CLIPPING DETECTION & DIAGNOSTICS

(see fig. 16)

An active pull-down circuit is provided to signal

out the occurrence of any of the conditions de-

scribed later. In order to use this function, the CD-

DIA pin (#4) has to be resistively connected to a

positive voltage reference (between 5V and Vs).

A) Clipping Detection

Current is sunk whenever the output clipping dis-

tortion level reaches a fixed 0.5% threshold; this

function allows gain compression facility when the

amplifier is overdriven.

B) Output Fault Diagnostics

Current is sunk as soon as one of the following

output faults is recognized:

- short-circuit to GND

- short-circuit to Vs

- short-circuit across the load (after turn-on)

- open load (before turn-on)

The diagnostics signal remains steadily on until

the fault is removed.

All the output fault conditions (listed above) can

be distinguished from the clipping detection (A)

because of their different time duration.

THERMAL WARNING (see fig. 17)

Thermal protection has been implemented in ac-

cordance to a new principle involving different

steps:

1) Thermal foldback (Linear Thermal Shutdown)

2) Shutdown with soft restart (Absolute Thermal

Shutdown)

As long as the junction temperature remains be-

low the preset threshold (140

°C) the IC delivers

the full power. Once the threshold has been

reached, a thermal foldback starts limiting the out-

put signal level; the output power is then reduced,

thus decreasing also the temperature without out-

put signal interruption (LTS). Supposing the ther-

mal foldback does not reduce the junction tem-

perature to a safe level, a complete shutdown will

occur at 160

°C (ATS).

Soft restart avoids large voltage disturbance

across the loudspeaker, due to the presence of

high input signals when the IC comes out of ther-

mal shutdown.

Current is sunk from the CD-DIA pin (#4)when the

thermal protection is acting. The voltage at pin #4

bounces back and forth (depending on the ampli-

fier input signal magnitude) during the linear ther-

mal intervention (LTS) and stays low (sinking cur-

rent) after the amplifier has been eventually

shut-down (Absolute Thermal Shutdown)

D93AU005A

CLIPPING

DETECTOR/

DIAGNOSTICS

OUTPUT

(pin 4)

Vo

0

CLIPPING

S/C TO GND

NORMAL OPERATION

FAULT DIAGNOSTICS

NORMAL OPERATION

Figure 16: Clipping Detection & Diagnostics Waveforms

TDA7396

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