Data Sheet

from power on/off and entering and leaving
shutdown.
Thermal protection on the PAM8403 prevents
damage to the device when the internal die
temperature exceeds 120 . There is a 15 degree
tolerance on this trip point from device to device.
Once the die temperature exceeds the thermal
set point, the device outputs are disabled. This is
not a latched fault. The thermal fault is cleared
once the temperature of the die is reduced by
40 . This large hysteresis will prevent motor
boating sound well and the device begins normal
operation at this point with no external system
interaction.
Figure 3: Ferrite Bead Filter to reduce EMI
Over Temperature Protection
℃
℃
Power On/Off Pop noise Reducing
Under Voltage Lock-out (UVLO)
Short Circuit Protection (SCP)
How to Reduce EMI (Electro Magnetic
Interference)
Power on pop noise reducing: The PAM8403
contains circuitry to minimize turn-on pop noise.
In this case, turn-on refers to either power supply
turn-on or device coming out shutdown mode.
When the device is turning on, the amplifiers are
internally muted. An internal current source
ramps up the voltage of VREF pin. The device will
remain in mute mode until the VREF pin has
reached its half supply voltage, 1/2 V . As soon
as the VREF node is stable, the device will
become fully operational.
Power off pop noise reducing: for the best power-
off pop performance, the amplifier should be
placed in the mute /shutdown mode prior to
removing the power supply voltage. An external
circuit shows in figure 2 also can minimize the
power off pop noise: the V is set around
1.3V@V =5V which is a little higher than the
mute/shutdown threshold voltage, R1 reduce the
internal resistor temperature coefficient and
capacitor C speeds up the response. Note that
this circuit can only work in between V = 4.5V to
5.5V, otherwise the PAM8403 can not work, other
than the ratio of the resistor divider needs to be
changed.
Figure 2: External Circuit to reduce power off pop
noise
The PAM8403 incorporates circuitry designed to
detect when the supply voltage is low. When the
supply voltage drops to 2.0V or below, the
PAM8403 outputs are disable, and the device
comes out of this state and starts to normal
functional until V 2.2V.
The PAM8403 has short circuit protection
circuitry on the outputs that prevents damage to
the device during output-to-output and 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.
A simple solution is to put an additional capacitor
1000uF at power supply terminal for power line
coupling if the traces from amplifier to speakers
are short (<20CM).
Most applications require a ferrite bead filter
which shows at Figure 3. The ferrite filter reduces
EMI around 1 MHz and higher. When selecting a
ferrite bead, choose one with high impedance at
high frequencies, but low impedance at low
frequencies.
DD
TH
DD
DD
DD
≥
9
English:www.poweranalog.com www.power-analog.com：
Application Information(continued)
PAM8403
Filterless 3W Class-D Stereo Audio Amplifier
C
1nF
R1
47K
R2
10K
VDD
V
TH
MUTE o r SH DN
200pF
200pF
OUT+
OUT-
Ferrite Bead
Ferrite Bead
03/2007
,Power Analog Microelectronics Inc