13.8V DC-in for a LM3886 chip amp?

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Canis Major

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Joined 2015
Question: Can a chip amp be powered with as little as 13.8V DC? I've done a little digging, but have not found many people doing this (though I did come across a few powering their chip amps with batteries - can't remember if they were LM3886 ones or not though). My naive thinking at the moment is this low of a voltage should be fine according to this spec sheet: http://www.ti.com/product/lm3886 If I'm reading it correctly, it specifies a minimum DC-in of 9V, right?

I have an old amateur radio power supply (linear and very heavy!) rated for 13.8V DC @ 10A continuous and was curious if I might employ that as the power supply for a chip amp. I was looking at building two of these LM3886 amp boards from Chipamp.com: LM3886 Amplifier PCB + Components | Chipamp Electronics and powering them with aforementioned power supply.

Thanks for your help!
 
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Canis Major

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Hi sreten, thanks for your assistance. I'm a bit confused though - You say Vmin is 20V for a LM3886 chip? What about on the LM3886 spec sheet (link in original post) where it says "Analog Supply Min [V]= 9" ? Is this not Vmin for this chip?

Or is it because using two LM3886 chips will necessitate 9V+9V=18V (approximately 20V)?
 
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Fast Eddie D

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Joined 2010
There are many bridge amps designed for car audio that can deliver 40 watts/channel into 4 ohms from a 13.8 volt supply. None come to mind right now and I will leave it to people with experience with these chips to comment.

You could build/buy a switching power supply to provide voltages suitable for the 3886. You could probably pirate some parts (especially the transformer) from an old mobile power amp.
 
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AndrewT

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Joined 2004
13.8Vdc allows ~1/3rd of that as an AC voltage to be delivered to a load when in single amplifier topology.

eg.
13.8Vdc gives <=4.6Vac to the load.
4.6Vac into 1r0 is equivalent to 21W, into 2r0 10.5W, into 4r0, 5.2W

If you then bridge two of these amplifiers you get double the power into double the impedance.
i.e. 42W into 2r0, 21W into 4r0 and 10.5W into 8r0.

Now reduce these predicted powers to allow for reactive speaker loads and sensible distortions and you are probably looking at 12W to 15W into 4ohms, when fed from 13.8Vdc
 
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consort_ee_um

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JMFahey

JMFahey

Member
Joined 2009
sofaspud said:
And the ellipsis should be taken to mean there are no worthy 13.8V chip amps? None?
Click to expand...

This unqualified "ellipsis" blanket statement turns this one also in an ellipsis ;)

There are qualified 13.8V chipamps ... tons of them .... but they can put out less than 20W/ch into 4v ohms.

Is that "qualified" enough?

Now if you expect more, there's only one: a TDA something which has some clever self bootstrapping capacitors inside and can deliver 60/4 in music bursts.
 
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twest820

Member
Joined 2009
Yeah, not none. LM4940 and LM4950 off the top of my head. Not as performant as the higher voltage parts TI acquired with National and hard to find in TO-220. But they're built for this application, support BTL, and would get the job done to the extent the rail voltage allows---TO-263-9's not difficult to solder. The LM4752 and LM4755 are similar but fixed to a rather high 34dB gain internally.

(Lots of options in class D, some offering better standalone performance than the 49x0. SSM3302 for one, though it's in QFN and I suspect more than the OP might wish to take on. TI probably has something too.)
 
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