AK4618 Datasheet, PDF (40/60 Pages) Asahi Kasei Microsystems – 192kHz 24-bit 6ch/12ch Audio CODEC with Microphone Interface

[AK4618]
■ MIC Bias
The AK4618 integrates power supply for microphone. When PMMB bit = “1”, the MICBIAS pin supplies power for the
microphone. This output voltage is typically 2.40V and the load resistance is minimum 0.3 k. (Figure 33, Figure 34)
Maximum interchannel isolation of microphone inputs is 70dB. The isolation depends on MICBIAS common impedance.
The microphone impedance and the microphone bias resistance is 2k ohm and MIC-Amp input voltage is ±500mVpp
(500mVpp). At this time, internal MICBIAS common impedance is 600m ohms or less, and external MICBIAS common
impedance should be 200m ohms or less.
PMMB bit
0
1
MICBIAS pin
Hi-Z
Output
Table 17. MICBIAS pin
(default)
MICBIAS pin
AK4618
PMMB bit
Microphone
2k
IN6-1 pin
MIC-Amp
IN6-1 pin
2k
Figure 33. MIC Input Block Circuit (differential input)
MICBIAS pin
AK4618
PMMB bit
Microphone
IN6-1 pin
MIC-Amp
Figure 34. MIC Input Block Circuit (single-ended input)
015000617-E-00
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2015/01