TPA3255: TPA3255 BTL MODE, OUT C&D SHUTDOWN WHEN POWER IS 40W

Hi Tien Nguyen,

can you help to share more information?

1 can you check the marking of the chipset? it should be "3255" or "3255T".

2 can you check the input signal of channel A/B and channel C/D? if possible, can you swap the input signals?

3 can you check the fault listed in datasheet  page 17"8.3.1 Error Reporting"?

4 regarding the channel C/D, is there ever any signal when the device power on? or never has output?

Br,

Wenbin

Hello Wenbin,

Good day.

1. can you check the marking of the chipset? it should be "3255" or "3255T".

>> From the image below, it is 3255.

2 can you check the input signal of channel A/B and channel C/D? if possible, can you swap the input signals?

>> I tried swap the input signal, but it not a problem.

3 can you check the fault listed in datasheet  page 17"8.3.1 Error Reporting"?

4 regarding the channel C/D, is there ever any signal when the device power on? or never has output?

>> C & D output always has output, however only 30V P-P, BTL mode, power supply is 36V DC. When C & D output is shutdown , A & B output still work well.

Let me know if you still need further informations.

Regards,

TI-CSC

Hi Tien Nguyen,

thanks for the details.

from the marking, it is confirmed that it is TPA3255, not the -q version.

from the design files, I didn't find obvious errors.

to understand the output power limit, have you tested the signals of the c/d channel? the pwm signal before L. I want to know the voltage level, whether it is the limitation. and  the THD level of output signals on load, whether it is clipped.

beside that, is this happened on 1pcs unit? can you switch to another device or chipset?

Br,

Wenbin

Hello Wenbin,

Good day.

1.Have you tested the signals of the c/d channel?
-> yes, i try swapping input signal A/B to C/D and C/D to A/B then A/B output full range power, C/D 40W ( 30V P-P load 4-ohm).Signal output C/D is clear and beatyfull but shutdown when power achieve 40W.
2. The pwm signal before L. I want to know the voltage level.
-> I measured 0.42V DC. AC is 0V
3.The THD level of output signals on load, whether it is clipped?
-> NO, OUTPUT is clear.I use sine-wave signal input and output is full not is clipped. When I use load 8-ohm it not shutdown, maybe it overload but A/B out full range and is clipped when voltage is 70V p-p, A/B so good.
4.is this happened on 1pcs unit? can you switch to another device or chipset?
-> It happens to all my devices. I tried switching chipset and use a new device but error is still.

Regards,

TI-CSC

Hi Tien Nguyen,

I think it's better you can provide the scope shots of the bad ch input, output, and PWM before and during the fault, it can help to identify issue.

and check the error reporting status during fault.

and meanwhile, can you remove the inductors in C/D, and to check the output levels before the inductor? 

and 

Br,

Wenbin

Hi Tien Nguyen,

one more comments:

it maybe caused by the CB3C OC limiting. to confirm this, you can change the RU6 to 30k; and another test that keep the RU6=22k, but use lower tone frequency signals (such like 50Hz) to do test. expect to get different output signal level or even channel shutdown.

Br,

Wenbin

Hello Wenbin,

Good day.

As of this writing, I don't have the test equipments to help me provide what you're asking for.

I have seen many articles about the C/D output error shutting down when power 40W. May I ask if it is possible that it is an error in your chipset design? And I don't see any solution given in all those forums. 

Regards,

TI-CSC

Hi Tien Nguyen,

I had consulted this internally. many customer had used this part and released to market. it should not be an design error.

as mentioned in last reply, we had suspected the OC limiting mentioned in datasheet. and there are two ways to verify. if this confirmed, usually one solution is  fine tune the LC.

as this is old part, I will try to test one EVM to verify it. but now I have to apply one EVM first. and will feedback the results after that.

Br,

Wenbin

Hello Wenbin,

Good day and I understand.

Today I switch to PBTL mode and it shutdow when I use 3 load 8 ohm parallel power ~ 40Vp-p. PS is 36V DC. Load 4ohm is well. Is there any way to remove that protection? Protection is not necessary on my application.

Regards,

TI-CSC