I plan to build a stereo amp using STA540 (i.e., the BLT mode) to power a pair of 8 ohm full-range speakers.
What is the max current requirement for STA540? I have two 20v, 4.8A linear regulated power supplies. Would one be sufficient?
Are the two power pins, Vcc1 and Vcc2, connected internally? I am thinking powering each of the pins separately with my two power supplies. Obviously that would only work if the two pins are actually separate.
Finally, has anyone run STA540 at 23v? My power supplies can be adjusted to provide up to 23v at 4.8A as well. I have beefy heatsinks.
Thanks!
What is the max current requirement for STA540? I have two 20v, 4.8A linear regulated power supplies. Would one be sufficient?
Are the two power pins, Vcc1 and Vcc2, connected internally? I am thinking powering each of the pins separately with my two power supplies. Obviously that would only work if the two pins are actually separate.
Finally, has anyone run STA540 at 23v? My power supplies can be adjusted to provide up to 23v at 4.8A as well. I have beefy heatsinks.
Thanks!
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One power supply should be just sufficient.
I conclude from the example schematics in the datasheet that pins 3 and 13 are not connected internally. BUT, using two different power supplies may harm the chip because their start-up and turn-off times may be different. I did not find in the datasheet an explanation why you have two separate power supply pins. It could be because they want to split the current draw on two pins. The problem is also that we have no basis for concluding what will happen if the instantaneous supply voltage on the two pins are not the same.
I would do as shown in the datasheet: connect the two pins 3 and 13 and use a single power supply.
I conclude from the example schematics in the datasheet that pins 3 and 13 are not connected internally. BUT, using two different power supplies may harm the chip because their start-up and turn-off times may be different. I did not find in the datasheet an explanation why you have two separate power supply pins. It could be because they want to split the current draw on two pins. The problem is also that we have no basis for concluding what will happen if the instantaneous supply voltage on the two pins are not the same.
I would do as shown in the datasheet: connect the two pins 3 and 13 and use a single power supply.
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Thanks. Do you have an estimate as to the typical power draw when the amps are powering, say, 4 ohm speakers? I saw that the amp can OUTPUT 4A during a short, but am not sure what would be the power draw in a worst-case scenario that is just shy of a short. Asking because I have 3A linear power supplies as well.
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But that is assuming the amp is perfectly efficient (if we are thinking 32W could be the ballpark for power consumption as well), right? I was reading posts mentioning that the amp may get hot easily, so I was assuming that the amp is not too efficient.
The STA540 amplifier is class AB. True, that means less efficiency than class D. You asked what would be the power in a 4 Ohm load if the peak current was at 4A. That is 32W. The amplifier may heat a lot in particular if you keep the 20V supply voltage. The 20V supply is good for 8 Ohm speakers.
Sorry, I meant what the power consumption would be in a worst case scenario that is just shy of a short. I mentioned the power output level just as a reference. I am more focused on having sufficient headroom in the power supply department (but also not to use an unnecessary, oversized supply).
In the BLT mode, would my 8 ohm speakers seen by the amps as 4 ohm? What voltage would you recommend for 4 ohm loads?
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Figure 5 of the datasheet, "Dual bridge": 2x38W in 4 Ohm at 18V supply, 2x34W in 8 Ohm at 22V supply. This hints the maximum supply voltage the manufacturer recommend.
22V (for 8 Ohm) is really at the maximum for the supply voltage. The 20V you suggest for 8 Ohm is fine as it leaves a bit of margin for variation in the supply voltage.
With a 4 Ohm load, 16V (at the output) leaves the peak current of 4A. But, for a class AB amplifier the output cannot be pulled fully to the rail voltages. 18V supply is a qualified guess. As you already have a 20V supply I would use that one, eventually with a "voltage dropper" (3 power diodes in series before power supply line decoupling capacitors) to reduce the 20V to about 18V.
For the power supply capacity, your 4.8A are nominally a bit just. But, as you have a crest-factor for music, even the 4.8A should do.
22V (for 8 Ohm) is really at the maximum for the supply voltage. The 20V you suggest for 8 Ohm is fine as it leaves a bit of margin for variation in the supply voltage.
With a 4 Ohm load, 16V (at the output) leaves the peak current of 4A. But, for a class AB amplifier the output cannot be pulled fully to the rail voltages. 18V supply is a qualified guess. As you already have a 20V supply I would use that one, eventually with a "voltage dropper" (3 power diodes in series before power supply line decoupling capacitors) to reduce the 20V to about 18V.
For the power supply capacity, your 4.8A are nominally a bit just. But, as you have a crest-factor for music, even the 4.8A should do.
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