AK4683_07 Datasheet, PDF (44/84 Pages) Asahi Kasei Microsystems – Asynchronous Multi-Channel Audio CODEC with DIR/T

[AK4683]
■ Headphone Output
Power supply voltage for the Headphone-Amp is supplied from the HVDD pin and centered on the HVDD/2 voltage.
When the MUTEN bit is “0”, the common voltage of Headphone-Amp falls and the outputs (HPL and HPR pins) go to
“L” (HVSS). When the MUTEN bit is “1”, the common voltage rises to HVDD/2. A capacitor between the MUTET pin
and ground reduces click noise at power-up. Rise/Fall time constant is proportional to HVDD voltage and the capacitor
at MUTET pin.
[Example]: A capacitor between the MUTET pin and ground = 1.0μF, HVDD=5V:
Rise/fall time constant: τ = 120ms(typ)
When PWHP bit is “0”, the Headphone-Amp is powered-down, and the outputs (HPL and HPR pins) go to “L”
(HVSS).
PWHP bit
MUTEN bit
HPL pin,
HPR pin
(1) (2)
(3)
(̐)
(̑)
Figure 25. Power-up/Power-down Timing for Headphone-Amp
(1) Headphone-Amp power-up (PWHP bit = “1”). The outputs are still HVSS.
(2) Headphone-Amp common voltage rises up (MUTEN bit = “1”). Common voltage of Headphone-Amp is rising.
(3) Start the audio output after finishing the setup pf common voltage to prevent the clipping.
(4) Headphone-Amp common voltage falls down (MUTEN bit = “0”). Common voltage of Headphone-Amp is falling.
(5) Headphone-Amp power-down (PWHP bit = “0”). The outputs are HVSS. If the power supply is switched off or
Headphone-Amp is powered-down before the common voltage goes to HVSS, some CLICK noise occurs.
The cut-off frequency (fc) of Headphone-Amp depends on the external resistor and capacitor. Table 41 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 = 5V.
HP-AMP
AK4683
R
C _Headphone
16Ω
Figure 26. External Circuit Example of Headphone
R [Ω]
0
6.8
16
C [μF]
220
100
100
47
100
47
fc [Hz]
Output Power [mW]@0dBFS
45
50
100
70
25
149
50
12.5
106
Table 41. External Circuit Example
MS0427-E-02
- 44 -
2007/04