MP7722 MPS, MP7722 Datasheet - Page 9

• Manufacturer Part Number: MP7722
• Description: 2 x 20W Class D Stereo Single Ended Audio Amplifer
• Manufacturer: MPS

PCB Layout
The circuit layout is critical for optimum
performance and low output distortion and
noise. Place the following components as close
to the MP7722 as possible:
Power Supply Bypass, C
C
the
overstressing of the MP7722 and excessive
noise at the output, place C
18 (VDD1) and 20 (PGND1) as possible and
also place C
15 (PGND2) as possible.
Output Catch Diodes
D
the dead-time while the MOSFET switches are
off. Place the diodes as close to the MP7722 as
possible.
Timing Capacitors
C
switching frequencies and are typically on the
order of a few nF. Place C
and 3 as possible to reduce distortion and
noise. Likewise, place C
and 8 as possible.
Reference Bypass Capacitors
C
Place C
possible to improve power supply rejection and
reduce distortion and noise at the output.
When laying out the PCB, use two separate
ground planes, analog ground (AGND) and
power ground (PGND), and connect the two
grounds together at a single point to prevent
noise injection into the amplifier input to reduce
distortion.
Make sure that any traces carrying the switch
node (SW) voltages are separated far from any
input signal traces. If it is required to run the
SW trace near the input, shield the input with a
ground plane between the traces. For multiple
channel applications, make sure that each
channel is physically separated to prevent
crosstalk. Make sure that all inductors used on
a single circuit board have the same orientation.
MP7722 Rev. 1.3
9/25/2006
BYP1
SH1
INT1
R1
and C
, D
switching
and C
and C
SL1
R1
, D
R2
and C
BYP2
INT2
BYP2
filter the ½ V
SH2
and D
as close to pins 13 (VDD2) and
are used to set the amplifier
carry the transient current for
power
R2
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
SL2
as close to the IC as
BYP
INT2
MP7722 – 2 x 20W CLASS D STEREO SINGLE ENDED AUDIO AMPLIFIER
DD
carry the current over
stage.
INT1
BYP1
reference voltages.
as close to pins 7
as close to pins 2
as close to pins
To
© 2006 MPS. All Rights Reserved.
prevent
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Also, 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.
Electro-Magnetic Interference (EMI)
Considerations
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
performance use toroidal inductors, since the
magnetic field is well contained inside the core.
However toroidal inductors can be expensive to
wind. For a more economical solution, use
shielded gapped ferrite or shielded ferrite
bobbin core inductors. These inductors typically
do not contain the field as well as toroidal
inductors, but usually can achieve a better
balance of good EMI performance with low
cost.
The size of high-current loops that carry rapidly
changing currents needs to be minimized. To
do this, make sure that the V
capacitors and the Schottky Catch diodes are
as close to the MP7722 as possible.
Nodes that carry rapidly changing voltages,
such as SW, need to be made as small as
possible. If sensitive traces run near a trace
connected to SW, place a ground shield
between the traces.
emissions.
For
the
best
DD
bypass
EMI
9