PAM8803
3W Filterless Stereo Class-D Audio Amplifier
with Digital Volume Control
by the
he output
noise produced
by coupling into t
signal. This noise
function is to reduce
power supply caused
drive
analog
Power supply decoupling
a high performance
that requires adequate
audio amplifier
is from the internal
, which appears
reference to the amplifier
CMOS
power
The PAM8803 is
THD+N.
degraded PSRR and
THD and
supply
as
to ensure the output
as possible. Power
supply decoupling
PSRR are as low
decoupling is affecting
Optimum decoupling
capacitors of different
types of noise o
higher frequency
hash on the line,
resistance (ESR)
1.0μF, placed as
0.47μF to
the best THD
(CBYP) values of
recommended for
Bypass capacitor
1.0μF ceramic is
and noise performance.
low frequency response.
two
types that target
is achieved by using
different
Increasing
the bypass
noise
and leaving
leads. For
or digital
n the power supply
transients, spikes,
clicking and popping
f and entering
capacitor reduces
from power on/of
shutdown.
a good low equivalent-series-
, typically
ceramic capacitor
to the device
close as possible
best. For filtering
capacitor of
signals, a larger
ock-out (UVLO)
Under Voltage L
The PAM8803 incorporates
upply voltage is low
detect when the s
lower-
VDD terminal works
to
. When the
circuitry designed
frequency noise
near the audio
10μF (ceramic) or greater placed
recommended.
power amplifier is
, the
to 1.85V or below
the device
to normal
supply voltage drops
are disable, and
state and starts
PAM8803 outputs
comes out of this
functional when the
(C )
i
Input Capacitor
supply voltage increases.
and
Clearly, a
are both expensive
Large input capacitors
portable designs.
space hungry for
(SCP)
Short Circuit Protection
in low
But in
is needed to couple
severe attenuation.
speakers used
internal or external,
certain sized capacitor
protection
to
has short circuit
The PAM8803
circuitry on the outputs
frequencies without
many cases the
systems, whether
that prevents damage
and output-
on
a short circuit is detected
in portable
have little
to
output-to-output
the device during
to-GND short. When
signals below 100Hz
ability to reproduce
150Hz. Thus, using
not increase actual
case, input capacitor
.
are disable immediately
activates
the outputs, the outputs
If the short was
again.
may
a large input capacitor
removed, the device
In this
system performance.
(Ci) and input resistance
filter with
form a high-pass
(Ri) of the amplifier
the corner frequency
Protection
Over Temperature
below,
determined equation
1
prevents
on the PAM8803
Thermal protection
fC=
internal die
device when the
damage to the
2πR
iC
i
a 15
device to
150°C. There is
on this trip point from
die temperature
temperature exceeds
and pop
of the input
cost and size, click
ffected by the size
In addition to system
performance is a
degree tolerance
device. Once the
thermal set point,
exceeds the
are
The thermal
coupling
reach its
, C . A larger input
coupling capacitor
capacitor requires
quiescent DC voltage
charge comes from
i
the device outputs
more charge to
not a latched fault.
disabled. This is
fault is cleared once
reduced by 60°C.
prevent motor boating
begins normal operation
external system interaction.
). This
via the
(nominally 1/2 VDD
f the die is
will
device
the temperature o
This large hysteresis
the internal circuit
upon device
apacitor size
low frequency response,
apt to create pops
minimizing the c
feedback and is
sound well and the
enable. Thus, by
based on necessary
be minimized.
turn-on pops can
no
at this point with
Magnetic
EMI (Electro
How to Reduce
Interference)
(C
)
Bypass Capacitor
Analog Reference
BYP
capacitor
power line
is to put an additional
supply terminal for
A simple solution
1000uF at power
coupling if the traces
are short (<20cm).
(CBYP) is
several
recovery
Bypass Capacitor
The Analog Reference
the most critical
important functions.
from shutdown mode,
which the amplifier
capacitor and serves
speakers
from amplifier to
During start-up or
C
determines the
rate at
second
BYP
starts up. The
Power Analog Microelectronics,Inc
www.poweranalog.com
12/2009 Rev 1.4
10
PAM [ POWER ANALOG MICOELECTRONICS ]
