Philips TDA8944J User Manual

TDA8944J
2 x 7 W stereo Bridge Tied Load (BTL) audio amplifier
Rev. 02 — 14 February 2000 Product specification

1. General description

The TDA8944J is a dual-channel audio power amplifier with an output power of 2 × 7 W at an 8 load and a 12 V supply. The circuit contains two Bridge Tied Load (BTL) amplifierswith an all-NPN output stage and standby/mutelogic. The TDA8944J comes in a 17-pin DIL-bent-SIL (DBS) power package. The TDA8944J is printed-circuit board (PCB) compatible with all other types in the TDA894x family. One PCB footprint accommodates both the mono and the stereo products.

2. Features

Few external components
Fixed gain
Standby and mute mode
No on/off switching plops
Low standby current
High supply voltage ripple rejection
Outputs short-circuit protected to ground, supply and across the load
c
c
Thermally protected
Printed-circuit board compatible.

3. Applications

Mains fed applications (e.g. TV sound)
PC audio
Portable audio.

4. Quick reference data

Table 1: Quick reference data
Symbol Parameter Conditions Min Typ Max Unit
V
CC
I
q
I
stb
supply voltage 6 12 18 V quiescent supply current VCC=12V; RL= - 2436mA standby supply current - - 10 µA
Philips Semiconductors
TDA8944J
2 x 7 W stereo BTL audio amplifier
Table 1: Quick reference data
Symbol Parameter Conditions Min Typ Max Unit
P
o
THD total harmonic distortion P G
v
SVRR supply voltage ripple

5. Ordering information

Table 2: Ordering information
Type number Package
TDA8944J DBS17P plastic DIL-bent-SIL power package;

6. Block diagram

dth
…continued
output power THD = 10%; RL=8Ω;
=12V
V
CC
= 1 W - 0.03 0.1 %
o
67- W
voltage gain 31 32 33 dB
50 65 - dB
rejection
Name Description Version
SOT243-1
17 leads (lead length 12 mm)
CC1
V
CC2
V
IN1 IN1+
IN2 IN2+
MODE
SVR
Fig 1. Block diagram.
8 6
9 12
10
STANDBY/
MUTE LOGIC
11
3
TDA8944J
16
V
CC
20
k
SHORT CIRCUIT
TEMPERATURE
20
k
GND115GND2
PROTECTION
2
AND
14
17
MBK933
1
OUT1
4
OUT1+
OUT2
OUT2+
9397 750 06861
© Philips Electronics N.V. 2000. All rights reserved.
Product specification Rev. 02 — 14 February 2000 2 of 21
Philips Semiconductors

7. Pinning information

7.1 Pinning

TDA8944J
2 x 7 W stereo BTL audio amplifier
handbook, halfpage
OUT1
GND1
V
CC1
OUT1+
n.c.
IN1+
n.c. IN1 IN2
MODE
SVR IN2+
n.c.
OUT2
GND2
V
CC2
OUT2+
1 2 3 4 5 6 7 8 9
TDA8944J
10 11 12 13 14 15 16 17
MBK936
Fig 2. Pin configuration.

7.2 Pin description

Table 3: Pin description
Symbol Pin Description
OUT1 1 negative loudspeaker terminal 1 GND1 2 ground channel 1 V
CC1
OUT1+ 4 positive loudspeaker terminal 1 n.c. 5 not connected IN1+ 6 positive input 1 n.c. 7 not connected IN1 8 negative input 1 IN2 9 negative input 2 MODE 10 mode selection input (standby, mute, operating) SVR 11 half supply voltage decoupling (ripple rejection) IN2+ 12 positive input 2
9397 750 06861
Product specification Rev. 02 — 14 February 2000 3 of 21
3 supply voltage channel 1
© Philips Electronics N.V. 2000. All rights reserved.
Philips Semiconductors
TDA8944J
2 x 7 W stereo BTL audio amplifier
Table 3: Pin description
Symbol Pin Description
n.c. 13 not connected OUT2 14 negative loudspeaker terminal 2 GND2 15 ground channel 2 V
CC2
OUT2+ 17 positive loudspeaker terminal 2

8. Functional description

The TDA8944J is a stereo BTL audio power amplifier capable of delivering 2 × 7W output power to an 8 load at THD = 10%, using a 12 V power supply and an external heatsink. The voltage gain is fixed at 32 dB.
With the three-level MODE input the device can be switched from ‘standby’ to ‘mute’ and to ‘operating’ mode.
The TDA8944J outputs are protected by an internal thermal shutdown protection mechanism and a short-circuit protection.
8.1 Input configuration
The TDA8944J inputs can be driven symmetrical (floating) as well as asymmetrical. In the asymmetrical mode one input pin is connected via a capacitor to the signal ground which should be as close as possible to the SVR (electrolytic) capacitor ground. Note that the DC level of the input pins is half of the supply voltage VCC, so coupling capacitors for both pins are necessary.
…continued
16 supply voltage channel 2
The input cut-off frequency is:
f
icut off()
=
1
------------------------------ -
2RiCi×()
(1)
For Ri=45kΩ and Ci= 220 nF:
f
i cut off()
------------------------------------------------------------------ -
24510
1
3
× 220× 109×()
16 Hz==
(2)
As shown in Equation 1 and 2, large capacitor 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: TopreventHF oscillations do not leave the inputs open, connect a capacitor of at least 1.5 nF across the input pins close to the device.
9397 750 06861
Product specification Rev. 02 — 14 February 2000 4 of 21
© Philips Electronics N.V. 2000. All rights reserved.
Philips Semiconductors
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:

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 8. The maximum output power is limited by the maximum 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=12V, RL=8Ω and Po= 4 W at THD = 0.1% (see Figure 6), the Average Listening Level (ALL) – music power – without any distortion yields:
P
TDA8944J
2 x 7 W stereo BTL audio amplifier
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.
= 4 W/15.85 = 252 mW.
o(ALL)
The power dissipation can be derived from Figure 11 on page 10 for 0 dB respectively 12 dB headroom.
Table 4: Power rating as function of headroom
Headroom Power output (THD = 0.1%) Power dissipation (P)
0 dB P 12 dB P
=4W 8W
o
= 252 mW 4 W
o(ALL)
For the average listening level a power dissipation of 4 W can be used for a heatsink calculation.

8.3 Mode selection

The TDA8944J has three functional modes, which can be selected by applying the proper DC voltage to pin MODE. See Figure 4 and 5 for the respective DC levels, which depend on the supply voltage level. The MODE pin can be driven by a 3-state logic output stage: e.g. a microcontroller with additional components for DC-level shifting.
Standby — In this mode the current consumption is very low and the outputs are floating. The device is in standby mode when (VCC− 0.5 V) < V the MODE pin is left floating (high impedance). The power consumption of the TDA8944J will be reduced to <0.18 mW.
MODE<VCC
, or when
9397 750 06861
Product specification Rev. 02 — 14 February 2000 5 of 21
© Philips Electronics N.V. 2000. All rights reserved.
Philips Semiconductors
Mute — In this mode the amplifier is DC-biased but not operational (no audio output);
the DC level of the input and output pins remain on half the supply voltage. This
allows the input coupling and Supply Voltage Ripple Rejection (SVRR) capacitors to be charged to avoid pop-noise. The device is in mute mode when 3V<V
Operating — In this mode the amplifier is operating normally. The operating mode is activated at V

8.3.1 Switch-on and switch-off

To avoid audible plops during supply voltage switch-on or switch-off, the device is set to standby mode before the supply voltage is applied (switch-on) or removed (switch-off).
The switch-on and switch-off time can be influenced by an RC-circuit on the MODE pin. Rapid on/off switching of the device or the MODE pin may cause ‘click- and pop-noise’. This can be prevented by proper timing of the RC-circuit on the MODE pin.
<(VCC− 1.5 V).
MODE
MODE
TDA8944J
2 x 7 W stereo BTL audio amplifier
< 0.5 V.

8.4 Supply Voltage Ripple Rejection (SVRR)

The SVRR is measured with an electrolytic capacitor of 10 µF on pin SVR at a bandwidth of 10 Hz to 80 kHz. Figure 13 on page 11 illustrates the SVRR as function of the frequency. A larger capacitor value on the SVR pin improves the ripple rejection behaviour at the lower frequencies.

8.5 Built-in protection circuits

The TDA8944J contains two types of protection circuits, i.e. short-circuit and thermal shutdown.

8.5.1 Short-circuit protection

Short-circuit to ground or supply line — This is detected by a so-called ‘missing
current’ detection circuit which measures the current in the positive supply line and the current in the ground line. A difference between both currents larger than 0.4 A, switches the power stage to standby mode (high impedance).
Short-circuit across the load — This is detected by an absolute-current measurement. An absolute-current larger than 2 A, switches the power stage to standby mode (high impedance).

8.5.2 Thermal shutdown protection

The junction temperature is measured by a temperature sensor; at a junction temperature of approximately 150 °C this detection circuit switches the power stage to standby mode (high impedance).
9397 750 06861
Product specification Rev. 02 — 14 February 2000 6 of 21
© Philips Electronics N.V. 2000. All rights reserved.
Philips Semiconductors
TDA8944J
2 x 7 W stereo BTL audio amplifier

9. Limiting values

Table 5: Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
Symbol Parameter Conditions Min Max Unit
V
CC
supply voltage no signal 0.3 +25 V
operating 0.3 +18 V
V
I
I
ORM
T
stg
T
amb
P
tot
V
CC(sc)
input voltage 0.3 VCC+ 0.3 V repetitive peak output current - 2 A storage temperature non-operating 55 +150 °C operating ambient temperature 40 +85 °C total power dissipation - 18 W supplyvoltagetoguaranteeshort-circuit
-15V
protection

10. Thermal characteristics

Table 6: Thermal characteristics
Symbol Parameter Conditions Value Unit
R
th(j-a)
R
th(j-mb)
thermal resistance from junction to ambient in free air 40 K/W thermal resistance from junction to mounting base both channels driven 6.9 K/W

11. Static characteristics

Table 7: Static characteristics
VCC=12V; T
Symbol Parameter Conditions Min Typ Max Unit
V
CC
I
q
I
stb
V
O
[3]
V
OUT
V
MODE
I
MODE
[1] With a load connected at the outputs the quiescent current will increase, the maximum of this increase being equal to the differential
output voltage offset (∆V [2] The DC output voltage with respect to ground is approximately 0.5VCC. [3] V
OUT
=25°C; RL=8Ω; V
amb
supply voltage operating 6 12 18 V quiescent supply current RL= standby supply current V DC output voltage differential output voltage offset - - 200 mV mode selection input voltage operating mode 0 - 0.5 V
mode selection input current 0 < V
= V
OUT+
V
=0V; Vi= 0 V; measured in test circuit Figure 14; unless otherwise specified.
MODE
) divided by the load resistance (RL).
OUT
OUT
[1]
- 2436mA
MODE=VCC
--10µA
[2]
-6-V
mute mode 3 - V standby mode V
MODE<VCC
0.5 - V
CC
--20µA
1.5 V
CC CC
V
9397 750 06861
Product specification Rev. 02 — 14 February 2000 7 of 21
© Philips Electronics N.V. 2000. All rights reserved.
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