PAM8404

Document number: DSxxxxx Rev. 1 - 1

13 of 18

www.diodes.com

November 2012

© Diodes Incorporated

PAM8404

A Product Line of

Diodes Incorporated

Application Information

For this reason, a low-leakage tantalum or ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the

Please note that it is important to confirm the capacitor polarity in the application.

If the corner frequency is within the audio band, the capacitors should have a tolerance ±10% or better, because any mismatch in capacitance

cause an impedance mismatch at the corner frequency and below.

Decoupling Capacitor (CS)

The PAM8404 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

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 as shown at Figure 1. The ferrite filter reduces EMI of around 1MHz and higher.

When selecting a ferrite bead, choose one with high impedance at high frequencies and low impedance at low frequencies.

Figure 1. Ferrite Bead Filter to Reduce EMI

Shutdown Operation

In order to reduce power consumption while not in use, the PAM8404 contains shutdown circuitry to turn off the amplifier's bias circuitry. It

switching the shutdown pin to GND, the PAM8404 supply current draw will be minimized in idle mode.

Short Circuit Protectrion (SCP)

The PAM8404 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.

Over Temperature Protection (OTP)

Thermal protection on the PAM8404 prevents the device from damage when the internal die temperature exceeds +150°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 50°C. This large

hysteresis will prevent motor boating sound well and the device begins normal operation at this point with no external system interaction.