TDA8947J Datasheet, PDF (6/24 Pages) NXP Semiconductors – 4-channel audio amplifier (SE: 1 W to 25 W; BTL: 4 W to 50 W)

Philips Semiconductors
TDA8947J
4-channel audio amplifier
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 supply voltage (V_CC = 26 V) and the
maximum output current (I_o = 4 A repetitive peak current).
For supply voltages V_CC > 22 V, a minimum load is required; see Figure 5:
• SE: R_L = 3 Ω
• BTL: R_L = 6 Ω.
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
distortion.
The Average Listening Level (ALL) music power, without any distortion, yields:
• SE at P_o(SE) = 5 W, V_CC = 18 V, R_L = 4 Ω and THD = 0.2 %:
P_o(ALL)SE = ⁵--₁---₅^â‹---_.1-₈--⁰-₅--³- = 315 mW
(4)
• BTL at P_o(BTL) = 10 W, V_CC = 18 V, R_L = 8 Ω and THD = 0.1 %:
P_{o( ALL)BTL}
=
1_----0_----⋅_---1_---0_---³_-
15.85
=
630 mW
(5)
The power dissipation can be derived from Figure 9 (SE and BTL) for a headroom of
0 dB and 12 dB, respectively.
Table 4: Power rating as function of headroom
Headroom
Power output
SE
BTL
0 dB
12 dB
P_o = 5 W
P_o(ALL) = 315 mW
P_o = 10 W
P_o(ALL) = 630 mW
Power dissipation
(all channels driven)
P_D = 17 W
P_D = 9 W
For heatsink calculation at the average listening level, a power dissipation of 9 W can
be used.
8.3 Mode selection
The TDA8947J has three functional modes which can be selected by applying the
proper DC voltage to pin MODE1.
Standby — The current consumption is very low and the outputs are floating. The
device is in the standby mode when V_MODE1 < 0.8 V, or when the MODE1 pin is
grounded. In the standby mode, the function of pin MODE2 has been disabled.
9397 750 10779
Preliminary data
Rev. 01 — 06 February 2004
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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