CSD97396Q4M: why the pins is short circuited?

user4253459

Part Number: CSD97396Q4M

HI,

I want to measure the voltage of the resistance in the RLC circuit. And I connected the 10uH inductance and 5.6Ω resistance to the P3.

Then two 5V power supply of DH1718D-4 is provided. PWM1 and PWM2 send the 100kHZ signal and the duty cycle is 50%.

Maybe I make some mistakes. The voltage of the resistance is wrong.

I use the multimeter to measure the pins.

The pin PWM1 , BOOT, BOOT-Rand the PGND is short circuited . The pwm2 and the VIN is short circuited.

Then I change the DSP and the CSD97396. I have a good result .

But then I find the pwm1 and PGND is short circuited again. And the U3 is fine.

why did these problem happen ? And the maximal current of power supply is 3.5A. Can the power supply result in the problems?

Regards,

TIANQING LI

over 6 years ago

0 Brett Barr1 over 6 years ago

TI__Mastermind 18200 points

Tianqing,
I have reached out to our apps engineers regarding this and hope to have an answer for you shortly.

0 user4253459 over 6 years ago in reply to Brett Barr1

Prodigy 180 points

Dear Brett ,
Today, I change the U1. Then I find the second pin of the VIN is connected to the pin 6. But the other pin of the VIN is not connected to the pin 6. And the phenomenon happens on the U1 and the U3. It is so amazing.
Regards,

TIANQING LI

0 Brett Barr1 over 6 years ago in reply to user4253459

TI__Mastermind 18200 points

The first thing our apps team advised is to double check the soldering.

"To damage PWM pin on IC, one possible reason is a short between BOOT and PWM which applies high voltage on PWM pin."

0 user4253459 over 6 years ago in reply to Brett Barr1

Prodigy 180 points

Dear Brett ,
Thank you for your answer. Your answer maybe solve one of my problems. I'm new at this and I'm sorry about some of my mistake.
Looking forward to your reply about the other problems.
Regards,

TIANQING LI

0 Brett Barr1 over 6 years ago in reply to user4253459

TI__Mastermind 18200 points

Great! We're happy to help.

0 user4253459 over 6 years ago in reply to Brett Barr1

Prodigy 180 points

Dear Brett,

you did not answer my question about this problem:

"Today, I change the U1. Then I find the second pin of the VIN is connected to the pin 6. But the other pin of the VIN is not connected to the pin 6. And the phenomenon happens on the U1 and the U3. "

And will the FCCM mode cause some bad effects? I want to know it.

the two signl PWM1 and PWM2 are like this .

TIANQING LI

0 user4253459 over 6 years ago in reply to Brett Barr1

Prodigy 180 points

should I add four fast recovery diodes ? is it my fault? Does the chip CSD97396 include fast recovery diodes ?
Regards,

TIANQING LI

0 Brett Barr1 over 6 years ago in reply to user4253459

TI__Mastermind 18200 points

Tianqing,
I will let you know what our apps team says.

0 Brett Barr1 over 6 years ago in reply to Brett Barr1

TI__Mastermind 18200 points

"The MOSFETs in CSD97396 have body diode, there is no need to add external diode.

FCCM mode shouldn’t cause any problem.

What does the second pin of VIN mean? All the VIN pins are connected together on CSD97396 package, I don’t understand why the second pin of the VIN is connected to pin 6 while the other pins of the VIN is not connected to pin 6. Is there any picture to explain this"

0 user4253459 over 6 years ago in reply to Brett Barr1

Prodigy 180 points

Thank you for your answer . I will check it again.
TIANQING LI

0 user4253459 over 6 years ago in reply to Brett Barr1

Prodigy 180 points

only U3 is working and the pin VSW of U1 always is low. And the PWM1 is correct.what's the problem？thank you for your help.

TIANQING LI

0 Brett Barr1 over 6 years ago in reply to user4253459

TI__Mastermind 18200 points

Can you test U1 and U3 independently to make sure there is no soldering issue?

Do not connect anything to the P3 connector (Vsw for power stages are floating), just apply Vin, Vdd, and one pwm, then check the related Vsw pin.

If the device is correctly soldered, Vsw should go to Vin at PWM high and the GND at PWM low.

0 user4253459 over 6 years ago in reply to Brett Barr1

Prodigy 180 points

thank you for your help. And I make a new board.

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CSD97396Q4M: why the pins is short circuited?