AS3543 datasheet(22/92 Pages) AMSCO

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AS3543 3v2

Data Sheet - D e t a i l e d D e s c r i p t i o n - A u d i o F u n c t i o n s

8.4.1

Phantom Ground

There are 2 ways to connect a headphone to the AFE. In order to spare the bulky ac/dc de-coupling capacitors at pins

HPR/HPL a buffered ground (Phantom Ground) is provided. This Common Mode Buffer needs to be switched on if

utilized. If form factor considerations are less stringent, the headphones can be conventionally connected via 2x200µF

capacitors.

Figure 7. Headphone Output using Common Mode Buffer

8.4.2

No-Pop Function

The output is automatically set to mute when the output stage is disabled.

To avoid Pop-Click noise during power-up and shut-down of the headphone amplifier, a charge/discharge control of

HPGND (0V-HPVDD/2-0V) at pins HPR/HPL is incorporated into the AFE. The 470nF capacitor at pin HPGND is used

to form the charge/discharge slope. Pls observe that pin HPGND is a high impedance node which must not be

connected to any other external device than the 470nF buffer capacitor. To avoid Pop-Click noise one has to wait for

750ms in between a power-down (switch-off) and a power-up (switch-on) of the headphone amplifier.

8.4.3

Auto Fading

By setting a new output volume level, the stage does a automatic fading from the current gain setting to the new target.

Changing the input multiplexer from one source to another will be done by fading out to mute, source changing and

fading in of the new source to the target volume. Change from HPH-out to LINE-out is done by fading out of HPH-out

to mute and fading in of the LINE-out to the target volume.

The fading speed can be programmed to 3 different speed levels. The immediate response can be selected as 4th

state.

Figure 8. Headphone Startup with MaxGain Settings

AS3543 Datenblatt(PDF) 22 Page - ams AG