Power Amplifier; Output Power Measurement; Headroom; Mode Selection - Philips Tda8946J Specification Sheet

Philips Semiconductors
8.2 Power amplifier

8.2.1 Output power measurement

8.2.2 Headroom

8.3 Mode selection

9397 750 06863
Product specification
The power amplifier is a Bridge Tied Load (BTL) amplifier with an all-NPN output
stage, capable of delivering a peak output current of 2 A.
The BTL principle offers the following advantages:
•
Lower peak value of the supply current
•
The ripple frequency on the supply voltage is twice the signal frequency
•
No expensive DC-blocking capacitor
•
Good low frequency performance.
The output power as a function of the supply voltage is measured on the output pins
at THD = 10%; see Figure
supply voltage of 18 V and the maximum available output current: 2 A repetitive peak
current.
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, R
CC
Average Listening Level (ALL) – music power – without any distortion yields:
P = 10 W/15.85 = 631 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 8 W can be used for a heatsink
calculation.
The TDA8946J 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
TDA8946J will be reduced to <0.18 mW.
Rev. 02 — 14 March 2000
2 x 15 W stereo BTL audio amplifier
8. The maximum output power is limited by the maximum
= 8 and P = 10 W at THD = 0.1% (see
L o
Figure 11 on page 11
= 10 W
= 631 mW
Figure 4 and
TDA8946J
Figure
for 0 dB
Power dissipation (P)
18 W
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
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