Philips TFA9843AJ 8.3 Mode selection, 8.4 Supply voltage ripple rejection

Preliminary data sheet Rev. 01 — 28 April 2006 5 of 19

Philips Semiconductors TFA9843AJ

20 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 = 18 V and Po= 6.5 W (SE with RL=4Ω) at THD < 0.5 % (see Figure 5), the

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

(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.

8.3 Mode selection

The TFA9843AJ has four functional modes, which can be selected by applying the proper

DC voltage to pin VC; see Table 5.

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.

Table 4. Power rating as function of headroom

Headroom Power output (THD < 0.5 %)

(SE) Power dissipation (P);

both channels driven

0dB P

o= 6.5 W 8.2 W

12 dB Po(ALL) = 410 mW 4.2 W

PoALLSE,()

6.5

15.85

------------- 410 mW==

Table 5. Mode selection

VI(VC) Status Deﬁnition

0 V to 0.8 V Standby 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

1.2 V to 1.5 V Mute 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 plop

noise; the device is in Mute mode when

1.2V<V

I(VC) < 1.5 V

1.5 V to 5.0 V Volume control in this mode the volume of the ampliﬁer can be

controlled; the gain can be adjusted between the

range of 1.5V<V

I(VC) < 5.0 V

5.0 V to VCC On (maximum gain) in this mode the ampliﬁer has its maximum gain; the

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