I just recently built a amplifier circuit using the TDA7391 audio chip by ST MICROELECTRONICS. I assembled the circuit according to the data sheet and no matter what I have tried it continues to get extremely hot on the case. I have made several attempts to contact the manufacturer about it but have not had much luck. I have build copies of the circuit with the same outcome. I am driving it into a 4 ohm load. The power supply does not show any sign of high current consumption at 12vdc input (0.04A) with the chip disabled. When disabled the chip does not overheat. The PWB has been designed with heavy heat sink copper pours, but I feel that the temperature is still rather extreme. I know there has been some talk about counterfeit parts, however I did purchase all of my components from Digikey. Has anyone else had any experience with using this class AB bridge audio power amplifier?

 

You forgot to attach the schematic.

If you disconnect the speaker does it still get hot?

 

The power supply does not show any sign of high current consumption at 12vdc input (0.04A) with the chip disabled.

How about when it is enabled but there is no signal present? And you do realize it is a bridged output, and neither of the output pins can be grounded, right?

 

1. There is no ground on the output. (I realize that it is a bridge amp)
2. it does not get hot when there is no input and it is enabled.
3. it does not get hot when there is input and the speakers are dis-connected and it is enabled.
4. I have attached the schematic below...Thanks Guys!

 

It sounds like either:
1. Insufficient heat-sinking.
2. It isn't actually overheating - temperature is within spec.

If number 1 is the problem then the chip will shut itself down if it gets too hot so that's the test. Leave it running for a while and see if it shuts down. If it does it needs more heat-sinking (or better air cooling - ventilation/fan).

 

It sounds like either:
1. Insufficient heat-sinking.
2. It isn't actually overheating - temperature is within spec.

If number 1 is the problem then the chip will shut itself down if it gets too hot so that's the test. Leave it running for a while and see if it shuts down. If it does it needs more heat-sinking (or better air cooling - ventilation/fan).

Wow....it is so hard to believe that the efficiency can be that poor?
I do notice that as it gets hotter the sound quality starts to decline.

 

Class A/B amplifiers you can expect to give between 50% and 70% efficiency so at 32W output the chip would be disipating between 14W and 32W.
What impedance speaker is connected?
What supply voltage are you using?

 

Class A/B amplifiers you can expect to give between 50% and 70% efficiency so at 32W output the chip would be disipating between 14W and 32W.
What impedance speaker is connected?
What supply voltage are you using?

4 ohm impedance
12VDC

 

If you want an amp with high efficiency that stays cool, you should go to a Class D type switching amp.
TI makes a number of them, among others.

 

If you want an amp with high efficiency that stays cool, you should go to a Class D type switching amp.
TI makes a number of them, among others.

Thank you!