Diodes PAM8003 - Manual (Page 9)

PAM8003
Document number: DSxxxxx Rev. 1 - 1
9 of 12
www.diodes.com
November 2012
© Diodes Incorporated
PAM8003
A Product Line of
Diodes Incorporated
Application Information (cont.)
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 caused by the power
supply coupling into 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
) with values of 0.1μF 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 PAM8003 incorporates circuitry designed to detect low supply voltage. When the supply voltage drops to 2.0V or below, the PAM8003
outputs are disabled, and the device comes out of this state and starts to normal function when V
DD
≥ 2.2V.
Short Circuit Protection (SCP)
The PAM8003 has short circuit protection circuitry on the outputs to prevent damage to the device when output-to-output or output-to-GND short
occurs. When a short circuit is detected on the outputs, the out puts are disabled immediately. If the short was removed, the device activates
again.
Over Temperature Protection
Thermal protection on the PAM8003 prevents the device from damage when the internal die temperature exceeds +140°C. 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 30°C. This large hysteresis will prevent motor
boating sound well and the device begins normal operation at this point without external system intervention.
How to Reduce EMI (Electro Magnetic Interference)
A simple solution is to put an additional capacitor 1000μF 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 as shown in Figure 2. The ferrite filter reduces EMI of around 1 MHz and higher. When selecting a
ferrite bead, choose one with high impedance at high frequencies, and low impedance at low frequencies.
Figure 2. Ferrite Bead Filter to Reduce EMI