TDA7498

mc2 · ‎2016-09-09

Posted on September 09, 2016 at 12:58

Hi ST. I have a few questions regarding the application of the TDA7498 and TDA7498E.

The TDA7498E application circuit has schottky diodes on the output but the TDA7498 does not, is there a reason for this?

The loudspeaker design I am wanting to drive has high inductance due to both the voice coil and crossover network with a combined inductance of approximately 4mH. Can you assist in calculating the correct values for C and R for the snubber circuit. I am basing my low pass filter on the 6 ohm filter values (due to speaker impedance dips). The data brief says 330pF and 22R as a starting point, I suspect I need to differ from this.

The loudspeaker system is an 8 ohm system but has a minimum impedance of 4.9 ohms. Is it better for me to change my PCB to use the TDA7498E instead of the TDA7498 and from a reliability point of view which IC is better.

The design is intended to be as reliable as practically possible starting with a 0.4K/W heatsink to keep the package running cold.

Thanks,

Marcus

Nickname1623_O · ‎2016-09-18

Posted on September 19, 2016 at 02:55

hi Marcus,

due to TDA7498E can deliver higher output current to drive low impedance load (2 ohm ) in mono BTL mode , then those diode had been used to reduce spike voltage level.

I supposed you are talking about snubber networks 22R+330pF between BTL output, you may change it to 10R+680pF between output and ground . but regarding inductive load , you need to check the real frequency response with speaker plus crossover filter in low output power(otherwise your tweeter may be burnt out) , then adjusted L+C value to flat your response in upper audio band .

since your load impedance could be 4.9 ohm , then output current may be marginal with 36V supply , it's better to use TDA7498E .

Thanks

YT