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AS3418

Functional Description

Datasheet

• PUBLIC

DS000507

• v4-00 • 2020-Jan-23

│ 19

Figure 16:

Microphone THD+N vs. Vinput ECO Mode (A-weighted)

6.3

Microphone Supply

The AS3418 features an integrated microphone supply voltage regulator and a charge pump to source

the microphone LDO even with a 1.4V chip supply voltage in order to increase the sensitivity of the

microphone. The microphone supply charge pump is in default configuration enabled and can be

controlled in ANC and Monitor operation mode with register ANCMON_MICS_CP_ON bit. For PBO

operation mode there is a dedicated control bit PBO_MICS_CP_ON.

The output of the charge pump is directly connected to an internal microphone supply ultra-low noise

voltage regulator. This low dropout (LDO) regulator is in default configuration enabled and can be

controlled with ANCMON_MICS_ON bit. The default output voltage of the regulator is 2.9V. If there is

a lower output voltage desired in an application the voltage level can be changed via register

MICS_V_SEL register.

If the AS3418 is connected to a 1.5V battery the input voltage will of course drop during operation

because the battery is discharging during operation. In order to make sure the microphone supply

LDO has enough headroom to regulate properly the device features an automatic output voltage

adjustment feature. This function makes sure the voltage regulator has enough headroom and adjusts

the output voltage of the LDO accordingly.

0,0001

0,001

0,01

0,1

100

Vinput [mV]

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