TPA3255: TPA3255 Short circuit protection issue

Ning Li

Part Number: TPA3255

Dears,

Customer use TPA3255 for signal channel,power is 250W with 4Ω load,Vin is DC50V,OC_ADJ is 30K, now when they do the short circuit protection then find some device is break down,pls find below information:

1. Test power amplifier has signal output, which can output 32V with 4 Ω , and then short-circuit output under full load, power amplifier chip will be burned.When they use good TPA3255 replace with bured TPA3255,function is good.

2.Set the current limit of the power supply at 0.5A, the output is not connected to the load, and then adjust the input signal to make the power amplifier output 32V, and then short-circuit output, the power amplifier chip will be burned.When they use good TPA3255 replace with bured TPA3255,function is good.

3.AP test:The low-frequency 100HZ signal input of the signal generator may burn the power amplifier chip. It worked fine after the chip was replaced.

4.After the chip OC_ADJ is changed to 64K, short circuit will not burn the chip, but it is easy to protect low frequency music playback.

5. After the chip power supply is changed to 36V, the short-circuit output will not burn, but it will not enter the protection state, and the chip will enter the thermal protection after overheating for a while.

6.Total test 280PCS,60PCS have issue.

Customer want TI help to check the schematic and PCB Layout have any issue or not.Pls kindly help.

Thanks

INPUT_SCH_1.0.SchDoc PCB_AMP_V1.8_220110.PcbDoc PCB_E_V1.1_201219.PcbDoc PCB_INPUT_V1.1_200918.PcbDoc SCH_AMP_V1.8_220110.SchDoc SCH_AMP_V1.8_220110.pdf INPUT_SCH_1.0.pdf

over 2 years ago

0 Jesse Ji over 2 years ago

TI__Mastermind 20541 points

Hi LI

we will feedback you asap after we checked above data.

thanks.

jesse

0 Jesse Ji over 2 years ago

TI__Mastermind 20541 points

Hi Li

it seems like high current so that problem happen.

about the pcb, my comment is as below:

1.the decoupling cap is too far away from output pin, please move them close to the chip to reduce the parasitic inductance.

also, not just the cap at pvdd side, the cap at other power supply pin also having same problem.

please check our pcb layout reference in the datasheet. it will help a lot at high power application.

2. can you tell me the Isat of the inductor of LC filter?

your output is 32v/4ohm, at least 8A x 1.4 = 11.2A is necessary. otherwise, oc will be very easy be triggered.

thanks.

jesse

0 Ning Li over 2 years ago in reply to Jesse Ji

Intellectual 760 points

Hi Jesse,

I have reply customer,Isat of the inductor is 10A,now they will replace the inductor to test then feedback to you.BTW,beside the cap issue at power supply PIN PCB Layout,their design have any problem or not?

Thanks

0 Ning Li over 2 years ago in reply to Ning Li

Intellectual 760 points

Hi Jesse,

Customer want to know whether replace the inductor with 15uh/22uh is better when they do the short test.

Thanks

0 Jesse Ji over 2 years ago in reply to Ning Li

TI__Mastermind 20541 points

Hi Li

it depends.

if the isat is enough, it should be able to help improve their issue.

i think maybe they can take a measurement for their output current to see whether it is very severe.

About PCB, i haven't seen other strange points.

thanks.

jesse

0 Ning Li over 2 years ago in reply to Jesse Ji

Intellectual 760 points

Hi Jesse,

I will check with customer.

Thanks

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TPA3255: TPA3255 Short circuit protection issue