chip burn-out when plug-in or plug-out DVD signal lines

xujing79 · 26th July 2010, 05:45 AM

I've designed a class-d amplifier with one internal LDO. when I plug-in or plug-out DVD signal lines, the chip is ease to burn-out. if I add one zener(5.7V) between LDO output and ground, everything is ok. I don't know why this happen? please give me some suggestion to find this cause, thank you! Kenneth

m-tech · 26th July 2010, 12:13 PM

Too much capacitance on LDO output ?
Adding a diode from output to input can solve this problem.

xujing79 · 28th July 2010, 11:46 AM

m-tech, thanks for your suggestion.
I've try your solution:
1) add 1 schottky diode between LDO output and Vin, it's improved, but finally it's also broken.
2) change LDO output capacitor from 1uF to 0.1uF, it's also improved, but it's also broken finally.
could you please explain your original idear in detail?
my design is high-power class-d audio amplifier. if add external schottky between output and gnd, and add 1 zener between LDO output and gnd, everything is ok. I'm not very clear about the root cause.

xujing79 · 3rd August 2010, 05:07 AM

Hi, all,
I have more testing for this problem. when it occurs, ldo output will fly to 10V, and then it will latch to 3V(normal is 5V). I don't know what happene for the internal circuit. please give your experience, thank you!

26th July 2010, 05:45 AM	#1
xujing79 diyAudio Member Join Date: Jul 2010	chip burn-out when plug-in or plug-out DVD signal lines I've designed a class-d amplifier with one internal LDO. when I plug-in or plug-out DVD signal lines, the chip is ease to burn-out. if I add one zener(5.7V) between LDO output and ground, everything is ok. I don't know why this happen? please give me some suggestion to find this cause, thank you! Kenneth

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26th July 2010, 12:13 PM	#2
m-tech diyAudio Member Join Date: Feb 2006 Location: Belgrade	Too much capacitance on LDO output ? Adding a diode from output to input can solve this problem.

28th July 2010, 11:46 AM	#3
xujing79 diyAudio Member Join Date: Jul 2010	m-tech, thanks for your suggestion. I've try your solution: 1) add 1 schottky diode between LDO output and Vin, it's improved, but finally it's also broken. 2) change LDO output capacitor from 1uF to 0.1uF, it's also improved, but it's also broken finally. could you please explain your original idear in detail? my design is high-power class-d audio amplifier. if add external schottky between output and gnd, and add 1 zener between LDO output and gnd, everything is ok. I'm not very clear about the root cause.

3rd August 2010, 05:07 AM	#4
xujing79 diyAudio Member Join Date: Jul 2010	Hi, all, I have more testing for this problem. when it occurs, ldo output will fly to 10V, and then it will latch to 3V(normal is 5V). I don't know what happene for the internal circuit. please give your experience, thank you!

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