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TDA8948J

4-channel audio amplifier

NXP Semiconductors. 

NXP Semiconductors

TDA8948J

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 7.

The maximum output power is limited by the supply voltage (VCC = 26 V) and the

maximum output current (IO = 4 A repetitive peak current).

For supply voltages VCC > 22 V, a minimum load is required; see Figure 5:

• SE: RL = 3 Ω

• BTL: RL = 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 Po(SE) = 5 W, VCC = 17 V, RL = 4 Ω and THD = 0.2 %:

Po(ALL)SE = 5--1---5⋅---.1-8--0-5--3- = 315 mW

(4)

• BTL at Po(BTL) = 10 W, VCC = 17 V, RL = 8 Ω and THD = 0.1 %:

Po(ALL)BTL = 1---1-0--5--⋅-.--81---50---3- = 630 mW

(5)

The power dissipation can be derived from Figure 8 (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

Power dissipation

(all channels driven)

0 dB

12 dB

Po = 5 W

Po(ALL) = 315 mW

Po = 10 W

Po(ALL) = 630 mW

P = 17 W

P=9W

For heat sink calculation at the average listening level, a power dissipation of 9 W can be

used.

8.3 Mode selection

The TDA8948J 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 standby mode when VMODE1 < 0.8 V, or when the MODE1 pin is grounded. In standby

mode, the function of pin MODE2 has been disabled.

Mute - The amplifier is DC-biased, but not operational (no audio output). This allows the

input coupling capacitors to be charged to avoid pop-noise. The device is in mute mode

when 4.5 V < VMODE1 < (VCC - 3.5 V).

TDA8948J_1

Product data sheet

Rev. 01 — 27 February 2008

© NXP B.V. 2008. All rights reserved.

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