[AK4679]
<HP-Amp External Circuit>
It is necessary to put an oscillation prevention circuit (0.22μF±20% capacitor and 15Ω±20% resistor) because it has the
possibility that Headphone-Amp oscillates.
HP-Amp
Headphone
16Ω
AK4679
0.22μF
15Ω
Figure 85. HP-Amp oscillation prevention circuit example
When PMHPL or PMHPR bit = “1”, headphone outputs are in normal operation after the charge pump circuit is powered
up. When PMHPL and PMHPR bits = “0”, the headphone-amps and the charge pump circuit are powered-down
completely. At that time, the HPL and HPR pins go to VSS1 voltage via the internal pulled-down resistor. The
pulled-down resistor is 120Ω (typ).
The power-up time of HP-Amp block is 28ms and then HPL and HPR pins output 0V (VSS1). The power-down is
executed immediately.
PMVCM
bit
PMHPL/R
bits
Mode
HPL/R pins
x
1
0
1
Power-down & Mute
Normal Operation
(default)
Pull-down by 120Ω (typ)
Normal Operation
Table 110. Headphone-Amp Mode Setting (x: Don’t’ care)
MS1402-E-06
2013/02
- 118 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
