tm4c123 gets heated because of VBUS (PB1) pin

Dhanush Nair

Expert 1360 points

Other Parts Discussed in Thread: TPS2051, EK-TM4C123GXL

Hi,

I have configured my PB1 as

-> " GPIOPinTypeUSBAnalog(GPIO_PORTB_BASE, GPIO_PIN_0 | GPIO_PIN_1 );

-> " USBHCDPowerConfigInit(0, USBHCD_VBUS_AUTO_HIGH | USBHCD_VBUS_FILTER); "

I connected PB1 directly to the TPS2051 IC's 6,7,8 pin . I found that after connecting PB1 to TPS2051 IC's 6,7,8 pin (+5v) my controller gets heated.

After removing PB1's connection controller does not get heated.

Regards,

Dhanush

over 11 years ago

0 Amit Ashara over 11 years ago

TI__Guru**** 244440 points

Hello Dhanush,

There is a known issue of IO Latch Up on TM4C123 which would occur when a fast fall time is seen by the pin. This is already there in the errata and WA mentioned as well.

Regards
Amit

0 Dhanush Nair over 11 years ago in reply to Amit Ashara

Expert 1360 points

Hello Amit,
Im4c123 is getting heated too much, please provide me solution for it.
Regards,
Dhanush

0 Amit Ashara over 11 years ago in reply to Dhanush Nair

TI__Guru**** 244440 points

Hello Dhanush,

Did you look at the errata for the suggested workaround?

Regards
Amit

0 Sham Sunder over 10 years ago in reply to Amit Ashara

Prodigy 130 points

Dear Amit,

I am new to this community and also EK-T4C123GXL launchpad. I have one related question schematic of launchpad shows PB1 (USB0VBUS) of controller is directly connected to +USB_VBUS (without regulator). In data sheet it is explicitly mentioned that this pin (PB1) is not 5V tolerant, so why it is done in launchpad?

0 Amit Ashara over 10 years ago in reply to Sham Sunder

TI__Guru**** 244440 points

Hello Sham

On the LaunchPad, there is a 0Ohm resistor required to connect the PB1 to USB_VBUS

Secondly, it not 5V tolerant when in GPIO Mode. In USB Mode it is not in GPIO mode and this is clear in the data sheet as well

Regards
Amit

0 Sham Sunder over 10 years ago in reply to Amit Ashara

Prodigy 130 points

Hi Amit,

I have one question regarding schematic of Ek-TM4C123GXL. I noted in the user manual that capacitors C31, C34 of main oscillator (Crystal 16MHz) for U1 (main controller not ICDI controller) are not populated. Can you please explain why it is done? It means I should not be able to enable/use main oscillator.

0 Amit Ashara over 10 years ago in reply to Sham Sunder

TI__Guru**** 244440 points

Hello Sham,

I checked my EK-TM4C123GXL and they are mounted.

Regards
Amit

0 Sham Sunder over 10 years ago in reply to Amit Ashara

Prodigy 130 points

Thanks for rep amit..Yes, i guss they are mounted on my launchpad too..but it was contrary to what is written in manual that's why asked.

0 Amit Ashara over 10 years ago in reply to Sham Sunder

TI__Guru**** 244440 points

Hello Sham,

Thanks for pointing it out. The C31 is not in the correct section. I will file in a documentation report.

Regards
Amit

0 Sham Sunder over 10 years ago in reply to Amit Ashara

Prodigy 130 points

Thanks again for reply..i have another small question:
For main oscillator crystalls (Y2, Y5) it is mentioned that ABM3-16.000 MHz-B2- T and NX5032GA-16.000000 MHz crystal can be used. But ABM3-16.000 MHz-B2- T has load capacitance (specified in data sheet) 18pf, so if I calculate the value of C1, C2 using the formula suggested in controller data sheet. C1 comes 30pF which exceeds the limit of maximum value for C1or C2 which is 24pF !! Can you please clear on that.

0 Amit Ashara over 10 years ago in reply to Sham Sunder

TI__Guru**** 244440 points

Hello Sham

For the ABM3 crystal, CL=18 pF and Cshunt=7 pF. So by the equation the (C1 * C2)/(C1 + C2) comes out to be 11pF. That means the C1 comes to 22 pF

Regards
Amit

0 Sham Sunder over 10 years ago in reply to Amit Ashara

Prodigy 130 points

Thanks for previous reply Amit..

I have one question regarding combined bulk capacitance on the TM4C123 controller VDD and VDDA pins. I noticed in system design guideline for tiva series that "The combined VDD and VDDA bulk capacitance of the microcontroller is typically between 2 μF and 22 μF" but in launchpad schematic its kept around 1.23 uF. I guess this coupling capacitance isn't critical for most of application, but it doesn't fall even above the minimum specified limit in design guideline. I just wanted to be clear on that weather is it OK if i keep the same as in launchpad schematic or it should be between the limits specified in guideline.

Merry Christmas & Happy New Year in advance.

0 Amit Ashara over 10 years ago in reply to Sham Sunder

TI__Guru**** 244440 points

Hello Sham,

I agree per device it should be 2-22uF. Note that it depends on the quality of supply as well. The USB supply is very stable with low noise on it. This along with the amount of device current consumption and the two devices put together make up for the voltage supply stability.

This however is not an excuse or exception and System Design Guidelines will take precedence.

Regards
Amit

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tm4c123 gets heated because of VBUS (PB1) pin