TMS320F28379S: 1.2V Core, VREGENZ clarification.

PowerGuy

Part Number: TMS320F28379S

Please help me understand better the input voltages for the 320F28379S.

The spec sheet says, VDD needs 1.2V.

I have a prototype board, where I did not supply 1.2V to any VDD pins. I do have 2.2uF caps to ground from each VDD pin but not voltage going to them.
The rest, VDDIO,VDDA,VDD3VFL,VDDOSC have 3.3V going to them with the corresponding decoupling capacitors.

I have been able to run and debug code on the processor.

1 - Do I need to supply 1.2V to the VDD pins ?
(what is the short coming of not doing this, after all my code "seems" to operate fine)

2- What is 1.2V VDD used for ?

3 - VREGENZ pin.
Currently I have it pulled to ground, and code runs.
But the spec sheet says it needs to be disabled and pulled to VDDIO. When I connect VREGENZ to VDDIO my processor does not boot up.

over 6 years ago

0 Frank Ankapong over 6 years ago

TI__Mastermind 28275 points

Hi PowerGuy,

The documentation is correct. Internal VREG is not supported on the F28379S device. VDD is the core voltage. When you tie VREGENZ low, the internal VREG is enabled however, it will not be able to provide enough current to power the device through all operating conditions. What will happen is, as device activity and load increases, the device will reset due to insufficient current to VDD. So you will need to supply VDD externally and tie VREGENZ high as highlighted in the datasheet.

0 PowerGuy over 6 years ago in reply to Frank Ankapong

Intellectual 415 points

Thank you very much for the clarification.

Now that I need to add a 1.2V source to my board I'm looking into the power consumption.

From the graph below, is it safe to assume that most of the power the tms320f28379s needs to run comes from the 1.2V ?
Am I looking at a 400mA max current draw from 1.2V ?

0 Frank Ankapong over 6 years ago in reply to PowerGuy

TI__Mastermind 28275 points

PowerGuy,

The 400mA you are seeing is a typical max but it's a good estimate and yes, most of the power draw is on the Vdd rail. However, as mentioned in the section, this could vary across operation conditions. Sizing your supply to be 2x will be the safer approach. So you should probably use something around 800mA.

0 PowerGuy over 6 years ago in reply to Frank Ankapong

Intellectual 415 points

ok!

thank you again!

0 Frank Ankapong over 6 years ago in reply to PowerGuy

TI__Mastermind 28275 points

No problem. Let us know if you ran into anymore issues.

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TMS320F28379S: 1.2V Core, VREGENZ clarification.