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NotSoFast , 01-04-2025, 02:23 AM

I'm not sure this is allowed so please tell me if not. I am putting my Altium Essentials course to use and designing my own project. But am unsure of the audio amp component. Can someone review?

I have configured the device with Ri = Rf for unity gain. Which according to the data sheet should actually be 2*Rf/Ri given the amp is a BTL configuration.

My +3v3 is coming off an LDO.

The DAC driving -IN is on my STM32L052k8T6 chip and its datasheet says it has an output voltage of 0.2V to VDDA-0.2V. I'm concerned about clipping but figure I can attenuate the signal in software if it's an issue. Does that make sense? The DAC also has an internal buffer I can turn on the accommodate the high impedance load of the Amp's input.

Can someone sanity check this configuration given the information I've provided?

NotSoFast , 01-04-2025, 02:28 AM

I was a bit shy to put the entire schematic in here.. but I'd like to learn from people with experience if they're willing to critique. So here it is.

NotSoFast , 01-04-2025, 03:05 AM

QDrives , 01-04-2025, 03:18 AM

1) The 'feedback' should be on Vo1 and not Vo2.
2) Do not have the Gnd 'pointing' upward.
3) Extend the lines to go over the the entire net name.
4) Better connect the hold_reset to the MCU or draw the pull-up direct to the chip and not as a general pull-up.
5) I wonder if a single 1uF decoupling cap is enough for the amp. I would add a big bulk capacitor too.

NotSoFast , 01-04-2025, 03:24 AM

First, thank you so much for checking it out.
Good catch on the wrong output for feedback.

4) Better connect the hold_reset to the MCU or draw the pull-up direct to the chip and not as a general pull-up.

For 4 here in my design I don't think I need the hold pin and it's active low, so I was going to pull it high. Do you mean that I should have the pullup actually attached to the chip as a better way of doing the schematic layout?

NotSoFast , 01-04-2025, 03:26 AM

I guess the same goes for Write Protect too then.

QDrives , 01-04-2025, 04:53 AM

Yes, so the two pull-ups are next to the NRST pull-up.
A MCU can be very crowded if you place everything just next to it, but for this memory chip, there is plenty of space to place them close in the schematic.

And I forgot to mention:
6) Add the "not" line if a pin is (always) active low. I think it was s\h\u\t\-\d\o\w\n but you will see it when you write it.

NotSoFast , 01-04-2025, 11:01 AM

Great, thanks for the review. Much, much appreciated.