AK5730 Datasheet, PDF (27/50 Pages) Asahi Kasei Microsystems – 4-Channel Differential Audio ADC for Line & Mic Inputs

[AK5730]
■ Analog Input Mode
The AK5730 has 4 Analog Input modes. Analog Input mode is controlled by LIN*1-0 bits. The input mode is fixed by
each set. The AC signal is input from IN*P/N, and the DC signal is input from INM*P/N. Except for Microphone Input
mode, the input voltage of IN*P/N(=1.65Vrms (Typ.), Differential) should be adjusted with external resistors. As for the
accuracy of external resistance, 0.1% is required for CMRR.
The input voltage of INM*P/N(=AVDD) should be adjusted with external resistors. Fault conditions are calculated
digitally, so the value of external resistance is fixed to 7:3. The input voltage of INM*P/N becomes 30% of VDC+/-. As
for the accuracy of external resistance, 0.1% is required for the accuracy of SAR.
The full scale of SAR is normalized to 11V (@AVDD=3.3V) for calculations of Fault Condition detection.
(A) Microphone Input Mode (LIN*1-0 bits = “00”)
The microphones are connected in a fully balanced manner. A separate cable shield for each microphone may be
connected to chassis ground. In this use case, a gain correction of 9.5dB by GAIN* bit = “1” is available.
Parameter
Mic Impedance
Mic Audio Output
Interchannel Isolation(max) of
Microphone inputs
Mic Phantom Voltage(Vbias)
Mic Supply Current
Resistors (symmetrical)
Specification
1 - 2kohm, 10kohm(max)
10...100mVrms, 1.75Vrms(max)
70dB
Remarks
5V - 9V
depending on type of microphone
0.1 - 10mA
per microphone
depending on type of microphone
200 - 10k
Table 9 Specification(Microphone Input mode)
Maximum Interchannel Isolation of Microphone inputs is 70dB.The isolation depends on MPWR common impedance.
In Figure 24, the microphone impedance and the microphone bias resistance is 2k ohm and MPWR voltage is 8.0V. At
this time, MPWR common impedance should be 0.2 ohms or less.
MPWR
+8.0V
max: 0.2ohm
AK5730
2kohm
1kHz Sin Wave
100mVpp
2kohm(Mic)
2kohm
Isolation measured
2kohm(Mic)
2kohm
2kohm
Figure 24. Interchannel Isolation of Microphone Inputs
Rev 0.8
- 27 -
2013/06