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Philips Semiconductors
8.2.2 Headroom
8.3 Mode selection
8.4 Supply voltage ripple rejection
TFA9843AJ_1
Preliminary data sheet
Typical CD music requires at least 12 dB (factor 15.85) dynamic headroom, compared to
the average power output, for transferring the loudest parts without distortion. At
V
= 18 V and P
= 6.5 W (SE with R
CC
o
Average Listening Level (ALL) music power without any distortion yields:
6.5
P
=
------------ -
=
410 mW
o ALL SE
15.85
The power dissipation can be derived from
headroom; see
Table
For the average listening level a power dissipation of 4.2 W can be used for a heatsink
calculation.
Table 4.
Power rating as function of headroom
Headroom
0 dB
12 dB
The TFA9843AJ has four functional modes, which can be selected by applying the proper
DC voltage to pin VC; see
Table 5.
Mode selection
V
Status
I(VC)
0 V to 0.8 V
Standby
1.2 V to 1.5 V
Mute
1.5 V to 5.0 V
Volume control
5.0 V to V
On (maximum gain)
CC
The supply voltage ripple rejection (SVRR) is measured with an electrolytic capacitor of
150 F connected to pin SVR with a bandwidth of 20 Hz to 22 kHz. The SVRR as a
function of the frequency is illustrated in
improves the ripple rejection behavior at the lower frequencies.
20 W stereo power amplifier with volume control
= 4 ) at THD < 0.5 % (see
L
4.
Power output (THD < 0.5 %)
(SE)
P
= 6.5 W
o
P
= 410 mW
o(ALL)
Table
5.
Definition
in this mode the current consumption is very low
and the outputs are floating; the device is in
Standby mode when V
in this mode the amplifier is DC-biased but not
operational (no audio output); this allows the input
coupling capacitors to be charged to avoid plop
noise; the device is in Mute mode when
1.2 V < V
in this mode the volume of the amplifier can be
controlled; the gain can be adjusted between the
range of 1.5 V < V
in this mode the amplifier has its maximum gain; the
Operating mode is activated at V
Figure
Rev. 01 — 28 April 2006
Figure 8
(SE) for 0 dB respectively 12 dB
Power dissipation (P);
both channels driven
8.2 W
4.2 W
< 0.8 V
I(VC)
< 1.5 V
I(VC)
< 5.0 V
I(VC)
10. A larger capacitor value on pin SVR
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
TFA9843AJ
Figure
5), the
> 5.0 V
I(VC)
5 of 19
(3)
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