Circuit Track below TMS320F28027

Hi Ashutosh,

Ashutosh Pailwan1 said:

While Developing board. the tracks are suppose to come below the Chip

Please avoid this!

1. As there is no clearance between the chip body and PCB, wont the tracks below it get shorted thorugh body.

Body is insulated and also the track.... but the track insulation is the one that can get compromised after certain period due to heat generated by mcu. But atleast the body is insulated. So the above case can happen if proper clearances are not provided.

For eg. F28027 controlCard have tracks below the part:

Ashutosh Pailwan1 said:

If body is (electrical)insulating, then heat generating due to current flowing through track might conduct the heat to Chip.

Yes... the tracks might get heated up resulting to some unstable or undeserved operation. Hence critical signals like ePWM, ADCs, COMn are not suggested.

Linking Ground signals is the best option as heat is dissipated in ground pads :)

Regards,

Gautam

Hi Ashotosh,

I would not have significant concern with putting traces directly under the chip, especially low current ones. The chip's body is insulated. 

Often a decent layout will have IOs and ADC inputs attach distally to an MCU pad whereas grounds, power and decoupling circuitry will attach to their respective pads in a more proximal way.  This often happens because the layout person will want to keep traces as short as possible.

That being said, it is best to keep traces that are known to be high current, high noise, or high temperature further away from the chip if possible. 


Thank you,
Brett