AK4691 Datasheet, PDF (30/80 Pages) Asahi Kasei Microsystems – 4ch ADC + 2ch DAC with MIC/HP/SPK-AMP

[AK4691]
■ MIC BLOCK
1. Pre- Amp
Pre-Amp includes a selector, Internal MIC or External MIC Mode can be selected by PRSL2-1 and PRSR2-1 bits. The
Pre-Amp is non-inverting amplifier and internally biased to VCOM voltage with 100kΩ (typ.). The gain from Pre-Amp
#1 to MIXL/R-Amp is set by PRG12-10, and the gain from Pre-Amp #2 to MIXL/R-Amp is set by PRG22-20 bits
(Table 15).
PRSL1 bit
0
1
Lch Pre-Amp #1
Input Signal Source
INTL1 pin
EXTL1 pin
PRSR1 bit
0
1
Rch Pre-Amp #1
Input Signal Source
INTR1 pin
EXTR1 pin
PRSL2 bit
0
1
Lch Pre-Amp #2
Input Signal Source
PRSR2 bit
Rch Pre-Amp #2
Input Signal Source
INTL2 pin
0
INTR2 pin
EXTL2 pin
1
EXTR2 pin
Table 14. Pre-Amp Input Signal Source Select
An external capacitor (C1) is needed to cancel DC gain. The cut-off frequency is determined by an external capacitor
(C1) and internal feedback resistor (Rn). The internal feedback resistor (Rn) depends on Pre-Amp Gain and is typ ±
30%.
PRG12 bit
PRG22 bit
PRG11 bit
PRG21 bit
PRG10 bit
PRG20 bit
Gain
FB bit = “0”
FB bit = “1”
Rn(typ)
0
0
0
-4.4dB (Note 49) 0dB (Note 49)
3.5kΩ
0
0
1
+18dB
+22.4dB
4.4 kΩ
0
1
0
+20dB
+24.4dB
3.5kΩ
0
1
1
+24dB (default)
+28.4dB
2.2kΩ
1
0
0
+28dB
+32.4dB
1.4kΩ
1
0
1
1
1
0
N/A
1
1
1
Note 49. Input signal is bypassed to Pre-Amp and is inputted to MIX-Amp. The cut-off frequency is determined by input
impedance (typ. 100kΩ) and external capacitors (C2, C3).
Table 15. Relationship between Pre-Amp Gain and Feedback resistor (N/A: Not available)
C1
+
C2
INT pin
+
EXT pin
+
C3
PRSx bit
Rn
-
To MIX-Amp
+
Pre-Amp
To MIX-Amp (@ PRG12-10/PRG22-20 bits = “000”)
Figure 21. Pre-Amp
MS0672-E-00
- 30 -
2007/11