TMS570LC4357: N2HET PWM Pin drops from 3.3V to 2.1V

JoeW

Part Number: TMS570LC4357

Hello,

For our safety-critical system, we are using the TMS570LC43 to generate a PWM with the N2HET module. All worked well until we saw that the N2HET pin max voltage dropped from 3.3V to 2.1V. So, I build a new project using the same N2HET pin as a GIO but we are facing the same issue: when the pin is driven HIGH the output voltage is 2.1V and not 3.3V.

Any ideas on how to solve this problem please?

Thanks

over 4 years ago

0 QJ Wang over 4 years ago

TI__Guru**** 192196 points

Hello,

Which board did you use? Which N2HET pin is measured?

One N2HET pins (N2HET1[14]) is not routed to J11 connectors if the ethernet switch (DIP switch on HDK) is turned ON. Please turn off the ethernet switch, then probe N2HET1[14] on J11.

0 JoeW over 4 years ago in reply to QJ Wang

Prodigy 120 points

Hi,

We are using the TMS570LC4357 HDK and using the N2HET1[30] pin to generate the PWM.

Regards,

0 QJ Wang over 4 years ago in reply to JoeW

TI__Guru**** 192196 points

NHET1[30] should be fine. Do you get a PWM signal with correct frequency or period? Can you please turn off the DIP switch for USB and Ethernet?

0 JoeW over 4 years ago in reply to QJ Wang

Prodigy 120 points

Hi,

Turning off the DIP switch for USB and Ethernet did not solve our problem.

I've changed the HDK and the output pin is at 3.3V with the same code. I'm going to let it run for a while to see if there is any effect. We are wondering if it is not an ESD effect but it seems weird to me as there was just an oscilloscope connected to the pin during the test.

I am opened to any explanation on how this issue could occurred.

Regards,

0 QJ Wang over 4 years ago in reply to JoeW

TI__Guru**** 192196 points

Hello Joe,

Did you see the same issue on the 2nd HDK?

0 JoeW over 4 years ago in reply to QJ Wang

Prodigy 120 points

Hello,

Nothing on the 2nd HDK, we try to reproduce the issue but nothing yet.

Regards,

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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TMS570LC4357: N2HET PWM Pin drops from 3.3V to 2.1V