Electronics > Projects, Designs, and Technical Stuff

Texas Instruments 3116D (ClassD) amp chip

<< < (8/10) > >>

DW1961:

--- Quote from: rsjsouza on August 17, 2020, 09:58:23 pm ---
Nope. As Kai's reply on e2e also clarifies, to get 100W RMS from one 3116D you can run it in BTL (stereo) at 4 ohms, which yields 50W per channel or 100W total, or in PBTL (mono) at 2 ohms, which yields 100W on a single channel. According to figures 14 and 22, you can get all this power using "only" 19V.

Keep going up in voltage and you will get up to 170W from a single 3116D, either in BTL or PBTL modes.


--- Quote from: DW1961 on August 17, 2020, 06:17:46 am ---
--- Quote from: rsjsouza on August 17, 2020, 03:15:30 am ---"24V * 5A = 120W. Where did the 72W come from? "
--- End quote ---
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?
--- End quote ---
Well, a resistor would consume 72W, which is equal to 242/8, but that is where you need to consider the amplifier efficiency. The datasheet tells you that 42W per channel is the maximum under these load and supply conditions. As TimFox mentioned, the amplifier will draw whatever it needs from the power supply - in other words, the power supply will passively provide whatever is within its limits, compensating with a reduction in voltage in case the amplifier consumes more than it will provide (thus clipping the output voltage).

--- End quote ---

"Nope. As Kai's reply on e2e also clarifies, to get 100W RMS from one 3116D you can run it in BTL (stereo) at 4 ohms, which yields 50W per channel or 100W total, or in PBTL (mono) at 2 ohms, which yields 100W on a single channel. According to figures 14 and 22, you can get all this power using "only" 19V. "

Yep, I failed to correct that statement last night. Sure, it says right there on the spec sheet a single 3116D amp will do 100 watts total at 4 ohms and 21 V. And, 100 watts mono at 2 ohms.

"Keep going up in voltage and you will get up to 170W from a single 3116D, either in BTL or PBTL modes. "

Ok, yes, from one chip running at 4 ohms with 26V and 6.5 amps = 170 watts total.


And we know that a single 3116D amp chip can put out 100 watts RMS at 4 ohms @ 21V (top of spec page).

Using the chart on page ten for a single 3116D and 8 ohms and 26V, which is maximum voltage the chip is rated for:
Approx. 85 watts total RMS at 26V @3.3A.


My question is:

Using two of these amp chips in PBTL mode for stereo, and leaving out efficiency factors of the amp package they come in, how many total watts RMS is it going to put out at 8 ohms using a 24V/5A PSU*? And, to my point, is to going to be anymore than using the same PSU with a single 3116D chip at 8 ohms?

*Because that's what comes with the amp package.

DW1961:

--- Quote from: cv007 on August 18, 2020, 12:57:06 am --->What is the benefit of running two of these when the power stays the same, and one amp chip is capable of putting out the same wattage using the same driver for both chips?


You also have a set of mosfets that have to dissipate power (8x120 milliohm 'resistors', 4 active at a time). If a single ic is 'heat happy' putting out 50Wx2 (BTL, 100W total), then its probably also happy putting out 100Wx1 (PBTL, 100W total). Since there is a voltage limit, the only way to get to the 100W is by decreasing the impedance. The PBTL mode is simply a way to share the heat. Since there is no perfect mosfet, I imagine heat is the monster that lurks everywhere in the datasheet.

If you are using 8ohm speakers, you cannot take advantage of the possible extra power (because of voltage limit), but you still get the benefit of sharing the heat among 2 ic's. That may mean you do not need a heatsink, or could mean the wimpy heatsinks used in an enclosed little case will not cause thermal shutdown.

You need to look at any seller of audio gear the same way you look at laundry detergent that says '2x the cleaning power'. Its a waste of time trying to sort out the claims being made. Just look beyond the sales pitch, and look at the ingredients to figure out what you have.

--- End quote ---

Yeah agree with all of that, for sure. That's why I originally started the thread.

rsjsouza:

--- Quote from: DW1961 on August 18, 2020, 01:43:54 am ---My question is:

Using two of these a,mp chips in PBTL mode for stereo, and leaving out efficiency factors of the amp package they come in, how many total watts RMS is it going to put out at 8 ohms using a 24V/5A PSU*? And, to my point, is to going to be anymore than using the same PSU with a single 3116D chip at 8 ohms?

*Because that's what comes with the amp package.

--- End quote ---
TI did not seem to have characterized the device under these conditions, thus any conclusion is pure extrapolation based on the data.

In this case, I would assume the relationship between figures 14 and 22 could also be applied to figure 13, that is: at 24V, power at 8 ohms in PBTL would be double when compared to BTL, thus yielding 42W * 2 or 84W (THD+N = 10%) - figure 13 shows 42W in BTL (stereo) mode when driving 8 ohms at 24V.

Given the power supply can put out 120W, it is enough for a single 3116D operating in PBTL at 8 ohms at maximum output continuous power.

Putting two 3116Ds in PBTL would require at least 168W + efficiency losses (about 87% or 88% according to the various graphs) - about 200W with safe margin or around 24V / 8.5A.

Hopefully I didn't mess up my calculations.

DW1961:

--- Quote from: rsjsouza on August 18, 2020, 02:36:07 am ---
--- Quote from: DW1961 on August 18, 2020, 01:43:54 am ---My question is:

Using two of these a,mp chips in PBTL mode for stereo, and leaving out efficiency factors of the amp package they come in, how many total watts RMS is it going to put out at 8 ohms using a 24V/5A PSU*? And, to my point, is to going to be anymore than using the same PSU with a single 3116D chip at 8 ohms?

*Because that's what comes with the amp package.

--- End quote ---
TI did not seem to have characterized the device under these conditions, thus any conclusion is pure extrapolation based on the data.

In this case, I would assume the relationship between figures 14 and 22 could also be applied to figure 13, that is: at 24V, power at 8 ohms in PBTL would be double when compared to BTL, thus yielding 42W * 2 or 84W (THD+N = 10%) - figure 13 shows 42W in BTL (stereo) mode when driving 8 ohms at 24V.

Given the power supply can put out 120W, it is enough for a single 3116D operating in PBTL at 8 ohms at maximum output continuous power.

Putting two 3116Ds in PBTL would require at least 168W + efficiency losses (about 87% or 88% according to the various graphs) - about 200W with safe margin or around 24V / 8.5A.

Hopefully I didn't mess up my calculations.

--- End quote ---

Regardless of your calculations, I think you are saying the same thing I was thinking when I started this thread: How do you get any more power out of two chips vs one chip when the power supply only puts out 120 watts @ 0hms or 72 watts at 24v/8 ohms?

"Given the power supply can put out 120W, it is enough for a single 3116D operating in PBTL at 8 ohms at maximum output continuous power."

It cannot put that much power out when you add resistance: 72 watts @ 8 ohms and you run up against the PSU's voltage max, which is 24v. (If I am understanding this now.)

It just seems like they can do everything with one chip vs two, especially since the amp package has a sub out for an active sub. I mean at 21V and just under 5 amps, you can get what they say at 4 ohms: 100 watts. IF you had ONE chip in the same amp package with a sub out for an active sub, you would still have the same power to play with given you are usually not going any lower than  4 ohms.

But when they say you get 100 watts at 2 ohms, sure, if you have a PSU that puts out 7 amps at 14v.

Again, the PSU we're dealing with is 24v/5A. That's all we get. It would be different is you had a 24V 10A power supply, then yeah, you would get a LOT more benefit form using 2 chips vs one becasue you would run up against voltage  restrictions using one chip and would need two of them to put out more power.

For instance, using a 26V power supply with a single chip, you can get max RMS at 8 ohms (according to the graph) and 3.3 amps of 86 watts. If you want more power at 8 ohms, then you need to use two of them. And, you would need to increase the PSU voltage (not necessarily the amperage) past 26V, which I assume could be regulated to each chip to not exceed 26V. Then, yeah, I can see the benefit of using two of them, but not with the same power supply that only puts out 24V.

So the question remains, why build a dual 3116D amp with a 24V/5A power supply?

cv007:
>In this case, I would assume the relationship between figures 14 and 22 could also be applied to figure 13, that is: at 24V, power at 8 ohms in PBTL would be double when compared to BTL

You are missing the fact that the PBTL graph is using 2 Ohms. All the graphs essentially end up the same (BTL 8,4,PBTL 2), each is just changing the load impedance to increase the power. PBTL is already BTL, its just parallel to share the heat.

If you have 24v and 8 Ohms, it makes no difference if you run in BTL or PBTL as your total output will be the same. What you get, as I have said previously, is the ability to direct all the power into a single low impedance speaker if wanted. With 8 ohms and PBTL, all you get is less heat for each ic, which is a good enough reason and could be the main reason they run them in PBTL.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod