Applications information

TDA7293

12/21

Doc ID 6744 Rev 8

4.4

Modular application (ref. figure 12)

The modular application is where several devices operate in parallel.

The modular application allows very high power be delivered to very low-impedance loads.

In this type of application one device acts as a master and the others as slaves.

The slave power stages are driven by the master device and work in parallel together while

the input and the gain stages of the slave devices are disabled. The figure below shows the

connections required to configure two devices to work together.

The master chip connections are the same as the normal single ones.

The outputs can be connected together without the need of any ballast resistor.

The slave SGND pin must be tied to the negative supply.

The slave STANDBY and MUTE pins must be connected to the master STANDBY and

MUTE pins.

The bootstrap lines must be connected together and the bootstrap capacitor must be

increased: for N devices the bootstrap capacitor must be 22 µF times N.

The slave IN pin must be connected to the negative supply.

4.5

Bootstrap capacitor

For compatibility purpose with the previous devices of the family, the bootstrap capacitor can

be connected either between the bootstrap pin (6) and the output pin (14) or between the

bootstrap pin (6) and the bootstrap loader pin (12).

When the bootstrap is connected between pins 6 and 14 the maximum supply voltage in the

presence of an output signal is limited to 100 V, due the bootstrap capacitor overvoltage.

When the bootstrap is connected between pins 6 and 12 the maximum supply voltage

extends to the full voltage that the technology can stand, in this case 120 V.

This is accomplished by the clamp introduced at the bootstrap loader pin (12). This pin

follows the output voltage up to 100 V and remains clamped at 100 V for higher output

voltages.

This feature lets the output voltage swing up to a gate-source voltage from the positive

supply (VS -3 to 6 V).