PAM8009

Document number: DS37224 Rev. 1 - 2

8 of 12

www.diodes.com

January 2015

© Diodes Incorporated

PAM8009

Application Information

AGC Function

When output reaches the maximum power-setting value, the Internal Programmable Gain Amplifier will decrease the gain to prevent the output

waveform from clipping. This feature prevents speaker damage from occurring using the AGC pin to set the AGC function, limiting the output

power.

Table 1: AGC Setting Threshold vs. Output

AGC Function

Output Power

VDD ~ 0.45VDD or

AGC Floating

AGC function Disable

0.45VDD ~ 0.27VDD

Po=[[8(1/2VDD-VAGC)^2]/Rl] x 0.95

0.27VDD ~ GND

Po=2.3W (Max. output power 4Ω)

Po=1.2W (Max. output power 8Ω)

Mute Operation

The MUTE pin is an input for controlling the Class-D output state of the PAM8009. A logic low on this pin enables the outputs, and a logic high on

this pin disables the outputs. This pin may be used to quickly disable or enable the outputs without a volume fade. Quiescent current is listed in the

electrical characteristics table. The MUTE pin can be left floating due to the internal pull-down.

Shutdown Operation

In order to reduce power consumption while not in use, the PAM8009 contains shutdown circuit to turn off the amplifier’s bias circuit. The amplifier

is turned off when logic low is placed on the /SD pin. When switching the /SD pin to low level, the amplifier enters a low-consumption current status.

The /SD pin can be left floating due to the internal pull-up.

Undervoltage Protection

External undervoltage detection can be used to shut down the PAM8009 before an input device can generate a pop. The shutdown threshold at the

UVP pin is 1.2V. The user selects a resistor divider to obtain the shutdown threshold and hysteresis for the specific application.

The threshold can be determined as below:

With the condition: R3 >> R1//R2

Hysteresis = 5uA x R3 x (R1+R2)/ R2

Power Supply Decoupling

The PAM8009 is a high performance CMOS audio-amplifier that requires adequate power supply decoupling to ensure the outputs of THD and

PSRR are as low as possible. Power supply decoupling also prevents oscillation caused by long lead between the amplifier and the speaker. The

optimum decoupling is achieved by using two capacitors of different types that target 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 0.1uF is

greater placed near the audio amplifier is recommended.