TFA9842AJ 데이터 시트보기 (PDF) - NXP Semiconductors.

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TFA9842AJ

7.5 W stereo power amplifier with volume control

NXP Semiconductors. 

Philips Semiconductors

TFA9842AJ

7.5 W stereo power amplifier with volume control

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. At

VCC = 17 V and Po = 5 W (SE with RL = 4 Ω) at THD < 0.5 % (see Figure 5), the Average

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

Po(ALL) = 1----5--5-.-8---5- = 315 mW

(3)

The power dissipation can be derived from Figure 8 (SE) for 0 dB respectively 12 dB

headroom (see Table 4).

For the average listening level a power dissipation of 4.2 W can be used for a heatsink

calculation.

Table 4. Power rating as function of headroom

Headroom

Power output SE

(THD < 0.5 %)

0 dB

Po = 5 W

12 dB

Po(ALL) = 315 mW

Power dissipation (P);

both channels driven

8.4 W

4.2 W

8.3 Mode selection

The TFA9842AJ has four functional modes, which can be selected by applying the proper

DC voltage to pin VC (see Table 5).

Table 5. Mode selection

VI(VC)

Status

0 V to 0.8 V

Standby

1.2 V to 1.5 V

Mute

1.5 V to 5.0 V

5.0 V to VCC

Volume control

On (maximum gain)

Definition

in this mode the current consumption is very low

and the outputs are floating; the device is in

Standby mode when VI(VC) < 0.8 V.

in this mode 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

1.2 V < VI(VC) < 1.5 V.

in this mode the volume of the amplifier can be

controlled; the gain can be adjusted between the

range of 1.5 V < VI(VC) < 5.0 V.

in this mode the amplifier has its maximum gain;

the Operating mode is activated at VI(VC) > 5.0 V.

8.4 Supply voltage ripple rejection

The supply voltage ripple rejection (SVRR) is measured with an electrolytic capacitor of

150 µF connected to pin SVR with a bandwidth of 20 Hz to 22 kHz. The SVRR as a

function of the frequency is illustrated in Figure 10. A larger capacitor value on pin SVR

improves the ripple rejection behavior at the lower frequencies.

TFA9842AJ_1

Preliminary specification

Rev. 01 — 28 April 2006

© Koninklijke Philips Electronics N.V. 2006. All rights reserved.

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