6*lm3886 Bpa

[Tim__x]

Here's my idea.

• Bridged Parallel, 3 IC's an arm. (based on the BPA-200 in the app note)
• Driving a 4 ohm load. Each arm seeing a 2 ohm load, each IC seeing a 6 ohm load.
• Running on 30+30 volt rails (unregulated)
• With DC servo's running on 15+15 volts regulated that will also power the input buffers
• Each LM3886 running in inverted configuration. (one inverting buffer, one non-inverting)

My math is as follows.

30v+30v=60v

60v-6v(for output dropout) = 54v

54v/4ohms=13.5amps

13.5amps/3ic's=4.5amps peak per IC. Seems reasonable to me, what do you guys think?

4.5amps(peak per IC)/1.414 ~3.2amps RMS per IC

I haven't done any power dissipation calculations yet, but with 30+30 rails and a 6ohm load I imagine they'll work fine.
Is this doable?
If so, should I make one big PCB or perhaps design one small pcb with just a single LM3886 and a servo on it and make six of them? Either way I'll make the input buffers on a seperate board.

Edit: With a bridged amp is it necessary to connect the main supply caps to ground or just across the rails?

[Mattyo5]

BPA-300 :-D Pcb designed!



-Matthew K. Olson