AS3435 datasheet(20/102 Pages) AMSCO

20 / 102 page

AS3415/AS3435 – 20

ams Datasheet, Confidential: 2014-Jun-13 [v1-30]

De tail ed De sc rip t ion

Microphone Inputs

The AS3415/35 offers two low noise microphone inputs with

full digital control and a dedicated DC offset cancellation pin

for each microphone input. In total each gain stage offers up to

63 gain steps of 0.5dB resulting in a gain range from 0dB to

+31dB. The microphone gain is stored digitally during

production, in OTP on the ANC chipset. Besides the standard

microphone gain register for left and right channel, the chip

also features two additional microphone gain registers for

monitor mode. Thus, in monitor mode, a completely different

gain setting for left and right microphone can be selected to

implement voice filter functions to amplify the speech band for

better intelligibility.

Figure 19:

Stereo Microphone Input

Stereo Microphone Input: This diagram shows the internal structure of the stereo microphone preamplifier

including the mute switch as well as the automatic gain control (AGC).

To avoid unwanted start-up pop noise, a soft-start function is

implemented for an automatic gain ramping of the device. In

case of an overload condition on the microphone input (e.g.

high sound pressure level), an internal state machine reduces

the microphone gain automatically. For some designs it might

be useful to switch off this feature. Especially in feed-back

systems very often infrasound can cause an overload condition

of the microphone preamplifier which results in low frequency

noise which can be avoided by disabling the AGC.

AS3435 Datenblatt(PDF) 20 Page - ams AG