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PDF TFA9842AJ Data sheet ( Hoja de datos )
| Número de pieza | TFA9842AJ | |
| Descripción | 7.5W Stereo Power Amplifier | |
| Fabricantes | Philips | |
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TFA9842AJ
7.5 W stereo power amplifier with volume control
Rev. 01 — 28 April 2006
Preliminary specification
1. General description
The TFA9842AJ contains two identical audio power amplifiers. The TFA9842AJ can be
used as two Single-Ended (SE) channels with a volume control. The maximum gain is
26 dB.
The TFA9842AJ comes in a 9-pin DIL-bent-SIL (DBS9P) power package. The TFA9842AJ
is pin compatible with the TFA9843AJ, TFA9843(B)J, TFA9842(B)J and TFA9841J. The
difference between the TFA9843AJ and the TFA9843(B)J, TFA9842(B)J, TFA9841J is the
functionality of pin 7. The TFA9843AJ has a Volume Control (VC) on pin 7. The
TFA9843(B)J, TFA9842(B)J and TFA9841J have a mode select (MODE) on pin 7.
The TFA9842AJ contains a unique protection circuit that is solely based on multiple
temperature measurements inside the chip. This gives maximum output power for all
supply voltages and load conditions with no unnecessary audio holes. Almost any supply
voltage and load impedance combination can be made as long as thermal boundary
conditions (number of channels used, external heatsink and ambient temperature) allow
it.
2. Features
I 2 channel SE: 1 W to 7.5 W operation possibility
I Soft clipping
I Input clamps
I Volume control
I Standby and Mute mode
I No on or off switching plops
I Low standby current
I High supply voltage ripple rejection
I Outputs short-circuit protected to ground, supply and across the load
I Thermally protected
I Pin compatible with the TFA9843AJ, TFA9843(B)J, TFA9842(B)J and TFA9841J
3. Applications
I CRT TV and LCD TV
I Monitors
I PC speakers
I Boom box
I Mini and micro audio receivers
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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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TFA9842AJ
7.5 W stereo power amplifier with volume control
13.1.2 Volume control drive options
R1
10 kΩ
D1
5.6 V
GND
VCC
T1
5V
R2
1 kΩ
PWM
3.3 V
R5
1 kΩ
T2
R3
1 kΩ
R4
1 kΩ
T3
Fig 12. Volume control drive circuit with 3.3 V PWM
VC
C1
10 µF
001aae337
PWM
5V
R4
1 kΩ
VC
C1
10 µF
R1
10 kΩ
D1
10 V
VCC
T1
R5
16 kΩ
R6
16 kΩ
VC
C1
10 µF
001aae338
001aae339
Fig 13. Volume control drive circuit with 5 V Fig 14. Volume control drive circuit with
PWM
potentiometer
13.2 Printed-circuit board
13.2.1 Layout and grounding
To obtain a high-level system performance, certain grounding techniques are essential.
The input reference grounds have to be tied with their respective source grounds and
must have separate tracks from the power ground tracks; this will prevent the large output
signal currents from interfering with the small AC input signals. The small-signal ground
tracks should be physically located as far as possible from the power ground tracks.
Supply and output tracks should be as wide as possible for delivering maximum output
power.
TFA9842AJ_1
Preliminary specification
Rev. 01 — 28 April 2006
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
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