PAM8606 datasheet(13/16 Pages) PAM

13 / 16 page

Power Analog Microelectronics Inc

08/2008 Rev 1.1

PAM8606

6W Stereo Class-D Audio Power Amplifier with DC Volume Control

www.poweranalog.com

Volume Control

FADE Operation

MUTE Operation

Shutdown Operation

A DC volume control section is integrated in

PAM8606, controlling via VREF, VOLUME and

VREFGND terminals. The voltage on VOLUME

pin, without exceeding VREF, determines internal

amplifier gain as listed in Table 1.

If a resistor divider is used to fix gain of the

amplifier, the VREF terminal can be directly

connected to AVDD and the resistor divider

connected across VREF and REFGND. For fixed

gain, the resistor divider values are

center the voltage given in the Table 1.

The

terminal is a logic input that controls

the operation of the volume control circuitry

during transitions to and from the shutdown state

and during power-up.

A logic low on this terminal will set the amplifier in

fade mode. During power-up or recovery from the

shutdown state (a logic high is applied to the

terminal), the volume is smoothly ramped up from

the mute state, -75dB, to the desired volume set

by the voltage on the volume control terminal.

Conversely, the volume is smoothly ramped down

from the current state to the mute state when a

logic low is applied to the

terminal. A logic high

on this pin disables the volume fade effect during

transitions to and from the shutdown state and

during power-up. During power-up or recovery

from the shutdown state (a logic high is applied to

the

terminal), the transition from the mute

state, -75dB, to the desired volume setting is less

than 1ms. Conversely, the volume ramps down

from current state to the mute state within 1ms

when a logic low is applied to the

terminal.

The MUTE pin is an input for controlling the output

state of the PAM8606. A logic high on this pin

disables the outputs and low enables the outputs.

This pin may be used as a quick disable or enable

of the outputs without a volume fade.

For power saving, the

pin should be used to

reduce the quiescent current to the absolute

minimum level. The volume will fade, increasing

or decreasing slowly, when leaving or entering the

shutdown state if the

terminal is held low. If

the

terminal is held high, the outputs will

transit very quickly. Refer to the

operation

section.

The PAM8606 employs a shutdown operation

mode to reduce supply current to the absolute

minimum level during periods of non-use to save

power. The

input terminal should be held high

during normal operation when the amplifier is in

use. Pulling

low causes the outputs to mute

and the amplifier to enter a low-current state.

should never be left unconnected to prevent the

amplifier from unpredictable operation.

For the best power-off pop performance, the

amplifier should be set in shutdown mode prior to

removing the power supply voltage.

FADE

calculated

The internal 2.5V bias generator (V2P5) provides

the internal bias for the preamplifier stage. The

external input capacitors and this internal

reference allow the inputs to be biased within the

optimal common-mode range of the input

preamplifiers.

The selection of the capacitor value on the V2P5

terminal is critical for achieving the best device

performance. During startup or recovery from

shutdown state, the V2P5 capacitor determines

the rate at which the amplifier starts up. When the

voltage on the V2P5 capacitor equals 0.75 x

V2P5, or 75% of its final value, the device turns

on and the class-D outputs start switching. The

startup time is not critical for the best de-pop

performance since any heard pop sound is the

result of the class-D output switching-on other

than that of the startup time. However, at least a

0.47µF capacitor is recommended for the V2P5

capacitor.

Another function of the V2P5 capacitor is to filter

high frequency noise on the internal 2.5V bias

generator.

The PAM8606 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 oscillations 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

Internal 2.5V Bias Generator Capacitor

Selection

Power Supply Decoupling, C

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