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PDF TFA9842BJ Data sheet ( Hoja de datos )
| Número de pieza | TFA9842BJ | |
| Descripción | 2-channel Audio Amplifier (SE: 1 W to 7.5 W) | |
| Fabricantes | NXP Semiconductors | |
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TFA9842BJ
2-channel audio amplifier (SE: 1 W to 7.5 W)
Rev. 01 — 1 March 2004
Preliminary data sheet
1. General description
The TFA9842BJ contains two identical audio power amplifiers. The TFA9842BJ can be
used as two Single-Ended (SE) channels with a fixed gain of 26 dB.
The TFA9842BJ comes in a 9-pin DIL-bent-SIL (DBS9P) power package. The TFA9842BJ
is pin compatible with the TFA9841J, TFA9842J, TFA9843J and the TFA9843BJ.
The TFA9842BJ 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
s 1 W to 7.5 W operation possibility
s Soft clipping
s Standby and mute mode
s No on or off switching plops
s Low standby current
s High supply voltage ripple rejection
s Outputs short-circuit protected to ground, supply and across the load
s Thermally protected
s Pin compatible with the TFA9841J, TFA9842J, TFA9843J and the TFA9843BJ.
3. Applications
s Televisions
s Monitors
s PC speakers
s Boom boxes
s Mini and micro audio receivers.
1 page  
Philips Semiconductors
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TFA9842BJ
2-channel auto amplifier (2 × SE)
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, Po = 5 W and RL = 4 Ω at THD = 0.2 % (see Figure 6), the Average Listening
Level (ALL) music power without any distortion yields:
Po(ALL)
=
5-----×-----1---0---3-
15.85
=
315 mW
(3)
The power dissipation can be derived from Figure 9 for 0 dB respectively 12 dB headroom
(see Table 4).
Table 4: Power rating as function of headroom
Headroom
Power output (THD = 0.2 %) Power dissipation;
both channels driven
0 dB
12 dB
Po = 5 W
Po(ALL) = 315 mW
PD = 8.4 W
PD = 4.2 W
For the average listening level a power dissipation of 4.2 W can be used for a heatsink
calculation.
8.3 Mode selection
The TFA9842BJ has three functional modes, which can be selected by applying the
proper DC voltage to pin MODE (see Table 5 and Figure 3).
Table 5: Mode selection
VMODE
0 V to 0.8 V
4.5 V to (VCC − 3.5 V)
(VCC − 2.0 V) to VCC
Amplifiers 1 and 2
standby
mute
on
Standby — In this mode the current consumption is very low and the outputs are floating.
The device is in standby mode when VMODE < 0.8 V, or when pin MODE is grounded.
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 pop-noise. The device is
in mute mode when 4.5 V < VMODE < (VCC − 3.5 V).
On — In this mode the amplifier is operating normally. The operating mode is activated at
VMODE > (VCC − 2.0 V).
standby
all mute
1/2 on
0.8 4.5
Fig 3. Mode selection.
9397 750 12847
Preliminary data sheet
Rev. 01 — 1 March 2004
VCC − 3.5 VCC − 2.0 VCC
VMODE (V)
001aaa416
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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TFA9842BJ
2-channel auto amplifier (2 × SE)
AUDIO POWER CS NIJMEGEN
PF / 3002 .naJ 72
TVA
100 nF
220
nF
CIV
22
µF
CIV
SGND
IN2+
220
nF
IN1+
1000 µF
+VP
150 µF
MODE
10
kΩ
10 kΩ
SB ON
MUTE
001aaa426
Fig 13. Printed-circuit board layout (single-sided); components view.
13.2.2 Power supply decoupling
Proper supply bypassing is critical for low-noise performance and high supply voltage
ripple rejection. The respective capacitor location should be as close as possible to the
device and grounded to the power ground. Proper power supply decoupling also prevents
oscillations.
For suppressing higher frequency transients (spikes) on the supply line a capacitor with
low ESR, typical 100 nF, has to be placed as close as possible to the device. For
suppressing lower frequency noise and ripple signals, a large electrolytic capacitor, e.g.
1000 µF or greater, must be placed close to the device.
The bypass capacitor on pin SVR reduces the noise and ripple on the mid rail voltage. For
good THD and noise performance a low ESR capacitor is recommended.
13.3 Thermal behavior and heatsink calculation
The measured maximum thermal resistance of the IC package, Rth(j-c), is 2.0 K/W.
A calculation for the heatsink can be made, with the following parameters:
Tamb(max) = 60 °C (example)
VCC = 17 V and RL = 4 Ω
Tj(max) = 150 °C (specification).
9397 750 12847
Preliminary data sheet
Rev. 01 — 1 March 2004
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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