SAA8200HL Datasheet, PDF (45/71 Pages) NXP Semiconductors – Ensation Base integrated wireless audio baseband

Philips Semiconductors
SAA8200HL
Ensation Base integrated wireless audio baseband
7.20.2 Headphone
7.20.2.1 Headphone driver
The headphone driver can deliver 22 mW (at 3.0 V power supply) into16 Ω load.
The headphone driver does not need external DC decoupling capacitors because it can
be DC-coupled with respect to a special headphone output reference voltage. This saves
two external capacitors. Changes in the load on the DAC outputs influence the output of
the headphone. This is because the headphone inputs are directly connected to the DAC
outputs.
7.20.2.2 Headphone Limiter
To protect the headphone amplifier from serious damage due to short-circuiting of the
outputs (e.g. during the connection of a headphone jack plug) a current limiter is
incorporated. The activation of this current limiter is signaled by individual logic clip
signals (CLIP_L, CLIP_R and CLIP_C). The level at which the current limiter is activated
can be set to four different levels for each amplifier.
The current level to which the output stage is limited can be set with the bits
SET_LIMITER_L/R/C[1:0] inputs from 80 mA to 140 mA for the left and right channels and
from 180 mA to 240 mA for the common channel (see Table 22). The maximum current for
the common ground channel is larger (double on average) as this channel must be able to
sink and source the left and right channel output currents. When the current through the
output stage exceeds the programmed current level, the monitor bit CLIP_L, CLIP_R or
CLIP_C is set to a logic 1 and the output stage is shut down.
These values are based on the worst case situation of two in-phase full scale input signals
of 1.0 V (RMS) and a minimum headphone impedance of 16 Ω. This results in left and
right channel peak output currents of 1.41 V / 16 Ω = 88.4 mA and a common ground peak
output current of 2 × 88.4 mA = 176.8 mA. The maximum current that is actually flowing in
the common ground amplifier is always the sum of the left and right channel maximum
currents.
Table 22: Output current limiter settings
SET_LIMITER_L[1:0],
SET_LIMITER_R[1:0],
SET_LIMITER_C[1:0]
Maximal output current
Left and right channel
00
OFF
01
100 mA (default)
10
120 mA
11
140 mA
Common channel
OFF
200 mA (default)
220 mA
240 mA
SAA8200HL_2
Preliminary data sheet
Rev. 02 — 17 October 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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