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Texas Instruments 3116D (ClassD) amp chip

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DW1961:

--- Quote from: rsjsouza on August 17, 2020, 01:06:31 am ---
--- Quote from: DW1961 on August 17, 2020, 12:02:20 am ---
Yes, they are talking about "max" power output, so sure, you can get 200 watts out of a 24V RMS power supply rated at 5A.

Back to my original problem, I'm not seeing how you get anymore than 100 watts continuous power at 4 Ohms using that 24V/5A power supply.

I think some of my problem is that I don't see where contious power or peak power is stated int eh Texeas Instruments spec file:

--- End quote ---
Table at section 6.6 of the datasheet indicates 50W continuous at 4 ohms with 21Vcc.  According to the description, this is per channel - in BTL it will do 100W under the same conditions. A side note: keep in mind this is under 10% of signal distortion - far from a hi-fi under these conditions (it will have less distortion if driven at lower power).


--- Quote from: DW1961 on August 17, 2020, 12:02:20 am ---So you can get 100 watts @ 20V and 5A and 4 Ohms from a 24V/5A continuous power supply.
--- End quote ---
The output power equals the supply power minus losses - in other words, the efficiency of the circuit. 24V/5A will give you 120W of supply, which may be just enough for continuous operation of 100W total or 50W per channel - the efficiency is shown at figure 23 of the datasheet.

Higher peak power may or may not be attained. Section 7 describes the drivers will pull up to 7.5A at peak conditions (which gives a 200W peak under 4 ohms).

--- End quote ---

Hey, thanks for chiming in.

Just so I can understand the technical language, where in that table at 6.6 does it say "per channel" at the 10%THD row?

Power to efficiency are understood. It's a good point, but for now I'm just keeping it at theoretical output for simplicity.

I just want t get the continuous power aspect down given the power supply of 24V at 5A @ 4 Ohms.

If I understand you correctly, this all mean that with two 3316D chips using a 24V / 5A power supply, bridged at 2 Ohms each, for a total, again, of 4 Ohms, they can get theoretical power of 100 watts continuous at 10% THD?

If so, we can move on to the problem I have about 8 Ohms loads and using two of these chips. That would be about 72 watts continuous from the power supply. Well, I'll jsut sate it again:

At 8  Ohms and 24V / 5A = 72 watts.

That's as much power as it can make.

This graph shows a single 3116D chip can do 80 watts continuous. However, the PSU is only going to give it 72 watts.

At .1% THD it will do 66 watts total.

Again, the graph says "maximum power" and says nothing about peak or continuous. I don't know what "Maximum Output Power" means: Peak/Continuous? In any event, if you are running ONE 3116D with a 24v/5A PSU, you get 72 watts total. If you use 2 3116D amps, your continuous output is still going to be no more than 72 watts @ 8 Ohms. I'm only talking about continuous power from the dual 3116D amp chips at 8 Ohms. So what is the benefit of having two chips if you power does not increase over 72 watts, and one chip can use all of it,a nd what's more, at less than .1% THD? I assume you could have even lower THD if both amp chips were putting out a total of 72 watts, but each one was only being driven at 50% power?

rsjsouza:

--- Quote from: DW1961 on August 17, 2020, 02:16:27 am ---Just so I can understand the technical language, where in that table at 6.6 does it say "per channel" at the 10%THD row?
--- End quote ---
The table itself does not say it. The description at sections 1 and 3 says the device puts out 2 x 50W continuous and section 7.4.1 says in PBTL mode (mono) it puts out 100W. With all that, I infer the information there is related to a single channel. 



--- Quote from: DW1961 on August 17, 2020, 02:16:27 am ---Power to efficiency are understood. It's a good point, but for now I'm just keeping it at theoretical output for simplicity.

I just want t get the continuous power aspect down given the power supply of 24V at 5A @ 4 Ohms.

If I understand you correctly, this all mean that with two 3316D chips using a 24V / 5A power supply, bridged at 2 Ohms each, for a total, again, of 4 Ohms, they can get theoretical power of 100 watts continuous at 10% THD?

--- End quote ---
If I understood correctly your amplifier has two devices in PBTL (mono) mode and each is driving its own 2\$\Omega\$ loudspeaker. If so, figure 22 tells me that, at 24V, it can go as high as 150W each device, rendering your 24V/5A rather inadequate to supply this "beast". To get absolute maximum continuous power, you would need to have a minimum of 300W + efficiency losses.


--- Quote from: DW1961 on August 17, 2020, 02:16:27 am ---If so, we can move on to the problem I have about 8 Ohms loads and using two of these chips. That would be about 72 watts continuous from the power supply. Well, I'll jsut sate it again:

--- End quote ---
So, why are you talking about 2\$\Omega\$? Sorry, I really don't get exactly the circling around.


--- Quote from: DW1961 on August 17, 2020, 02:16:27 am ---At 8  Ohms and 24V / 5A = 72 watts.

Also, figure 13 says the maximum power at 24V is 42W for 8\$\Omega\$. Given the graph is

That's as much power as it can make.

--- End quote ---
24V * 5A = 120W. Where did the 72W come from?

With all that, two devices in PBTL mode driving 8\$\Omega\$ should be properly driven by your 24V/5A power supply, given the efficiency would still be well within the tolerance of your power supply.


--- Quote from: DW1961 on August 17, 2020, 02:16:27 am ---Again, the graph says "maximum power" and says nothing about peak or continuous.

--- End quote ---
The characterization having THD+N measurements suggest to me this is continuous - distortion measurements in peak signals is quite difficult to obtain and not very practical.

DW1961:

--- Quote from: rsjsouza on August 17, 2020, 03:15:30 am ---

--------------------
"If I understood correctly your amplifier has two devices in PBTL (mono) mode and each is driving its own 2\$\Omega\$ loudspeaker. If so, figure 22 tells me that, at 24V, it can go as high as 150W each device, rendering your 24V/5A rather inadequate to supply this "beast". To get absolute maximum continuous power, you would need to have a minimum of 300W + efficiency losses. "

I dunno. That's why I'm trying to figure out if how the magic in these chips works.

The single 3116D2 chip runs in BTL mode, which tells me it is really 4 amps on one chip. In BTL mode, you need two chips running mono. However, the 3116D chip runs in stereo. So if it is running in BTL mode all of the time, and it is stereo, then it must have 4 amps on the chip. That's how they can run x2 3116D chips in mono and get stereo in the amp I have, I assume. Otherwise, if it were just two amp chips, they would be only getting a mono amp out of it. So the way I understand it, to get stereo from a BTL system, you need 4 amps.

So the amp I have must really have 8 amps on it (x2 3116D2 chips @ 4 amplifiers each), but they are running the 3116D in mono mode, so they need another one to do stereo.

How they are connecting them together, I have no idea! PBTL? I just dunno.

"If I understood correctly your amplifier has two devices in PBTL (mono) mode and each is driving its own 2\$\Omega\$ loudspeaker. If so, figure 22 tells me that, at 24V, it can go as high as 150W each device, rendering your 24V/5A rather inadequate to supply this "beast". To get absolute maximum continuous power, you would need to have a minimum of 300W + efficiency losses."

As far as power output goes, the chips have a max voltage each of 26V, "Wide Voltage Range: 4.5 V to 26 V" (page 1).

"So, why are you talking about 2\$\Omega\$? Sorry, I really don't get exactly the circling around. "

To get 100 watts RMS from one 3116D, it has to run at 2 Ohms in mono.

"24V * 5A = 120W. Where did the 72W come from? "
Using this calculator: https://www.rapidtables.com/calc/electric/watt-volt-amp-calculator.html
Add resistance at 8 ohms: 8 ohms/3 amps/24v/72 watts. You could increase current, but then you would need to increase voltage too. I guess Ohms law?

They say in the spec sheet that you can get 50w x2 at 21V and 4 ohms.
Using this calculator: https://www.rapidtables.com/calc/electric/watt-volt-amp-calculator.html
It spits out:
4 ohms
5 amps
20 volts

So, ok right on. But, more confusion now. On the right side of the same page, it says:
'The TPA 31xxD2 series are stereo efficient digital amplifier power stage for driving speakers up to 100W / 2Ωin mono."

Page 1

-- 2 × 50 W Into a 4-ΩBTL Load at 21 V (TPA3116D2)
-- The TPA 31xxD2 series are stereo efficient digital amplifier power stage for driving speakers up to 100W / 2Ωin mono.

I have two confusions here.
Using this calculator: https://www.rapidtables.com/calc/electric/watt-volt-amp-calculator.html

(1) 100 watts at 2 ohms:
2 ohms
7 A
14 V
I guess it's ohms law that prevents you from increasing voltage and decreasing amperage to get the same power. If true, then you need a 7 amp PSU to get the 100 watts at 2 ohms in mono.

And I'm assuming again that the 100 watts figure at 2 ohms mono is RMS.

My brain is fried today. I'm still not understanding how they benefit from using two of these chips with a 24v/5A PSU taking into consideration RMS only.

-----------

I found this on the TI website forum and discusses exactly what we were discussing with feedback from a TI rep about RMS and channels etc. Then add that bridging two amps doubles the ohms, so now I'm even more confused than I was earlier today.

"In section 6.6 output power is specified for a 1kHz sine. So, the output power specification is RMS. The output power of 50W is valid for a 4R load in stereo configuration. The TPA3116D2 can drive 2 x 50W into 4R. The TPA3116D2 can also drive 100W into 2R mono, like shown in section 7.4.1 of datasheet (figure 36)." https://e2e.ti.com/support/audio/f/6/t/688690

--- End quote ---

TimFox:
So far, the discussion has related to definitions, arithmetic, and careful reading of the data sheets.
Do you have the basic equipment (audio generator, oscilloscope, AC voltmeter, and 4 ohm power resistor) to measure any of this?

DW1961:

--- Quote from: TimFox on August 17, 2020, 01:25:38 pm ---So far, the discussion has related to definitions, arithmetic, and careful reading of the data sheets.
Do you have the basic equipment (audio generator, oscilloscope, AC voltmeter, and 4 ohm power resistor) to measure any of this?

--- End quote ---

You forgot knowledge to use the equipment, too.

You've done more than necessary, Tim, and, I appreciate it. I understand if you no longer want to participate in this discussion. It's probably all really mundane for you :(

It just seems like there should be a way to deduce general power output given knows in the spec sheet/diagrams, driver, and resistance. We did that for one chip and came to some conclusions. It was easy after understanding the terminology they were using for "max" power, per channel, etc., which is confusing the way they worded everything--and confirmed by the thread at TI forums.

Now I'm trying to figure out the same thing with another amp that uses x2 3116Ds.

Still not understanding how they get any more power at 8 ohms using two chips, instead of one (which puts out 100 watts total RMS at 20V and 5 amps @ 4 ohms). That's pretty much the max behind the 24v / 5A power supply they provide.

And, again, I'm talking about RMS not peak.

I did get a reply back from the seller that said continuous power is 50 watts per channel at 8 ohms. I doubt it, since:

8 ohms
3.5 amps
28 volts
= 100 watts

I mean they are almost there, but it's a 24 v PSU, not a 28V. Max power for a 24V PSU is 72 watts at 8 ohms (Given the calculator).

Just another quick question, and a quick, simplistic answer, that is bothering me and I've searched for it but no love: Why can't we decrease voltage and increase current (w/o changing resistance) when dealing with resistance in order to get the same power? I know it has to do with Ohms law, and the calculators for ohms and power do not allow trading volts for amps and vice versa, w/o changing ohms too.

By a quick answer, I mean am I right about that? If so, if you want, you could explain it very simplistically. I don't need to know all the physics behind it. Just knowing that you cannot trade volts and amps w/o changing ohms around when dealing with resistance would suffice.

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