TDA7498ETR missing data

[DanielFFF]

I have to say I am unimpressed with ST's tech support (there is none: they just referred me to the forums).  And when I selected the 'Analog and audio' group, I couldn't post there as it was 'read-only'!!  If there's a more appropriate product forum I *can* post to, please advise.

Anyway, here goes with my request for help...

Re: TDA7498E (Class-D audio amplifier)

This device appears to be an old product, though apparently still in production. Is there a more recent similar device available? Is there likely to be a GaN version released anytime soon?

The datasheet for this device shows that there are two 3.3V output pins (VDDPW, VDDS), and these supplies are maybe used internally. But nowhere in the datasheet is a specification for the maximum current available to be drawn externally from either of these 3.3V outputs!

This also raises the question of why the AN4015 application note includes an *external* 3.3V low-current supply. Why, if this voltage is available from the device pins?

Also, regarding the DIAG pin, when/what does it output?

[Peter BENSCH]

Welcome @DanielFFF, to the community!

You’re in the right forum. The ‘Analog and audio’ section got moved to ‘Other hardware’ due to low activity.

So far, the global demand for GaN-based Class D amps hasn’t been high enough to justify developing a device for it. Roughly how much annual demand would you expect for your project?

About VDDPW and VDDS: these are indeed outputs for buffering the internal 3.3V rails. As you can see in the data sheet, you can load them with 100kΩ, but I wouldn’t recommend drawing more than a few milliamps from them.

Regarding the extra 3.3V regulator (IC2) mentioned in AN4015, I can only guess since the design dates back to around 2010. It’s likely that the voltage on VDDS and VDDPW only becomes available and staable after some delay, so the MUTE and/or STBY functions selectable via S1 and S2 aren’t active immediately after power-up.

The DIAG pin, as the data sheet explains in Section 5.8, goes to a high-impedance state when protection mechanisms are activated. These protections are triggered by STBY and MUTE, which you can also find detailed in Section 5.2 of the data sheet.

Does this answer your questions?

Regards
/Peter

[DanielFFF]

Thanks for your attempt, Peter, but it answers none of my technical questions!

[TDA7498E datasheet: DS8807 - Rev 4 - June 2020;  TDA7498 datasheet: DS6437 - Rev 10 - August 2020]

My original questions related to the TDA7498E device, but your answers come from the TDA7498 datasheet, a different – though presumably related – device, with different features.

Even then, one of your answers does not seem to be confirmed in the TDA7498 datasheet – I can find nothing in that datasheet saying anything about current or load limits for the two 3.3V outputs.  Perhaps you can point me to it?

Nowhere in the TDA7498E datasheet is there a statement saying something like: "For the mountain of information missing from *this* datasheet, refer to the TDA7498 datasheet."

I have to say the STM product documentation is abysmal, even worse than Infineon's (and that's saying something!).

I simply can't design-in a device without full and reliable technical information.  I will continue my search for suitable Class-D amplifier devices.

Regards,

Daniel

[Peter BENSCH]

I sincerely apologize for mistakenly referring to the TDA7498 instead of the TDA7498E. Indeed, the documentation for the TDA7498E lacks certain details that were mentioned in the TDA7498 documentation. Unfortunately, no additional information is available on this matter.

However, the previous statement regarding the load limits of the internal 3.3 V rails also applies here.

I wish you success in your continued search for suitable devices for your project.

Regards
/Peter