Diodes PAM8303C - Manual (Page 11)

PAM8303C
Document number: DSxxxxx Rev. 1 - 2
11 of 17
www.diodes.com
June 2013
© Diodes Incorporated
PAM8303C
A Product Line of
Diodes Incorporated
Application Information
(cont.)
Decoupling Capacitor (C
S
)
The PAM8303C 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 equivalentseries- resistance (ESR) ceramic capacitor, typically
1µF, is placed as close as possible to the device each V DD and PV DD pin for the best operation. For filtering lower frequency noise signals, a
large ceramic capacitor 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.
Figure 1: Ferrite Bead Filter to Reduce EMI
In order to reduce power consumption while not in use, the PAM8303C 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 SD pin. By switching the shutdown pin connected to GND,
the PAM8303C supply current draw will be minimized in idle mode.
Shutdown Operation
In order to reduce power consumption while not in use, the PAM8303C 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 pin. By switching the shutdown pin connected to GND, the
PAM8303C supply current draw will be minimized in idle mode.
Under Voltage Lock-Out (UVLO)
The PAM8303C incorporates circuitry designed to detect low supply voltage. When the supply voltage drops to 2.3V or below, the PAM8303C
goes into a state of shutdown, and the device comes out of its shutdown state and restore to normal function only when reset the power supply
or SD pin.
Thermal protection on the PAM8303C prevents the device from damage when the internal die temperature exceeds +135°C. There is a 15°C
tolerance on this trip point from device to device. Once the die temperature exceeds the set point, the device will enter the shutdown state and
the outputs are disabled. This is not a latched fault. The thermal fault is cleared once the temperature of the die decreased by 30°C. This large
hysteresis will prevent motor boating sound well and the device begins normal operation at this point with no external system interaction.
POP and Click Circuitry
The PAM8303C contains circuitry to minimize turn-on and turn-off transients or “click and pops”, where turn-on refers to either power supply turn-
on or device recover from shutdown mode. When the device is turned on, the amplifiers are internally muted. An internal current source ramps
up the internal reference voltage. The device will remain in mute mode until the reference voltage reach half supply voltage, 1/2 V
DD
. As soon as
the reference voltage is stable, the device will begin full operation. For the best power-off pop performance, the amplifier should be set in
shutdown mode prior to removing the power supply voltage.