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Philips Semiconductors
8.2.2 Headroom
8.3 Mode selection
8.3.1 Switch-on and switch-off
9397 750 06865
Product specification
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
= 12 V, R
CC
Average Listening Level (ALL) – music power – without any distortion yields:
P
= 4 W/15.85 = 252 mW.
o(ALL)
The power dissipation can be derived from
respectively 12 dB headroom.
Table 4:
Power rating as function of headroom
Headroom
Power output (THD = 0.1%)
0 dB
P
o
12 dB
P
o(ALL)
For the average listening level a power dissipation of 1.8 W can be used for a
heatsink calculation.
The TDA8943SF has three functional modes, which can be selected by applying the
proper DC voltage to pin MODE. See
which depend on the supply voltage level. The MODE pin can be driven by a 3-state
logic output stage: e.g. a microcontroller with additional components for DC-level
shifting.
Standby — In this mode the current consumption is very low and the outputs are
floating. The device is in standby mode when (V
the MODE pin is left floating (high impedance). The power consumption of the
TDA8943SF will be reduced to <0.18 mW.
Mute — In this mode the amplifier is DC-biased but not operational (no audio output);
the DC level of the input and output pins remain on half the supply voltage. This
allows the input coupling and Supply Voltage Ripple Rejection (SVRR) capacitors to
be charged to avoid pop-noise. The device is in mute mode when
3 V < V
< (V
1.5 V).
MODE
CC
Operating — In this mode the amplifier is operating normally. The operating mode is
activated at V
< 0.5 V.
MODE
To avoid audible plops during supply voltage switch-on or switch-off, the device is set
to standby mode before the supply voltage is applied (switch-on) or removed
(switch-off).
The switch-on and switch-off time can be influenced by an RC-circuit on the MODE
pin. Rapid on/off switching of the device or the MODE pin may cause 'click- and
pop-noise'. This can be prevented by proper timing of the RC-circuit on the MODE
pin.
Rev. 02 — 7 April 2000
6 W mono Bridge Tied Load (BTL) audio amplifier
= 8
and P
= 4 W at THD = 0.1% (see
L
o
Figure 11 on page 10
= 4 W
= 252 mW
Figure 4
and
TDA8943SF
Figure
for 0 dB
Power dissipation (P)
3.8 W
1.8 W
5
for the respective DC levels,
0.5 V) < V
< V
CC
MODE
© Philips Electronics N.V. 2000. All rights reserved.
6), the
, or when
CC
5 of 20
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