AS3515_08 Datasheet, PDF (17/67 Pages) ams AG – Stereo Audio Codec with System Power Management

AS3515 V15
Data Sheet, Confidential
austriamicrosystems
6.4 Microphone Inputs (2x)
6.4.1 General
AS3515 includes two identical microphone inputs. The blocks have differential inputs to a microphone amplifier with adjustable gain. This
stage also includes an AGC.
The following volume control has an independent gain regulation for left and right channel with 32 steps @ 1.5dB each. The gain can be
set from –40.5dB to +6dB. The stage is set to mute by default. If the microphone input is not enabled, the volume settings are set to their
default values. Changing of volume and mute control can only be done after enabling the input.
Figure 5 Microphone Input
ams ^{AnGtent still valid 6.4.2 AGC}
The microphone amplifier includes an AGC, which is limiting the signal to 1Vp. The AGC has 15 steps with a dynamic range of about
o _{29dB. The AGC is ON by default but can be disabled by a microphone register bit.}
c _{6.4.3 Supply & Detection}
l Each microphone input generates a supply voltage of 1.5V above HPHCM. The supply is designed for ≤2mA and has a 10mA current
limit. In OFF mode the MICSUP terminal is pulled to AVDD with 30kohm. A current of typically 50uA generates an interrupt to inform the
a CPU, that a circuit is connected. When using HPHCM as headset ground the HPH–stage gives the interrupt. After enabling the HPH-stage
through the CPU the microphone detection interrupt will follow.
ic ^{6.4.4 Remote Control}
Fast changes of the supply current of typically 500uA are detected as a remote button press, and an interrupt is generated. Then the CPU
n _{can start the measurement of the microphone supply current with the internal 10-bit ADC to distinguish which button was pressed. As the}
current measurement is done via an internal resistor, only two buttons generating a current of about 0.5mA and 1mA can be detected.
Tech ^{With this 1mA as microphone bias is still available.}
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