ASAHI KASEI
[AK4370]
< Analog Mixing Circuit for Headphone Output >
DALHL, LIN1HL, RIN1HL, LIN2HL and RIN2HL bits control each path switch of HPL output. DARHR, LIN1HR,
RIN1HR, LIN2HR and RIN2HR bits control each path switch of HPR output.
When L1HM=L2HM bits = “0”, HPG1-0 bits = “00” (R1H= R2H= RDH= 100k) and ATTH4-0 bits = “00H” (0dB), the
mixing gain is +0.95dB (typ). When HPG1-0 bit = “01” (RDH= 50k), the mixing gain of DAC path is +6.95dB (typ).
When HPG1-0 bit = “10” (RDH= 25k), the mixing gain of DAC path is +12.95dB (typ). When L1HM and L2HM bits are
“1”, LIN1/RIN1 and LIN2/RIN2 signals are output from HPL/R pins as (L+R)/2, respectively (R1H= R2H= 200k).
When LDIF=LDIFH=LIN1L=RIN1R bits = “1”, LIN1 and RIN1 pins becomes IN+ and IN− pins, respectively. IN+ and
IN− pins can be used as full-differential mono line input for analog mixing for headphone-amp. In this case, LIN1HL,
RIN1HL, LIN1HR and RIN1HR bits should be “0”.
If the path is OFF and the signal is input to the input pin, the input pin should be biased to a voltage equivalent to VCOM
voltage (= 0.475 x AVDD) externally. Figure 39 shows the external bias circuit example.
100k(typ)
Figure 23
LDIFH bit
R1H
LIN1 pin
LIN1HL bit
R1H
RIN1 pin
RIN1HL bit
R2H
LIN2 pin
LIN2HL bit
R2H
100k(typ)
RIN2 pin
1.11RH
RIN2HL bit
DALHL bit
RDH
RH
DAC Lch
−
+
−
+
HPL pin
HP-Amp
100k(typ)
R1H
Figure 23
LDIFH bit
LIN1 pin
RIN1 pin
LIN2 pin
RIN2 pin
LIN1HR bit
R1H
RIN1HR bit
LIN2HR bit
R2H
R2H
100k(typ)
1.11RH
RIN2HR bit
DARHR bit
RDH
RH
DAC Rch
−
+
−
+
HPR pin
HP-Amp
Figure 21. Summation circuit for HPL/R output
MS0595-E-00
2007/03
- 26 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
