Tiva 129X unable to program and heating up

Chandanasree Krishnan

Other Parts Discussed in Thread: TM4C1294KCPDT

Hi,

I redesigned a touch screen device that was using Stellaris MCU to work with TIva MCU- TM4C1294KCPDT .

3.3 V (500mA) at the output of regulator and 3.3 V supply at all points near the Tiva is correct with out the Tiva on board. Once Tiva is soldered on to the board , and when the board is powered up ,the 3.3 V supply drops to 2.6 V at all points. Tiva gets really hot ,and I have not been able to program the board.

Ethernet ,SPI1,UART0, USB and Analog I/O are used. Port A pins used as UART /SPI and are not directly connected to ground. Port B is not used No connection. ( GPIO #9 issue mentioned in errata)

The datasheet recommends all unused pins to be grounded ,but all unused pins are NC

I have checked for shorts between pins, any chances for static discharge , changed the Tiva on board 3 times. What could be the reason for this heating and voltage drop issue ?

I was not sure if it is worth trying to program when the supply is less than 2.9 V ,still tried . The error obtained is

CORTEX_M3_0: GEL Output:
Memory Map Initialization Complete
CS_DAP_0: Error connecting to the target: (Error -1170 @ 0x0) Unable to access the DAP. Reset the device, and retry the operation. If error persists, confirm configuration, power-cycle the board, and/or try more reliable JTAG settings (e.g. lower TCLK). (Emulation package 0.0.0.0)

Thanks,

Chandana

over 9 years ago

0 Amit Ashara over 9 years ago

TI__Guru**** 244400 points

Hello Chandana

Can you please share the schematics?

Regards
Amit

0 Robert Adsett72 over 9 years ago

Guru 10570 points

All unused pins are NC? That's bad, bad, bad, bad. Did I mention it was bad? That should never ever be done with CMOS inputs. It is one of THE classic ways to cause latchup.

Seriously, fix this and replace the micro before any other step.

Next triple check that all power connections are present. Verify against the data sheet, not the schematic.

Disconnect as many I/O circuits as you can while not leaving any pin NC.

Now if this fails you should be left with only power connections that must be wrong. If it works you can start adding your I/O circuits back slowly.

It is probably a good idea to add a way to measure current draw while you are doing this. Knowing that a particular circuit is drawing substantially more current than expected is potentially quite valuable.

Robert

Personally, I've found when this happens it's usually because the power pinout has been misread or the package mirrored. That's why I suggest verifying to the data sheet not the schematic and disconnecting I/O. The latter makes it easier to verify that you have not connected a power rail to an I/O point

0 Amit Ashara over 9 years ago in reply to Robert Adsett72

TI__Guru**** 244400 points

Hello Robert

Agreed. I want to make sure that some power rails have not been connected in the schematic or some other not so obvious design rule violated. I have found it useful to review the schematic v/s the data sheet and design guidelines.

Regards
Amit

0 Robert Adsett72 over 9 years ago in reply to Amit Ashara

Guru 10570 points

Indeed Amit, and one other thing to check. Reverify that you have pin one located correctly on the package. There are different pin numbering systems used on four sided packages. Make sure you are using the correct one

Robert

0 Amit Ashara over 9 years ago in reply to Robert Adsett72

TI__Guru**** 244400 points

Hello Robert,

Yes, I agree with your assessment. On the 128QFP package there is the EPHY and non EPHY parts which have a variation of VDD and GND pads on the PHY pin side

Regards
Amit

0 Chandanasree Krishnan over 9 years ago in reply to Amit Ashara

Prodigy 130 points

Hi ,

Attached the schematics.

Next version of the board will be designed with all unused pins grounded. The data sheet specified NC as an acceptable practice and ground as a preferred practice.

I would like to find out all the issues leading to this problem and fix it before ordering a new design.

Thanks,

Chandana

@Amit : Will share the pdf files

0 Amit Ashara over 9 years ago in reply to Chandanasree Krishnan

TI__Guru**** 244400 points

Hello Chandana

A pdf would be more suitable for review.

Regards
Amit

0 Chandanasree Krishnan over 9 years ago in reply to Amit Ashara

Prodigy 130 points

Hi Amit,

Could you please send me your email id ? I will email the files

Thanks,
Chandana

0 Amit Ashara over 9 years ago in reply to Chandanasree Krishnan

TI__Guru**** 244400 points

Hello Chandana,

I have sent you a friend request where you can use the PM to send me the files (in PDF)

Regards
Amit

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Tiva 129X unable to program and heating up