSC 0.00 0.15
1.20 MAX SEATING PLANE SEE DETAIL "A"
0.09 0.20
SIDE VIEW FRONT VIEW
GAUGE PLANE 0.25 BSC 3.80 4.30 0o-8o 0.45 0.75
DETAIL A
2.60 3.10
NOTE:
1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSION OR GATE BURR. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.10 MILLIMETERS MAX. 5) DRAWING CONFORMS TO JEDEC MO-153, VARIATION ACT. 6) DRAWING IS NOT TO SCALE.
BOTTOM VIEW
NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications.
MP7731 Rev. 1.8 9/25/2006 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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