TM
MP7782
50W Class D
Mono Bridged Audio Amplifier
The Future of Analog IC Technology
TM
DESCRIPTION
FEATURES
The MP7782 is a mono, 50W Class D Audio
Amplifier. It is one of MPS’ second generation
fully integrated audio amplifiers which
dramatically reduces solution size by integrating
four 180mΩ power MOSFETs in a space saving
TSSOP20 package. The MP7782 utilizes a full
bridge output structure capable of delivering
50W into 6Ω 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
ADAMTM (Analog Digital Adaptive Modulation),
MPS’ proprietary variable frequency modulation
topology (patents pending) that delivers
excellent PSRR, fast response time and
operates on a single power supply.
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EVALUATION BOARD REFERENCE
Board Number
Dimensions
EV7782DF-00A
4.0”X x 3.5”Y x 1.0”Z
50W into 6Ω with VDD = 24V @10% THD+N
90% Efficiency at 50W
Amplifies Full Audio Range with Low THD+N
THD+N = 0.06% @ 1W
9.5V to 24V 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
Thermally Enhanced 20-Pin TSSOP
Package with Exposed Pad
APPLICATIONS
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MP3 Systems
Surround Sound Systems
Multimedia Computers
Televisions
Home Stereos
DVD and VCD Players
Game Devices and Systems
Subwoofers
“MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic
Power Systems, Inc.
ADAM (Analog Digital Adaptive Modulation) is a Trademark of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
VDD
MP7782
2
AUDIO IN
3
4
GND
5
6
7
8
9
EN
OFF ON
10
NC
PGND1
FB2
SW1
FB1
VDD1
AGND
BS1
NC
NC
EN
PGND2
FB2
SW2
FB1
VDD2
AGND
EN
BS2
NC
+
100
20
19
18
17
16
10
+
15
14
13
THD+N (%)
1
1
0.1
12
11
0.01
0.1
1
10
OUTPUT POWER (W)
MP7782-TAC01
MP7782 Rev. 1.2
8/3/2005
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100
MP7782-EC01
1
TM
MP7782 – 50W CLASS D MONO BRIDGED AUDIO AMPLIFIER
ABSOLUTE MAXIMUM RATINGS (1)
PACKAGE REFERENCE
NC*
1
20
PGND1
FB2
2
19
SW1
FB1
3
18
VDD1
AGND
4
17
BS1
NC*
5
16
NC*
Supply Voltage VDD ...................................... 26V
BS Voltage.................. VSW – 0.3V to VSW + 6.5V
Enable Voltage VEN ........................ –0.3V to +6V
VSW, VFB2, VFB1 ........................... –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
EN
6
15
PGND2
Recommended Operating Conditions
FB2
7
14
SW2
FB1
8
13
VDD2
Supply Voltage VDD .......................... 9.5V to 24V
Operating Temperature TA......... –40°C to +85°C
AGND
9
12
BS2
Thermal Resistance
EN
10
11
NC*
TSSOP20F ............................. 40 ....... 6.... °C/W
TOP VIEW
EXPOSED PAD
* ALL NC PINS SHOULD BE GROUNDED IN LAYOUT
MP7782_PD01-TSSOP20F
*
Part Number*
Package
Temperature
MP7782DF
TSSOP20F
–40°C to +85°C
(3)
θJA
(2)
θJC
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. MP7782DF–Z)
For Lead Free, add suffix –LF (eg. MP7782DF–LF–Z)
ELECTRICAL CHARACTERISTICS
(VDD = 24V, VEN = 5V, TA = +25˚C, unless otherwise noted.)
Parameter
Symbol Condition
Supply Current
Standby Current
Quiescent Current
Output Drivers
SW On Resistance
Short Circuit Current
Inputs
FB1, FB2
Input Common Mode Voltage Range
FB1, FB2
Input Current
EN Enable Threshold Voltage
EN Enable Input Current
Thermal Shutdown
Thermal Shutdown Trip Point
Thermal Shutdown Hysteresis
MP7782 Rev. 1.2
8/3/2005
Min
VEN = 0V
Sourcing and Sinking
Sourcing and Sinking
VFB2 = VFB1 = 8V
TJ Rising
Max
Units
2
3
10
6
µA
mA
0.18
5.0
0
VEN Rising
VEN Falling
VEN = 5V
Typ
0.4
Ω
A
VDD/2
VDD–1.5
V
1
5
µA
1.4
1.2
1
2.0
V
V
µA
150
°C
30
°C
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© 2005 MPS. All Rights Reserved.
2
TM
MP7782 – 50W CLASS D MONO BRIDGED AUDIO AMPLIFIER
OPERATING SPECIFICATIONS
(Circuit of Figure 1, VDD = 24V, VEN = 5V, TA = +25˚C, unless otherwise noted.)
Parameter
Condition
Standby Current
Quiescent Current
VEN = 0V
Power Output
THD+ Noise
Efficiency
Dynamic Range
Noise Floor
Power Supply Rejection
Min
f = 1KHz, THD+N = 10%, RL = 6Ω
f = 1KHz, THD+N = 10%, RL = 8Ω
POUT = 1W, f = 1KHz, RL = 6Ω
POUT = 1W, f = 1KHz, RL = 8Ω
f = 1KHz, POUT = 50W
A-Weighted
f = 1KHz
Typ
Max
700
28
50
40
0.06
0.08
90
100
187
60
Units
µA
mA
W
%
%
dB
µV
dB
PIN FUNCTIONS
Pin #
Name
Description
1, 5, 11, 16
NC
No Connect. Not internally connected.
3, 8
FB1
First Feedback. Receives feedback from SW1 via resistor(s) and the positive input
signal via resistor and capacitor. Both pins must be tied together.
2, 7
FB2
Second Feedback. Receives feedback from SW2 via resistor(s) and the negative
input signal via resistor and capacitor. Both pins must be tied together.
4, 9
AGND
6, 10
EN
Enable Input. Drive high to enable the MP7782, drive low to disable it. Both pins
must be tied together.
12
BS2
High-Side MOSFET Bootstrap Input for Channel 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.
13
VDD2
Power Supply Input. Bypass VDD2 to PGND2 with a 1µF X7R capacitor (in
addition to the main bulk capacitor), placed close to pins 13 and 15.
14
SW2
Switched Power Output. SW2 is the output of Channel 2. Connect the LC filter to
this pin. See Figure 1.
15
PGND2
Analog Ground. Both pins must be tied together.
Power Ground for Channel 2. Connect PGND2 to PGND1. See Figure 1.
High-Side MOSFET Bootstrap Input for Channel 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.
17
BS1
18
VDD1
Power Supply Input. Bypass VDD1 to PGND1 with a 1µF X7R capacitor (in
addition to the main bulk capacitor), placed close to pins 18 and 20.
19
SW1
Switched Power Output. SW1 is the output of Channel 1. Connect the LC filter to
this pin. See Figure 1.
20
PGND1
MP7782 Rev. 1.2
8/3/2005
Power Ground for Channel 1. Connect PGND1 to PGND2. See Figure 1.
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3
TM
MP7782 – 50W CLASS D MONO BRIDGED AUDIO AMPLIFIER
TYPICAL PERFORMANCE CHARACTERISTICS
Circuit of Figure 1, VDD = 24V, TA = +25˚C
100
+18
-40
+14
+10
-60
1
f=1KHz
+6
A-Weighted
GAIN (dBr)
-80
(dBV)
THD+N (%)
10
-20
-100
-120
0.1
1
10
OUTPUT POWER (W)
-180
100
-18
100
1K
FREQUENCY (Hz)
MP7782-EC01
20
100
1k
FREQUENCY (Hz)
MP7782-TPC02
10
10
THD+N (%)
100
THD+N (%)
-22
10K
100
1
POUT=1W
0.1
-6
-14
-160
0.1
-2
-10
-140
0.01
+2
MP7782-TPC03
1
POUT=1W
0.1
0.01
0.01
20
100
1k
FREQUENCY (Hz)
10k
20
100
1k
FREQUENCY (Hz)
MP7782-TPC04
100
-20
+18
-40
+14
+10
1
+6
GAIN (dBr)
-80
A-Weighted
-100
-120
f=1KHz
0.1
1
10
OUTPUT POWER (W)
100
MP7782-TPC06
MP7782 Rev. 1.2
8/3/2005
-2
-6
-14
-160
-180
+2
-10
-140
0.01
10k
MP7782-TPC05
-60
(dBV)
THD+N (%)
10
0.1
10k
-18
100
1K
FREQUENCY (Hz)
10K
-22
20
MP7782-TPC07
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100
1k
FREQUENCY (Hz)
10k
MP7782-TPC08
4
TM
MP7782 – 50W CLASS D MONO BRIDGED AUDIO AMPLIFIER
TYPICAL APPLICATION CIRCUIT
C1
27pF
C6
1µF
16V
1
2
C4
2.2nF
AUDIO IN
3
4
GND
5
C9
1µF
16V
6
7
8
9
10
EN
OFF ON
VDD
MP7782
C10
1pF
NC
PGND1
FB2
SW1
FB1
VDD1
AGND
BS1
NC
NC
EN
PGND2
FB2
SW2
FB1
VDD2
AGND
EN
BS2
NC
+
20
C2
1000µF
35V
D3B
OPTIONAL
L1
15µH
19
18
17
C3
1µF
25V
C5
1µF
D2
6.2V
D3A
MBRS130LTR
D1
1N4148
15
13
12
C11
1µF
D5A
MBRS130LTR
C16
390pF
11
C13
1pF
D4
6.2V
C30
0.47µF
50V
+
L2 = L1
15µH
D5B
OPTIONAL
14
C8
1µF
25V
C7
0.22µF
50V
C15
390pF
16
C12
0.22µF
50V
D6
1N4148
C14
27pF
MP7782_F01
Figure 1 — 50W Class D BTL Amplifier (VDD = 24V)
APPLICATION INFORMATION
COMPONENT SELECTION
The MP7782 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:
AV =
R1
R3
R8 = R1
R 4 = R3
MP7782 Rev. 1.2
8/3/2005
The maximum output voltage swing is limited by
the power supply. The MP7782 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
approximately equal to VDD. To achieve the
maximum output power of the MP7782 amplifier,
set the amplifier gain such that the maximum
peak-to-peak input signal results in at least the
maximum peak-to-peak output voltage swing.
Setting the Switching Frequency
The idle switching frequency (the switching
frequency with no audio input signal) is a
function of the supply voltage, VDD, capacitors
C4, C10 and C13 and resistors R1, R3, R4 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 to 600KHz.
C10 and C13 are typically 1pF to 2.2pF. C4 is
used to program the idle switching frequency.
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5
TM
MP7782 – 50W CLASS D MONO BRIDGED AUDIO AMPLIFIER
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. 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:
f0 =
1
2π LC
where:
L = L1 + L2 , L1 = L2
C7 × C12
C = C30 +
, C7 = C12
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 Q value 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.
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
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.
MP7782 Rev. 1.2
8/3/2005
Input Coupling Capacitor
The input coupling capacitors, C6 and C9, 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 usually
centered around the circuit ground, while the
MP7782 input is at half the power supply
voltage (VDD/2). The input coupling capacitor
transmits the AC signal from the source to the
MP7782 while blocking the DC voltage. This
input coupling capacitor creates a low-pass filter
with the input resistor of the MP7782. 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
2π × R3 × C6
R 4 = R3
C9 = C6
Where fIN is the -3dB cutoff frequency, R3 and
R6 are the input resistors and C6 and C9 are
the input AC coupling capacitors.
Power Source
For maximum output power, the amplifier circuit
requires a regulated external power source to
supply power to the amplifier. The higher the
power supply voltage provided, the more power
that can be delivered to a given load resistance.
However, if the power source voltage exceeds the
maximum operating voltage of 24V, the MP7782
may sustain damage.
The power supply rejection of the MP7782 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 MP7782 VDD supply
pins.
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6
TM
MP7782 – 50W CLASS D MONO BRIDGED AUDIO AMPLIFIER
Circuit Layout
Proper circuit layout is critical for optimum
performance and low output distortion and
noise. Place the following components as close
to the MP7782 as possible:
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 MP7782 as
possible.
1. Power Supply Bypass, C3, C8
C3 and C8 carry the transient current for the
switching power stage. Place a 1µF power
supply bypass capacitor as close to pin 18
(VDD1) and pin 20 (PGND1) as possible. Also
place a 1µF power supply bypass capacitor as
close to pin 13 (VDD2) and pin 15 (PGND2) 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.
2. Output Catch Diodes, D3A, D3B, D5A, D5B
D3A, D3B, D5A, and D5B carry the current over
the dead-time while the MOSFET switches are
off. Place D3A between pin 19 (SW1) and pin
20 (PGND1) to prevent the voltage at SW1 from
swinging excessively below ground, and place
D3B between SW2 and pin 18 (VDD1) to
prevent the voltage at SW1 from swinging
excessively above VDD. Place D5A and D5B
similarly to minimize the overshoot and
undershoot of SW2 node.
3. Input Modulator Capacitors, C4
C4 is used to set the amplifier switching
frequency. Place C4 as close to the differential
inputs, pin 2 and pin 3, as possible to reduce
distortion and noise.
4. 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 EMI due to the amplifier switching
can be minimized.
Power Dissipation and Thermal
Considerations
The power dissipation of the MP7782 arises
mostly from the conduction loss of the internal
main switches. This power loss is estimated to
be:
PLOSS ≅
POUT
× 2 × 0.18Ω × 1.3
RL
Where 1.3 is a temperature coefficient factor
that reflects the increase in the RDS(ON)
resistance at elevated temperatures.
For example, for a 6Ω speaker, the max POUT is
50W:
PLOSS ≅
50
× 2 × 0.18Ω × 1.3 = 3.9 W
6
Because the thermal resistance θJC is 6°C/W,
the resulting temperature rise between junction
and case is approximately 24°C.
Therefore, caution must be exercised when
using the MP7782 in applications with
continuous high output power.
A heat sink is required if the MP7782 is applied
at continuous 50W output power.
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.
MP7782 Rev. 1.2
8/3/2005
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7
TM
MP7782 – 50W CLASS D MONO BRIDGED AUDIO AMPLIFIER
PACKAGE INFORMATION
TSSOP20F (EXPOSED PAD)
0.0256(0.650)TYP
0.004(0.090)
0.010(0.250)
GATE PLANE
0.105 (2.67)
0.118 (3.00)
pad width
0.169
0.177
0.244
0.260
(4.300)
(4.500)
(6.200)
(6.600)
0.004(0.090)
0o-8o
0.018(0.450)
0.030(0.750)
DETAIL "A"
0.039(1.000)REF
0.030(0.750)
SEE DETAIL "B"
PIN 1
IDENT.
0.150 (3.80)
0.165 (4.19)
pad length
0.030(0.750)
SEE DETAIL "A"
0.252 (6.400)
0.260 (6.600)
0.075(0.190)
0.012(0.300)
0.032(0.800)
0.041(1.050)
0.047(1.200)
max
0.007(0.190)
0.012(0.300)
SEATING PLANE
0.002(0.050)
0.006(0.150)
NOTE:
1) Control dimension is in inches. Dimension in bracket is millimeters.
0.004(0.090)
0.008(0.200)
0.004(0.090)
0.006(0.160)
0.007(0.190)
0.010(0.250)
DETAIL "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.
MP7782 Rev. 1.2
8/3/2005
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MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
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