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AS3421 AS3422

Datasheet - D e t a i l e d D e s c r i p t i o n

The second mode, with the name CHAREGPUMP_MODE, is the most commonly used mode which is per default enabled. In this mode the

internal charge pump is enabled. The charge pump doubles the supply voltage of AS3421/22 with a high output impedance of the charge pump

in order to make external passive filters more effective. If doubling the supply voltage is not enough the microphone supply can be switched to a

special regulated mode which increases the output voltage but with a little bit higher output noise. This setting can be found in register 0x35.

The third mode is the OFF MODE. This mode allows the user to switch of the microphone supply if not needed (e.g. playback without ANC)

9.2.3

Parameter

Table 5. Microphone Input Parameter

Symbol

Parameter

Condition

Min

Typ

Max

Unit

Input Signal Level

40

20

10

Input Impedance

MICP to AGND

7.5

k

Ω

Input Impedance Tolerance

-7

+33

%

Input Capacitance

5

pF

Programmable Gain

-11.25

+36

dB

Gain Steps

Discrete logarithmic gain steps

0.375

dB

Gain Step Precision

0.15

dB

Gain Ramp Rate

Tinit=64ms

4

ms/step

Limiter Activation Level

0.67

1

Limiter Release Level

0.4

1

Limiter Gain Overdrive

127 @ 0.375dB

36

dB

Limiter Attack Time

5

s/step

Limiter Decay Debouncing Time

64

ms

Limiter Decay Time

4

ms/step

Microphone Output Voltage

no output load

2.7

V

Microphone Supply Current

no output load

30

A

CP Output Resistance

400 A load

900

Ω

Microphone Output Current

Recommended minimum microphone output

current @ Vbat = 1.5V

170

A

Recommended minimum microphone output

current @ Vbat = 1.8V

300

A

Microphone Output Current

Recommended maximum microphone output

current @Vbat = 1.5V

500

A

Recommended maximum microphone output

current @Vbat = 1.8V

700

A