ak4644 AKM Semiconductor, Inc., ak4644 Datasheet - Page 60

• Manufacturer Part Number: ak4644
• Description: Stereo Codec With Mic/hp/rcv-amp
• Manufacturer: AKM Semiconductor, Inc.

ASAHI KASEI
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
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.
<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.
MS0477-E-01
HPG bit
0
1
R [Ω]
Common Voltage [V]
100
6.8
16
0
0
VBAT bit
C [µF]
220
100
100
100
220
100
47
47
22
10
Figure 56. External Circuit Example of Headphone
HP-AMP
AK4644
Note 38. Output power at 16Ω load.
Note 39. Output signal is clipped.
Table 53. HP-Amp Common Voltage
BOOST
Table 52. External Circuit Example
fc [Hz]
=OFF
100
149
106
100
137
45
70
50
45
62
10Ω
0.22µ
0.5 x HVDD
C
fs=44.1kHz
- 60 -
BOOST
fc [Hz]
=MIN
0
17
43
28
78
19
47
17
43
25
69
R
Headphone
HVDD=3.0V
AVDD=3.0V
(Note 39)
16Ω
25.3
12.5
6.3
1.1
51
Output Power [mW]@0dBFS
L
is 16Ω. Output powers are shown at
0.64 x AVDD
HVDD=3.3V
AVDD=3.3V
(Note 39)
1
30.6
15.1
7.7
1.3
62
AVDD=3.3V
HVDD=5V
30.6
15.1
7.7
1.3
70
[AK4644]
2006/10