Philips Semiconductors

TDA8944J

2 x 7 W stereo BTL audio amplifier

Product specification

Rev. 02 — 14 February 2000

5 of 21

9397 750 06861

© Philips Electronics N.V. 2000. All rights reserved.

8.2 Power amplifier

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:

8.2.1

Output power measurement

The output power as a function of the supply voltage is measured on the output pins

at THD = 10%; see Figure 8. The maximum output power is limited by the maximum

supply voltage of 12 V and the maximum available output current: 2 A repetitive peak

current.

8.2.2

Headroom

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

Average Listening Level (ALL) – music power – without any distortion yields:

The power dissipation can be derived from Figure 11 on page 10 for 0 dB

respectively 12 dB headroom.

For the average listening level a power dissipation of 4 W can be used for a heatsink

calculation.

8.3 Mode selection

The TDA8944J has three functional modes, which can be selected by applying the

proper DC voltage to pin MODE. See Figure 4 and 5 for the respective DC levels,

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

the MODE pin is left floating (high impedance). The power consumption of the

TDA8944J will be reduced to <0.18 mW.

Table 4:

Power rating as function of headroom

Headroom

Power output (THD = 0.1%)

Power dissipation (P)

0 dB

8W

12 dB

4 W