AK4648 Datasheet, PDF (70/119 Pages) Asahi Kasei Microsystems – Stereo CODEC with MIC/HP/SPK-AMP

[AK4648]
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.
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_L is 16Ω. The output voltage of headphone is typ.
(0.6 x AVDD) Vpp @HPG = 0dB.
R [Ω]
C [μF]
fc [Hz]
5-band EQ =
OFF
fc [Hz]
5-band EQ = ON
(+6dB/100Hz @
fs=44.1kHz)
Output Power [mW]@0dBFS
HVDD=3.0V HVDD=3.3V HVDD=5V
AVDD=3.0V AVDD=3.3V AVDD=3.3V
0
220
100
45
100
17
43
25.3
30.6
30.6
6.8
100
70
28
12.5
15.1
15.1
47
149
78
100
50
19
16
47
106
47
6.3
7.7
7.7
10
137
69
Note 59. Output power at 16Ω load.
Table 59. External Circuit Example
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.
HVDD
Capacitor value of
MUTET pin
HPMTN bit= “0” Æ “1”
(Note 60)
typ.
max
HPMTN bit = “1” Æ “0”
(Note 61)
typ.
max.
3.6V
4.2V
1μF±30%
120ms
-
210ms
230ms
140ms
-
260ms
270ms
5.0V
-
260ms
-
290ms
3.6V
260ms
460ms
310ms
560ms
4.2V
2.2μF±30%
-
500ms
-
570ms
5.0V
-
550ms
-
590ms
Note 60. Rising time of HP-Amp (0.8 x HVDD/2)
Note 61. Time until the common voltage goes to VSS2.
Table 60. Relationship between capacitor value of MUTET pin and MUTE ON/OFF time (VBAT bit = “0”)
MS0625-E-01
- 70 -
2007/06