
www.austriamicrosystems.com
Revision 1.10
21 - 86
AS3542 3v2
Data Sheet, Strictly Confidential - D e ta i l e d D e s c r i p t i o n - A u d i o F u n c t i o n s
Figure 9. Headphone Change Gain Settings
8.4.4 Headphone
Detection
When the headphone amplifier is powered down, one can detect the connection of a headset. It only work if the
headset is connected between pins HPR/HPL and HPCM. As long as the headphone amplifier is powered down,
HPCM is biased to 150mV and acting as the sense pin. There is a corresponding interrupt available to be enabled.
8.4.5 Over-current
Protection
The headphone amplifier has an over-current protection (e.g. HPR/HPL is shorted). This over-current protection will
power down the headphone amplifier for a programmable time-out period (512ms, 0ms). There is a corresponding
interrupt available to be enabled.
Figure 10. Headphone Overcurrent OFF-ON Sequence
8.4.6 Ground Noise Cancelation
As separate ground input allows to connect a ground sense line direct from the dock connector ground or headphone
jack shield to make the audio output independent from PCB ground noise.
8.4.7 Power
Options
To save power, especially when driving 32 Ohm loads, a reduction of the bias current is selected. For 16Ohm loads
the bias current can be increased.
8.4.8 Parameter
AVDD17=1.7, AVDD27=2.7, HPVDD = 2.7V, T
A
= 25
o
C, unless otherwise mentioned
Table 12. Headphone Output Parameter
Symbol
Parameter
Condition
Min
Typ
Max
Unit
R
L_HP
Load Impedance
stereo mode
16
Ω
C
L_HP
Load Capacitance
stereo mode
100
pF
P
HP
Nominal Output Power
RL=16
Ω
, limiter enabled
RL=32
Ω
, limiter enabled
40
20
mW
A
HP
Programmable Gain
-40.5
+6
dB
Gain Steps
discrete logarithmic gain steps
1.5
dB