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.
...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...
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 AVDD and AVSS pins must be connected independent of the ADC
voltage reference source. The voltage difference between AVDD and VDD cannot
exceed 300 mV at any time during operation or start-up.
I suppose the possibly of all four devices being defective exists, although exceedingly remote.
BigDog