Thermal protection

TDA7563B

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6

Thermal protection

Thermal protection is implemented through thermal foldback (Figure 28).

Thermal foldback begins limiting the audio input to the amplifier stage as the junction

temperatures rise above the normal operating range. This effectively limits the output power

capability of the device thus reducing the temperature to acceptable levels without totally

interrupting the operation of the device.

The output power will decrease to the point at which thermal equilibrium is reached.

Thermal equilibrium will be reached when the reduction in output power reduces the

dissipated power such that the die temperature falls below the thermal foldback threshold.

Should the device cool, the audio level will increase until a new thermal equilibrium is

reached or the amplifier reaches full power. Thermal foldback will reduce the audio output

level in a linear manner.

Figure 28. Thermal foldback diagram

6.1

Fast muting

The muting time can be shortened to less than 1.5ms by setting (IB2) D5 = 1. This option

can be useful in transient battery situations (i.e. during car engine cranking) to quickly

turnoff the amplifier for avoiding any audible effects caused by noise/transients being

injected by preamp stages. The bit must be set back to “0” shortly after the mute transition.

Tj ( °C)

TH. SH.

START

TH. SH.

END

Vout

TH. WARN.

ON

Tj ( °C)

Vout

Tj ( °C)

SD

(with same input

signal)

CD out

TH. WARN.

ON

TH. WARN.

ON

125°

140°

155°

> T