AK4640_05 Datasheet, PDF (37/78 Pages) Asahi Kasei Microsystems – 16-Bit ΔΣ CODEC with MIC/HP/SPK-AMP

ASAHI KASEI
[AK4640]
The cut-off frequency of Headphone-amp output depends on the external resistor and capacitor used. Table 21 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
R
C _Headphone
AK4640
0.22µ +/- 20%
16Ω
10Ω +/- 20%
R [Ω]
6.2
16
6.2
16
Figure 26. External Circuit Example of Headphone
C [µF]
47
47
100
100
fc [Hz]
fc [Hz]
Output Power [mW]
BOOST=OFF BOOST=MID _2.7V
3.0V
3.3V
152.5
63
10.0
12.4
15.0
105.8
43
4.8
6.0
7.2
71.2
27
10.0
12.4
15.0
49.7
20
4.8
6.0
7.2
Table 21. External Circuit Example
MS0273-E-02
- 37 -
2005/04