Philips TDA7056A

July 1994 4

Philips Semiconductors Product speciﬁciation

3 W BTL mono audio output ampliﬁer with

DC volume control TDA7056A

FUNCTIONAL DESCRIPTION

The TDA7056A is a mono BTL output amplifier with DC

volume control, designed for use in TV and monitor but

also suitable for battery-fed portable recorders and radios.

In conventional DC volume circuits the control or input

stage is AC coupled to the output stage via external

capacitor to keep the offset voltage low.

In the TDA7056A the DC volume stage is integrated into

the input stage so that coupling capacitors are not required

and a low offset voltage is maintained.

At the same time the minimum supply voltage remains low.

The BTL principle offers the following advantages:

•lower peak value of the supply current

•the frequency of the ripple on the supply voltage is twice

the signal frequency

Thus, a reduced power supply and smaller capacitors can

be used which results in cost savings.

For portable applications there is a trend to decrease the

supply voltage, resulting in a reduction of output power at

conventional output stages. Using the BTL principle

increases the output power.

The maximum gain of the amplifier is fixed at 35.5 dB. The

DC volume control stage has a logarithmic control

characteristic.

The total gain can be controlled from 35.5 dB to −44 dB.

If the DC volume control voltage is below 0.3 V, the device

switches to the mute mode.

The amplifier is short-circuit proof to ground, VP and

across the load. A thermal protection circuit is also

implemented. If the crystal temperature rises above

+150 °C the gain will be reduced, thereby reducing the

output power.

Special attention is given to switch-on and off clicks, low

HF radiation and a good overall stability.

LIMITING VALUES

In accordance with the Absolute Maximum System (IEC 134).

THERMAL RESISTANCE

Note to the thermal resistance

VP = 12 V; RL = 16 Ω; The maximum sine-wave dissipation is = 1.8 W. The Rth vj-a of the package is 55 K/W;

Tamb (max) = 150 − 55 x 1.8 = 51 °C

SYMBOL PARAMETER CONDITIONS MIN. MAX. UNIT

VPsupply voltage range −18 V

IORM repetitive peak output current −1.25 A

IOSM non repetitive peak output current −1.5 A

Ptot total power dissipation Tcase < 60 °C−9W

amb operating ambient temperature range −40 +85 °C

Tstg storage temperature range −55 +150 °C

Tvj virtual junction temperature −+150 °C

Tsc short-circuit time −1hr

3input voltage pin 3 −8V

5input voltage pin 5 −8V

SYMBOL PARAMETER THERMAL RESISTANCE

Rth j-a from junction to ambient in free air 55 K/W

Rth j-c from junction to case 10 K/W