AK4650 Datasheet, PDF (39/86 Pages) Asahi Kasei Microsystems – 16Bit ΔΣ CODEC with MIC/HP/SPK-AMP & TSC

[AK4650]
■ 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 HPMT bit is “1” at PMHPL=PMHPR= “1”, the common
voltage rises to 0.44 x AVDD. When the HPMT bit is “1”, the common voltage of Headphone-amp falls and the outputs
(HPL and HPR pins) go to HVSS.
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 32 depend on the
capacitance and ESR of the external capacitor at MUTET pin.
t_r: Rise Time up to 0.44 x AVDD
100k x C (typ)
t_f: Fall Time down to 0V
200k x C (typ)
Table 32. Headphone-Amp Rise/Fall Time
[Example]: A capacitor between the MUTET pin and ground = 1.0μF:
Rise Time up to 0.44 x AVDD: t_r = 100kΩ x 1μF = 100ms(typ)
Fall Time down to 0V: t_f = 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 HVSS.
PMHPL/R bit
HPMT bit
0.44 x AVDD
HPL/R pin ^{0.22 x AVDD}
t_r
(1) (2)
t_f
(3)
(4)
Figure 26. Power-up/Power-down Timing for Headphone-amp
(1) Headphone-amp power-up (PMHPL and PMHPR bits = “1”). The outputs are still HVSS.
(2) Headphone-amp common voltage rises up (HPMT bit = “0”). 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 0.44 x AVDD is t_r = 100k x
C(typ) when the capacitor value on MUTET pin is “C”.
(3) Headphone-amp common voltage falls down (HPMT bit = “1”). Common voltage of Headphone-amp is falling to
HVSS. This fall time depends on the capacitor value connected with the MUTET pin. The fall time down to 0V is t_f =
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 HVSS. If the power supply is switched
off or Headphone-amp is powered-down before the common voltage goes to HVSS, some pop noise occurs.
MS0502-E-01
- 39 -
2007/04