AK4640_05 AKM [Asahi Kasei Microsystems], AK4640_05 Datasheet - Page 36

• Manufacturer Part Number: AK4640_05
• Description: 16-Bit ?? CODEC with MIC/HP/SPK-AMP
• Manufacturer: AKM [Asahi Kasei Microsystems]

ASAHI KASEI
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.20Ω. When the PMHPL and PMHPR bits are “0”, the common voltage of
Headphone-amp falls and the outputs (HPL and HPR pins) go to “L” (HVSS). When the PMHPL and PMHPR bits are
“1”, 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:
When HPL and HPR bits are “1”, the Headphone-amp is powered-down, and the outputs (HPL and HPR pins) go to “L”
(HVSS).
(1) Headphone-amp power-up (HPL, HPR bit= “0”). The outputs are still HVSS.
(2) Headphone-amp common voltage rises up (PMHPL, PMHPR bit= “1”). Common voltage of Headphone-amp is
(3) Headphone-amp common voltage falls down (PMHPL, PMHPR bit= “0”). Common voltage of Headphone-amp is
(4) Headphone-amp power-down (HPL, HPR bit= “1”). The outputs are HVSS. If the power supply is switched off or
MS0273-E-02
Headphone Output
rising. This rise time depends on the capacitor value connected with the MUTET pin. The time constant is
100k(typ) x C when the capacitor value on MUTET pin is “C”.
falling. This fall time depends on the capacitor value connected with the MUTET pin. The time constant is
100k(typ) x C when the capacitor value on MUTET pin is “C”.
Headphone-amp is powered-down before the common voltage goes to HVSS, some click noise occurs. It takes 2times
of
τ
that the common voltage goes to GND.
Rise/fall time constant:
Time until the common goes to HVSS when PMHPL/R bits = “1”
PMHPL/R bit
HPL/R bit
HPL/R pin
Figure 25. Power-up/Power-down Timing for Headphone-amp
(1) (2)
τ
= 100ms(typ), 250ms(max)
- 36 -
(3)
(4)
“0”: 500ms(max)
[AK4640]
τ
τ
=
2005/04
=