ASAHI KASEI
[AK4367]
Headphone Output
Power supply voltage for the Headphone-amp is supplied from the HVDD pin and centered on the MUTET voltage. The
Headphone-amp output load resistance is min.16Ω. When the MUTEN bit is “1” at PMHPL=PMHPR= “1”, the common
voltage rises to 0.45 x VDD. When the MUTEN bit is “0”, the common voltage of Headphone-amp falls and the outputs
(HPL and HPR pins) go to VSS.
A capacitor between the MUTET pin and ground reduces pop noise at power-up/down. It is
recommended that the capacitor with small variation of capacitance and low ESR (Equivalent Series
Resistance) over all temperature range, since the rise and fall time in Table 9 depend on the
capacitance and ESR of the external capacitor at MUTET pin.
In case only one path is connected,
DAC or LIN/RIN/MIN.
In case both paths are connected,
DAC and LIN/RIN/MIN.
120k x C (typ)
tr: Rise Time up to VCOM/2
tf: Fall Time down to 0V
100k x C (typ)
200k x C (typ)
150k x C (typ)
Table 9. Headphone-Amp Rise/Fall Time
[Example] : A capacitor between the MUTET pin and ground = 1.0µF, and only DAC path is connected:
Time constant of rise time: tr = 100kΩ x 1µF = 100ms(typ)
Time constant of fall time: tf = 200kΩ x 1µF = 200ms(typ)
When PMHPL and PMHPR bits are “0”, the Headphone-amp is powered-down, and the outputs (HPL and HPR pins) go
to VSS.
PMHPL/R bit
MUTEN bit
VCOM
VCOM/2
HPL/R pin
tf
tr
(1) (2)
(3)
(4)
Figure 15. Power-up/Power-down Timing for Headphone-amp
(1) Headphone-amp power-up (PMHPL and PMHPR bits = “1”). The outputs are still VSS.
(2) Headphone-amp common voltage rises up (MUTEN bit = “1”). Common voltage of Headphone-amp is rising. This
rise time depends on the capacitor value connected with the MUTET pin. The rise time up to VCOM/2 is tr = 100k x
C(typ) when the capacitor value on MUTET pin is “C”.
(3)Headphone-amp common voltage falls down (MUTEN bit = “0”). Common voltage of Headphone-amp is falling to
VSS. This fall time depends on the capacitor value connected with the MUTET pin. The fall time down to 0V is tf =
200k x C(typ) when the capacitor value on MUTET pin is “C”.
(4)Headphone-amp power-down (PMHPL, PMHPR bits = “0”). The outputs are VSS. If the power supply is switched off
or Headphone-amp is powered-down before the common voltage goes to VSS, some pop noise occurs.
MS0247-E-02
2005/10
- 19 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
