ak4648 AKM Semiconductor, Inc., ak4648 Datasheet - Page 72

• Manufacturer Part Number: ak4648
• Description: Stereo Codec With Mic/hp/spk-amp
• Manufacturer: AKM Semiconductor, Inc.

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.
When PMHPL, PMHPR, and PMHPC bits are “0”, the Headphone-Amp is powered-down, and HPL, HPR, HVCM pins
go to “L” (VSS2).
(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
<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.
MS0625-E-01
is switched off or Headphone-Amp is powered-down before the common voltage goes to VSS2, some POP noise
occurs.
Table 61. Relationship between capacitor value of MUTET pin and MUTE ON/OFF time (VBAT bit = “0”)
Note 62. Rising time of HP-Amp (0.8 x HVDD/2)
Note 63. Time until the common voltage goes to VSS2.
HVDD
3.6V
4.2V
5.0V
3.6V
4.2V
5.0V
PMHPL bit,
PMHPR bit
PMHPC bit
HPMTN bit
HPL pin,
HPR pin,
HVCM pin
Common Voltage [V]
Figure 54. Power-up/down sequence for Headphone-Amp (Pseudo Cap-less Mode)
VBAT bit
Capacitor value of
MUTET pin
2.2 μ F ± 30%
1 μ F ± 30%
(1) (2)
Table 62. HP-Amp Common Voltage
0.5 x HVDD
HPMTN bit= “0”
120ms
260ms
- 72 -
typ.
-
-
-
-
(3)
0
(Note 62)
210ms
230ms
260ms
460ms
500ms
550ms
(4)
max
“1”
HPMTN bit = “1”
0.64 x AVDD
140ms
310ms
typ.
-
-
-
-
1
(Note 63)
260ms
270ms
290ms
560ms
570ms
590ms
max.
“0”
[AK4648]
2007/06