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PDF TDA8944AJ Data sheet ( Hoja de datos )
| Número de pieza | TDA8944AJ | |
| Descripción | 2 x 7 W BTL audio amplifier | |
| Fabricantes | Philips | |
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TDA8944AJ
2 x 7 W BTL audio amplifier with DC gain control
Rev. 01 — 01 March 2002
M3D541
Product data
1. General description
The TDA8944AJ is a dual-channel audio power amplifier with DC gain control. It has
an output power of 2 × 7 W at an 8 Ω load and a 12 V supply. The circuit contains two
Bridge-Tied Load (BTL) amplifiers with an all-NPN output stage and standby/mute
logic. The overall gain can be adjusted from +30 dB down to −50 dB using a DC
control voltage. This feature can be used for volume control or a preset gain.
The TDA8944AJ comes in a 17-pin DIL-bent-SIL (DBS) power package and is pin
compatible with the TDA8944J.
2. Features
s Gain/volume adjustment via a DC control pin
s Soft clipping
s Operating at a low supply voltage
s Standby and mute mode
s No on/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 Printed-circuit board compatible with TDA8946AJ and TDA8580J.
3. Applications
s Mains fed applications (e.g. TV sound)
s PC audio
s Portable audio.
4. Quick reference data
Table 1: Quick reference data
Symbol Parameter
VCC supply voltage
Iq quiescent supply current
Istb standby supply current
Po output power
THD total harmonic distortion
Conditions
VCC = 12 V; RL = ∞
THD = 10%; RL = 8 Ω;
VCC = 12 V
Po = 1 W
Min Typ Max Unit
4.5 12 18 V
- 40 50 mA
- - 10 µA
67-
W
- 0.07 0.5 %
1 page  
Philips Semiconductors
TDA8944AJ
2 x 7 W BTL audio amplifier with DC gain control
The input cut-off frequency is:
f i(cut – off ) = 2----π----(--0---.-5-----×-1----R----i---×----C-----i--)
For Ri = 32 kΩ and Ci = 220 nF:
(1)
f i(cut – off ) = -2---π----(--0---.-5-----×-----3---2----×-----1---10---3----×-----2---2---0-----×----1---0----–--9---) = 45.2 Hz
(2)
As shown in Equation 2, large capacitors values for the inputs are not necessary; so
the switch-on delay during charging of the input capacitors can be minimized. This
results in a good low frequency response and good switch-on behaviour.
Remark: To prevent high frequency oscillations do not leave the inputs open, connect
a capacitor of 4.7 nF across the input pins close to the device (see Figure 15).
8.2 Power amplifier
The power amplifier is a Bridge-Tied Load (BTL) amplifier with an all-NPN output
stage, capable of delivering a peak output current of 2 A.
The BTL principle offers the following advantages:
• Lower peak value of the supply current
• The ripple frequency on the supply voltage is twice the signal frequency
• No expensive DC-blocking capacitor
• Good low frequency performance.
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 10. The maximum output power is limited by the supply
voltage of 12 V and the maximum available output current: 2 A repetitive peak
current.
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 = 12 V, RL = 8 Ω and Po = 4 W at THD = 0.2% (see Figure 8), the
Average Listening Level (ALL) - music power - without any distortion yields:
Po(ALL) = 1--4--5---.W-8---5-- = 252.4 mW
The power dissipation can be derived from Figure 12 on page 11 for 0 dB
respectively 12 dB headroom.
(3)
9397 750 09433
Product data
Rev. 01 — 01 March 2002
© Koninklijke Philips Electronics N.V. 2002. All rights reserved.
5 of 20
5 Page 
Philips Semiconductors
TDA8944AJ
2 x 7 W BTL audio amplifier with DC gain control
10
handbook, halfpage
P
(W)
8
MGW598
0
handbαocoks, halfpage
(dB)
− 20
MGW599
6 −40
4 −60
2 −80
0
0 2 4 6 8 Po (W) 10
− 100
10
102 103 104 105
f (Hz)
VCC = 12 V; RL = 8 Ω
Fig 12. Power dissipation as function of output power.
VCC = 12 V; no bandpass filter applied
Fig 13. Channel separation as function of frequency.
0
handbook, halfpage
SVRR
(Hz)
− 20
MGW600
− 40
B
A
− 60
− 80
− 100
10
102 103 104 105
f (Hz)
VCC = 12 V; Rsource = 0 Ω; Vripple = 707 mV (RMS); a bandpass filter of 10 Hz to 80 kHz has been applied.
Curve A: inputs short-circuited
Curve B: inputs short-circuited and connected to ground.
Fig 14. Supply voltage ripple rejection as function of frequency.
9397 750 09433
Product data
Rev. 01 — 01 March 2002
© Koninklijke Philips Electronics N.V. 2002. All rights reserved.
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