AK4644 Datasheet, PDF (60/96 Pages) Asahi Kasei Microsystems – Stereo CODEC with MIC/HP/RCV-AMP

ASAHI KASEI
[AK4644]
When BOOST=OFF, the cut-off frequency (fc) of Headphone-Amp depends on the external resistor and capacitor. This
fc can be shifted to lower frequency by using bass boost function. Table 52 shows the cut off frequency and the output
power for various resistor/capacitor combinations. The headphone impedance R_L is 16Ω. Output powers are shown at
HVDD = 2.7, 3.0 and 3.3V. The output voltage of headphone is 0.6 x AVDD (Vpp).
When an external resistor R is smaller than 12Ω, put an oscillation prevention circuit (0.22µF±20% capacitor and
10Ω±20% resistor) because it has the possibility that Headphone-Amp oscillates.
HP-AMP
AK4644
CR
0.22µ
10Ω
Headphone
16Ω
HPG bit R [Ω]
0
0
6.8
16
0
1
100
Figure 56. External Circuit Example of Headphone
fc [Hz]
fc [Hz]
Output Power [mW]@0dBFS
C [µF]
BOOST
=OFF
BOOST
=MIN
fs=44.1kHz
HVDD=3.0V HVDD=3.3V HVDD=5V
AVDD=3.0V AVDD=3.3V AVDD=3.3V
220
45
17
25.3
30.6
30.6
100
100
43
100
70
28
12.5
15.1
15.1
47
149
78
100
50
19
6.3
7.7
7.7
47
106
47
220
45
100
100
17
43
51
(Note 39)
62
(Note 39)
70
22
62
25
1.1
1.3
1.3
10
137
69
Table 52. External Circuit Example
Note 38. Output power at 16Ω load.
Note 39. Output signal is clipped.
<Headphone-Amp PSRR>
When HVDD is directly supplied from the battery in the mobile phone system, RF noise may influences headphone
output performance. When VBAT bit is set to “1”, HP-Amp PSRR for the noise applied to HVDD is improved. In this
case, HP-Amp common voltage is 0.64 x AVDD (typ). When AVDD is 3.3V, common voltage is 2.1V. Therefore, when
HVDD voltage becomes lower than 4.2V, the output signal will be clipped easily.
VBAT bit
0
Common Voltage [V]
0.5 x HVDD
Table 53. HP-Amp Common Voltage
1
0.64 x AVDD
MS0477-E-01
- 60 -
2006/10