TDA7491P datasheet(36/42 Pages) STMICROELECTRONICS

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TDA7491P

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Doc ID 13540 Rev 6

5.7

Protection functions

The TDA7491P is fully protected against undervoltages, overcurrents and thermal overloads

as explained here.

Undervoltage protection (UVP)

If the supply voltage drops below the value of VUVP given in Table 5: Electrical specifications

on page 11 the undervoltage protection is activated which forces the outputs to the

high-impedance state. When the supply voltage recovers the device restarts.

Overcurrent protection (OCP)

If the output current exceeds the value of IOCP given in Table 5: Electrical specifications on

page 11 the overcurrent protection is activated which forces the outputs to the

high-impedance state. Periodically, the device attempts to restart. If the overcurrent

condition is still present then the OCP remains active. The restart time, TOC, is determined

by the R-C components connected to pin STBY.

Thermal protection (OTP)

If the junction temperature, Tj, reaches 145 °C (nominal), the device goes to mute mode and

the positive and negative PWM outputs are forced to 50% duty cycle. If the junction

temperature reaches the value for Tj given in Table 5: Electrical specifications on page 11

the device shuts down and the output is forced to the high impedance state. When the

device cools sufficiently the device restarts.

5.8

Diagnostic output

The output pin DIAG is an open drain transistor. When the protection is activated it is in the

high-impedance state. The pin can be connected to a power supply (<18 V) by a pull-up

resistor whose value is limited by the maximum sinking current (200 µA) of the pin.

Figure 48.

Behavior of pin DIAG for various protection conditions

TDA7491P

Protection logic

DIAG

VDD

Overcurrent

protection

Restart

UV, OT

protection

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