Transcript
MP7731 5W - 30W Class D Mono Bridged Audio Amplifier The Future of Analog IC Technology
DESCRIPTION
FEATURES
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 180mΩ Power MOSFETs Mute / Standby Mode The MP7731 utilizes a full bridge output structure capable of delivering 5W - 30W into 4Ω 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 (AAM™, Patent No. 6,420,930; other patents pending) that delivers excellent PSRR, fast response time and operates on a single power supply.
EVALUATION BOARD REFERENCE
30W into 4Ω 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 180mΩ 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
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc.
Board Number
Dimensions
EV0045DF
4.8cm x 3.0cm x 1.5cm
TYPICAL APPLICATION THD+N vs Output Power VDD
MP7731
REF
2 3
AUDIO IN
4
GND
5 6 7
REF
8 9
EN OFF ON
10
NC
PGND1
PIN1
SW1
NIN1
VDD1
AGND1 NC EN1
BS1 NC PGND2
NIN2
SW2
PIN2
VDD2
AGND2 EN2
BS2 NC
+
20 19 18 17 16
+
15 14 13 12 11
THD+N (%)
1
50 20 10 5
f=1kHz
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
1
10
50
OUTPUT POWER (W) MP7731-TAC-G01
MP7731-TAC-S01
MP7731 Rev. 1.6 11/23/2005
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MP7731 – 5W – 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
ABSOLUTE MAXIMUM RATINGS (1)
PACKAGE REFERENCE
NC
1
20
PGND1
PIN1
2
19
SW1
NIN1
3
18
VDD1
AGND1
4
17
BS1
NC
5
16
NC
EN1
6
15
PGND2
NIN2
7
14
SW2
PIN2
8
13
VDD2
AGND2
9
12
BS2
EN2
10
11
NC
MP7731
MP7731-PD-01
Part Number*
Package
Temperature
MP7731
TSSOP20
–40°C to +85°C
*
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......................................150˚C Lead Temperature ...........................................260˚C Storage Temperature ....................... -65˚C to 150˚C
Recommended Operating Conditions
(2)
Supply Voltage VDD ................................ 9.5V to 18V Operating Temperature TA ................. -40˚C to 85˚C
Thermal Resistance
(3)
θJA
θJC
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.
For Tape & Reel, add suffix –Z (eg. MP7731DF–Z) For Lead Free, add suffix –LF (eg. MP7731DF–LF–Z)
ELECTRICAL CHARACTERISTICS (4) VDD = 16.5V, VEN = 5V, RL = 4Ω, TA = +25°C, unless otherwise noted. Parameter
Symbol Condition
Standby Current
Min
VEN = 0V
Quiescent Current
Typ
Max
Units
2
10
3
6
µA mA
SW On Resistance
Sourcing and Sinking
0.18
Short Circuit Current PIN, NIN Input Common Mode Voltage Range PIN, NIN Input Current
Sourcing and Sinking
5.0 VDD/2
EN Enable Threshold Voltage EN Enable Input Current
MP7731 Rev. 1.6 11/23/2005
0
Ω A VDD-1.5
V
VPIN=VNIN=8V
1
5
µA
VEN Rising
1.4
2.0
V
VEN Falling VEN = 5V
0.4
1.2 1
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V µA
2
MP7731 – 5W – 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
ELECTRICAL CHARACTERISTICS (4) (continued) VDD = 16.5V, VEN = 5V, RL = 4Ω, TA = +25°C, unless otherwise noted. Parameter
Symbol Condition
Thermal Shutdown Trip Point
TJ Rising
Thermal Shutdown Hysteresis Standby Current
VEN = 0V
Quiescent Current f=1KHz, THD+N=10% f=1KHz, THD+N=10% , RL=8Ω POUT=1W, f=1KHz
Power Output
THD+ Noise Efficiency Maximum Power Bandwidth Dynamic Range Noise Floor Power Supply Rejection
Min
Typ
Max
Units
150
°C
30
°C
700 28 30
µA mA W
17
W
0.2
%
POUT=1W, f=1KHz, RL=8Ω f=1KHz, POUT=10W
0.1
%
85
%
f=1KHz, POUT=10W, RL=8Ω
88
%
A-Weighted f=1KHz
20 90 370 60
KHz dB µV dB
Notes: 4) The device is not guaranteed to function outside its operating rating.
MP7731 Rev. 1.6 11/23/2005
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MP7731 – 5W – 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
TYPICAL PERFORMANCE CHARACTERISTICS Circuit of Figure 1, VDD=16.5V, TA=25°C, unless otherwise noted. THD+N vs Output Power
20 10 5
20 10 5
20 10 5
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
1 10 OUTPUT POWER (W)
50
THD+N (%)
50
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
1 10 OUTPUT POWER (W)
MP7731-TPC-01
0.2 0.1 0.05 0.02 0.01 100M
THD+N vs Output Power
20 10 5
20 10 5
20 10 5
1 10 OUTPUT POWER (W)
50
THD+N (%)
50
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
1 10 OUTPUT POWER (W)
40 VDD=12V
90
OUTPUT POWER (W)
EFFICIENCY (%)
70 60 50 40 30 20
30 25 20 15 10 5
10
MP7731-TPC-07
THD=10%
35
80
0
50
Output Power vs Supply Voltage
100
10K20K
1 10 OUTPUT POWER (W)
MP7731-TPC-06
Efficiency vs Output Power
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)
MP7731 Rev. 1.6 11/23/2005
50
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
MP7731-TPC-05
MP7731-TPC-04
50
THD+N vs Output Power
50
2 1 0.5 0.2 0.1 0.05 0.02 0.01 100M
1 10 OUTPUT POWER (W)
MP7731-TPC-03
50
THD+N (%)
THD+N (%)
50
2 1 0.5
MP7731-TPC-02
THD+N vs Output Power
AMPLITUDE (dBV)
THD+N vs Output Power
50
THD+N (%)
THD+N (%)
THD+N vs Output Power 50
0
5 10 15 20 OUTPUT POWER (W)
25
0
5
10 15 SUPPLY VOLTAGE (VDD)
MP7731-TPC-08
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MP7731-TPC-09
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MP7731 – 5W – 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
PIN FUNCTIONS Pin #
Name
1, 5, 11, 16 NC 2 PIN1 3
NIN1
4 6
AGND1 EN1
7
NIN2
8
PIN2
9 10
AGND2 EN2
12
BS2
13
VDD2
14
SW2
15 17
PGND2 BS1
18
VDD1
19
SW1
20
PGND1
MP7731 Rev. 1.6 11/23/2005
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 1µF capacitor from SW2 to BS2. See Figure 1. Power Supply Input. Bypass VDD2 to PGND2 with a 1µF 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 1µF capacitor from SW1 to BS1. See Figure 1. Power Supply Input. Bypass VDD1 to PGND1 with a 1µF 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.
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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.
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 ⎞ A V = 2 ⎜⎜ 1 ⎟⎟ ⎝ R3 ⎠
Setting the Switching Frequency The idle switching frequency (the frequency at the output pin with no audio input signal) is a function of the supply voltage, VDD, the capacitor C4 and resistor R1. Lower switching frequencies result in more inductor ripple, causing more quiescent output voltage ripple, increasing the output noise and distortion. Higher switching frequencies result in more power loss. The optimum quiescent switching frequency is approximately 600KHz-700KHz. Refer to Table 4 for recommended values. Table #—Switching Frequency vs. Capacitor and Resistor Values Gain (dB) 17.8 24.3 27.6 30.6 34.2
MP7731 Rev. 1.6 11/23/2005
R1 (Ω) 39K 82K 120K 169K 120K
R3 (Ω) 10K 10K 10K 10K 4.7K
Two identical LC filters are required in the typical application. The inductor-capacitor (LC) filter is a second order filter which converts the pulse train at SW (Pins 14, 19) to the output differential signal that drives the speaker. Typical values for the LC filters are a 10µH inductor and a 0.47µF capacitor. The characteristic frequency of the LC filter needs to be high enough to allow high frequency audio to the output, yet needs to be low enough to filter out high frequency products of the pulses from SW. The characteristic frequency of the LC filter is:
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.
Gain (V/V) 7.8 16.4 24.0 33.8 51.1
Choosing the LC Filter
C4 (nF) 6.8 3.3 2.2 2.2 2.2
FSW (Hz) 660K 660K 610K 700K 610K
f0 =
1 2π LC
where: L = L 1 = L2 C = C7 = C12 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 circuit Q is set by the load resistance (speaker resistance, typically 4Ω or 8Ω). The Q is calculated as:
Q=
R L C
It is best to use an LC filter with Q of around 0.7. 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
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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.
Input Coupling Capacitor The input coupling capacitor, C6, is 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 pass-band frequency. The formula for the corner frequency is:
fIN =
1 (2π × R3 × C6)
where: fIN is the -3dB cutoff frequency R3 is the input resistor C6 is the input AC coupling capacitor
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 1µF ceramic capacitors at the MP7731 VDD supply pins.
MP7731 Rev. 1.6 11/23/2005
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, C3, C8. C3 and C8 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, D3, D5. D3 and D5 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. Also, place D5 between Pin 14 (SW2) and Pin 15 (PGND2) to prevent the voltage at SW2 from swinging excessively below ground. 3. Input Modulator Capacitors, C4, C10. C4 and C10 are used to set the amplifier switching frequency and is typically 2.2nF. Place C4 as close to the differential inputs, Pin 2 and Pin 3, as possible to reduce distortion and noise. Also, place C10 as close to the differential inputs, Pin 7 and Pin 8, as possible to reduce distortion and noise. 4. Reference Bypass Capacitor C13. C13 filters the VDD/2 reference voltage at the pin inputs (Pin 2, Pin 8). Place C13 as close to these pins as possible to improve power supply rejection and reduce distortion and noise at the output.
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MP7731 – 5W – 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
It is best to use two separate ground planes, analog ground (AGND) and power ground (PGND), and connect the 2 grounds together at a single point to reduce noise and distortion. The power switching components on the output side of the IC (Pins 11-20) should be connected to the power ground. R6 and C13 should be connected to AGND. Make sure that any traces carrying the switching node (SW) voltage are far from any input signal traces. If multiple amplifiers are used on a single board, make sure that each channel is physically separated to prevent crosstalk. Shield the audio inputs with a ground plane between the traces. Use vias to connect the top and bottom ground planes. Make sure that all inductors used on a single circuit board have the same orientation. If multiple channels are used on a single board, make sure that the power supply is routed from the source to each channel individually, not serially. This prevents channel-to-channel coupling through the power supply input.
MP7731 Rev. 1.6 11/23/2005
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 (C3 and C8) 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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MP7731 – 5W – 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
TYPICAL APPLICATION CIRCUITS C1 15pF
VDD
MP7731 1
C6 1µF 16V
REF
AUDIO IN
2
C4 2.2nF
3 4
GND
5
C9 1µF 16V
6 7
REF
C10 2.2nF
8 9 10
EN OFF ON
NC
PGND1
PIN1
SW1
NIN1
VDD1
AGND1 NC EN1
BS1 NC PGND2
NIN2
SW2
PIN2
VDD2
AGND2 EN2
BS2 NC
+
20
C2 22µF 25V
L1 10µH 4A
19 18 17
C3 1µF 25V
C5 1µF
D2 6.2V
D3 MBRS130LTR
L2 10µH 4A
D1 1N4148
15 14 13 12
C7 0.47µF 50V
C32 390pF
16
C8 1µF 25V
C11 1µF
D4 6.2V
C30 0.47µF 50V +
D5 MBRS130LTR C33 390pF
11
C12 0.47µF 50V
D6 1N4148
C14 15pF VIN
VDD
GND REF C13 4.7µF 16V MP7731-F01
Figure 1— Mono Full Bridged Circuit
MP7731 Rev. 1.6 11/23/2005
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MP7731 – 5W – 30W CLASS D MONO BRIDGED AUDIO AMPLIFIER
PACKAGE INFORMATION TSSOP20F (Exposed Paddle)
0. 0256( 0. 650) TYP
0. 004( 0. 090) 0. 010( 0. 250) GATE PLANE
PI N 1 I DENT.
0. 169 0. 177
0. 244 0. 260
( 4. 300) ( 4. 500)
( 6. 200) ( 6. 600)
0. 004( 0. 090) 0o- 8o
0. 030( 0. 750)
0. 018( 0. 450) 0. 030( 0. 750)
DETAI L " A"
0. 039( 1. 000) REF
SEE DETAI L " B"
0. 030( 0. 750)
EXPOSED PADDLE VERSI ON SEE DETAI L " A" 0. 252 ( 6. 400) 0. 260 ( 6. 600) 0. 032( 0. 800) 0. 041( 1. 050)
0. 033( 0. 850) 0. 047( 1. 200) 0. 007( 0. 190) 0. 012( 0. 300)
NOTE: 1) Cont r ol di mensi on i s i n i nches.
0. 075( 0. 190) 0. 012( 0. 300) SEATI NG PLANE
0. 002( 0. 050) 0. 006( 0. 150)
0. 004( 0. 090) 0. 008( 0. 200)
0. 004( 0. 090) 0. 006( 0. 160)
0. 007( 0. 190) 0. 010( 0. 250) Di mensi on i n br acket i s mi l l i met er s.
DETAI L " B"
NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications. 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. 1.6 11/23/2005
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