TDA7564BPD datasheet(20/34 Pages) STMICROELECTRONICS

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Thermal protection

TDA7564B

20/34

Doc ID 12734 Rev 4

Thermal protection

Thermal protection is implemented through thermal foldback (Figure 29).

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.

Three thermal warning are available through the I2C bus data.

Figure 29. Thermal foldback diagram

6.1

I2C programming/reading sequences

A correct turn on/off sequence respectful of the diagnostic timings and producing no audible

noises could be as follows (after battery connection):

Turn-on: (standby out + diag enable) --- 500 ms (min.) --- muting out

Turn-off: muting in --- 20 ms --- (diag disable + standby in)

Car radio Installation: diag enable (write) --- 200 ms --- I2C read (repeat until all faults

disappear).

AC test: feed h.f. tone -- AC diag enable (write) --- wait > 3 cycles --- I2C read

(repeat I2C reading until tweeter-off message disappears).

Offset test: device in play (no signal) -- offset enable - 30ms - I2C reading

(repeat I2C reading until high-offset message disappears).

Tj ( °C)

TH. SH.

START

TH. SH.

END

Vout

TH. WARN.

Tj ( °C)

Vout

Tj ( °C)

(with same input

signal)

< TSD

CD out

TH. WARN.

125°

140°

155°

> T

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