ASAHI KASEI
[AK4370]
< External Circuit of Headphone-Amp >
The cut-off frequency of the headphone-amp output depends on the external resistor and capacitor used. Table 13 shows
the cut off frequency and the output power for various resistor/capacitor combinations. The headphone impedance RL is
16Ω. Output powers are shown at AVDD = 2.4, 3.0 and 3.3V. The output voltage of the headphone-amp is 0.48 x AVDD
(Vpp) @−3dBFS.
HP-AMP
R
C
Headphone
16Ω
AK4370
Figure 19. External Circuit Example of Headphone
fc [Hz]
BOOST=OFF
fc [Hz]
BOOST=MIN
Output Power [mW]
R [Ω]
C [μF]
2.4V
21
3.0V
33
3.3V
40
220
100
100
47
100
47
45
100
70
149
50
17
43
28
78
19
47
0
6.8
16
10
5
16
8
20
10
106
Table 13. Relationship of external circuit, output power and frequency response
< Wired OR with External Headphone-Amp >
When PMVCM=PMHPL=PMHPR bits = “0” and HPZ bit = “1”, Headphone-amp is powered-down and HPL/R pins are
pulled-down to VSS1 by 200kΩ (typ). In this setting, it is available to connect headphone-amp of AK4370 and external
single supply headphone-amp by “wired OR”.
PMVCM
PMHPL/R
HPMTN
HPZ
Mode
Power-down & Mute
Power-down
Mute
Normal Operation
HPL/R pins
VSS1
Pull-down by 200kΩ
VSS1
x
0
1
1
0
0
1
1
x
x
0
1
0
1
x
x
Default
Normal Operation
Table 14. HP-Amp Mode Setting (x: Don’t care)
HPL pin
AK4370
Headphone
HPR pin
Another
HP-Amp
Figure 20. Wired OR with External HP-Amp
MS0595-E-00
2007/03
- 25 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
