AK4648 Datasheet, PDF (71/119 Pages) Asahi Kasei Microsystems – Stereo CODEC with MIC/HP/SPK-AMP

[AK4648]
When PMHPL and PMHPR bits are “0”, the Headphone-Amp is powered-down, and HPL and HPR pins go to “L”
(VSS2).
PMHPL bit,
PMHPR bit
HPMTN bit
HPL pin,
HPR pin
(1) (2)
(3)
(4)
Figure 52. Power-up/down sequence for Headphone-Amp (Single-ended Mode)
(1) Headphone-Amp power-up (PMHPL, PMHPR bit = “1”). The outputs are still VSS2.
(2) Headphone-Amp common voltage rises up (HPMTN bit = “1”). Common voltage of Headphone-Amp is rising.
(3) Headphone-Amp common voltage falls down (HPMTN bit = “0”). Common voltage of Headphone-Amp is falling.
(4) Headphone-Amp power-down (PMHPL, PMHPR bit = “0”). The outputs are VSS2. If the power supply is switched
off or Headphone-Amp is powered-down before the common voltage goes to VSS2, some POP noise occurs.
2. Pseudo Cap-less Mode (In case of using common buffer for Headphone-Amp)
HP-Amp
VCOM Amp for
HP-Amp
HPL pin
R
0.22μF
10Ω
HVCM pin
Headphone
16Ω
HP-Amp
16Ω
HPR pin
R
0.22μF
10Ω
Figure 53. External circuit example for Headphone-Amp (Pseudo Cap-less Mode)
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.
MS0625-E-01
- 71 -
2007/06