NXP Semiconductors TDA8944J Manuale utente

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

2×7Watan8Ωload 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 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

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

VCC supply voltage 6 12 18 V

Iqquiescent supply current VCC =12V;R

L=∞- 2436mA

Istb standby supply current - - 10 μA

NXP Semiconductors TDA8944J

2 x 7 W stereo BTL audio amplifier

Product specification Rev. 02 — 14 February 2000 2 of 22

5. Ordering information

6. Block diagram

Pooutput power THD = 10%; RL=8Ω;

VCC =12V 67- W

THD total harmonic distortion Po= 1 W - 0.03 0.1 %

Gvvoltage gain 31 32 33 dB

SVRR supply voltage ripple

rejection 50 65 - dB

Table 1: Quick reference data…continued

Symbol Parameter Conditions Min Typ Max Unit

Table 2: Ordering information

Type number Package

Name Description Version

TDA8944J DBS17P plastic DIL-bent-SIL power package;

17 leads (lead length 12 mm) SOT243-1

Fig 1. Block diagram.

wid

MBK933

STANDBY/

MUTE LOGIC SHORT CIRCUIT

AND

TEMPERATURE

PROTECTION

kΩ

12 17

VCC1

VCC

OUT2+

GND1

GND2

SVR

OUT2−

IN2−

IN2+

TDA8944J

VCC2

OUT1+

OUT1−

IN1−

IN1+

MODE

NXP Semiconductors TDA8944J

2 x 7 W stereo BTL audio amplifier

Product specification Rev. 02 — 14 February 2000 3 of 22

7. Pinning information

7.1 Pinning

7.2 Pin description

Fig 2. Pin configuration.

handbook, halfpage

TDA8944J

MBK936

OUT1−

GND1

VCC1

OUT1+

n.c.

IN1+

n.c.

IN1−

IN2−

MODE

SVR

IN2+

n.c.

OUT2+

GND2

VCC2

OUT2−

Table 3: Pin description

Symbol Pin Description

OUT1−1 negative loudspeaker terminal 1

GND1 2 ground channel 1

VCC1 3 supply voltage channel 1

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

NXP Semiconductors TDA8944J

2 x 7 W stereo BTL audio amplifier

Product specification Rev. 02 — 14 February 2000 4 of 22

8. Functional description

The TDA8944J is a stereo BTL audio power amplifier capable of delivering 2 ×7W

output power to an 8 Ωload 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.

The input cut-off frequency is:

(1)

For Ri=45kΩand Ci= 220 nF:

(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: To prevent HF oscillations do not leave the inputs open, connect a capacitor

of at least 1.5 nF across the input pins close to the device.

n.c. 13 not connected

OUT2−14 negative loudspeaker terminal 2

GND2 15 ground channel 2

VCC2 16 supply voltage channel 2

OUT2+ 17 positive loudspeaker terminal 2

Table 3: Pin description…continued

Symbol Pin Description

ficut off–() 1

iCi

×()–

------------------------------

fi cut off–() 1

24510

×220×10 9–

×()–

-------------------------------------------------------------------16 Hz==

NXP Semiconductors TDA8944J

2 x 7 W stereo BTL audio amplifier

Product specification Rev. 02 — 14 February 2000 5 of 22

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 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,R

L=8Ωand Po= 4 W at THD = 0.1% (see Figure 6), the

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

Po(ALL) = 4 W/15.85 = 252 mW.

The power dissipation can be derived from Figure 11 on page 10 for 0 dB

respectively 12 dB headroom.

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 5for 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) < VMODE <V

CC, or when

the MODE pin is left floating (high impedance). The power consumption of the

TDA8944J will be reduced to <0.18 mW.

Table 4: Power rating as function of headroom

Headroom Power output (THD = 0.1%) Power dissipation (P)

0 dB Po=4W 8W

12 dB Po(ALL) =252mW 4W

NXP Semiconductors TDA8944J

2 x 7 W stereo BTL audio amplifier

Product specification Rev. 02 — 14 February 2000 6 of 22

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

MODE <(V

CC −1.5 V).

Operating — In this mode the amplifier is operating normally. The operating mode is

activated at VMODE <0.5V.

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.

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).

NXP Semiconductors TDA8944J

2 x 7 W stereo BTL audio amplifier

Product specification Rev. 02 — 14 February 2000 7 of 22

9. Limiting values

10. Thermal characteristics

11. Static characteristics

[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 (ΔVOUT) divided by the load resistance (RL).

[2] The DC output voltage with respect to ground is approximately 0.5VCC.

[3] ΔVOUT =⎪VOUT+ −VOUT−⎪

Table 5: Limiting values

In accordance with the Absolute Maximum Rating System (IEC 60134).

Symbol Parameter Conditions Min Max Unit

VCC supply voltage no signal −0.3 +25 V

operating −0.3 +18 V

VIinput voltage −0.3 VCC +0.3 V

IORM repetitive peak output current - 2 A

Tstg storage temperature non-operating −55 +150 °C

Tamb operating ambient temperature −40 +85 °C

Ptot total power dissipation - 18 W

VCC(sc) supply voltage to guarantee short-circuit

protection -15V

Table 6: Thermal characteristics

Symbol Parameter Conditions Value Unit

Rth(j-a) thermal resistance from junction to ambient in free air 40 K/W

Rth(j-mb) thermal resistance from junction to mounting base both channels driven 6.9 K/W

Table 7: Static characteristics

VCC =12V;T

amb =25°C; RL=8Ω; VMODE =0V;V

i= 0 V; measured in test circuit Figure 14; unless otherwise specified.

Symbol Parameter Conditions Min Typ Max Unit

VCC supply voltage operating 6 12 18 V

Iqquiescent supply current RL=∞[1] -2436mA

Istb standby supply current VMODE =V

CC --10μA

VODC output voltage [2] -6-V

ΔVOUT[3] differential output voltage offset - - 200 mV

VMODE mode selection input voltage operating mode 0 - 0.5 V

mute mode 3 - VCC −1.5 V

standby mode VCC −0.5 - VCC V

IMODE mode selection input current 0 < VMODE <V

CC --20μA

NXP Semiconductors TDA8944J

2 x 7 W stereo BTL audio amplifier

Product specification Rev. 02 — 14 February 2000 8 of 22

12. Dynamic characteristics

[1] The noise output voltage is measured at the output in a frequency range from 20 Hz to 20 kHz (unweighted), with a source impedance

Rs=0Ωat the input.

[2] Supply voltage ripple rejection is measured at the output, with a source impedance Rs=0Ωat the input. The ripple voltage is a sine

wave with a frequency fripple and an amplitude of 707 mV (RMS), which is applied to the positive supply rail.

[3] Output voltage in mute mode is measured with an input voltage of 1 V (RMS) in a bandwidth of 20 kHz, so including noise.

Fig 3. Quiescent current as function of supply

voltage. Fig 4. Quiescent current as function of mode voltage.

handbook, halfpage

00481216

VCC (V)

(mA)

MGL954

handbook, halfpage

00481216

VMODE (V)

(mA)

MGL955

VCC = 12 V

Table 8: Dynamic characteristics

VCC =12V;T

amb =25°C; RL=8Ω; f = 1 kHz; VMODE = 0 V; measured in test circuit Figure 14; audio pass band

22 Hz to 22 kHz; unless otherwise specified.

Symbol Parameter Conditions Min Typ Max Unit

Pooutput power THD = 10% 6 7 - W

THD = 0.5% 4 5 - W

THD total harmonic distortion Po= 1 W - 0.03 0.1 %

Gvvoltage gain 31 32 33 dB

Zi(dif) differential input impedance 70 90 110 kΩ

Vn(o) noise output voltage [1] -90120μV

SVRR supply voltage ripple rejection fripple = 1 kHz [2] 50 65 - dB

fripple = 100 Hz

to 20 kHz

[2] -60-dB

Vo(mute) output voltage mute mode [3] --50μV

αcs channel separation Rs=0Ω50 75 - dB

NXP Semiconductors TDA8944J

2 x 7 W stereo BTL audio amplifier

Product specification Rev. 02 — 14 February 2000 9 of 22

Fig 5. Output voltage as function of mode voltage.

No bandpass filter applied.

Fig 6. Total harmonic distortion as function of output

power. Fig 7. Total harmonic distortion as function of

frequency.

handbook, full pagewidth

2016 VMODE (V)

MGL957

840

(V)

−3

−2

−1

−4

−5

VCC = 12 V

handbook, halfpage

THD

(%)

−2

10110

−1

Po(W)

−1

−2

MGL952

VCC = 12 V

handbook, halfpage

THD

(%)

10 10

f (Hz)

−1

−2

MGL953

Po= 0.1 W

1 W

NXP Semiconductors TDA8944J

2 x 7 W stereo BTL audio amplifier

Product specification Rev. 02 — 14 February 2000 10 of 22

THD = 10%.

Fig 8. Output power as function of supply voltage. Fig 9. Total power dissipation as function of supply

voltage.

VCC =12V.

Fig 10. Efficiency as function of output power. Fig 11. Power dissipation as function of output power.

handbook, halfpage

00481216

VCC (V)

(W)

MGL959

RL= 8 Ω

16 Ω

handbook, halfpage

00481216

VCC (V)

Ptot

(W)

MGL960

RL= 8 Ω

16 Ω

handbook, halfpage

100

002468

Po(W)

(%)

MGL962

RL= 16 Ω

8 Ω

handbook, halfpage

002468

Po(W)

(W)

MGL961

RL= 8 Ω

16 Ω

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