DocID024094 Rev 2

11/15

TDA7387

Application hints

3.3

Standby and muting

Standby and muting facilities are both CMOS-compatible. If unused, a straight connection to

Vs of their respective pins would be admissible. Conventional low-power transistors can be

used to drive muting and stand-by pins in absence of true CMOS ports or microprocessors.

R-C cells have always to be used in order to smooth down the transitions for preventing any

audible transient noises.

Since a DC current of about 10 µA normally flows out of pin 22, the maximum allowable

reasonably small (about 1 µF).

above the 1.5 V threshold voltage and the device is consequently fails to turn OFF when the

mute line is brought down.

About the stand-by, the time constant to be assigned in order to obtain a virtually pop-free

transition has to be slower than 2.5 V/ms.

3.4

Stability and layout considerations

If properly layouted and hooked to standard car-radio speakers, the TDA7387 is intrinsically

stable with no need of external compensations such as output R-C cells. Due to the high

number of channels involved, this translates into a very remarkable components saving if

compared to similar devices on the market.

To simplify pc-board layout design, each amplifier stage has its own power ground externally

accessible (pins 2,8,18,24) and one supply voltage pin for each couple of them. Even more

important, this makes it possible to achieve the highest possible degree of separation

among the channels, with remarkable benefits in terms of cross-talk and distortion features.

to the signal GND, as close as possible to the audio inputs ground: this guarantees high

rejection of any common mode spurious signal.

located as close as possible to the Vs pins.

Pin 1, which is mechanically attached to the device’s tab, needs to be tied to the cleanest

power ground point in the pc-board, which is generally near the supply filtering capacitors.

The exposed pad package doesn't require any particular care compared to the ST standard

flexiwatt package. For particular PCB configurations, in order to maximize the rejection

against any disturbances coming from the battery line (SVR), it is suggested to use one of

the following IC metal slug (heat-sink) connections:



leave the slug simply electrically isolated from the PCB ground;



in case of 2 layers board, connect the slug to the PCB power ground (P-GND) and not

to the signal ground (S-GND);



in case of a PCB with a layer dedicated to grounding (wide / diffused GND area with no

distinction between P-GND and S-GND) connect the slug to the common board

ground.