PAM8012 Datasheet, PDF (8/13 Pages) Power Analog Micoelectronics – Mono 2.0WAnti-saturation Class D Audio Power Amplifier with Power Limit

PAM8012
Mono 2.0W Anti-saturation Class D
Audio Power Amplifier with Power Limit
Application Information
Input Capacitors (Ci )
In the typical application, an input capacitor, Ci,
is required to allow the amplifier to bias the input
signal to the proper DC level for optimum
operation. In this case, Ci and the minimum input
impedance Ri form is a high-pass filter with the
corner frequency determined in the follow
equation:
fc
=
1
2pRiCi
It is important to consider the value of Ci as it
directly affects the low frequency performance of
the circuit. For example,the specification calls
for a flat bass response are down to 150Hz.
Equation is reconfigured as followed:
Ci = ¹
2pRifc
When input resistance variation is considered,
the Ci is 34nF, so one would likely choose a value
of 33nF. A further consideration for this capacitor
is the leakage path from the input source through
the input network (Ci, Ri + Rf) to the load. This
leakage current creates a DC offset voltage at
the input to the amplifier that reduces useful
headroom, especially in high gain applications.
For this reason, a low-leakage tantalum or
ceramic capacitor is the best choice. When
polarized capacitors are used, the positive side
of the capacitor should face the amplifier input in
most applications as the DC level is held at V / _DD 2,
which is likely higher than the source DC level.
Please note that it is important to confirm the
capacitor polarity in the application.
Decoupling Capacitor (C_S )
The PAM8012 is a high-performance CMOS
audio amplifier that requires adequate power
supply decoupling to ensure the output total
harmonic distortion (THD) as low as possible.
Power supply decoupling also prevents the
oscillations causing by long lead length between
the amplifier and the speaker.
The optimum decoupling is achieved by using
two different types of capacitors that target on
different types of 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 1μF, is placed as close as possible to
VDD pin for the best operation. For filtering lower
frequency noise signals, a large ceramic
c apacitor of 10μF or greater placed near the
audio power amplifier is recommended.
How to Reduce EMI
Most applications require a ferrite bead filter for
EMI elimination shown at Figure 1. The ferrite
filter reduces EMI around 1MHz and higher.
When selecting a ferrite bead, choose one with
high impedance at high frequencies, but low
impedance at low frequencies.
OUT+
Fe rrit e Be ad
OUT-
Fe rrit e Bea d
20 0p F
20 0p F
Figure 1: Ferrite Bead Filter to Reduce EMI
Shutdown operation
In order to reduce power consumption while not
in use, the PAM8012 contains shutdown circuitry
that is used to turn off the amplifier’s bias
circuitry. This shutdown feature turns the
amplifier off when logic low is placed on the EN
pin. By switching the EN pin connected to GND,
the PAM8012 supply current draw will be
minimized in idle mode.
Short Circuit Protection (SCP)
The PAM8012 has short circuit protection
circuitry on the outputs to prevent the device
from damage when output-to-output shorts or
output-to-GND shorts occur. When a short circuit
occurs, the device immediately goes into
shutdown state. Once the short is removed, the
device will be reactivated.
Power Analog Microelectronics, Inc
www.poweranalog.com
8
06/2012 Rev1.3