ak4648 AKM Semiconductor, Inc., ak4648 Datasheet - Page 70

• Manufacturer Part Number: ak4648
• Description: Stereo Codec With Mic/hp/spk-amp
• Manufacturer: AKM Semiconductor, Inc.

When an external resistor R is smaller than 12 Ω , put an oscillation prevention circuit (0.22 μ F ± 20% capacitor and
10 Ω± 20% resistor) because it has the possibility that Headphone-Amp oscillates.
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 5-band equalizer function. Table 59 shows the cut off frequency and the output power for
various resistor/capacitor combinations. The headphone impedance R
(0.6 x AVDD) Vpp @HPG = 0dB.
When the HPMTN bit is “0”, the common voltage of Headphone-Amp falls and the outputs (HPL and HPR pins) go to
“L” (VSS2). When the HPMTN bit is “1”, the common voltage rises to HVDD/2 at VBAT bit = “0”. A capacitor between
the MUTET pin and ground reduces pop noise at power-up. Rise/Fall time constant is in proportional to HVDD voltage
and the capacitor at MUTET pin.
MS0625-E-01
Note 59. Output power at 16 Ω load.
Table 60. Relationship between capacitor value of MUTET pin and MUTE ON/OFF time (VBAT bit = “0”)
R [ Ω ]
Note 60. Rising time of HP-Amp (0.8 x HVDD/2)
Note 61. Time until the common voltage goes to VSS2.
6.8
16
0
HVDD
3.6V
4.2V
5.0V
3.6V
4.2V
5.0V
C [ μ F]
220
100
100
100
47
47
10
Capacitor value of
MUTET pin
2.2 μ F ± 30%
5-band EQ =
1 μ F ± 30%
fc [Hz]
OFF
100
149
106
137
45
70
50
Table 59. External Circuit Example
5-band EQ = ON
(
+6dB/100Hz @
fs=44.1kHz)
fc [Hz]
17
43
28
78
19
47
69
HPMTN bit= “0”
120ms
260ms
- 70 -
typ.
-
-
-
-
(Note 60)
HVDD=3.0V
AVDD=3.0V
L
25.3
12.5
6.3
210ms
230ms
260ms
460ms
500ms
550ms
is 16 Ω . The output voltage of headphone is typ.
max
Output Power [mW]@0dBFS
“1”
HVDD=3.3V
AVDD=3.3V
HPMTN bit = “1”
140ms
310ms
typ.
30.6
15.1
7.7
-
-
-
-
(Note 61)
AVDD=3.3V
HVDD=5V
260ms
270ms
290ms
560ms
570ms
590ms
max.
30.6
15.1
7.7
“0”
[AK4648]
2007/06