dspic33ep512mu814 ic getting over heated

i bought 4 dspic33ep512mu814 from microchip direct. i designed the pcb as per microchip specifications if i solder the chip to the pcb the chip grtting over heated and burned all the 3 chips same issue next what i tried is i took the last chip and connected only the vss and vdd pins alone to 3.3v supply that ic also got burned kindly tel me what could be wrong i am using esd mate with eds protected soldering rod. kindly help


regards
kalyan.

I assume you've connected ALL of V_DD, V_SS, AV_DD, AV_SS, V_USB3V3 and the V_CAP with a 10uF capacitor to their appropriate V_DD or GND as indicated in the device datasheet?

If so, I suspect one of the V_SS, AV_SS or possibly the -V_REF maybe either inadvertently switched or shorted to V_DD somewhere on your PCB.

I would test continuity with each of the V_SS, AV_SS and -V_REF pin pads consecutively with the V_DD rail.

Also carefully double check the location of each of the above pins with the pinout diagrams in the datasheet, you might also check the errata for any possible errors in the original datasheet.

The forum has dozens of similar threads posted each year concerning a similar issue and invariably the issue is either due to a short on the PCB, inadvertent switch of a V_SS connection with its corresponding V_DD pin connection, a floating AV_DD, AV_SS, V_USB3V3 or V_CAP or some permutation of the aforementioned.

raman00084 said:

...next what i tried is i took the last chip and connected only the vss and vdd pins alone to 3.3v supply that ic also got burned...

Click to expand...

Certainly, not recommended or wise:

Reference: dsPIC33EPXXX(GP/MC/MU)806/810/814 Datasheet ,Section: 2.0 GUIDELINES FOR GETTING STARTED WITH 16-BIT DIGITAL SIGNAL CONTROLLERS AND MICROCONTROLLERS, Page: 31

Note: The AV_DD and AV_SS pins must be connected independent of the ADC
voltage reference source. The voltage difference between AV_DD and V_DD cannot
exceed 300 mV at any time during operation or start-up.

Click to expand...

I suppose the possibly of all four devices being defective exists, although exceedingly remote.


BigDog

dear friend can i leave 77 pin vbus floating i am not using usb module?

raman00084 said:

can i leave 77 pin vbus floating i am not using usb module?

Click to expand...

Absolutely not.

Reference: dsPIC33EPXXX(GP/MC/MU)806/810/814 Datasheet ,Section: 2.0 GUIDELINES FOR GETTING STARTED WITH 16-BIT DIGITAL SIGNAL CONTROLLERS AND MICROCONTROLLERS, Page: 32

Note 1: If the USB module is not used, V_USB3V3 must be connected to V_DD, as shown.

Click to expand...

You also must ensure there are proper decoupling caps between each V_DD/V_SS and AV_DD and AV_SS and the V_CAP pin has a 10uF cap, preferably tantalum between it and GND.




BigDog

vusb3v3 i connected to vdd only, i am asking about the 77 pin vbus in data sheet they never mentioned the vbus where to connect when usb module is not used, can i leve floating.

raman00084 said:

vusb3v3 i connected to vdd only, i am asking about the 77 pin vbus in data sheet they never mentioned the vbus where to connect when usb module is not used, can i leve floating.

Click to expand...

My mistake, after awhile all this pin nomenclature starts to look the same.


Are the dsPIC33EP512MU814s the 144-pin TQFP/LQFP package? That's a lot of pins for a 16-bit microcontroller!

I took a look at the dspic33ep512mu814 on the 100-pin PIM and examined schematics for the dsPICDEM MCLV-2 board, Microchip leaves V_BUS pin 77 or pin 54 on the 100-pin PIM floating. I do not particularly like to leave anything floating, however I suppose as long as the USB module is not enabled it should not be an issue.

dsPIC33EP512MU814 Motor Control PIM Information Sheet

dsPICDEM MCLV-2 Development Board User's Guide




BigDog

raman00084 said:

dear friend can i leave 77 pin vbus floating i am not using usb module?

Click to expand...

yes you can leave it floating
connect all VDD to 3.3v , decouple them by 100nF capacitors with respect to Vss
connect AVDD through 1ohm resistor to Vdd , connect AVSS to Vss directly , put a capacitor between AVDD and AVSS preferably a 10uF (10v or 16v is enough)
since you are not using USB:
connect Vusb3.3 to VDD , no capacitor is needed , leave Vbus open . connect VCAP to an external capacitor 10uF ,donot short this PIN to VDD !!!!!!!
and please make sure that you donot have mistakes in the pin numbers if you have drawn this component in the PCB cad software by yourself , sometimes a small mistake can cause huge trouble

please post schematic so we can take a look at all the pins and connections , you maybe sourcing or sinking current higher that specifications from somewhere !

in my ic it is written dspic33ep512mu814-E/PL, I CHECKED ALL MY PCB CONNECTIONS VSS VDD EVERY THING IS FINE, CHECKED 3 TIMES NO ISSUE IN PCB

THE VOLTAGE ACROSS VSS TO VDD IS 3.27V USING LM2576 3.3V REGULATOR .

https://obrazki.elektroda.pl/4669669700_1438070794.jpg THE SCHEMATIC IS HEAR

raman00084 said:

in my ic it is written dspic33ep512mu814-E/PL, I CHECKED ALL MY PCB CONNECTIONS VSS VDD EVERY THING IS FINE, CHECKED 3 TIMES NO ISSUE IN PCB

THE VOLTAGE ACROSS VSS TO VDD IS 3.27V USING LM2576 3.3V REGULATOR .

https://obrazki.elektroda.pl/4669669700_1438070794.jpg THE SCHEMATIC IS HEAR

Click to expand...

your schematic looks fine except for this error , see the attachment , miss placed ground pin :

and wow that is one big schematic , looks like dual motor controller , but i am still wondering what are all those pins (callled output and connected to series resistors) , is these only for later expansion , or is there any load that might be consuming current from the dspic pins ??

the ground pin you mentioned is not a problem i corrected it before making the pcb. output pins are for later expansion only at present they do not consume any current