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AK4640_05 Datasheet, PDF (36/78 Pages) Asahi Kasei Microsystems – 16-Bit ΔΣ CODEC with MIC/HP/SPK-AMP | |||
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ASAHI KASEI
[AK4640]
 Headphone Output
Power supply voltage for the Headphone-amp is supplied from the HVDD pin and centered on the HVDD/2 voltage. The
Headphone output load resistance is min.20â¦. When the PMHPL and PMHPR bits are â0â, the common voltage of
Headphone-amp falls and the outputs (HPL and HPR pins) go to âLâ (HVSS). When the PMHPL and PMHPR bits are
â1â, the common voltage rises to HVDD/2. A capacitor between the MUTET pin and ground reduces click noise at
power-up.
[Example] : A capacitor between the MUTET pin and ground = 1.0µF:
Rise/fall time constant: Ï = 100ms(typ), 250ms(max)
Time until the common goes to HVSS when PMHPL/R bits = â1â Ã â0â: 500ms(max)
When HPL and HPR bits are â1â, the Headphone-amp is powered-down, and the outputs (HPL and HPR pins) go to âLâ
(HVSS).
PMHPL/R bit
HPL/R bit
HPL/R pin
(1) (2)
(3)
(4)
Figure 25. Power-up/Power-down Timing for Headphone-amp
(1) Headphone-amp power-up (HPL, HPR bit= â0â). The outputs are still HVSS.
(2) Headphone-amp common voltage rises up (PMHPL, PMHPR bit= â1â). Common voltage of Headphone-amp is
rising. This rise time depends on the capacitor value connected with the MUTET pin. The time constant is Ï =
100k(typ) x C when the capacitor value on MUTET pin is âCâ.
(3) Headphone-amp common voltage falls down (PMHPL, PMHPR bit= â0â). Common voltage of Headphone-amp is
falling. This fall time depends on the capacitor value connected with the MUTET pin. The time constant is Ï =
100k(typ) x C when the capacitor value on MUTET pin is âCâ.
(4) Headphone-amp power-down (HPL, HPR bit= â1â). 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. It takes 2times
of Ï that the common voltage goes to GND.
MS0273-E-02
- 36 -
2005/04
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