AK4648 Datasheet, PDF (72/119 Pages) Asahi Kasei Microsystems – Stereo CODEC with MIC/HP/SPK-AMP

[AK4648]
When the HPMTN bit is “0”, common voltages of Headphone-Amp and common buffer for Headphone-Amp fall and
HPL, HPR and HVCM pins go to “L” (VSS2). When the HPMTN bit is “1”, the common voltages rises to HVDD/2 at
VBAT bit = “0”. A capacitor between the MUTET pin and ground reduces pop noise at power-up. Rise/Fall time constant
is in proportional to HVDD voltage and the capacitor at MUTET pin.
HVDD
Capacitor value of
MUTET pin
HPMTN bit= “0” Æ “1”
(Note 62)
typ.
max
HPMTN bit = “1” Æ “0”
(Note 63)
typ.
max.
3.6V
120ms
210ms
140ms
260ms
4.2V
1μF±30%
-
230ms
-
270ms
5.0V
-
260ms
-
290ms
3.6V
260ms
460ms
310ms
560ms
4.2V
2.2μF±30%
-
500ms
-
570ms
5.0V
-
550ms
-
590ms
Note 62. Rising time of HP-Amp (0.8 x HVDD/2)
Note 63. Time until the common voltage goes to VSS2.
Table 61. Relationship between capacitor value of MUTET pin and MUTE ON/OFF time (VBAT bit = “0”)
When PMHPL, PMHPR, and PMHPC bits are “0”, the Headphone-Amp is powered-down, and HPL, HPR, HVCM pins
go to “L” (VSS2).
PMHPL bit,
PMHPR bit
PMHPC bit
HPMTN bit
HPL pin,
HPR pin,
HVCM pin
(1) (2)
(3)
(4)
Figure 54. Power-up/down sequence for Headphone-Amp (Pseudo Cap-less Mode)
(1) Headphone-Amp power-up (PMHPL=PMHPR=PMHPC bits = “1”). 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=PMHPC bits = “0”). Outputs become 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.
<Headphone-Amp PSRR>
When HVDD is directly supplied from the battery in the mobile phone system, RF noise may influences headphone
output performance. When VBAT bit is set to “1”, HP-Amp PSRR for the noise applied to HVDD is improved. In this
case, HP-Amp common voltage is 0.64 x AVDD (typ.). When AVDD is 3.3V, common voltage is 2.1V. Therefore, when
HVDD voltage becomes lower than 4.2V, the output signal will be clipped.
VBAT bit
0
Common Voltage [V]
0.5 x HVDD
Table 62. HP-Amp Common Voltage
1
0.64 x AVDD
MS0625-E-01
- 72 -
2007/06