TM4C1294NCPDT: TM4C1294NCPDTI MICROCONTROLLER SHORT BETWEEN 3.3V AND GND

sampreeth meti

Prodigy 190 points

Part Number: TM4C1294NCPDT
Other Parts Discussed in Thread: TM4C123GH6PM

Hi,

I am facing problem with TM4C1294NCPDTI3 MICROCONTROLLER showing the ground and supply getting shorted.

The schematics is exactly same as tiva series launchpad.

Below are the steps followed

1. Checked the bare PCB for any shorts.

2. Microcontroller and its related components are soldered.

3. No shorts are observed between uC pins.

4.Measured the resistance between +3.3v and Gnd it shows 330KOhms

5. Measured the resistance between VDDC and Gnd it shows 5.89KOhms

6. After Powering the Microcontroller the current drawn is 230mA and IC gets heated up. After Power OFF, The resistance between supply and GND is 1.5Ohms.

7. Replaced with two new IC and the problem exists.

the IC part no is TM4C1294NCPDTI369AVC5W G4

Kindly Help..

over 9 years ago

0 Tom Oldbury over 9 years ago

Intellectual 540 points

A silly question but is the device soldered the correct way around?

We have destroyed a TM4C123GH6PM by soldering it the wrong way around, you get an almost direct short between 3V3 and GND of the micro.

0 sampreeth meti over 9 years ago in reply to Tom Oldbury

Prodigy 190 points

with right orientation and soldered correctly even inspected under microscope..

0 Amit Ashara over 9 years ago

TI__Guru**** 244440 points

Hello Sampreeth

What is the VDDC pin connected to? Can you share the schematics?

0 sampreeth meti over 9 years ago in reply to Amit Ashara

Prodigy 190 points

0 Amit Ashara over 9 years ago in reply to sampreeth meti

TI__Guru**** 244440 points

Hello Sampreeth,

The schematic looks ok to me except that the VDD/VDDA supplu does not seem to have a bulk cap and overall the number of de-caps being used is less. Also as To did mention, check the quality of the solder especially when GND and VCC pins are close by.

Also since you are using an external USB PHY, I would ask you to compare the schematic and layout of your board v/s the following TI Design.

www.ti.com/.../TIDM-TM4C129USBHS

0 sampreeth meti over 9 years ago in reply to Amit Ashara

Prodigy 190 points

HI, Amith,
Does that de-cap does really effect the shorting of VCC and Gnd ? (personally i dont think as there is too much load on microcontroller since it it is very early stage before code being loaded ).REG shorting of leads i will check once again as you and Mr TOM Oldbury suggested .

( i will definitely review HS USB as us referred and also with tusb 211 for long range ).

0 Amit Ashara over 9 years ago in reply to sampreeth meti

TI__Guru**** 244440 points

Hello Sampreeth,

I am pointing to the fact that there is no bulk cap in the schematic. Generally having a bulk cap is useful when there is an inrush and it works as a temporary charge bank. Since the device heats up almost w/o loading any code, I would naturally suspect

(a) VDDC and VDD have been shorted (which is not the case here)
(b) Device footprint does not match the pin out (at least from Power and Ground pin definition does not look to be the case)
(c) Insufficient cap or general rule violation viz-a-viz System Design Guidelines?

0 Tom Oldbury over 9 years ago

Intellectual 540 points

Did you buy the part from an authorised TI reseller?

There are counterfeit parts out there - it is possible you received one. It is common for similarly shaped or packaged devices to be relabeled. Check the printing on the device and compare it to the datasheet or an example on a Launchpad board or similar.

0 cb1_mobile over 9 years ago in reply to Amit Ashara

Guru 117855 points

This properly directed to poster - not to Amit.

While you report "measuring" 3V3 - have you properly scoped that voltage upon board, "Power Up?" Brief transient voltage is (likely) suspect and your avoidance of bulk filter caps makes your board especially vulnerable to such transients... (we've encountered this several times w/client designs..)

Note too that VDD "going negative" (even briefly) is a known cause of MCU murder...

0 sampreeth meti over 9 years ago in reply to Amit Ashara

Prodigy 190 points

I will try to incorporate additional capacitors in my existing PCB,

0 sampreeth meti over 8 years ago in reply to sampreeth meti

Prodigy 190 points

Hi,

Problem was due to the power supply transient voltage.

Thanks to every one for the help.

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TM4C1294NCPDT: TM4C1294NCPDTI MICROCONTROLLER SHORT BETWEEN 3.3V AND GND