PAM8603M
3W Filterless Stereo Class-D Audio Amplifier with DC Volume Control
Application Information
Mute Operation
The MUTE pin is an input for controlling the
output state of the PAM8603M. A logic low on this
pin disables the outputs, and a logic high enables
the outputs. This pin may be used as a quick
disable or enable of the outputs without a volume
fade. Quiescent current is listed in the electrical
characteristic table. The MUTE pin can be left
floating due to the internal pull-up .
For better power-off pop performance, the
amplifier should be placed in the mute mode prior
to removing the power supply.
Shutdown Operation
In order to reduce power consumption while not in
use, the PAM8603M contains shutdown circuitry
to turn off the amplifier's bias circuitry. The
amplifier is turned off when logic low is placed on
the SHDN pin. By switching the SHDN pin
connected to GND, the PAM8603M supply current
draw will be minimized in idle mode. The SHDN
pin can be left floating due to the internal pull-up.
Power Supply Decoupling
The PAM8603M is a high performance CMOS
audio amplifier that requires adequate power
supply decoupling to ensure the output THD and
PSRR as low as possible. Power supply
decoupling affects low frequency response.
Optimum decoupling is achieved by using two
capacitors of different types that target different
noise on the power supply leads. For higher
frequency transients, spikes, or digital hash on
the line, a good low equivalent-series resistance
(ESR) ceramic capacitor, typically 1.0 μ F, placed
as close as possible to the device VDD terminal
works best. For filtering lower-frequency noise
signals, a large capacitor of 10μF (ceramic) or
greater placed near the audio power amplifier is
recommended.
Input Capacitor (C
i
)
Large input capacitors are both expensive and
space hungry for portable designs. Clearly, a
certain sized capacitor is needed to couple in low
frequencies without severe attenu ation. But in
many cases the speakers used in portable
systems, whether internal or external, have little
ability to reproduce signals below 100Hz to
150Hz. Thus, using a large input capacitor may
not increase actual system perfor mance. In this
case, input capacitor (C
i
) and input resistance (R
i
)
of the amplifier form a high-pass filter with the
corner frequency determined equation below,
1
2πR
i
C
i
In addition to system cost and size, click and pop
perfor mance is affected by the size of the input
coupling capacitor, C
i
. A larger input coupling
capacitor requires more charge to reach its
quiescent DC voltage (nominally 1/2 V
DD
). This
charge comes from the internal circuit via the
feedback and is apt to create pops upon device
enable. Thus, by minimizing the capacitor size
based on necessary low frequency response,
turn-on pops can be minimized.
f
C
=
Analog Reference Bypass Capacitor (C
BYP
)
The Analog Reference Bypass Capacitor (C
BYP
) is
the most critical capacitor and serves several
important functions. During start-up or recovery
from shutdown mode, C
BYP
determines the rate at
which the amplifier starts up. The second function
is to reduce noise produced by the power supply
coupling in the output drive signal. This noise is
from the internal analog reference to the amplifier
which appears as degraded PSRR and THD+N.
A ceramic bypass capacitor (C
BYP
) of 0.47μF to
1.0μF is recommended for the best THD and noise
performance. Increasing the bypass capacitor
reduces clicking and popping noise from power
on/off and entering and leaving shutdown.
Under Voltage Lock-out (UVLO)
The PAM8603M incorporates circuitry to detect
low supply voltage. When the supply voltage
drops to 1.8V or below, the PAM8603M outputs
are disable. The device resumes to normal
functional once V
DD
≥
2.0V.
Short Circuit Protection (SCP)
The PAM8603M has short circuit protection
circuitry on the outputs to prevent the device from
damage when output-to-output or output-to-GND
short. When a short circuit is detected on the
outputs, the outputs are disable immediately. If
the short was removed, the device activates
again.
Power Analog Microelectronics
,
Inc
www.poweranalog.com
10
10/2008 Rev 1.0
PAM [ POWER ANALOG MICOELECTRONICS ]
